Bone Density by Specific Anatomic Location Using Hounsfield Samples of the Lower Extremity: A Multi-center Retrospective Analysis

Understanding bone mineral density and its effects on patient outcomes is a useful tool for lower extremity surgeons. Historically, dual-energy X-ray absorptiometry scans have been the gold standard for quantifying bone mineral density. In this study, we look at an indirect way to measure bone mineral density using Hounsfield units on computed tomography. The aim of this study is to establish normal physiological Hounsfield ranges in specific bones of the foot by analyzing Hounsfield unit measurements and determining associated factors. We hypothesize that there will be a difference in density based on age, sex, and anatomic location. Patient data from January 2010 to January 2020 were retrospectively analyzed from 2 institutions. Nine anatomic locations (calcaneus, talar body, talar head, navicular, cuboid, medial cuneiform, head of first and fifth metatarsal, and base of first proximal phalanx) were measured for bone mineral density averages. In total, 137 patients were evaluated (71 males, 66 females) with an average age of 54 years. Significant differences in density were found between the 9 anatomic locations. Age was confirmed to be a significant covariate with inverse relation to Hounsfield units, p < .001. There were no density differences between sexes at any of the locations, except the talar head, p < .001. This is the first study to our knowledge to establish normal physiological ranges of bone density on computed tomography for specific anatomic locations of the foot. This quantitative approach to bone density and the established effect of age, sex, and location is pivotal for diagnostic and preoperative planning.

Routine chest CT combined with the osteoporosis self-assessment tool for Asians (OSTA): a screening tool for patients with osteoporosis

INTRODUCTION

The osteoporosis self-assessment tool for Asians (OSTA) is a common screening tool for osteoporosis. The seventh thoracic CT (CT-T7) Hounsfield unit (HU) measured by chest CT correlates with osteoporosis. This study aimed to investigate the diagnostic value of OSTA alone, CT-T7 alone, or the combination of OSTA and CT-T7 in osteoporosis.

MATERIALS AND METHODS

In this study, 1268 participants were grouped into 586 men and 682 women. We established multiple linear regression models by combining CT-T7 and OSTA. Receiver operating characteristic (ROC) curves were used to evaluate the ability to diagnose osteoporosis.

RESULTS

In the male group, the mean age was 59.02 years, and 108 patients (18.4%) had osteoporosis. In the female group, the mean age was 63.23 years, and 308 patients (45.2%) had osteoporosis. By ROC curve comparison, the CT-T7 (male, AUC = 0.789, 95% CI 0.745-0.832; female, AUC = 0.835, 95% CI 0.805-0.864) in the diagnosis of osteoporosis was greater than the OSTA (male, AUC = 0.673, 95% CI 0.620-0.726; female, AUC = 0.775, 95% CI 0.741-0.810) in both the male and female groups (p < 0.001). When OSTA was combined with CT, the equation of multiple linear regression (MLR) was obtained as follows: female = 3.020-0.028*OSTA-0.004*CT-T7. In the female group, it was found that the AUC of MLR (AUC = 0.853, 95% CI 0.825-0.880) in the diagnosis of osteoporosis was larger than that of CT-T7 (p < 0.01). When the MLR was 2.65, the sensitivity and specificity were 53.9% and 90%, respectively.

CONCLUSION

For a patient who has completed chest CT, CT-T7 (HU) combined with OSTA is recommended to identify the high-risk population of osteoporosis, and it has a higher diagnostic value than OSTA alone or CT-T7 alone, especially among females. For a female with MLR greater than 2.65, further DXA examination is needed.

Psoas weakness following oblique lateral interbody fusion surgery: a prospective observational study with an isokinetic dynamometer

BACKGROUND CONTEXT

Although the surgical corridor used for oblique lateral interbody fusion (OLIF) protects the intrapsoas nerves by causing minimal compression, transient weakness remains the most commonly reported postoperative complication.

PURPOSE

Using a dynamometer to evaluate how the hip flexor strength changes following OLIF.

STUDY DESIGN/SETTING

A prospective observational study.

PATIENT SAMPLE

Forty-six patients who underwent single or multi-level OLIF for lumbar spondylolisthesis.

OUTCOME MEASURES

Isokinetic dynamometer values (peak torque, total work, average power), visual analogue scale (VAS) scores for leg pain, hypoesthesia, subjective weakness of the left hip flexor muscle, Oswestry disability index, body mass index, bone mineral density, radiologic findings of the psoas muscle (cross-sectional area, Hounsfield unit (HU), fat portion grade), and psoas retraction time.

METHODS

The isokinetic muscle strength of the hip flexor was measured five times (preoperatively and postoperatively at 2 days, 1 week, 1 month, and 3 months) for both legs. The peak torque was defined as the postoperative strength of the left hip flexor muscles, and was compared to the preoperative baseline value. The strength of the left and right hip flexor muscles were also compared at each time point. For logistic regression analysis, when the peak torque was below the median value, it was defined as lower peak torque.

RESULTS

Up to 1 week after surgery, the strength of the left hip flexor muscle decreased significantly (paired difference in peak torque was 22.6%, p<.001). In the results of multivariate logistic regression analysis, diabetes (odds ratio [OR]=8.43, p=.020) and the HU of the psoas muscle (OR=0.916, p=.034) were associated with lower peak torque 1 week after surgery. From 1 month after surgery, postoperative weakness of the psoas muscle was not significant. In the questionnaire survey, subjective left hip flexion weakness was reported in 8.5% (4/47) of patients 1 week after surgery, and it remained in only 2.1% (1/47) of patients after 3 months of operation. The frequency of left anterior thigh pain and hypoesthesia decreased from 85.1% (40/47) at 1 week to 2.1% (1/47) at 3 months after surgery. The mean VAS score for left anterior thigh or groin pain decreased significantly at 1 month after surgery (PO2D: 4.04±1.84, PO1M: 1.67±1.10, p<.001).

CONCLUSIONS

Dynamometer measurement showed that psoas strength declined significantly up to 1 week after OLIF surgery. Patients with diabetes or lower HU of the psoas muscle showed delayed recovery from postoperative weakness of the psoas muscle. However, the weakness was insignificant from 1 month after surgery. At 3 months after surgery, the other psoas-related problems (left anterior thigh pain and hypoesthesia) also disappeared.

Association Between Hounsfield Units in Preoperative Wrist Computed Tomography Scans and Outcomes After Wrist Fracture Surgery

Purpose

This work aims to evaluate the hypothesis that the value of Hounsfield units (HU), as a marker of bone density, in preoperative wrist computed tomography (CT) scans correlates with the functional outcomes as measured by patient reported outcomes (PROs) after distal radius fracture surgery with volar locking plate fixation.

Methods

Of a database of 92 wrist fractures operated on in our hospital between 2011 and 2020, with a preoperative CT scan performed, we selected the cases with a minimum follow-up period of 12 months. After applying the exclusion criteria, the final cohort comprised 64 patients. Three measurements of HU were performed in correlative coronal sections of the capitate bone. PROs were determined using two functional questionnaires (DASH and PRWE) and one quality of life questionnaire (SF-12). The statistical relationship between PROs and the HU measurements obtained via a CT scan was analyzed.

Results

Patients were classified into two groups, osteoporotic (OST) or non-osteoporotic (non-OST), according to the optimal cut-off value of 323 HU selected using a ROC curve. The median DASH questionnaire score in the OST group was significantly higher (1.7 vs 10.0, p = 0.003).

Conclusion

HU values in preoperative wrist CT scans may help to identify osteoporotic bone in patients prior to wrist fracture surgery and lead to an improved surgical indication and treatment strategy.

Level of Evidence

Level of evidence: Prognostic III.

Prediction of osteoporosis and osteopenia by routine computed tomography of the lumbar spine in different regions of interest

Background

We aimed to investigate the utility of Hounsfield units (HU) obtained from different regions of interest in opportunistic lumbar computed tomography (CT) to predict osteoporosis coupling with data of dual-energy X-ray absorptiometry (DXA).

Methods

A total of 100 patients who attended a university hospital in Shanghai, China, and had undergone CT and DXA tests of the lumbar spine within 3 months were included in this retrospective review. Images were reviewed on axial sections, and regions of interest (ROI) markers were placed on the round, oval, anterior, left, and right of the L1–L4 vertebra to measure the HU. The mean values of CT HU were then compared to the bone mineral density (BMD) measured by DXA. Receiver operator characteristic curves were generated to determine the threshold for diagnosis and its sensitivity and specificity values.

Results

The differences in CT HU of different ROI based on DXA definitions of osteoporosis, osteopenia, and normal individuals were statistically significant (p < 0.01). The HU values of the different ROI correlated well with the BMD values (Spearman coefficient all > 0.75, p < 0.01). The threshold for diagnosing osteoporosis varies from 87 to 111 HU in different ROIs, and the threshold for excluding osteoporosis or osteopenia is 99–125 HU.

Conclusion

This is the first study on osteoporosis diagnosis of different ROI with routine CT lumbar scans. There is a strong correlation between CT HU of different ROI in the lumbar spine and BMD, and HU measurements can be used to predict osteoporosis.

Hounsfield unit measurement method and related factors that most appropriately reflect bone mineral density on cervical spine computed tomography

OBJECTIVE

Our study's purpose was to determine the most reliable Hounsfield unit (HU) measurement method to reflect bone mineral density (BMD) on cervical spine computed tomography (CT) and to identify any factors that influence these results.

MATERIALS AND METHODS

We retrospectively analyzed 439 consecutive patients with mild head and neck injuries. Mean HU values of the C2-C7 vertebra were determined on each sagittal, coronal, and axial CT image. Correlation patterns were analyzed between the HU value and corresponding dual-energy X-ray absorptiometry (DXA) in the lumbar vertebra (T-score) and femoral neck (T-score). A sub-group analysis was performed according to patient age, sex, and degree of spinal degeneration.

