Dose monitoring using the DICOM structured report: assessment of the relationship between cumulative radiation exposure and BMI in abdominal CT

An inventory of patient-image based risk/dose, image quality and body habitus/size metrics for adult abdomino-pelvic CT protocol optimisation

PURPOSE

Patient-specific protocol optimisation in abdomino-pelvic Computed Tomography (CT) requires measurement of body habitus/size (BH), sensitivity-specificity (surrogates image quality (IQ) metrics) and risk (surrogates often dose quantities) (RD). This work provides an updated inventory of metrics available for each of these three categories of optimisation variables derivable directly from patient measurements or images. We consider objective IQ metrics mostly in the spatial domain (i.e., those related directly to sharpness, contrast, noise quantity/texture and perceived detectability as these are used by radiologists to assess the acceptability or otherwise of patient images in practice).

MATERIALS AND METHODS

The search engine used was PubMed with the search period being 2010-2024. The key words used were: 'comput* tomography', 'CT', 'abdom*', 'dose', 'risk', 'SSDE', 'image quality', 'water equivalent diameter', 'size', 'body composition', 'habit*', 'BMI', 'obes*', 'overweight'. Since BH is critical for patient specific optimisation, articles correlating RD vs BH, and IQ vs BH were reviewed.

RESULTS

The inventory includes 11 BH, 12 IQ and 6 RD metrics. 25 RD vs BH correlation studies and 9 IQ vs BH correlation studies were identified. 7 articles in the latter group correlated metrics from all three categories concurrently.

CONCLUSIONS

Protocol optimisation should be fine-tuned to the level of the individual patient and particular clinical query. This would require a judicious choice of metrics from each of the three categories. It is suggested that, for increased utility in clinical practice, more future optimisation studies be clinical task based and involve the three categories of metrics concurrently.

The effect of age and sex on esophageal hiatal surface area among normal North American adults using multidetector computed tomography

The size of the esophageal hiatus is clinically important for preserving the integrity of the lower esophageal sphincter mechanism. The purpose of this study was to systematically establish the mean hiatal surface area (HSA) for normal North American adults under physiologic conditions and assess the relationship between sex and age on HSA. Multi-Detector Computer Tomogram (MDCT) images of the esophageal hiatus in 119 healthy adult subjects (61 males and 58 females with an age range of 24-88 years) were retrospectively analyzed using the multi-planar reconstruction (MPR) technique to directly measure their hiatal length (long axis), width (short axis) and surface area at end inspiration. The mean HSA for males was 2.88 cm², with a standard deviation of 0.74 cm². The mean HSA for females was 2.51 cm², with a standard deviation of 0.68 cm². There was a statistically significant difference in HSA between males and females (p = 0.0053); however, there was no statistically significant difference between the HSA among different age groups (p = 0.8439). Similarly, significant differences between males and females were demonstrated in both the length (p = 0.0263) and width (p = 0.0311) measurements, but there was no evidence of an association of these parameters with age. For the first time, the normal size of the hiatus at end inspiration has been established noninvasively for a population of healthy adults from MDCT images.

Comparison of low-dose CT with CT/CT fluoroscopy guidance in percutaneous sacral and supra-acetabular cementoplasty

PURPOSE

Percutaneous cementoplasty is a minimally invasive treatment modality for painful osteoporotic and pathologic sacral and supra-acetabular iliac fractures. This study compares the use of low-dose CT guidance with CT/CT fluoroscopy in sacral and supra-acetabular cementoplasty.

METHODS

A retrospective review of patients who had undergone sacral or supra-acetabular cementoplasty was performed with patients grouped by use of CT/CT fluoroscopy or low-dose CT guidance during the procedure. Parameters evaluated included type of fracture, laterality of lesions, pain scores, pain medication use, imaging parameters, procedure time, dose-length product, effective dose, cement volume, and complications.

RESULTS

There were 17 patients identified who underwent cementoplasty utilizing dual CT/CT fluoroscopy, while 13 patients had their procedures performed with low-dose CT. There was a statistically significant decrease in radiation dose in the low-dose CT group (1481 mGy•cm) compared with the CT/CT fluoroscopy group (2809 mGy•cm) (P = 0.013). There was a significant decrease in procedure time with low-dose CT for bilateral lesions (P = 0.016). There was no significant difference between groups in complication rate (P = 0.999). Clinically nonsignificant cement extravasation occurred in two patients (10%) in the CT/CT fluoroscopy group and in one patient (8%) in the low-dose CT group (P = 0.999). There was a significant decrease in pain scores compared with baseline on the visual analogue scale in both groups at 1 week (low-dose CT P = 0.002, CT/CT fluoroscopy P = 0.008) and 1 month postprocedure (low-dose CT P = 0.014, CT/CT fluoroscopy P = 0.004), but no difference between groups at 1 day (P = 0.196), 1 week (P = 0.368), or 1 month (P = 0.514).

CONCLUSION

Sacral and supra-acetabular cementoplasties can be performed safely and precisely using low-dose multiple-acquisition CT guidance while providing significant radiation dose reduction with no difference in extravasation rates, postprocedural pain reduction, and complications compared with CT/CT fluoroscopy.

