DXA-equivalent quantification of bone mineral density using dual-layer spectral CT scout scans

Quantitative calcium-based assessment of osteoporosis in dual-layer spectral CT

OBJECTIVES

To evaluate a novel calcium-only imaging technique (VCa) with subtracted bone marrow in osteoporosis in dual-layer CT (DLCT) compared to conventional CT images (CI) and dual-energy X-ray absorptiometry (DXA).

MATERIAL AND METHODS

Images of a multi-energy CT phantom with calcium inserts, quantitative CT calibration phantom, and of 55 patients (mean age: 64.6 ± 11.5 years) were acquired on a DLCT to evaluate bone mineral density (BMD). CI, calcium-suppressed images, and VCa were calculated. For investigating the association of VCa and CI with DXA a subsample of 30 patients (<90 days between DXA and CT) was used. Multiple regression analysis was performed to identify further factors improving the prediction of DXA BMD.

RESULTS

The calcium concentrations of the CT phantom inserts were significantly associated with CT numbers from VCa (R2 = 0.94) and from CI (R2 = 0.89-0.92). VCa showed significantly higher CT numbers than CI in the phantom (p ≤ 0.001) and clinical setting (p < 0.001). CT numbers from VCa were significantly associated with CI (R2 = 0.95, p < 0.001) and with DXA (R2 = 0.31, p = 0.007), whereas no significant association between DXA and CI was found. Prediction of DXA BMD based on CT numbers derived from VCa yielded R2 = 0.76 in multiple regression analysis. ROC for the differentiation of normal from pathologic BMD in VCa yielded an AUC of 0.7, and a cut-off value of 126HU (sensitivity: 0.90; specificity: 0.47).

CONCLUSION

VCa images showed better agreement with DXA and known calcium concentrations than CI, and could be used to estimate BMD. A VCa cut-off of 126HU could be used to identify abnormal bone mineral density.

An Image-Based Prior Knowledge-Free Approach for a Multi-Material Decomposition in Photon-Counting Computed Tomography

Photon-counting CT systems generally allow for acquiring multiple spectral datasets and thus for decomposing CT images into multiple materials. We introduce a prior knowledge-free deterministic material decomposition approach for quantifying three material concentrations on a commercial photon-counting CT system based on a single CT scan. We acquired two phantom measurement series: one to calibrate and one to test the algorithm. For evaluation, we used an anthropomorphic abdominal phantom with inserts of either aqueous iodine solution, aqueous tungsten solution, or water. Material CT numbers were predicted based on a polynomial in the following parameters: Water-equivalent object diameter, object center-to-isocenter distance, voxel-to-isocenter distance, voxel-to-object center distance, and X-ray tube current. The material decomposition was performed as a generalized least-squares estimation. The algorithm provided material maps of iodine, tungsten, and water with average estimation errors of 4% in the contrast agent maps and 1% in the water map with respect to the material concentrations in the inserts. The contrast-to-noise ratio in the iodine and tungsten map was 36% and 16% compared to the noise-minimal threshold image. We were able to decompose four spectral images into iodine, tungsten, and water.

Incident fractures of the distal radius: Dual-energy CT-derived metrics for opportunistic risk stratification

BACKGROUND

Dual-energy CT (DECT)-derived bone mineral density (BMD) of the distal radius and other CT-derived metrics related to bone health have been suggested for opportunistic osteoporosis screening and risk evaluation for sustaining distal radius fractures (DRFs).

METHODS

The distal radius of patients who underwent DECT between 01/2016 and 08/2021 was retrospectively analyzed. Cortical Hounsfield Unit (HU), trabecular HU, cortical thickness, and DECT-based BMD were acquired from a non-fractured, metaphyseal area in all examinations. Receiver-operating characteristic (ROC) analysis was conducted to determine the area under the curve (AUC) values for predicting DRFs based on DECT-derived BMD, HU values, and cortical thickness. Logistic regression models were then employed to assess the associations of these parameters with the occurrence of DRFs.

RESULTS

In this study, 263 patients (median age: 52 years; interquartile range: 36-64; 132 women; 192 fractures) were included. ROC curve analysis revealed a higher area under the curve (AUC) value for DECT-derived BMD compared to cortical HU, trabecular HU, and cortical thickness (0.91 vs. 0.61, 0.64, and 0.69, respectively; p <.001). Logistic regression models confirmed the association between lower DECT-derived BMD and the occurrence of DRFs (Odds Ratio, 0.83; p <.001); however, no influence was observed for cortical HU, trabecular HU, or cortical thickness.