RESULTS

The correlation coefficients for HU and DXA ranged from 0.52 to 0.65 in all cervical segments. A simple linear regression analysis revealed the following formula: T-score = 0.01 × (HU) - 4.55. The mean HU values for osteopenia and osteoporosis were 284.0 ± 63.3 and 231.5 ± 52.8, respectively. The ROC curve indicated that the HU method has a sensitivity of 89.2% and specificity of 88.7% to diagnose osteoporosis. The HU measurement showed a high correlation value (range: r = 0.64-0.70) with spine DXA score regardless of the degree of degeneration or patient age or sex.

CONCLUSION

HU values using the upper two cervical vertebrae (C2 and C3) reflected a more reliable BMD level than other segments. Additionally, the HU of cervical CT provided reliable information regardless of measurement plane, age or sex, and degree of degeneration.

Significance of Measuring Lumbar Spine 3-Dimensional Computed Tomography Hounsfield Units to Predict Screw Loosening

BACKGROUND

Osteoporosis is a well-known risk factor of screw loosening. Classically, dual-energy x-ray absorptiometry (DEXA) scan is an easy and cost-effective method of detecting bone mineral density (BMD). However, T-score on DEXA scan can be overestimated in patients with degenerative changes of the spine. Our objective was to identify correlation between Hounsfield unit (HU) measured by 3-dimensional computed tomography (3D-CT) and screw loosening.

METHODS

A total of 113 patients treated with lumbosacral spinal fusion were reviewed and categorized into a screw loosening group and a normal group to compare their average values of preoperative CT HU. Screw loosening was defined as radiolucent area around screw that was thicker than 1 mm with a "double halo sign".

RESULTS

There were statistically significant differences in patient age and steroid use between screw loosening and non-loosening groups. There was no significant difference in BMD or T-score between the 2 groups. However, HU values measured in axial, coronal, and sagittal images were significantly different between the 2 groups. In the receiver operating characteristic for HU values measured in CT images, the greatest area under the curve was 0.774 and that was in case of Hounsfield unit measured by axial CT images from L1 to L4.

CONCLUSIONS

Preoperative CT HU is associated with screw loosening. It can be a better predictor of screw loosening than DEXA scan. The best predictor of screw loosening in this study is the average value of HU from L1 to L4 in axial cut.

Hounsfield units: A promising non-invasive tool for diagnosing benign prostatic hyperplasia

OBJECTIVE

The clinical symptoms in benign prostatic hyperplasia (BPH) are directly proportional to prostate volume. We aimed to show whom and when to intervene in a noninvasive way, correlating the patient's subjective symptoms with objective diagnostic tools.

MATERIAL AND METHOD

International Prostate Symptom Score (IPSS) was evaluated in patients who consulted the urology outpatient clinic for the first time with lower urinary tract symptoms (LUTS). Subsequently, PSA, urea, creatinine, complete urinalysis, uroflowmetry, urinary tract ultrasound and non-contrast lower abdominal computed tomography (CT) examinations were requested. Prostate central (transitional zone) zone and peripheral zone HU scores, prostatic urethral length and bladder wall Hounsfield units (HU) scores were recorded by using computed tomography (CT). The ellipsoid formula was used for ultrasonographic and tomographic measurements of prostate size (anteroposterior diameter × transverse diameter × longitudinal diameter × 0.52).

RESULTS

A statistically significant negative correlation was found between the prostate peripheral zone/central zone HU ratio and the maximum flow rate measured in the uroflowmetry test.

CONCLUSION

This is the first study in the literature to evaluate the correlation between voiding parameters such as Qmax, Qave and IPSS scores, and prostate and bladder wall HU scores obtained by computed tomography examination in BPH patients. A significant relationship has been detected between the peripheral zone/central zone HU ratio and Q max. Additional studies with larger patient populations could better clarify the contribution of HU in the diagnosis of BPH and treatment decision making of these patients.

Dual-Energy CT-Based Bone Mineral Density Has Practical Value for Osteoporosis Screening around the Knee

Introduction: Adequate bone quality is essential for long term biologic fixation of cementless total knee arthroplasty (TKA). Recently, vertebral bone quality evaluation using dual-energy computed tomography (DECT) has been introduced. However, the DECT bone mineral density (BMD) in peripheral skeleton has not been correlated with Hounsfield units (HU) or central dual-energy X-ray absorptiometry (DXA), and the accuracy remains unclear. Materials and methods: Medical records of 117 patients who underwent TKA were reviewed. DXA was completed within three months before surgery. DECT was performed with third-generation dual source CT in dual-energy mode. Correlations between DXA, DECT BMD and HU for central and periarticular regions were analyzed. Receiver operating characteristic (ROC) curves were plotted and area under the curve (AUC), optimal threshold, and sensitivity and specificity of each region of interest (ROI) were calculated. Results: Central DXA BMD was correlated with DECT BMD and HU in ROIs both centrally and around the knee (all p < 0.01). The diagnostic accuracy of DECT BMD was higher than that of DECT HU and was also higher when the T-score for second lumbar vertebra (L2), rather than for the femur neck, was used as the reference standard (all AUC values: L2 > femur neck; DECT BMD > DECT HU, respectively). Using the DXA T-score at L2 as the reference standard, the optimal DECT BMD cut-off values for osteoporosis were 89.2 mg/cm3 in the distal femur and 78.3 mg/cm3 in the proximal tibia. Conclusion: Opportunistic volumetric BMD assessment using DECT is accurate and relatively simple, and does not require extra equipment. DECT BMD and HU are useful for osteoporosis screening before cementless TKA.

High-stress distribution in the lateral region of the subtalar joint in the patient with chronic lateral ankle instability

PURPOSE

Chronic lateral ankle instability (CLAI) is associated with osteoarthritis (OA). However, the characteristics of patients with CLAI who progress to OA are not clear. Measurement of Hounsfield Unit (HU) value on computed tomography (CT) is reported to be useful to evaluate the stress distribution. We aimed to evaluate the stress distribution in the ankle and subtalar joints and factors enhancing it in patients with CLAI.

MATERIALS AND METHODS

Thirty-three ankles with CLAI (CLAI group) and 26 ankles without CLAI (control group) were included. A mean age of CLAI was 35.2 years and control was 30.3 years. Color map was created in the ankle and subtalar joint according to the HU values using three-dimensional CT to identify the region with high HU values, and HU values in those regions were measured using two-dimensional CT and compared between control and CLAI groups. In CLAI group, the relationships between HU values and ankle activity score (AAS), OA, talar tilting angle (TTA), cartilage injury were assessed.

RESULTS

The HU values in the anteromedial region of the talus and lateral region in the subtalar joint were higher than those in the control. In CLAI, patients with an AAS of ≧ 6, over 10° of TTA, cartilage injury, and OA changes in the medial gutter had significantly higher HU values in the lateral region of the subtalar joint than those with an AAS of ≦5, less than 10° of TTA without cartilage injury and OA change.

CONCLUSIONS

CLAI patients, especially in the patients with high activity level, large TTA, cartilage injury, and OA changes at the medial gutter, have high HU values in the lateral region of the subtalar joint, which suggests that disruption of the subtalar compensation toward OA will occur. For these patients, instability should be completely eliminated to prevent ankle OA.

LEVEL OF EVIDENCE

Level III, comparative series.

Evaluation of femoral head bone quality by Hounsfield units: a comparison with dual-energy X-ray absorptiometry

BACKGROUND

Osteoporosis is associated with decreases in bone mineral density (BMD) and is diagnosed using dual-energy X-ray absorptiometry (DXA). Computed tomography (CT), performed in routine practice, can also be used to evaluate bone quality without additional cost.

PURPOSE

To determine whether Hounsfield units (HU), a standardized CT attenuation coefficient, measured from the femoral head correlated with DXA-measured BMD.

MATERIAL AND METHODS

We evaluated 82 patients (14 men, 68 women; mean age, 67 years) undergoing femoral DXA and CT (non-enhanced abdominopelvic and hip scans) with 130 kV to determine whether HU correlated with T-scores. HU were measured by two radiologists using the largest spherical region of interest including the medullary bone of the femoral head from the junction point of the most caudal section of the femoral head with the femoral neck in 5-mm axial sections. The correlations of both sides' HU values with their ages and DXA femur T-score were evaluated.

RESULTS

HU values obtained from both femoral heads showed significant variation between the osteoporotic and non-osteoporotic groups (both P = 0.000) and strongly correlated with each other and DXA femur T-scores (left r = 0.75, right r = 0.73, respectively). In ROC curve analysis, predictive power of left HU values in identifying patients with osteoporotic femur DXA T-score was 0.905, and for right HU values it was 0.924. Osteoporosis cutoff values were 198 HU and 204 HU for the left and right hips, respectively.

CONCLUSIONS

HU obtained from CT performed in routine practice correlated with the DXA scores, thus providing an alternative method to determine regional bone quality without additional cost. This may be useful when choosing a fixation method, especially in trauma cases with already-performed abdominopelvic or pelvic CT in emergency services.

Predicting Nonunions in Ankle Fractures Using Quantitative Tibial Hounsfield Samples From Preoperative Computed Tomography: A Multicenter Matched Case Control Study

The aim of this study is to use tibial Hounsfield unit measurements from preoperative computed tomography scans of ankle fractures to predict delayed union and nonunion. We hypothesize that patients with lower Hounsfield unit averages, an indirect measure of lower bone mineral density, in the distal tibia are more likely to develop delayed union and nonunion complications after ankle fracture surgery. Patient data from January 2010 to January 2020 were retrospectively analyzed from 2 institutions. Exposure cases of delayed union or nonunion that had preoperative computed tomography were compared to 5 controls matched for sex, age, and classification. 3 measurements were taken from the tibia on axial computed tomography and averaged to create a summative measure for overall bone health. Statistical analysis was used to analyze the relationship between the groups. 19 exposure patients were compared to 95 control patients. There were 16 females and 3 males in the exposure group aged from 30 to 88 years. Average follow-up was 1.6 years. The average exposure and control Hounsfield measurements were 186 (161-210) and 258 (248-269), respectively. Significant differences were found for all measured averages. This is the first study to our knowledge relating preoperative tibial Hounsfield measurements to healing rates of ankle fractures. Measurements taken from any of the 3 sites or the average could be an indicator of overall bone health. Using this technique on preoperative imaging will help surgeons adjust their perioperative planning for patients at higher risk for delayed union and nonunion.

