Patient doses in CT examinations in Switzerland: implementation of national diagnostic reference levels

Impact of artificial intelligence assistance on pulmonary nodule detection and localization in chest CT: a comparative study among radiologists of varying experience levels

The study aimed to evaluate the impact of AI assistance on pulmonary nodule detection rates among radiology residents and senior radiologists, along with assessing the effectiveness of two different commercialy available AI software systems in improving detection rates and LungRADS classification in chest CT. The study cohort included 198 participants with 221 pulmonary nodules. Residents' mean detection rate increased significantly from 64 to 77% with AI assist, while seniors' detection rate remained largely unchanged (85% vs. 86%). Residents showed significant improvement in segmental nodule localization with AI assistance, seniors did not. Software 2 slightly outperformed software 1 in increasing detection rates (67-77% vs. 80-86%), but neither significantly affected LungRADS classification. The study suggests that clinical experience mitigates the need for additional AI software, with the combination of CAD with residents being the most beneficial approach. Both software systems performed similarly, with software 2 showing a slightly higher but non-significant increase in detection rates.

Impact of Simulated Reduced-Dose Chest CT on Diagnosing Pulmonary T1 Tumors and Patient Management

To determine the diagnostic performance of simulated reduced-dose chest CT scans regarding pulmonary T1 tumors and assess the potential impact on patient management, a repository of 218 patients with histologically proven pulmonary T1 tumors was used. Virtual reduced-dose images were simulated at 25%- and 5%-dose levels. Tumor size, attenuation, and localization were scored by two experienced chest radiologists. The impact on patient management was assessed by comparing hypothetical LungRADS scores. The study included 210 patients (41% females, mean age 64.5 ± 9.2 years) with 250 eligible T1 tumors. There were differences between the original and the 5%-but not the 25%-dose simulations, and LungRADS scores varied between the dose levels with no clear trend. Sensitivity of Reader 1 was significantly lower using the 5%-dose vs. 25%-dose vs. original dose for size categorization (0.80 vs. 0.85 vs. 0.84; p = 0.007) and segmental localization (0.81 vs. 0.86 vs. 0.83; p = 0.018). Sensitivities of Reader 2 were unaffected by a dose reduction. A CT dose reduction may affect the correct categorization and localization of pulmonary T1 tumors and potentially affect patient management.

An Analysis of Computed Tomography Diagnostic Reference Levels in India Compared to Other Countries

Computed Tomography (CT) is vital for diagnosing and monitoring medical conditions. However, increased usage raises concerns about patient radiation exposure. Diagnostic Reference Levels (DRLs) aim to minimize radiation doses in CT imaging. This study examines CT DRLs in India compared to other countries to identify optimization opportunities. A literature review was conducted to gather data from published studies, guidelines, and regulatory authorities. Findings show significant international variations in CT DRLs, with differences up to 50%. In India, DRLs also vary significantly across states. For head CT exams, Indian DRLs are generally 20-30% lower than international standards (27-47 mGy vs. 60 mGy). Conversely, for abdominal CT scans, Indian DRLs are 10-15% higher (12-16 mGy vs. 13 mGy). Factors influencing DRL variations include equipment differences, imaging protocols, patient demographics, and regulatory conditions. Dose-optimization techniques like automatic exposure control and iterative reconstruction can reduce radiation exposure by 25-60% while maintaining image quality. Comparative data highlight best practices, such as the United Kingdom's 30% reduction in CT doses from 1984 to 1995 via DRL implementation. This study suggests that adopting similar practices in India could reduce radiation doses by 20-40% for common CT procedures, promoting responsible CT usage and minimizing patient exposure.

Proposing Multiregional Diagnostic Reference Levels for Common CT Angiography Examinations in Saudi Arabia

OBJECTIVES

Diagnostic reference levels (DRLs) are crucial tools for optimizing radiation exposure during different radiological examinations. This study aimed to establish preliminary DRLs for commonly performed computed tomographic angiography (CTA) examinations in Saudi Arabia.

METHODS

Data for three types of CTA examinations (cerebral, pulmonary, and lower-extremity) were collected from six medical cities across Saudi Arabia. Data sets related to 723 CTAs with a mean patient weight of 75 kg were analysed in detail. The DRL values were determined based on the 75th, median, and 25th CT dose index volume (CTDIvol) and dose length product (DLP) values.

RESULTS

The established DRLs were 1221 mGy cm for cerebral CTAs, 475 mGy cm for pulmonary CTAs, and 1040 mGy cm for lower-extremity CTAs. These values were comparable to those reported in other studies.

CONCLUSIONS

This study provides preliminary DRLs for three common CTA procedures in Saudi Arabia. The widespread implementation of a low kVp and a high level of image reconstruction (IR) presents an opportunity for further dose reduction. These findings can serve as a foundation for future nationwide DRL surveys and the optimization of CTA imaging protocols in Saudi Arabia.