CONCLUSIONS

DECT can be used to assess the BMD of the distal radius without dedicated equipment such as calibration phantoms to increase the detection rates of osteoporosis and stratify the individual risk to sustain DRFs. In contrast, assessing HU-based values and cortical thickness does not provide clinical benefit.

Visceral adipose tissue volume effect in Crohn's disease using reduced exposure CT enterography

PURPOSE

The purpose of this investigation was to assess the effect of visceral adipose tissue volume (VA) on reader efficacy in diagnosing and characterizing small bowel Crohn's disease using lower exposure CT enterography (CTE). Secondarily, we investigated the effect of lower exposure and VA on reader diagnostic confidence.

METHODS

Prospective paired investigation of 256 CTE, 129 with Crohn's disease, were reconstructed at 100% and simulated 50% and 30% exposure. The senior author provided the disease classification for the 129 patients with Crohn's disease. Patient VA was measured, and exams were evaluated by six readers for presence or absence of Crohn's disease and phenotype using a 0-10-point scale. Logistic regression models assessed the effect of VA on sensitivity and specificity.

RESULTS

The effect of VA on sensitivity was significantly reduced at 30% exposure (odds radio [OR]: 1.00) compared to 100% exposure (OR: 1.12) (p = 0.048). There was no statistically significant difference among the exposures with respect to the effect of visceral fat on specificity (p = 0.159). The study readers' probability of agreement with the senior author on disease classification was 60%, 56%, and 53% at 100%, 50%, and 30% exposure, respectively (p = 0.004). When detecting low severity Crohn's disease, readers' mean sensitivity was 83%, 75%, and 74% at 100%, 50%, and 30% exposure, respectively (p = 0.002). In low severity disease, sensitivity also tended to increase as visceral fat increased (ORs per 1000 cm3 increase in visceral fat: 1.32, 1.31, and 1.18, p = 0.010, 0.016, and 0.100, at 100%, 50%, and 30% exposure).

CONCLUSIONS

While the interaction is complex, VA plays a role in detecting and characterizing small bowel Crohn's disease when exposure is altered, particularly in low severity disease.

Comparison of volumetric and areal bone mineral density in CT and scout scans using spectral detector technology

BACKGROUND

To determine whether denoised areal bone mineral density (BMD) measurements from scout scans in spectral detector computed tomography (CT) correlate with volumetric trabecular BMD for opportunistic osteoporosis screening.

METHODS

A 64-slice single-source dual-layer spectral CT scanner was used to acquire scout scan data of 228 lumbar vertebral bodies within 57 patients. Scout scans in anterior-posterior (AP) view were performed with a dose of < 0.06 mSv and spectrally decomposed into areal BMD (aBMD) values. A spectral dictionary denoising algorithm was applied to increase the signal-to-noise ratio (SNR). Volumetric trabecular bone mineral density (vBMD) was determined via material decomposition. A 3D convolutional network for image segmentation and labeling was applied for automated vBMD quantification. Projected maps were used to compare the classification accuracy of AP and lateral scout scans.

RESULTS

The denoising algorithm led to the minimization of anticorrelated noise in spectral maps and an SNR increase from 5.23 to 13.4 (p < 0.002). Correlation analysis between vBMD and measured AP aBMD, projected AP, and lateral aBMD showed a Pearson correlation coefficient of 0.68, 0.81, and 0.90, respectively. The sensitivity and specificity for the osteoporosis classification task were higher in lateral projection images than in AP crystallizing in an increased area under the curve value of 0.99 versus 0.90.

CONCLUSION

Denoised material-specific aBMD maps show a positive correlation to vBMD, enabling spectral scout scans as an opportunistic predictor for osteoporotic patients. This could be applied routinely as a screening tool in patients undergoing a CT examination.

RELEVANCE STATEMENT

Scout-based DEXA could be applied routinely as a screening tool in patients undergoing a CT examination.

KEY POINTS

• Spectral scout scans can be used as a dual-energy x-ray absorptiometry-like screening tool. • Spectral dictionary denoising on projection images increases the signal-to-noise ratio. • Positive correlation between volumetric and areal bone mineral density is observed. • Lateral projections increase osteoporosis classification accuracy compared to anterior-posterior projections.