The diagnostic utility of unenhanced computed tomography of the brain and D-dimer levels in acute cerebral venous sinus thrombosis: A quantitative study

Objectives

(1) To calculate the sensitivity and specificity of the Hounsfield Unit (HU), the HU to hematocrit (H:H) ratio, and the D-dimer level in the diagnosis of acute CVST. (2) To assess the D-dimer level's linear relationship with the HU and the H:H ratio.

Materials and Methods

A single-center retrospective case-control study was conducted from 2005 to 2020. The inclusion criteria for the thrombosed and control groups were specified. A region of interest (ROI) was plotted on the respective sinuses to calculate the HU. The H:H ratio was calculated by dividing the HU value by the hematocrit value. The receiver operating characteristic curve was used to calculate the sensitivity and specificity of the HU and the H:H ratio at different cutoff values. The Pearson correlation was used to assess the linear relationship between the D-dimer level and the HU and H:H ratio.

Results

There were 19 patients in the thrombosed group and 28 patients in the control group. There were significant differences in the mean HU (71 ± 6.3 vs. 45 ± 4.8, P < 0.001) and the mean H:H ratio (2.11 ± 0.38 vs. 1.46 ± 0.63,P < 0.001). An optimal HU value of 56 yielded 100% sensitivity and specificity. An H:H value of 1.48 yielded a sensitivity of 100% and a specificity of 65%, an H:H ratio of 1.77 demonstrated a sensitivity of 85% and a specificity of 90%, and an H:H ratio of 1.88 yielded a sensitivity of 79% and a specificity of 93%. D-dimer levels had a 95% and 71% sensitivity and specificity, respectively. There was a significant moderately positive linear correlation between the D-dimer level and the HU (r = 0.52, P < 0.001) and the H:H ratio (r = 0.61, P < 0.001).

Conclusion

Unenhanced CT of the brain can be a valuable objective diagnostic tool for acute CVST diagnosis. Hounsfield blood density and its normalized ratio with hematocrit are positively correlated with D-dimer levels, which may indicate active blood coagulation in a cerebral venous sinus.

Distribution of hounsfield unit values in the pelvic bones: a comparison between young men and women with traumatic fractures and older men and women with fragility fractures: a retrospective cohort study

Background

The fixation strength of bone screws depends on bone mineral density (BMD), so it is important to evaluate bone strength at fracture sites. Few studies have investigated BMD in the pelvis. The aims of this study were to measure the regional Hounsfield unit (HU) values in the cancellous bone of the acetabulum and pelvic ring and to compare these values between young and older patients.

Methods

This study enrolled young patients with high-energy trauma (aged 20–44 years; young group) and older patients with low-energy trauma (aged 65–89 years; older group). Patients without pelvic computed tomography (CT) scans, those with pelvic bone implants, and those who died were excluded. The HU values on the contralateral (non-fractured) side of the pelvis were measured on CT scans. The CT data were divided into 7 areas: the pubic bone, the anterior and posterior walls and roof of the acetabulum, the ischial tuberosity, the body of the ilium, and the third lumbar vertebra. The HU values in each area were compared between the young and older groups.

Results

Sixty-one young patients and 154 older patients were included in the study. The highest HU value was in the roof of the acetabulum regardless of age and sex. HU values were significantly higher in the ischial tuberosity and body of the ilium and lower in the pubic bone and anterior wall. The HU values in all pelvic areas were significantly lower in the older group than in the young group, especially in the anterior area.

Conclusions

HU values in the 6 pelvic areas were not uniform and were strongly related to load distribution. The HU distribution and age-related differences could explain the characteristic causes and patterns of acetabular fractures in the older and may help in surgical treatment.

The Effect of COVID 19 on Liver Parenchyma Detected and measured by CT scan Hounsfield Units

BACKGROUND

COVID 19 may affect organs other than lungs, including liver, leading to parenchymal changes. These changes are best assessed by unenhanced computed tomography (CT). We aim to investigate the effect of COVID 19 on liver parenchyma by measuring the attenuation in CT scan Hounsfield unit (HU).

MATERIALS AND METHODS

A cohort of patients, who tested COVID 19 polymerase chain reaction positive, were enrolled and divided into two groups: fatty liver (FL) group (HU ≤ 40) and nonfatty liver (NFL) group (HU > 40) according to liver parenchyma attenuation measurements by high resolution noncontrast CT scan. The CT scan was performed on admission and on follow up (10-14 days later). Liver enzyme tests were submitted on admission and follow up.

RESULTS

Three hundred and two patients were enrolled. Liver HU increased significantly from 48.9 on admission to 53.4 on follow up CT scan (P<0.001) in all patients. This increase was more significant in the FL group (increased from 31.9 to 42.9 [P =0.018]) Liver enzymes were abnormal in 22.6% of the full cohort. However, there was no significant change in liver enzymes between the admission and follow up in both groups.

CONCLUSION

The use of unenhanced CT scan for assessment of liver parenchymal represents an objective and noninvasive method. The significant changes in parenchymal HU are not always accompanied by significant changes in liver enzymes. Increased HU values caused by COVID 19 may be due to either a decrease in the fat or an increase in the fibrosis in the liver.

Predicting ESWL success by determination of Hounsfield unit on non-contrast CT is clinically irrelevant in children

The necessity of determining stone density by non-contrast computerized tomography (NCCT) before extracorporeal shock wave lithotripsy (ESWL) is a controversial topic due to the radiation exposure. We aimed to investigate whether stone density is helpful in predicting the success of ESWL in pediatric patients or not. In this retrospective study, database of a single center was used to identify 232 children aged between 2 and 16 years. Patients with abnormal renal anatomy, distal obstruction, a known cystine stone disease, a previous history of an intervention regarding stone, and an insufficient follow-up period (< 3 months) were excluded from the study. A total of 209 patients were included in the study (94 with NCCT, 115 without NCCT). Groups were compared in terms of stone size, stone location, and stone-free rate at 3 months after a single ESWL session. The mean age was 6.17 ± 3.27 years and 120 (57.4%) of the patients were male and 89 (42.6%) were female. Mean stone size was 11.7 mm in NCCT group and 12.3 mm in non-NCCT group (p 0.128). The complete stone clearance rate in NCCT and non-NCCT group at 3 months after ESWL was 57.4% (54/94) and 54.7% (63/115), respectively, and there was no statistically significant difference (p 0.316). In conclusion, unnecessary NCCT use should be avoided before ESWL considering the similar success rates after ESWL and the risk of exposure to radiation.

Can gray values be converted to Hounsfield units? A systematic review

OBJECTIVES

The purpose of this systematic review was to answer the focus question: "Could the gray values (GVs) from CBCT (cone beam computed tomography) be converted to Hounsfield units (HUs) in multidetector computed tomography (MDCT)?"

METHODS

The included studies try to answer the research question according to the PICO strategy. Studies were gathered by searching several electronic databases and partial grey literature up to January 2021 without language or time restrictions. The methodological assessment of the studies was performed using The Oral Health Assessment Tool (OHAT) for in vitro studies and the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) for in vivo studies. The Grading of Recommendations Assessment, Development and Evaluation (GRADE system) instrument was applied to assess the level of evidence across the studies.

RESULTS

2710 articles were obtained in Phase 1, and 623 citations remained after removing duplicates. Only three studies were included in this review using a two-phase selection process and after applying the eligibility criteria. All studies were methodologically acceptable, although in general terms with low risks of bias. There are some included studies with quite low and limited evidence estimations and recommendation forces; evidencing the need for clinical studies with diagnostic capacity to support its use.

CONCLUSIONS

This systematic review demonstrated that the GVs from CBCT cannot be converted to HUs due to the lack of clinical studies with diagnostic capacity to support its use. However, it is evidenced that three conversion steps (equipment calibration, prediction equation models, and a standard formula (converting GVs to HUs)) are needed to obtain pseudo Hounsfield values instead of only obtaining them from a regression or directly from the software.

Hounsfield Unit for Assessing Bone Mineral Density Distribution Within Cervical Vertebrae and Its Correlation With the Intervertebral Disc Degeneration

STUDY DESIGN

Retrospective radiological analysis.

OBJECTIVE

To assess bone mineral mass distribution within cervical vertebrae based on Hounsfield unit (HU) measurement, and explore its correlation with intervertebral disc degeneration.

METHOD

Three hundred and twenty-four patients with degenerative cervical spine disease were retrospectively reviewed and divided into six groups according to age. HU measurement of the whole vertebrae from C3 through C7 was obtained, then HU measurement within upper and lower part of the vertebrae on sagittal plane were obtained from C3 through C7. Disc degeneration on MRI was graded from I to V using the Pfirrmann classification.

RESULTS

There was a significant difference in the HU value from C3 to C7 among Group II to Group VI, the HU value presented consistently decreasing trend from young patients to old patients. In C6 and C7 vertebrae, there were significant differences in HU values between upper and lower parts of the vertebrae. More importantly. In all groups, HU values were highest in the upper part of the C4 vertebrae and then gradually decreased towards C3 and C7. HU value of both upper and lower vertebrae presented decreasing trend along with the aggravation of the disc degeneration.

CONCLUSION

HU values are not typically consistent throughout all levels of the cervical spine and the distribution within the vertebrae is not homogeneous. Decreased vertebral BMD and vertebral osteoporosis may trigger or exacerbate the adjacent intervertebral disc degeneration.

Correlation between Hounsfield unit derived from head, thorax, abdomen, spine and pelvis CT and t-scores from DXA

OBJECTIVES

CT examination can potentially be utilised for early detection of bone density changes with no additional procedure and radiation dose. We hypothesise that the Hounsfield unit (HU) measured from CT images is correlated to the t-scores derived from dual energy X-ray absorptiometry (DXA) in multiple anatomic regions.

MATERIALS & METHODS

Data were obtained retrospectively from all patients who underwent both CT examinations - brain (frontal bone), thorax (T7), abdomen (L3), spine (T7 & L3) or pelvis (left hip) - and DXA between 2014 and 2018 in our centre. To ensure comparability, the period between CT and DXA studies must not exceed one year. Correlations between HU values and t-scores were calculated using Pearson's correlation. Receiver operating characteristic (ROC) curves were generated, and the area under the curve (AUC) was used to determine threshold HU values for predicting osteoporosis.