Radiation dose reduction for musculoskeletal computed tomography of the pelvis with preserved image quality

OBJECTIVE

To analyze the impact of pelvic computed tomography (CT) technique optimization on estimated dose and subjective and objective image quality.

MATERIALS AND METHODS

An institutional review board (IRB)-approved retrospective records review was performed with waived informed consent. Five CT scanners (various manufacturers/models) were standardized to match the lowest dose profile on campus via subjective assessment of clinical images by experienced musculoskeletal radiologists. The lowest dose profile had previously been established through image assessment by experienced musculoskeletal radiologists after a department-wide radiation dose reduction initiative. A consecutive series of 60 pre- and 59 post-optimization bony pelvis CTs were analyzed by two residents, who obtained signal-to-noise ratio for femoral cortex and marrow, gluteus medius muscle, and subcutaneous and visceral fat in a standardized fashion. Two blinded attending radiologists ranked image quality from poor to excellent.

RESULTS

Pre- and post-optimization subjects exhibited no difference in gender, age, or BMI (p > 0.2). Mean CT dose index (CTDIvol) and dose-length product (DLP) decreased by approximately 45%, from 39± 14 to 18± 12 mGy (p < 0.0001) and 1,227± 469 to 546± 384 mGy-cm (p < 0.0001). Lower body mass index (BMI) was associated with a larger dose reduction and higher BMI with higher DLP regardless of pre- or post-optimization examination. Inter-observer agreement was 0.64-0.92 for SNR measurements. Cortex SNR increased significantly for both observers (p < 0.02). Although qualitative image quality significantly decreased for one observer (p < 0.01), adequate mean quality (3.3 out of 5) was maintained for both observers.

CONCLUSION

Subjective and objective image quality for pelvic CT examination remains adequate, despite a substantially reduced radiation dose.

Determining and updating PET/CT and SPECT/CT diagnostic reference levels: A systematic review

The aim of this systematic review is to investigate the national diagnostic reference level (NDRL) methods for positron emission tomography/computed tomography (PET/CT) and single photon emission tomography/computed tomography (SPECT/CT) procedures. A search strategy was based on the preferred, reporting items for systematic review and meta-analysis (PRISMA). Relevant articles retrieved from Medline, Scopus, Web of Science, Embase, Cinahl, and Google Scholar published up to October 2017. The search yielded 1057 articles. Fourteen articles were included in the review after a screening process. Relevant information from the selected articles were summarised and analysed. Discrepancies were found between the methodologies utilised to establish and report both PET/CT and SPECT/CT NDRLs, e.g. patient sampling and administered activity. Further research should focus on reporting more NDRLs for hybrid PET/CT and SPECT/CT examinations, and establish a robust NDRL standard for the CT portion associated with PET/CT and SPECT/CT examinations. This review provides updated NDRL reommndations to deliver more comparable international radation doses for administered activity and CT dose across PET/CT and SPECT/CT clinics.

AUTOMATIC ACQUISITION OF CT RADIATION DOSE DATA: USING THE DIAGNOSTIC REFERENCE LEVEL FOR RADIATION DOSE OPTIMIZATION

The present work describes that we try to construct a system that collects dose information that performed CT examination from multiple facilities and unified management. The results of analysis are compared with other National diagnostic reference level (DRL), and the results are fed back to each facility and the cause of the abnormal value is investigated for dose optimization. Medical information collected 139 144 tests from 33 CT devices in 13 facilities. Although the DRL of this study is lower than that of Japan DRL, it was higher than the DRL of each country. When collecting all the examination, it is thought that the variation of the dose due to the error other than the intended imaging site is large. In future, we should continue to collect information in order to DRL renewal and we also think that it is desirable to collect information on physique and detailed scan region as well.

Use of a Web-Based Calculator and a Structured Report Generator to Improve Efficiency, Accuracy, and Consistency of Radiology Reporting

While medical calculators are common, they are infrequently used in the day-to-day radiology practice. We hypothesized that a calculator coupled with a structured report generator would decrease the time required to interpret and dictate a study in addition to decreasing the number of errors in interpretation. A web-based application was created to help radiologists calculate leg-length discrepancies. A time motion study was performed to evaluate if the calculator helped to decrease the time for interpretation and dictation of leg-length radiographs. Two radiologists each evaluated two sets of ten radiographs, one set using the traditional pen and paper method and the other set using the calculator. The time to interpret each study and the time to dictate each study were recorded. In addition, each calculation was checked for errors. When comparing the two methods of calculating the leg lengths, the manual method was significantly slower than the calculator for all time points measured: the mean time to calculate the leg-length discrepancy (131.8 vs. 59.7 s; p < 0.001), the mean time to dictate the report (31.8 vs. 11 s; p < 0.001), and the mean total time (163.7 vs. 70.7 s; p < 0.001). Reports created by the calculator were more accurate than reports created via the manual method (100 vs. 90%), although this result was not significant (p = 0.16). A calculator with a structured report generator significantly improved the time required to calculate and dictate leg-length discrepancy studies.