Slot-scan dual-energy bone densitometry using motorized X-ray systems

PURPOSE

We investigate the feasibility of slot-scan dual-energy (DE) bone densitometry on motorized radiographic equipment. This approach will enable fast quantitative measurements of areal bone mineral density (aBMD) for opportunistic evaluation of osteoporosis.

METHODS

We investigated DE slot-scan protocols to obtain aBMD measurements at the lumbar spine (L-spine) and hip using a motorized x-ray platform capable of synchronized translation of the x-ray source and flat-panel detector (FPD). The slot dimension was 5 × 20 cm² . The DE slot views were processed as follows: (1) convolution kernel-based scatter correction, (2) unfiltered backprojection to tile the slots into long-length radiographs, and (3) projection-domain DE decomposition, consisting of an initial adipose-water decomposition in a bone-free region followed by water-CaHA decomposition with adjustment for adipose content. The accuracy and reproducibility of slot-scan aBMD measurements were investigated using a high-fidelity simulator of a robotic x-ray system (Siemens Multitom Rax) in a total of 48 body phantom realizations: four average bone density settings (cortical bone mass fraction: 10-40%), four body sizes (waist circumference, WC = 70-106 cm), and three lateral shifts of the body within the slot field of view (FOV) (centered and ±1 cm off-center). Experimental validations included: (1) x-ray test-bench feasibility study of adipose-water decomposition and (2) initial demonstration of slot-scan DE bone densitometry on the robotic x-ray system using the European Spine Phantom (ESP) with added attenuation (polymethyl methacrylate [PMMA] slabs) ranging 2 to 6 cm thick.

RESULTS

For the L-spine, the mean aBMD error across all WC settings ranged from 0.08 g/cm² for phantoms with average cortical bone fraction w_cortical  = 10% to ∼0.01 g/cm² for phantoms with w_cortical  = 40%. The L-spine aBMD measurements were fairly robust to changes in body size and positioning, e.g., coefficient of variation (CV) for L1 with w_cortical  = 30% was ∼0.034 for various WC and ∼0.02 for an obese patient (WC = 106 cm) changing lateral shift. For the hip, the mean aBMD error across all phantom configurations was about 0.07 g/cm² for a centered patient. The reproducibility of hip aBMD was slightly worse than in the L-spine (e.g., in the femoral neck, the CV with respect to changing WC was ∼0.13 for phantom realizations with w_cortical  = 30%) due to more challenging scatter estimation in the presence of an air-tissue interface within the slot FOV. The aBMD of the hip was therefore sensitive to lateral positioning of the patient, especially for obese patients: e.g., the CV with respect to patient lateral shift for femoral neck with WC = 106 cm and w_cortical  = 30% was 0.14. Empirical evaluations confirmed substantial reduction in aBMD errors with the proposed adipose estimation procedure and demonstrated robust aBMD measurements on the robotic x-ray system, with aBMD errors of ∼0.1 g/cm² across all three simulated ESP vertebrae and all added PMMA attenuator settings.

CONCLUSIONS

We demonstrated that accurate aBMD measurements can be obtained on a motorized FPD-based x-ray system using DE slot-scans with kernel-based scatter correction, backprojection-based slot view tiling, and DE decomposition with adipose correction.

Assessment of Bone Mineral Density From a Computed Tomography Topogram of Photon-Counting Detector Computed Tomography-Effect of Phantom Size and Tube Voltage

PURPOSE

The aim of this study was to assess the accuracy and impact of different sizes and tube voltages on bone mineral density (BMD) assessment using a computed tomography (CT) topogram acquired with photon-counting detector CT in an osteopenic ex vivo animal spine.

MATERIALS AND METHODS

The lumbar back of a piglet was used to simulate osteopenia of the lumbar spine. Five fat layers (each with a thickness of 3 cm) were consecutively placed on top of the excised spine to emulate a total of 5 different sizes. Each size was repeatedly imaged on (A) a conventional dual-energy x-ray absorptiometry scanner as the reference standard, (B) a prototype photon-counting detector CT system at 120 kVp with energy thresholds at 20 and 70 keV, and (C) the same prototype system at 140 kVp with thresholds at 20 and 75 keV. Material-specific data were reconstructed from spectral topograms for B and C. Bone mineral density was measured for 3 lumbar vertebrae (L2-L4). A linear mixed-effects model was used to estimate the impact of vertebra, imaging setup, size, and their interaction term on BMD.