RESULTS

The inclusion criteria were met by 1043 CT examinations (136 head, 537 thorax, 159 lumbar and 151 left hip). The left hip consistently provided the most robust correlations (r = 0.664-0.708, p < 0.001) and the best AUC (0.875-0.893). Meanwhile, thorax T7 and lumbar L3 showed average correlations (range of r values is 0.497-0.679, p < 0.001, AUC range = 0.680-0.783, 95% CI 0.561-0.922, all p < 0.02) and moderate AUC (0.680-0.783). Frontal bone shows low correlation and weak AUC with r < 0.5, AUC = 0.538-0.655, all p > 0.05.

CONCLUSION

HU values derived from the hip, T7 and L3 provided a good to moderate correlation to t-scores with a good prediction for osteoporosis. The suggested optimal thresholds may be used in clinical settings after external validations are performed.

Evaluation of celiac disease with uniphasic and multiphasic dynamic MDCT imaging

PURPOSE

An analysis of dynamic contrast MRI has been shown to provide valuable information about disease activity in Crohn's disease and Celiac disease (CD). However, there are no reports of dynamic multi-detector computer tomography use in patients with CD. The aim of this study is to determine and compare the perfusion dynamics of the patients treated with control subjects and the perfusion dynamics in patients with untreated CD, using dynamic contrast in MDCT and compare studying contrast dynamics in Marsh types as well.

METHODS

In this retrospective study, uniphasic and multiphasic MDCT, untreated, treated, incompatible CD patients and healthy control group duodenum wall thickness and HU values were compared in terms of patient groups and modified Marsh types.

RESULT

In dynamic CT, the highest contrast curve was observed in the untreated group and Marsh type 1. While the contrast curve of the untreated and non-compliant patients increased rapidly and showed wash out, the type 4 contrast curve was observed, whereas the treated and control group slowly increased type 5 contrast curve. In the contrast-enhanced CT in the venous phase, in the ROC analysis between Marsh 1-2 and Marsh 3a-c, the sensitivity was 97% and the specificity was 87% when the cut off was taken as 4.45 mm for wall thickness (p: 0.005).

CONCLUSION

Contrast-enhanced single-phase and dynamic MDCT imaging in CD patients may be useful in evaluating the inflammatory and pathological process in the small intestine.

Clinical features and literature review related to the material differences in thread rhinoplasty: Two case reports

BACKGROUND

Thread rhinoplasty can trigger a reaction to thread material, which is a foreign body. We compared clinical features induced by absorbable and non-absorbable threads following thread rhinoplasty.

CASE SUMMARY

Two patients who underwent different thread materials showed different clinical courses and different Hounsfield unit (HU) values in computed tomography. Patients with absorbable thread showed high HU values similar to a metallic material, and the HU value of inflammation was similar to vascular tissues with a lot of water (250). In the intraoperative field, absorbable thread materials and micro-abscesses were observed. In contrast, in the case of a non-absorbable thread, an object presumed to be thread was seen on the computed tomography (CT), and the HU value of inflammatory tissues was less than 100. In both patients, post-operative HU decreased to less than 100 and the clinical course improved. In both cases, histopathologic findings revealed foreign body granuloma associated with inflammation.

CONCLUSION

Absorbable threads were more aggressive and are more easily detected on CT.

Objective Evaluation of Cerebral Venous Sinus Attenuation on Plain CT Brain and Detecting Anemia. Noticing the "Unnoticed"

Context

Plain computed tomography (CT) of the brain is an important first-line investigation of choice in an acute neurologic setup. Unless clinically suspected concealed areas like the confluence of venous sinuses often go unnoticed. Diagnosing anemia, thrombosis, or polycythemia correlating the CT attenuation values might prove to be fruitful in early patient management where the mode of varied clinical presentations causes a clinical dilemma.

Aims

1) To determine the objective correlation between CT attenuation of the cerebral venous sinus and hemoglobin (Hb) as well as hematocrit (HCT) value and 2) to detect anemia from measuring venous sinus attenuation.

Methods and Materials

An exploratory study design of 200 patients, who had plain CT of the head and Hb and HCT levels obtained within 24 h of the scan.

Statistical Analysis Used

Two-tailed unpaired t-test was used to test the difference between two independent samples. Correlation and regression analyses were used to assess the correlation between two quantitative variables.

Results

A significant correlation was observed between the Hb-Hounsfield unit (HU) and HCT-HU. The simple linear regression model revealed that HU (P value < 0.001) was significantly correlated with Hb and the regression model was, Hb = 2.1 + 0.2 × HU. Similarly, HU (P value < 0.001) was significantly correlated with HCT and regression model was HCT = 6.2 + 0.7 × HU.

Conclusions

Objective attenuation values of dural sinuses on plain CT can be positively correlated with Hb and HCT values. Considering the cutoff of 35.5 HU, we were able to show the specificity of 100% for the detection of anemia.

Value of Hounsfield Units in the Evaluation of Isolated Sphenoid Sinus Lesions

Radiologic findings of fungal sinus disease are generally opacification in paranasal computed tomography (CT) images. The Hounsfield unit (HU) is a standardized objective unit that is also suitable for measuring remodeling and opacifications on CT scans of bone sections of patients with chronic rhinosinusitis. We hypothesized that HU values could provide valuable information in isolated sphenoid sinus lesions before surgery. Between 2012 and 2019, 35 patients underwent functional endoscopic sinus surgery for sphenoid sinus lesions. Tissues obtained from the sphenoid sinus were divided into two groups, fungal and nonfungal, according to the findings of histopathologic examinations. HU values were measured in sphenoid sinus sections on paranasal CT scans of these two groups. Differences in mean and maximum HU values between the two groups were statistically significant (p < .05). The maximum HU values calculated from the sphenoid sinus were 435.08 and 196.23 (p ≤ .05) in the fungal group and nonfungal group, respectively. The mean HU values calculated from the sphenoid sinus were 64.31 and 29 (p ≤ .05) in the fungal and nonfungal groups, respectively. At the maximum cutoff value of 241, the sensitivity and specificity of the HU maximum were 84.6% and 77.3%, respectively. At the mean cutoff value of 41.5, the sensitivity and specificity of the HU mean were 76.9% and 86.4%, respectively. HU is an objective value used in radiographic density measurement. The HU values were higher in fungal lesions than in nonfungal inflammations, and they are useful in preoperative measurement.

Diagnostic Value of Hounsfield Unit and Hematocrit Levels in Cerebral Vein Thrombosis in the Emergency Department

BACKGROUND

Unenhanced computed tomography (CT) is a frequently used imaging method in patients who are evaluated in the emergency department with suspected cerebral vein thrombosis (CVT).

OBJECTIVES

The aim of this study was to investigate the usefulness of the Hounsfield unit (HU) value determined by CT and its ratio to the patient's hematocrit (Htc) value in the diagnosis of cerebral vein thrombosis.

METHODS

This retrospective study evaluated 41 patients with acute cerebral venous sinus thrombosis and 41 age- and sex-matched control participants. Two experienced observers independently evaluated the CT scan and measured the attenuation of the dural sinuses.

RESULTS

There was no significant difference in age, gender, hemoglobin, and Htc values between the two groups. The mean HU value was 75 ± 7 HU in the CVT group and 52 ± 6 HU in the control group (p < 0.001). The mean HU/Htc ratio was 1.9 ± 0.3 in the CVT group and 1.3 ± 0.1 in the control group (p < 0.001). The optimal threshold value for HU was determined as 66, and sensitivity at this value was 93%, and specificity was 98%. The optimal threshold value for HU/Htc was determined as 1.64, and the sensitivity at this value was 90% and the specificity was 100%.

CONCLUSION

Hyperattenuation in the dural sinuses and the HU/Htc ratio in unenhanced brain CT scans have high diagnostic value in detecting CVT.

Effect of osteoporotic conditions on the development of peritumoral brain edema after LINAC-based radiation treatment in patients with intracranial meningioma

PURPOSE

Disruption of the tumor-brain barrier in meningioma is a crucial factor in peritumoral brain edema (PTBE). We previously reported the possible effect of osteoporosis on the integrity of the arachnoid trabeculae because both the bone and the arachnoid trabeculae are composed of type 1 collagen. We hypothesized that osteoporotic conditions may be associated with PTBE occurrence after radiation treatment in patients with meningioma.

METHODS

A receiver operating characteristic curve analysis was used to identify the optimal cut-off values of mean skull Hounsfield unit for predicting osteopenia and osteoporosis in patients from our registry. Multivariate Cox regression analysis was used to determine whether possible osteoporosis independently predicted PTBE development in patients with meningioma after radiation.

RESULTS

A total of 106 intracranial meningiomas were included for the study. All patients received linear accelerator-based radiation therapy in our hospital over an approximate 6-year period. Multivariate Cox regression analysis identified that hypothetical osteoporosis was an independent predictive factor for the development of PTBE in patients with meningioma after linear accelerator-based radiation treatment (hazard ratio 5.20; 95% confidence interval 1.11-24.46; p = 0.037).

CONCLUSIONS

Our study suggests that possible osteoporotic conditions may affect PTBE development after linear accelerator-based radiation treatment for intracranial meningioma. However, due to the study's small number of patients, these findings need to be validated in future studies with larger cohorts, before firm recommendations can be made.

Plain CT vs MR venography in acute cerebral venous sinus thrombosis: Triumphant dark horse

Context

Most patients with cerebral venous sinus thrombosis (CVST) present with nonspecific signs and symptoms and are likely to undergo nonenhanced head computed tomography (NCT) at presentation, which may show a normal report in up to two-thirds of patients. However, in case of acute thrombosis, sensitivity of diagnosing CVST is high as sinuses are hyperdense. Though magnetic resonance imaging (MRI) is considered the imaging modality of choice for diagnosing CVST, it is not universally available in an acute setting.

Aims

To evaluate whether increased attenuation in cerebral venous sinuses in acute condition can be used to diagnose acute CVST and to determine its diagnostic value.