Comparison of effective radiation doses from X-ray, CT, and PET/CT in pediatric patients with neuroblastoma using a dose monitoring program

PURPOSE

We aimed to evaluate the use of a dose monitoring program for calculating and comparing the diagnostic radiation doses in pediatric patients with neuroblastoma.

METHODS

We retrospectively reviewed diagnostic and therapeutic imaging studies performed on pediatric patients with neuroblastoma from 2003 to 2014. We calculated the mean effective dose per exam for X-ray, conventional computed tomography (CT), and CT of positron emission tomography/computed tomography (PET/CT) from the data collected using a dose monitoring program (DoseTrack group) since October 2012. Using the data, we estimated the cumulative dose per person and the relative dose from each modality in all patients (Total group). The effective dose from PET was manually calculated for all patients.

RESULTS

We included 63 patients with a mean age of 3.2±3.5 years; 28 had a history of radiation therapy, with a mean irradiated dose of 31.9±23.2 Gy. The mean effective dose per exam was 0.04±0.19 mSv for X-ray, 1.09±1.11 mSv for CT, and 8.35±7.45 mSv for CT of PET/CT in 31 patients of the DoseTrack group. The mean estimated cumulative dose per patient in the Total group was 3.43±2.86 mSv from X-ray (8.5%), 7.66±6.09 mSv from CT (19.1%), 18.35±13.52 mSv from CT of PET/CT (45.7%), and 10.71±10.05 mSv from PET (26.7%).

CONCLUSION

CT of PET/CT contributed nearly half of the total cumulative dose in pediatric patients with neuroblastoma. The radiation dose from X-ray was not negligible because of the large number of X-ray images. A dose monitoring program can be useful for calculating radiation doses in patients with cancer.

Wide Variation in Radiation Exposure During Computerized Tomography

OBJECTIVE

To determine the variance in computeed tomography (CT) radiation measured via dose-length product (DLP) and effective dose (ED) during stone protocol CT scans.

METHODS

We retrospectively examined consecutive records of patients receiving stone protocol diagnostic CT scans (n = 1793) in 2010 and 2014 in our health system. Patient age, body mass index (BMI), and gender were recorded, along with the hospital, machine model, year, DLP, and ED of each scan. Multivariate regression was performed to identify predictive factors for increased DLP. We also collected data on head (n = 837) CT scans to serve as a comparison.

RESULTS

For stone CT scans, mean patient age was 55.1 ± 18.4 years with no significant difference in age (P=.2557) or BMI (P=.1794) between 2010 and 2014. Gender, BMI, and machine model were independent predictors of radiation dosage (P < .0001). Within each BMI class, there was an inexplicable 6-fold variation in the ED for the same imaging test when comparing the lowest and highest CT dose patients. There was no significant change in DLP over time for stone CT scans, but head scan patients in 2014 received lower radiation doses than those in 2010 (P < .0001). Low-dose scans for renal colic (defined as <4 mSv) were underutilized. Substantial variation exists for head scan radiation doses.

CONCLUSION

Our data demonstrate large variations in diagnostic CT radiation dosage. Such differences within a single institution suggest similar trends elsewhere, warranting more stringent dosage guidelines and regulations for diagnostic CT scans within institutions.

Does body mass index outperform body weight as a surrogate parameter in the calculation of size-specific dose estimates in adult body CT?

OBJECTIVE

To assess the value of body mass index (BMI) in comparison with body weight as a surrogate parameter for the calculation of size-specific dose estimates (SSDEs) in thoracoabdominal CT.

METHODS

401 CT examinations in 235 patients (196 chest, 205 abdomen; 95 females, 140 males; age 62.5 ± 15.0 years) were analysed in regard to weight, height and BMI (kg m(-2)). Effective diameter (Deff, cm) was assessed on axial CT images. The correlation between BMI, weight and Deff was calculated. SSDEs were calculated based on Deff, weight and BMI and lookup tables were developed.

RESULTS

Overall height, weight, BMI and Deff were 172.5 ± 9.9 cm, 79.5 ± 19.1 kg, 26.6 ± 5.6 kg m(-2) and 30.1 ± 4.3 cm, respectively. There was a significant correlation between Deff and BMI as well as weight (r = 0.85 and r = 0.84; p < 0.05, respectively). Correlation was significantly better for BMI in abdominal CT (r = 0.89 vs r = 0.84; p < 0.05), whereas it was better for weight in chest CT (r = 0.87 vs r = 0.81; p < 0.05). Surrogated SSDEs did not differ significantly from the reference standard with a median absolute relative difference of 4.2% per patient (interquartile range 25-75: 3.1-7.89, range 0-25.3%).

CONCLUSION

BMI and weight exhibit a significant correlation with Deff in adult patients and can be used as surrogates in the calculation of SSDEs. Using the herein-developed lookup charts, SSDEs can be calculated based on patients' weight and BMI.

ADVANCES IN KNOWLEDGE

In abdominal CT, BMI has a superior correlation with effective diameter compared with weight, whereas weight is superior in chest CT. Patients' BMI and weight can be used as surrogates in the calculation of SSDEs.