RESULTS

The BMD of the lumbar spine corresponded to a T score in humans between -4.2 and -4.8, which is seen in osteoporosis. Averaged across the 3 vertebrae and 5 sizes, mean BMD was 0.56 ± 0.03, 0.55 ± 0.02, and 0.55 ± 0.02 g/cm2 for setup A, B, and C, respectively. There was no significant influence of imaging setup (P = 0.7), simulated size (P = 0.67), and their interaction term (both P > 0.2) on BMD. Bone mineral density decreased significantly from L2 to L4 for all 3 setups (all P < 0.0001). Bone mineral density was 0.59 ± 0.01, 0.57 ± 0.01, and 0.52 ± 0.02 g/cm2 for L2, L3, and L4, respectively, for setup A; 0.57 ± 0.02, 0.55 ± 0.01, and 0.53 ± 0.01 g/cm2 for setup B; and 0.57 ± 0.01, 0.55 ± 0.01, and 0.53 ± 0.01 g/cm2 for setup C.

CONCLUSION

A single CT topogram acquired on photon-counting detector CT with 2 energy thresholds enabled BMD quantification with similar accuracy compared with dual-energy x-ray absorptiometry over a range of simulated sizes and tube voltages in an osteopenic ex vivo animal spine.

Dual-Energy Computed Tomography Virtual Noncalcium Technique in Diagnosing Osteoporosis: Correlation With Quantitative Computed Tomography

Objective

The aim of this study was to evaluate dual-energy computed tomography (CT) virtual noncalcium (VNCa) technique as a means of quantifying osteoporosis.

Methods

Dual-energy CT scans were obtained prospectively, targeting lumbar regions of 55 patients with chronic low back pain. A standard quantitative CT (QCT) phantom was positioned at the waist during each procedure, using proprietary software (QCT Pro; Mindways, Tex) to measure bone mineral density (BMD) in each vertebral body. Vendor dual-energy analytic software was altered with a specially modified configuration file to produce a “Virtual Non Calcium” or “VNCa” output, as such output variables were remapped to produce the following calcium values rather than iodine, yielding the following QCT parameters: CT value of calcium (originally “contrast media” [CM]), CT value of mixed energy imaging (regular CT value [rCT]), calcium density (originally “contrast agent density” [CaD]), and fat fraction (FF). Pearson test served to assess correlations between BMD and these parameters. Multiple linear regression analysis was applied to construct an equation for generating regressive BMD (rBMD) values. In gauging diagnostic accuracies, the criterion-standard BMD cutoff point (<80 mg/cm³) was adopted for QCT, whereas the rBMD threshold was defined by receiver operating characteristic curve.

Results

Contrast media, rCT, CaD, and FF values (reflecting CT value of calcium, regular CT value, calcium density, and fat fraction, respectively) significantly correlated with BMD (r values: 0.885, 0.947, 0.877, and 0.492, respectively; all P < 0.01). Contrast media, CaD, and FF showed independent associations with BMD; the regressive equation was formulated as follows: rBMD = 54.82 − 0.19 × CM + 20.03 × CaD − 1.24 × FF. The area under the curve of rBMD in diagnosing osteoporosis was 0.966 ± 0.009 (P < 0.01). At an rBMD threshold of less than 81.94 mg/cm³, sensitivity and specificity were 90.0% and 92.0%, respectively.

Conclusions

Dual-energy CT VNCa technique may constitute a valid alternative method for quantifying the mineral content and marrow fat composition of bone in diagnostic assessments of osteoporosis.

Serum nuclear factor IB as a novel and noninvasive indicator in the diagnosis of secondary hyperparathyroidism

BACKGROUND

Chronic renal failure (CRF) referred to chronic progressive renal parenchymal damage caused by various causes, with metabolite retention and imbalance of water, electrolyte, and acid-base balance as the main clinical manifestations. Secondary hyperparathyroidism (sHPT) was a common complication in maintenance hemodialysis patients with CRF. Nuclear factor IB (NFIB) was a newly found tumor suppressor gene in various cancers. The present study aimed to illustrate the role of NFIB in sHPT clinical diagnosis and treatment response.

METHODS

A retrospective, case-control study, including 189 patients with sHPT and 106 CRF patients without sHPT, compared with 95 controls. Serum NFIB and 1,25(OH)₂ D₃ levels were measured by RT-qPCR and ELISAs, respectively. ROC analysis was conducted to verify the diagnostic value of NFIB in sHPT. Spearman's correlation analysis was conducted to verify the association between NFIB and bone mineral density (BMD) scores. After 6 months of treatment, the variance of NFIB and 1,25(OH)₂ D₃ in different groups was recorded.