Materials and Methods

The study involves two independent groups. One group of patients with sinus thrombosis were confirmed by MR venography (group A). The other group included patients without sinus thrombosis (group B). The HU (CT attenuation), hemoglobin (HGB), hematocrit (HCT), and H: H (HU: HCT) ratio of both groups were compared. Thirty-six patients (59 thrombotic sinuses) were studied in group A and 40 in group B.

Statistical Analysis

Average HU and H: H ratio were compared using two-tailed t-test, and linear regression analysis was used to assess correlation between HCT and HU.

Results

Average HU (73.7 vs 48.6) and H: H ratio values were higher in group A patients compared to group B (P < 0.05). Linear regression analysis showed positive correlation between HGB and HCT with HU among both the groups (P < 0.05).

Conclusions

Our study demonstrates that acute CVST can be diagnosed using HU values in NCT.

Quantitative Analysis of Deltoid Ligament Degradation in Patients With Chronic Ankle Instability Using Computed Tomographic Images

BACKGROUND

Rotational ankle instability (RAI) is associated with the faster onset of severe ankle osteoarthritis via dysfunction of the anterior talofibular ligament, calcaneofibular ligament, and deltoid ligament. No specific clinical examination is available for RAI, and diagnostic imaging has limitations in evaluating ligament degradation. This study investigated the deltoid ligament degeneration using Hounsfield unit (HU) values on computed tomography (CT) images.

METHODS

Patients were enrolled in this retrospective analysis if they had undergone magnetic resonance imaging (MRI) and CT scans of the ankle. The chronic ankle instability (CAI) group comprised 20 ankles with CAI (9 men, 11 women; mean age, 28.7 years) and the control group comprised 28 ankles (16 men, 12 women, mean age, 41.3 years). The average HU values of the deep posterior tibiotalar ligament (dPTL) that constitutes the deltoid ligament were measured on coronal CT images, and MRI results were used as a reference. All patients were subdivided based on the MRI findings of dPTL injury such as fascicular disruption, irregularity, and the loss of striation.

RESULTS

A strong negative correlation was identified between age and HU values for all patients (Spearman ρ = -0.63; P < .001). The mean HU values of the dPTL for participants aged <60 years were 81.0 HU for the control group (21 ankles) and 69.5 HU for the CAI group (P = .0075). No significant differences in the HU values were observed for the dPTL among the MRI subgroups.

CONCLUSION

In addition to the conventional imaging examination such as stress radiographs and MRI, HU measurements of CT images could be useful for quantitatively and noninvasively evaluating degenerative changes in the deltoid ligament for CAI patients to assist the diagnosis of RAI.

LEVEL OF EVIDENCE

Level III. case-control study.

Role of hepatosteatosis in the prognosis of COVID 19 disease

Purpose

To measure the degree of fatty liver using non-contrast enhanced chest computed tomography (CT) and investigate its relationship with the severity and prognosis of coronavirus disease 2019 (COVID-19) in adult patients.

Methods

This retrospective study included consecutive patients who had been diagnosed with COVID-19 using real-time reverse-transcription polymerase chain reaction (RT-PCR) and subsequently underwent non-contrast enhanced chest CT between October 10 and December 10, 2020. Hepatic attenuation values were measured from Couinaud segments 2, 4, and 8 based on the CT images and the relationships between these values and the Pneumonia Severity Score (PSS), requirement of hospitalization, and the length of hospital and intensive care unit (ICU) stay were analyzed.

Results

The study included 414 patients (182 were female, 43.96%), among whom 106 (25.6%) were diagnosed with hepatosteatosis (HS). In the patients with HS, the PSS scores were higher (10.8 ± 4.96 vs. 8.07 ± 5.12; p < 0.001), and 69 (65%) received inpatient care. Moreover, the number of HS patients who received inpatient care was 1.99 (95% confidence interval (CI) 1.26–3.15, p < 0.003) times higher than that of the non-HS patients. No significant difference was found between the HS and non-HS patients with regard to the length of hospital or ICU stay.

Conclusion

HS can be easily evaluated using non-contrast enhanced chest CT in COVID-19 patients and can be used as a prognostic marker to determine the requirement of hospitalization.

Effect of Possible Osteoporosis on Parenchymal-Type Hemorrhagic Transformation in Patients with Cardioembolic Stroke

Background: hemorrhagic transformation (HT) is a frequent complication of ischemic stroke, and parenchymal hematoma (PH)-type HT has been shown to correlate with symptomatic deterioration. Because both bone and vascular smooth muscle cells are composed of type 1 collagen, we hypothesized that the integrity of blood vessels around the infarction area might be more damaged in osteoporotic conditions after a cardioembolic stroke. Methods: we measured frontal skull Hounsfield unit (HU) values on brain CT images from cardioembolic stroke patients. We conducted a receiver operating characteristic curve analysis in a large sample registry to identify the optimal HU threshold for predicting osteopenia and osteoporosis. Hazard ratios were estimated using a Cox regression analysis to identify whether osteoporotic conditions were an independent predictor of PH-type HT in patients with cardioembolic stroke. Results: altogether, 600 consecutive patients (>18 years old) with cardioembolic stroke were enrolled over a 12-year period at our hospital. The infarction volume and hypothetical osteoporosis were independent predictive factors for PH-type HT development in patients with cardioembolic stroke. In the male group, hypothetical osteoporosis was an independent predictor for PH-type HT development after cardioembolic stroke (hazard ratio, 4.12; 95% confidence interval, 1.40–12.10; p = 0.010). Conclusions: our study suggests an association between possible osteoporosis and the development of PH-type HT in patients with cardioembolic stroke. Our findings could help to predict PH-type HT by providing a convenient method for measuring the HU value using brain CT images.

Histopathological and Radiographic Features of Osteolysis After Fixation of Osteochondral Fragments Using Poly-L-Lactic Acid Pins for Osteochondral Lesions of the Talus

BACKGROUND

Fixation of osteochondral fragments is a potential option for treating an osteochondral lesion of the talus (OLT) involving large lesions in the remaining articular cartilage surface. Bioabsorbable devices, especially those made of poly-L-lactic acid (PLLA), can be used for the fixation of an OLT. Postoperative osteolysis surrounding the PLLA pins is occasionally observed; however, the significance of osteolysis remains unknown.

PURPOSE

To elucidate the association between osteolysis surrounding the PLLA pins, histopathological findings in subchondral bone, and preoperative Hounsfield unit (HU) values at the pin fixation site.

STUDY DESIGN

Case Series; Level of evidence, 4.

METHODS

This retrospective analysis included 20 patients with OLT (11 men and 9 women; mean age, 20.9 years; 1 bilateral case). Tissue from the osteochondral fragment was collected intraoperatively using a bone biopsy needle for histological evaluation. The fragment was fixed through the biopsy hole using a PLLA pin. Osteolysis surrounding the PLLA pin was assessed at 1 year postoperatively using magnetic resonance imaging (MRI). Histopathological scores were assigned based on trabecular bone loss, empty lacunae, inflammatory granulation tissue, cartilage-like tissue, and the presence of osteoclasts. The HU values around the pin insertion site, detected on the postoperative MRI scans, were measured using the region of interest based on the preoperative coronal and sagittal computed tomography (CT) images.

RESULTS

Osteolysis was observed postoperatively in 9 ankles (42.9%). Histopathological evaluation revealed that the osteolysis group had a significantly higher pathological score than the nonosteolysis group (10.2 vs 6.3; P < .001). Lower HU values were identified in the osteolysis group on preoperative coronal and sagittal CT images (P < .05). The histopathological score negatively correlated with preoperative HU values (Pearson r = -0.46; P = .037).

CONCLUSION

Intraoperative biopsy of the OLT allowed for histopathological evaluation of the same site as that of the PLLA pin fixation. Our findings suggest that preoperative subchondral trabecular deterioration is associated with the incidence of postoperative osteolysis surrounding the PLLA pin. Additionally, low preoperative HU values in subchondral bone under OLT may serve as a predictor of osteolysis surrounding the PLLA pin.

Qualitative assesement of newly formed bone after distraction osteogenesis of mandible in patients with facial asymmetry using 3 dimensional computed tomography

Introduction

Distraction osteogenesis is a surgical technique of new bone formation between the osteotomized bone segments with the help of gradual incremental traction. As distraction osteogenesis is slow biologic process, soft tissue changes gradually follow the new bone formation. Mandibular distraction is one of the accepted modalities to treat the triad of TMJ ankylosis, obstructive sleep apnoea & micrognathia and also for facial asymmetry cases like hemifacial microsomia, mandibular hypoplasia etc. After the distraction osteogenesis, some relapse has been noticed in patients. Therefore, this study was conducted to assess the quality of the newly formed bone after distraction osteogenesis of mandible using 3 dimensional computed tomography (3DCT Scan) to evaluate its relation with relapse if any.

Objectives

1) To objectively analyse the quality of bone formed after mandibular distraction osteogenesis.2) To observe the site & architecture of newly formed bone after distraction is complete.

Material and methods

Total 5 patients of facial asymmetry reported to the Department of Oral and Maxillofacial Surgery were enrolled. Distraction osteogenesis of mandible was carried out in all the patients. Radiographic analysis (CT Scan) was done after 1 year of surgery for further planning and management of deformity. The non-distracted site was considered as a control side and it was compared with newly formed bone at distraction site. The standard & universally accepted radio density measuring Hounsfield Unit (HU) in 3DCT scan was calculated in axial,coronal, sagittal sections from distraction site and it was compared with non-distraction site, as Hounsfield unit is considered as a standard tool for measuring the bone density to evaluate the quality as well as quantity of newly formed bone.

Results

The total mean Hounsfield Unit of distracted site of all three sections was 359.8 HU and non-distracted site was 545.2 HU. Statistical analysis was carried out using students paired ttest and p value was obtained which was <0.01 suggestive of statistically significant difference between the quality of bone in distracted site and non-distracted site.

Conclusion

The findings of our study concluded that the quality of bone formed after distraction osteogenesis was satisfactory but it was less mineralized with less dense trabecular pattern compared to non-distracted bone region of mandible which leads to some relapse. Therefore it was advisable to reinforce the distracted bone segment by cutting the activation arm of distractor itself or mini plate or reconstruction plate to prevent relapse.