RESULTS

The expression of NFIB was significantly lower in serum samples from sHPT and non-sHPT CRF patients, compared to controls. Clinicopathological information verified sHPT was associated with NFIB, parathyroid hormone (PTH), serum calcium, serum phosphorus, time of dialysis, and serum 1,25(OH)₂ D₃ levels. Spearman's correlation analysis illustrated the positive correlation between NFIB levels and BMD scores. At receiver operator characteristic (ROC) curve analysis, the cutoff of 1.6508 for NFIB was able to identify patients with sHPT from healthy controls; meanwhile, NFIB could also discriminate sHPT among CRF patients as well (cutoff = 1.4741). Furthermore, we found that during 6 months of treatment, NFIB levels were gradually increased, while PTH and serum P levels were decreased.

CONCLUSIONS

Serum NFIB was a highly accurate tool to identify sHPT from healthy controls and CRF patients. Due to its simplicity, specificity, and sensitivity, this candidate can be proposed as a first-line examination in the diagnostic workup in sHPT.

Computed tomography-based opportunistic osteoporosis assessment: a comparison of two software applications for lumbar vertebral volumetric bone mineral density measurements

Background

We aimed to compare two volumetric bone mineral density (vBMD) analysis programs, regarding (I) agreement of vBMD values based on mono- and dual-energy computed tomography (MECT and DECT) scans and (II) suitability for analyzing DECT data obtained at different energies.

Methods

We retrospectively analyzed two abdominal CT datasets: one performed in a MECT scan (vertebrae L1-L3) and one in a DECT scan (vertebrae L1-L4). Each dataset included different individuals [MECT 15 patients (45 vertebrae) and DECT 12 patients (48 vertebrae), respectively]. vBMD analysis was conducted using Philips IntelliSpace (IP) and Mindways qCT Pro (MW). Regarding the DECT scans, vBMD analysis was done at three different energies: 80, 150 and synthetic 120 kVp and for MECT scan at 120 kVp. For comparison of vBMD results between different software (aim 1) MECT 120 kVp and DECT synthetic 120 kVp data was used. For analyzing suitability of using different DECT energies for vBMD assessment (aim 2) all three DECT energies were used and results from each software was analyzed separately.

Results

vBMD assessed with MW and IP, respectively correlated significantly for both the MECT (r=0.876; P<0.001) and DECT (r=0.837; P<0.001) scans, but the vBMD values were lower in using IP for vBMD assessment (8% and 14% lower for MECT and DECT, respectively; P=0.001). Regarding the different DECT energies, using MW for vBMD assessment showed significant correlations in vBMD results between 120 kVp and the two other energies (r=0.988 and r=0.939) and no significant differences in absolute vBMD values (P>0.05). The IP analysis as well showed significant correlation between 120 kVp and the other energies (r=0.769 and r=0.713, respectively), but differences in absolute vBMD values between the energies (P≤0.001).

Conclusions

We show that the correlations between the vBMD derived from the two investigated software solutions were generally good but that absolute vBMD value did differ and might impact the clinical diagnosis of osteoporosis. Though small, our study data indicate that vBMD might be assessed in energies other than 120 kVp when using MW but not when using IP.

Dual-Layer Detector CT With Virtual Noncalcium Imaging: Diagnostic Performance in Patients With Suspected Wrist Fractures

OBJECTIVE. The purpose of this study was to evaluate the diagnostic utility of dual-layer CT (DLCT) for evaluating wrist injuries and to compare it with MRI. MATERIALS AND METHODS. The cases of 62 patients with suspected wrist fractures who underwent imaging with both DLCT and MRI from January 2018 through February 2019 were retrospectively reviewed. By means of a calcium suppression algorithm, virtual noncalcium (VNCa) image reconstruction was performed, and the images were reviewed by two readers to identify fractures, bone contusions, and nontraumatic lesions in the radius, ulna, and carpal bones. Sensitivity, specificity, PPV, and NPV were calculated and compared between standard CT and VNCa images with a combination of standard CT and MRI as the reference standard. RESULTS. Use of DLCT with VNCa reconstruction increased the sensitivity of diagnosis of fractures in the radius and carpal bones over that of standard CT alone; occult fractures were detected that were not seen with standard CT. The sensitivity and specificity for detecting radius fracture were 98.1% and 93.8% for DLCT and 96.3% and 93.8% for standard CT. For detecting carpal bone fracture, sensitivity and specificity were 100% and 98.9% for DLCT and 93.8% and 100% for standard CT. VNCa reconstruction also had good diagnostic accuracy with regard to diagnosing nonfracture bone contusions in carpal bones. The accuracy was comparable to that of MRI with sensitivity of 92.9% and specificity of 94.5%. Interreader agreement in interpreting VNCa images was generally good to excellent. CONCLUSION. DLCT with VNCa reconstruction is a promising tool for identifying occult wrist fractures and nonfracture contusion injuries in patients with wrist trauma.