The evaluation of degeneration of posterior cruciate ligament using CT Hounsfield unit in knee osteoarthritis

Background

Posterior cruciate ligament (PCL) degeneration is often seen in knee osteoarthritis (OA); however, there is no established method for its evaluation. The purpose of this study is to investigate whether the Hounsfield unit (HU) using computed tomography (CT) could be a useful scale to evaluate the degeneration of PCL in knee OA.

Methods

Knee OA treated with total knee arthroplasty (21 patients, 21 knees) and non-osteoarthritic knees (21 patients, 21 knees) were retrospectively observed and studied. All PCLs in the knees were analyzed using CT. The PCL in the sagittal section was divided into three regions: proximal, middle, and distal sections. The HU value of the PCL at each area was measured. In osteoarthritic knees, tissues from the PCL were collected and histologically graded. The correlation between the radiological classification by Kellgren and Lawrence and the histological grade was analyzed. The average CT HU values for each degenerative grade were also calculated and compared.

Results

The HU values in OA and non-OA were 70.7 and 88.4 HU (p < 0.05) at the proximal region, 75.7 and 85.3 HU (p < 0.05) in the central region, and 82.3 and 86.5 HU (p > 0.05) in the distal region, respectively. The degeneration of PCL was graded as follows: one, three, and 17 mild, moderate, and severe cases at the proximal portion, and 16, 4, and one mild, moderate, and severe cases at the distal portion, respectively. The radiological classification and the grade of degeneration were not correlated in either the proximal (r = 0.047, p = 0.84) or the distal (r = − 0.21, p = 0.35) portions. The HU value was 84.5, 72.1, and 70.6 HU for mild, moderate, and severe grades, respectively (mild versus moderate: p < 0.05, mild versus severe: p < 0.05, moderate versus severe: p > 0.05).

Conclusions

In knee OA, a lower HU value in the PCL indicates the progression of degeneration. The CT HU value could be a useful measurement to predict the grade of PCL degeneration.

A novel fast kilovoltage switching dual-energy CT with deep learning: Accuracy of CT number on virtual monochromatic imaging and iodine quantification

PURPOSE

A novel fast kilovoltage switching dual-energy CT with deep learning [Deep learning based-spectral CT (DL-Spectral CT)], which generates a complete sinogram for each kilovolt using deep learning views that complement the measured views at each energy, was commercialized in 2020. The purpose of this study was to evaluate the accuracy of CT numbers in virtual monochromatic images (VMIs) and iodine quantifications at various radiation doses using DL-Spectral CT.

MATERIALS AND METHODS

Two multi-energy phantoms (large and small) using several rods representing different materials (iodine, calcium, blood, and adipose) were scanned by DL-Spectral CT at varying radiation doses. Images were reconstructed using three reconstruction parameters (body, lung, bone). The absolute percentage errors (APEs) for CT numbers on VMIs at 50, 70, and 100 keV and iodine quantification were compared among different radiation dose protocols.

RESULTS

The APEs of the CT numbers on VMIs were <15% in both the large and small phantoms, except at the minimum dose in the large phantom. There were no significant differences among radiation dose protocols in computed tomography dose index volumes of 12.3 mGy or larger. The accuracy of iodine quantification provided by the body parameter was significantly better than those obtained with the lung and bone parameters. Increasing the radiation dose did not always improve the accuracy of iodine quantification, regardless of the reconstruction parameter and phantom size.

CONCLUSION

The accuracy of iodine quantification and CT numbers on VMIs in DL-Spectral CT was not affected by the radiation dose, except for an extremely low radiation dose for body size.

The Impact of Stone Density on Operative Complications of Retrograde Intrarenal Surgery: A Multicenter Study with Propensity Score Matching Analysis

Background: The aim of the study was to evaluate the impact of stone density on operative complication rates in retrograde intrarenal surgery (RIRS). Materials and Methods: A total of 473 consecutive patients undergoing RIRS for the treatment of upper tract urinary stones were included. To adjust for baseline confounders, one-to-one propensity score matching was performed. After matching, the patients were divided into two groups according to stone density (low density [LD] group, ≤970 Hounsfield unit [HU]; high density [HD] group, >970 HU). The patients' demographics, stone-related features, stone-free rates, and intraoperative and postoperative complication rates were compared between the groups. The primary objective was to evaluate whether the intraoperative and postoperative complication rates were higher in patients whose stone density was greater than 970 HU. Results: After propensity score matching, 170 of 210 LD and 170 of 263 HD patients undergoing RIRS were included. The baseline characteristics did not differ significantly between the groups. There were no significant differences between LD and HD patients with respect to intraoperative (5.9% and 8.8%, respectively; P = .29), postoperative (10.6% and 15.3%, respectively; P = .14), and overall complication rates (15.2% and 21.1%, respectively; P = .16). Stone-free status was achieved in 143 patients (84.1%) in the LD group and 148 patients (87%) in the HD group; the difference was not statistically significant (P = .27). Conclusion: Our results show that RIRS is a safe and effective minimally invasive procedure for the treatment of upper urinary tract stones, even in HD stones.

Investigation of tube voltage dependence on CT number and its effect on dose calculation algorithms using thorax phantom in Monaco treatment planning system for external beam radiation therapy

Introduction

The accuracy of dose calculation algorithms depends on the electron density and computed tomography (CT) number of medium scanned. Our study aimed to verify the impact of different CT scanning protocols on Hounsfield unit (HU) and effect on dose calculation algorithms.

Materials and Methods

CIRS thorax phantom with different density material plugs was scanned at varying tube voltages from CT scanner and HU values were measured in treatment planning system (TPS). Calibration curves of electron density at different tube voltages were plotted and used for dose calculation with different calculation algorithms at varying high energy megavoltage photon energies.

Results

Insignificant difference is obtained in electron density curves plotted at different tube voltages. The mean variation in HU values was found at different tube voltages for bone, lung, and water are 896.75 (standard deviation [SD] 122.88), -799.25 (SD 5.74), and -17.5 (SD 0.57), respectively. The estimated P values for change in HU values were 0.089, 0.258, and 0.121 for bone, lung, and water, respectively. Pencil beam (PB) convolution and collapsed cone algorithms show no significant dose difference, i.e., <1% variation and Monte Carlo (MC) shows maximum dose difference up to 1.4%.

Conclusion

Third-generation algorithms such as MC shows dependence on varying tube voltages in dose calculation. Calibration curves plotted at different kVp in TPS advised to be chosen wisely to avoid any dosimetric errors in different medium.

Computed Tomography Evaluation of Forearm and Hand Muscles in Patients With Distal Radius Fracture

INTRODUCTION

Computed tomography (CT) can be used to assess bone status with measurement of Hounsfield unit (HU). The objective of this study was to evaluate whether HU of muscle might be associated with parameters of bone and muscle status.

METHODS

We reviewed 71 women aged over 50 yr of age who had distal radius fracture and underwent CT evaluation of affected wrist. We assessed HUs of forearm flexor muscles (flexor digitorum superficialis) and thenar muscles and bone HUs at the capitate and the ulnar head. Other parameters included femur neck and lumbar bone mineral density (BMD), upper extremity lean mass, hand grip strength, and muscle fiber cross-sectional area. We performed correlation analyses to determine associations between variables.

RESULTS

Thenar and forearm muscle HUs were significantly correlated with each other, but not with other parameters. HUs of the capitate and ulnar head were positively correlated with femur neck and lumbar BMDs and inversely correlated with age. Ulnar head HU was positively correlated hand grip strength.

CONCLUSIONS

HUs of forearm and thenar muscles did not show significant correlations with bone or muscle parameters, although bone HUs correlated well with bone mineral densities. These results support the opportunistic use of CT for evaluating bone fragility. Clinical usefulness of muscle HU measurement needs further studies.

Correlation of vertebral trabecular attenuation in Hounsfield units and the upper instrumented vertebra with proximal junctional failure after surgical treatment of degenerative lumbar disease

OBJECTIVE

The aim of this study was to investigate whether bone mineral density (BMD) measured in Hounsfield units (HUs) is correlated with proximal junctional failure (PJF).

METHODS

A retrospective study of 104 patients with adult degenerative lumbar disease was performed. All patients underwent posterior instrumented fusion of 4 or more segments and were followed up for at least 2 years. Patients were divided into two groups on the basis of whether they had mechanical complications of PJF. Age, sex ratio, BMI, follow-up time, upper instrumented vertebra (UIV), lower instrumented vertebra, and vertebral body osteotomy were recorded. The spinopelvic parameters were measured on early postoperative radiographs. The HU value of L1 trabecular attenuation was measured on axial and sagittal CT scans. Statistical analysis was performed to compare the difference of continuous and categorical variables. Receiver operating characteristic (ROC) curve analysis was used to obtain attenuation thresholds. A Kaplan-Meier curve and log-rank test were used to analyze the differences in PJF-free survival. Multivariate analysis via a Cox proportional hazards model was used to analyze the risk factors.

RESULTS

The HU value of L1 trabecular attenuation in the PJF group was lower than that in the control group (p < 0.001). The spinopelvic parameter L4-S1 lordosis was significantly different between the groups (p = 0.033). ROC curve analysis determined an optimal threshold of 89.25 HUs (sensitivity = 78.3%, specificity = 80.2%, area under the ROC curve = 0.799). PJF-free survival significantly decreased in patients with L1 attenuation ≤ 89.25 HUs (p < 0.001, log-rank test). When L1 trabecular attenuation was ≤ 89.25 HUs, PJF-free survival in patients with the UIV at L2 was the lowest, compared with patients with their UIV at the thoracolumbar junction or above (p = 0.028, log-rank test).

CONCLUSIONS

HUs could provide important information for surgeons to make a treatment plan to prevent PJF. L1 trabecular attenuation ≤ 89.25 HUs measured by spinal CT scanning could predict the incidence of PJF. Under this condition, the UIV at L2 significantly increases the incidence of PJF.

Is bone mineral density lower in the necrotic lesion in pre-collapse osteonecrosis of the femoral head?