Bone Mineral Density Quantification from Localizer Radiographs: Accuracy and Precision of Energy-integrating Detector CT and Photon-counting Detector CT

Background Bone mineral density (BMD) could be derived from CT localizer radiographs and could potentially enable opportunistic osteoporosis screening. Purpose To assess the accuracy and precision of BMD measurement using two localizer radiographs obtained with energy-integrating detector CT and a single localizer radiograph obtained with photon-counting detector CT. Materials and Methods A calibration phantom and a porcine phantom with lumbar vertebrae were imaged with a dual-energy x-ray absorptiometry (DXA) scanner, a clinical energy-integrating detector CT scanner, and a prototype photon-counting detector CT scanner. Two localizer radiographs at different combinations of tube voltages were obtained with energy-integrating detector CT, and one localizer radiograph was obtained with photon-counting detector CT using different energy thresholds. BMD was calculated for all three approaches and compared with the known specifications in the calibration phantom. In the animal phantom, BMDs from both CT systems were compared with those from the DXA scanner (the reference standard). Accuracy was defined as the measurement error of BMD (ΔBMD), and precision was defined as the coefficient of variation (in percentage). Radiation doses were estimated. Nonparametric tests were applied. Results In the calibration phantom, ΔBMD was smaller with both CT systems compared with the DXA scanner (both P < .05). ΔBMD ranged from -5% to -1.8% for DXA, from -2.3% to -1.7% for energy-integrating detector CT, and from -1.6% to 1.6% for photon-counting detector CT. Precision (range, 0.3%-2.8%) was high for both CT systems. In the animal phantom, ΔBMD ranged from -0.6% to 0.1% for energy-integrating detector CT and from -0.1% to 0.6% for photon-counting detector CT, with no significant differences between CT systems (P = .65). The dose-area product in the animal phantom was 4.6 cGy ∙ cm² for DXA, 3.5-11.5 cGy ∙ cm² for energy-integrating detector CT, and 7.2-11.2 cGy ∙ cm² for photon-counting detector CT, depending on tube voltage and energy threshold combination. Conclusion Experimental evidence suggests that bone mineral density measurements are accurate and precise using two localizer radiographs at different tube voltages from energy-integrating detector CT and a single localizer radiograph with different energy thresholds from photon-counting detector CT. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Pourmorteza in this issue.

Incidence and risk factors of osteoporotic status in outpatients who underwent gastrectomy for gastric cancer

Background and Aim

Disorders in bone metabolism have long been recognized as typical sequelae of gastrectomy; however, the pathogenesis has not been fully elucidated, resulting in a variation of reported incidence. This study aimed to evaluate current bone health by measuring bone mineral density (BMD) in patients treated by gastrectomy for gastric cancer, with a focus on incidence and risk factors of osteoporosis.

Methods

The study enrolled 81 patients who underwent gastrectomy for gastric cancer at Kochi Medical School. BMD of the lumbar spine was measured by dual‐energy X‐ray mineral absorptiometry, with the results expressed as a percentage of the young adult mean (YAM). Clinical data were also obtained to investigate associations with BMD.

Results

Of the 81 study patients, 12 (14.8%) were deemed to have osteoporosis, defined by a percentage of YAM <70, with a dominance of females over males (66.7% vs 17.4%; P < 0.001). The median body weight, hemoglobin concentration, and serum alkaline phosphatase (ALP) level of the patients with osteoporosis was significantly lower than in those with a percentage of YAM ≥70 group (39.6 kg vs 53.1 kg, P < 0.001; 10.9 mg/dL vs 12.5 mg/dL, P = 0.010; 210 U/L vs 251 U/L, P = 0.002). Further analyses revealed a significant positive correlation between body weight and percentage of YAM (r = 0.441, P < 0.001). Despite the administration of bisphosphonates in these patients during this study, one acquired a bone fracture.