The purpose of this study was to clarify whether bone mineral density (BMD) of the necrotic lesion in precollapse osteonecrosis of the femoral head (ONFH) is reduced according to Hounsfield unit (HU) values on computed tomography (CT). The superior one-third of the femoral head in the coronal section was set as the region of interest (ROI) for the measurement of HU values. First, HU values of 101 control participants were assessed to identify relevant confounding factors. Next, the relationship between HU values and BMD on dual-energy X-ray absorptiometry (DXA) was verified. Then the mean HU value of the ROI in patients with pre-collapse ONFH was compared with that in propensity score-matched control participants. Finally, the HU values of the lateral boundary in the patients with and without subsequent collapse were compared. Multivariable analysis showed that both age and BMI were significantly correlated with the HU value, which showed a strong correlation with the BMD of the femoral neck on DXA (r = 0.92). In 25 ONFH patients and 25 propensity-matched control participants, no significant difference was found in the HU value of the ROI (p = .54). The mean HU value of the lateral boundary in patients with subsequent collapse was found to be significantly higher than that in patients without subsequent collapse (p < .01). The assessment of HU values on CT was useful for the evaluation of BMD of the femoral head. The current assessment did not demonstrate reduced bone mineral density of the necrotic lesion in pre-collapse ONFH.

Usability of shear wave elastography to predict the success of extracorporeal shock-wave lithotripsy: prospective pilot study

The present study is intended to investigate the usability of shear wave elastography (SWE) in predicting the success of extracorporeal shock-wave lithotripsy (ESWL) used in kidney stone treatment. ESWL was performed on a total number of 52 patients diagnosed with kidney stones between May 2019 and July 2020. The presence of a residual stone greater than 4 mm was accepted as failure. The patients were divided into two groups as ESWL success and ESWL failure. SWE and Hounsfield unit (HU) measurements of stones were performed in all patients before ESWL. The two groups were compared in terms of age, gender, stone localisation, stone size, body mass index (BMI), skin-to-stone distance, HU, and SWE values of the stones. ESWL was successful in 30 of the 52 patients included in the study, while it failed in 22 of them. While the mean SWE value was 7.3 (7.9 ± 2.2) kPa in patients with success in ESWL, it was 14.6 (17.9 ± 10.2) kPa in those with failed ESWL. The mean HU was 883.5 (841.4 ± 191.1) in patients with success in ESWL and 1078 (1115.5 ± 183) in those with failed ESWL. Both SWE and HU values of the stones were found to be statistically significantly lower in the successful group (p < 0.05). It was seen that SWE and HU values were correlated to each other. The groups of successful and failed ESWL did not differ significantly in terms of age, gender distribution, stone size, BMI, and skin-to-stone distance (p > 0.05). With SWE, the hardness of the stone can be measured and its suitability for ESWL can be evaluated. It can be used as an alternative parameter to HU before ESWL treatment, since it has a lower cost compared to computed tomography (CT) and does not contain radiation.

Ultraslow full-power shock wave lithotripsy protocol in the management of high attenuation value upper ureteric stones: A randomized comparative study

OBJECTIVES

To evaluate the efficacy and safety of ultraslow full-power shock wave lithotripsy protocol in the management of high attenuation value upper ureteric stones compared with slow-rate, power-ramping shock wave lithotripsy.

METHODS

This was a randomized trial enrolling patients with a single high attenuation value (≥1000 HU) upper ureteric stones between January 2019 and July 2019. Ultraslow full-power shock wave lithotripsy (54 patients) was applied at a rate of 30 shock waves/min with power ramping from 6 to 18 kV for 100 shock waves, then a safety pause for 2 min, followed by ramping 18-22 kV for 100 shock waves, then a safety pause for 2 min. Then, full power (22 kV) was maintained until the end of the session. Slow-rate, power-ramping shock wave lithotripsy (47 patients) was applied at a rate of 60 shock waves/min with power ramping from 6 to 10 kV during the first 500 shock waves, then from 11 to 22 kV during the next 1000 shock waves, then maintained on 22 kV in the last 1500 shock waves. Up to three sessions were carried out with a follow up 3 months after the last session. The primary outcome was the stone-free rate. Perioperative data of the two protocols were compared.

RESULTS

There was no significant difference in preoperative data. The stone-free rate was significantly higher in ultraslow full-power shock wave lithotripsy after single (92.6% vs 23.4%) and multiple (96.3% vs 63.8%) sessions. Most complications were mild, with no significant difference between both groups (9.3% vs 12.8%; P = 0.573). Logistic regression analysis identified ultraslow full-power shock wave lithotripsy protocol as the only significant independent factor for the stone-free rate (odds ratio 12.589, P = 0.025).

CONCLUSION

Ultraslow full-power shock wave lithotripsy for high attenuation value upper ureteric stones is associated with a significantly higher stone-free rate, and with mild complications that are comparable to those of standard shock wave lithotripsy.

Effects of Possible Osteoporotic Conditions on the Recurrence of Chronic Subdural Hematoma

The recurrence rate of chronic subdural hematoma (CSDH) has been reported to range from 2.3 to 33%. As bridging veins are composed of abundant collagen bundles and bone matrix, we aimed to investigate the possible associations between skull Hounsfield unit (HU) values and the recurrence of CSDH. We retrospectively enrolled patients with CSDH who underwent burr hole surgery. The HU values of the frontal skull were measured on brain CT scans. The cumulative hazard for recurrence was estimated according to predictive factors. To identify the independent predictors associated with the recurrence of CSDH, hazard ratios (HRs) were estimated using multivariate Cox regression analysis. A total of 208 consecutive patients who underwent burr hole trephination for CSDH over a 7-years period at a single institution were enrolled in this study. We found that age, greater midline shift (≥10.5 mm), lower skull HU (<769.5), and diabetes were independent predictors for the recurrence of CSDH (HR 1.06, 95% confidence interval [CI] 1.00–1.12, p = 0.042; HR 5.37, 95% CI 1.48–19.46, p = 0.010; HR 6.71, 95% CI 1.84–24.45, p = 0.004; and HR 3.30, 95% CI 1.05–10.43, p = 0.042, respectively). A relationship between possible low bone mineral density (BMD) and CSDH recurrence was observed. In addition, age, greater preoperative midline shift, and diabetes were also identified as predictive factors for recurrence. We expect that our findings may facilitate our understanding of the possible association between CSDH and BMD.

Bone density of the calcaneus correlates with radiologic and clinical outcomes after calcaneal fracture fixation

BACKGROUND

This study aimed to determine whether bone density correlates with radiologic and clinical outcomes after screw fixation of displaced intra-articular calcaneal fractures (DIACF) with the sinus tarsi approach.

MATERIALS AND METHODS

We retrospectively evaluated 43 consecutive cases of unilateral DIACF between March 2015 and December 2017. Radiologic evaluations were performed using preoperative, postoperative, and last follow-up calcaneal lateral and axial radiographs. In all patients, preoperative CT scanning of both injured and uninjured calcaneus were performed at one scanning and dual x-ray absorptiometry (DXA) scans were obtained. Hounsfield unit (HU) measurement values were determined by placing an elliptical region of interest confined to the cancellous region of the uninjured calcaneus. Clinical outcomes were assessed at a minimum of 12 months postoperatively using Foot and Ankle Outcome Scores (FAOS).

RESULTS

Mean HU values of the uninjured calcaneus significantly correlated with bone mineral density scores obtained from DXA scans of the lumbar and femur (Spearman ρ = 0.656 - 0.748; p < 0.001 for both). Decreased HU values of the uninjured calcaneus significantly correlated with decreased Böhler's angle and widening of calcaneal width from postoperative to last follow-up. (Pearson r = 0.348, p = 0.022; Pearson r = -0.582, p < 0.001, respectively). Increased HU values of the uninjured calcaneus significantly correlated with improved clinical outcomes in three of five FAOS domains, including activities of daily living, sports, and quality of life (beta = 0.283 - 0.322; p < 0.05 for all).

CONCLUSION

Decreased preoperative bone density significantly correlated with decreased Böhler's angle, widening of calcaneal width, and inferior short-term clinical outcomes after screw fixation of DIACF. By quantifying bone density using HU value in area where DXA cannot be performed, such foot bones, determining whether different fixation methods or systemic treatments can be tailored to bone density could help in optimizing clinical outcomes.

LEVEL OF EVIDENCE

Level III, Retrospective case series.

Evaluate the Differences in CT Features and Serum IgG4 Levels between Lymphoma and Immunoglobulin G4-Related Disease of the Orbit

BACKGROUND

Benign immunoglobulin G4 (IgG4)-related orbital disease (IgG4-ROD)-characterized as tumors mimicking malignant orbital lymphoma (OL)-responds well to steroids, instead of chemotherapy, radiotherapy and/or surgery of OL. The objective of this study was to report the differences in computed tomography (CT) features and- serum IgG4 levels of IgG4-ROD and OL.

METHODS

This study retrieved records for patients with OL and IgG4-ROD from a pathology database during an eight-year-and-five-month period. We assessed the differences between 16 OL patients with 27 lesions and nine IgG4-ROD patients with 20 lesions according to prebiopsy CT features of lesions and prebiopsy serum IgG4 levels and immunoglobulin G (IgG) levels This study also established the receiver-operating curves (ROC) of precontrast and postcontrast CT Hounsfield unit scales (CTHU), serum IgG4 levels, serum IgG levels and their ratios.

RESULTS

Significantly related to IgG4-ROD (all p < 0.05) were the presence of lesions with regular borders, presence of multiple lesions-involving both lacrimal glands on CT scans-higher median values of postcontrast CTHU, postcontrast CTHU/precontrast CTHU ratios, serum IgG4 levels and serum IgG4/IgG level ratios. Compared to postcontrast CTHU, serum IgG4 levels had a larger area under the ROC curve (0.847 [95% confidence interval (CI): 0.674-1.000, p = 0.005] vs. 0.766 [95% CI: 0.615-0.917, p = 0.002]), higher sensitivity (0.889 [95% CI: 0.518-0.997] vs. 0.75 [95% CI: 0.509-0.913]), higher specificity (0.813 [95% CI: 0.544-0.960] vs. 0.778 [95% CI: 0.578-0.914]) and a higher cutoff value (≥132.5 mg/dL [milligrams per deciliter] vs. ≥89.5).