Conclusion

Osteoporosis was found in 14.8% of postoperative gastric cancer patients, with female gender, low body weight, and low ALP proposed as risk factors for osteoporosis and thus future bone fracture.

Accuracy, agreement, and reliability of DECT-derived vBMD measurements: an initial ex vivo study

OBJECTIVES

To assess the agreement and reliability of DECT (dual-energy CT)-derived vBMD (volumetric bone mineral density) measurements from excised human femoral heads and to compare DECT-derived BMD with that measured by DXA (dual-energy X-ray absorptiometry) and QCT (quantitative CT) to determine its accuracy.

METHODS

Twenty patients that underwent total hip arthroplasty were enrolled to this study. Femoral heads were excised to rectangles without cortical bones for scanning. A dual-source DECT scanner generated images under 80/Sn140 kVp and 100/Sn140 kVp scanning conditions. Specimens were subsequently scanned by QCT and DXA to produce QCT-derived vBMD (mg/cm³) and DXA-derived BMM (bone mineral mass, g). DECT images were loaded to a post-processing workstation to calculate DECT-derived vBMD and BMM.

RESULTS

Higher DECT-derived vBMD and BMM were found under 80/Sn140 and 100/Sn140 kVp compared with those for QCT and DXA (p = 0.005). DECT-derived vBMD was highly correlated with QCT-derived vBMD (r = 0.961 ~ 0.993, p < 0.05). Similarly, DECT-derived BMM was strongly correlated with DXA-derived BMM (r = 0.927 ~ 0.943, p < 0.05). Agreement of the inter- and intra-observation of DECT-derived vBMD was excellent. Linear regression was carried out to calibrate DECT-derived vBMD of 80/Sn140 kVp (14 + 0.7 × DECT-derived vBMD) and 100/Sn140 kVp (74 + 0.4 × DECT-derived vBMD) with the reference of QCT-derived vBMD. After calibration, excellent agreement was found for vBMD and BMM within various imaging modalities.

CONCLUSIONS

Our study showed that DECT-derived vBMD exhibited high agreement and reliability features, and after calibration, it also displayed a high degree of accuracy. However, in vivo studies are needed to extend its potential utility in clinical settings.

KEY POINTS

• Measurements of DECT-derived vBMD had high intra- and inter-observer agreement and reliability. • Measurements of DECT-derived vBMD and BMM had a high correlation with those derived from QCT and DXA. • DECT-derived vBMD and BMM were accurate after calibration compared with QCT and DXA.

Phantomless assessment of volumetric bone mineral density using virtual non-contrast images from spectral detector computed tomography

OBJECTIVE

To evaluate phantomless assessment of volumetric bone mineral density (vBMD) based on virtual non-contrast images of arterial (VNC_a) and venous phase (VNC_v) derived from spectral detector CT in comparison to true non-contrast (TNC) images and adjusted venous phase conventional images (CI_V(adjusted)).

METHODS

104 consecutive patients who underwent triphasic spectral detector CT between January 2018 and April 2019 were retrospectively included. TNC, VNC_a, VNC_v and venous phase images (CI_V) were reconstructed. vBMD was obtained by two radiologists using an FDA/CE-cleared software. Average vBMD of the first three lumbar vertebrae was determined in each reconstruction; vBMD of CI_V was adjusted for contrast enhancement as suggested earlier.

RESULTS

vBMD values obtained from CI_V(adjusted) are comparable to vBMD values derived from TNC images (91.79 ± 36.52 vs 90.16 ± 41.71 mg/cm³, p = 1.00); however, vBMD values derived from VNC_a and VNC_v (42.20 ± 22.50 and 41.98 ± 23.3 mg/cm³ respectively) were significantly lower as compared to vBMD values from TNC and CI_V(adjusted) (all p ≤ 0.01).

CONCLUSION

Spectral detector CT-derived virtual non-contrast images systematically underestimate vBMD and therefore should not be used without appropriate adjustments. Adjusted venous phase images provide reliable results and may be utilized for an opportunistic BMD screening in CT examinations.

ADVANCES IN KNOWLEDGE

Adjustments of venous phase images facilitate opportunistic assessment of vBMD, while spectral detector CT-derived VNC images systematically underestimate vBMD.