CONCLUSIONS

IgG4-ROD showed distinct CT features and elevated serum IgG4 (≥132.5 mg/dL), which could help distinguish IgG4-ROD from OL.

Technical note: age estimation by using pubic bone densitometry according to a twofold mode of CT measurement

In forensic anthropology, age estimation is a major element in the determination of a biological profile and the identification of individuals. Thus, many anatomical structures have been studied, such as the pubic symphysis, which is a source of major interest due to its late maturation. One of the most well-known methods of assessment is the Suchey-Brooks (SB) system based on the morphological characteristics of the pubic symphysis. The aim of this study was to propose linear regression formulae in order to deduce chronological age from bone density, using both Hounsfield unit (HU), and mean bone density (mBD) values of the pubic symphysis. Moreover, we intended to test the reliability and then to explore the feasibility of using HU instead of mBD values for age estimation. We built retrospectively a reference sample of 400 pubic symphyses using computed tomography at a French hospital and a test sample of 120 pubic symphyses. Equations were created to establish linear regression models for age estimation. Inaccuracy and bias were calculated for individuals aged more or less than 40 years. We highlighted homogeneous mean absolute errors for both HU and mBD values, most of them being less than 10 years. Moreover, we reported a moderate overestimation for younger individuals and a very small underestimation for older individuals. This study proposes a correlation between the bone density and age of individuals with a valuable level of reliability. Finally, HU measurements seem to be suitable for linking bone density with the age of individuals in forensic practice.

Ultraslow full-power shock wave lithotripsy versus slow power-ramping shock wave lithotripsy in stones with high attenuation value: A randomized comparative study

OBJECTIVES

To compare the efficacy and safety of ultraslow full-power versus slow rate, power-ramping shock wave lithotripsy in the management of stones with a high attenuation value.

METHODS

This was a randomized comparative study enrolling patients with single high attenuation value (≥1000 Hounsfield unit) stones (≤3 cm) between September 2015 and May 2018. Patients with skin-to-stone distance >11 cm or body mass index >30 kg/m² were excluded. Electrohydraulic shock wave lithotripsy was carried out at rate of 30 shock waves/min for group A versus 60 shock waves/min for group B. In group A, power ramping was from 6 to 18 kV for 100 shock waves, then a safety pause for 2 min, followed by ramping 18-22 kV for 100 shock waves, then a safety pause for 2 min. This full power (22 kV) was maintained until the end of the session. In group B, power ramping was carried out with an increase of 4 kV each 500 shock waves, then maintained on 22 kV in the last 1000-1500 shock waves. Follow up was carried out up to 3 months after the last session. Perioperative data were compared, including the stone free rate (as a primary outcome) and complications (secondary outcome). Predicting factors for success were analyzed using logistic regression.

RESULTS

A total of 100 patients in group A and 96 patients in group B were included. The stone-free rate was significantly higher in group A (76% vs 38.5%; P < 0.001). Both groups were comparable in complication rates (20% vs 19.8%; P = 0.971). The stone-free rate remained significantly higher in group A in logistic regression analysis (odds ratio 24.011, 95% confidence interval 8.29-69.54; P < 0.001).

CONCLUSIONS

Ultraslow full-power shock wave lithotripsy for high attenuation value stones is associated with an improved stone-free rate without affecting safety. Further validation studies are required using other shock wave lithotripsy machines.

Comparison of Tibial and Talar Bone Density in Patients Undergoing Total Ankle Replacement vs Non-Ankle Arthritis Matched Controls

BACKGROUND

Bone quality in the distal tibia and talus is an important factor contributing to initial component stability in total ankle replacement (TAR). However, the effect of ankle arthritis on bone density in the tibia and talus remains unclear. The objective of this study was to compare bone density of tibia and talus in arthritic and nonarthritic ankles as a function of distance from ankle joint.

METHODS

We retrospectively reviewed 93 end-stage ankle arthritis patients who had preoperative nonweightbearing ankle computed tomography (CT) and identified a cohort of 83 nonarthritic ankle patients as a demographic-matched control group. A region of interest tool was used to calculate Hounsfield unit (HU) values in the cancellous region of the tibia and talus. Measurements were obtained on axial cut CTs from 6 to 12 mm above the tibial plafond, and 1 to 4 mm below the talar dome. HU measurements between groups and the decrease of HU at the relative level in each group were compared.

RESULTS

Arthritic ankles demonstrated significantly greater mean bone density than nonarthritic ankles at between 6 and 10 mm above the joint in the tibia (P < .05). No significant difference in bone density between 10 and 12 mm from the joint in the tibia nor at any level of the talus was found between groups. In both groups, bone density decreased significantly at each successive level away from the ankle joint.

CONCLUSION

Ankle arthritis patients demonstrated greater or equal bone density in both the tibia and talus compared to demographic-matched controls. In both groups, bone density decreased with increasing distance away from the articular surface. In TAR, tibial bone resection between 6 and 8 mm may provide improved initial implant stability.

LEVEL OF EVIDENCE

Level III, comparative study.

Should radiologists care about kV? Phantom and clinical study of effects of kV on hemoperitoneum HU in the setting of splenic injuries

PURPOSE

Evaluate the potential effects of X-ray tube voltage (kV) changes on Hounsfield unit (HU) measurements of hemoperitoneum in patients with blunt splenic injuries.

METHODS

Eight different tissue equivalent electron density plugs in the Electron Density Phantom were scanned (muscle, adipose, breast, liver, lung (exhale), lung (inhale), trabecular bone, and dense bone). The phantom was scanned at different kV values (70, 80, 100, 120, and 140 kV). In the clinical study, the local trauma registry database was queried for splenic injuries between January 2015 and December 2016 with a final cohort of 110 patients. The average HU numbers of hemoperitoneum found in three different anatomic locations (pelvic, perisplenic, and perihepatic) were compared at different kV values (100 kV, 120 kV, and 140 kV). ANOVA and pairwise t tests were performed for statistical analysis.

RESULTS

In both studies, HU measurements generally decreased as kV increased, and vice versa. One hundred ten patients were reviewed: 29 for 100 kV, 66 for 120 kV, and 15 for 140 kV. For the perihepatic group, significant differences were observed in average HU in the following pairwise comparisons: 100/140 (13.7 (5.3), p < 0.05) and 120/140 (10.3 (4.5), p < 0.05). For the perisplenic group, significant differences were observed in 100/120 (7.0 (3.5), p < 0.05) and 100/140 (13.2 (4.9), p < 0.05). No significant difference was observed in the pelvic location (p = 0.5594).

CONCLUSIONS

HU measurements of hemoperitoneum in patients with blunt splenic injuries significantly varied with the use of different kV values. Radiologists should be aware of the possible effects of altering kV on HU.

Computed tomography-based psoas skeletal muscle area and radiodensity are poor sentinels for whole L3 skeletal muscle values

Background and aims

Computed tomography (CT)-based measurement of skeletal muscle cross-sectional area (CSA) and Hounsfield unit (HU) radiodensity are used to assess the presence of sarcopenia and myosteatosis, respectively. The validated CT-based technique involves analysis of skeletal muscle at the third lumbar vertebral (L3) level. Recently there has been increasing interest in the use of psoas muscle alone as a sentinel. However, this technique has not been extensively investigated or compared with the previous validated standard approach.

Methods

Portovenous phase CT images at the L3 level were identified retrospectively from a single institution in 150 patients who had non-emergency scans and were analysed by a single assessor using SliceOmatic software v5.0 (TomoVision, Canada). Manual segmentation based upon validated HU thresholds for skeletal muscle density was performed for all skeletal muscle, as well as the individual muscle groups. The muscle CSA and mean radiodensity of each group were compared against the whole L3 slice values.

Results

When compared with whole L3 slice CSA, anterior abdominal wall CSA had the strongest correlation (r = 0.9315, p < 0.0001) followed by paravertebral (r = 0.8948, p < 0.0001), then psoas muscle (r = 0.7041, p < 0.0001). The mean ± SD density of the psoas muscle (42 ± 8.4 HU) was significantly higher than the whole slice radiodensity (32.3 ± 9.5 HU, p < 0.0001), with paravertebral radiodensity being a more accurate estimation (34.5 ± 10.8 HU). There was a significant difference in the prevalence of myosteatosis when the density measured from the psoas was compared with that of the whole L3 skeletal muscle (27.7% vs. 66.0%, p < 0.0001).

Conclusion

Whole L3 slice CSA correlated positively with psoas muscle CSA but was subject to wide variability in results. Psoas muscle radiodensity was significantly greater than whole L3 slice density and resulted in underestimation of the prevalence of myosteatosis. Given the lack of equivalence from individual muscle groups, we recommend that further work be undertaken to investigate which muscle group, or indeed whether the gold standard of whole L3 skeletal muscle, provides the best correlation with clinical outcomes.

Hounsfield unit density in the characterisation of bile duct lesions

Purpose

To study the density of lesions in the lumens of extrahepatic bile ducts through computed tomography examinations, and to compare their characterisations with the results of pathology and/or endoscopic retrograde cholangiopancreatography (ERCP).

Methods

The density of lesions along extrahepatic bile ducts were measured and compared with pathology and/or ERCP. The lesions were evaluated in two main groups: benign or malignant. The bile duct wall enhancement, intrahepatic bile ducts, and gallbladder were also evaluated.

Results

The study was conducted with computed tomography scans of 197 cases (93 females, 104 males) who had optimal imaging. The results regarding density of extrahepatic intraductal lesions that were studied at BT were compared with pathology and magnetic resonance cholangiopancreatography results. Of 197 lesions, 125 (63.5%) were reported as benign and 72 (36.5%) were reported as malignant. The results for benign lesions showed an average density of 66.67 ± 17.30 Hounsfield units (HU), and for malignant lesions the average density was 82.38 ± 13.67 HU.

Conclusion

Lesion density level (HU) gives valuable information for the differentiation between benign and malign lesions in intraluminal extrahepatic bile ducts.