Radiation doses and diagnostic reference levels for common CT scans in adults in Northwest region of Iran

This study aims to estimate organ dose and cancer risks, establish region-specific diagnostic reference levels (DRLs), and determine achievable doses (ADs) for common CT procedures in adults in the northwest of Iran. Effective and organ doses were estimated using VirtualDoseCT software in a sample of 480 adult patients who underwent head, sinus, chest, and abdomen-pelvis (AP) CT scans. The guidelines provided by the BEIR VII report were utilized to estimate cancer risks. Effective and organ doses for specific procedures were determined, with the highest mean organ dose being observed in the brain during head CT examinations, with a value of 54.02 mGy. It was observed that the lungs in chest examinations and the colon in AP examinations had the highest risk of cancer, with rates of 30.72 and 21.37 per 100,000 persons, respectively. Higher cancer risk values were generally exhibited by females compared to males. The DRLs for common CT examinations were established as follows: Head CT (CTDIvol 41 mGy, DLP 760 mGy cm), Sinus CT (CTDIvol 16 mGy, DLP 261 mGy cm), Chest CT (CTDIvol 8 mGy, DLP 287 mGy cm), and AP CT (CTDIvol 9 mGy, DLP 508 mGy cm). Significant variations in dose distribution among facilities were identified, indicating the need for optimization. The study highlights the importance of minimizing radiation exposure to critical organs and promoting patient safety in CT examinations. The establishment of region-specific DRLs and ADs can help optimize radiation doses and reduce cancer risks for patients.

Impact of equipment technology on reference levels in fluoroscopy-guided gastrointestinal procedures

OBJECTIVES

To evaluate the effect of equipment technology on reference point air kerma (Ka,r), air kerma-area product (PKA), and fluoroscopic time for fluoroscopically-guided gastrointestinal endoscopic procedures and establish benchmark levels.

METHODS

This retrospective study included the consecutive patients who underwent fluoroscopically-guided gastrointestinal endoscopic procedures from May 2016 to August 2023 at a tertiary care hospital in the U.S. Fluoroscopic systems included (a) Omega CS-50 e-View, (b) GE Precision 500D, and (c) Siemens Cios Alpha. Radiation dose was analyzed for four procedure types of endoscopic retrograde biliary, pancreas, biliary and pancreas combined, and other guidance. Median and 75th percentile values were computed using software package R (version 4.0.5, R Foundation).

RESULTS

This large study analyzed 9,459 gastrointestinal endoscopic procedures. Among four procedure types, median Ka,r was 108.8-433.2 mGy (a), 70-272 mGy (b), and 22-55.1 mGy (c). Median PKA was 20.9-49.5 Gy∙cm2 (a), 13.4-39.7 Gy∙cm2 (b), and 8.91-20.9 Gy∙cm2 (c). Median fluoroscopic time was 2.8-8.1 min (a), 3.6-9.2 min (b), and 2.9-9.4 min (c). Their median value ratio (a:b:c) was 8.5:4.8:1 (Ka,r), 2.7:2.1:1 (PKA), and 1.0:1.1:1 (fluoroscopic time). Median value and 75th percentile are presented for Ka,r, PKA, and fluoroscopic time for each procedure type, which can function as benchmark for comparison for dose optimization studies.

CONCLUSION

This study shows manifold variation in doses (Ka,r and PKA) among three fluoroscopic equipment types and provides local reference levels (50th and 75th percentiles) for four gastrointestinal endoscopic procedure types. Besides procedure type, imaging technology should be considered for establishing diagnostic reference level.

SUMMARY

With manifold (2 to 12 times) variation in doses observed in this study among 3 machines, we recommend development of technology-based diagnostic reference levels for gastrointestinal endoscopic procedures.

Exposure frequency and radiation dose from CT examinations in Huaian

This study quantified the exposure frequency and established the local diagnostic reference levels (DRLs) for the most common computed tomography (CT) examinations. A combined method census and sampling survey was used to quantify both frequency and radiation dose of CT examinations. Data were acquired through Picture Archiving and Communication System (PACS) or Radiology Information System (RIS). The annual frequency of CT examinations was 239.8 per 1000 inhabitants. The P75 of volume CT dose index (CTDIvol) to adult patients from CT scanning for head, chest, abdomen and lumbar spine examinations were 63.0, 12.4, 20.0 and 24.0 mGy, respectively. The P75 of dose-length product were 858.6, 416.0, 620.7 and 559.2 mGy·cm, respectively. This dose audit of CT practice can act as a starting point for establishing Huaian local DRLs and could be a reference for dose optimisation in China. This study compared DRLs in different countries and analysed some reasons for the rapid growth of CT examination frequency in Huaian.

Diagnostic reference levels in spinal CT: Jordanian assessments and global benchmarks

BACKGROUND

To reduce radiation dose and subsequent risks, several legislative documents in different countries describe the need for Diagnostic Reference Levels (DRLs). Spinal radiography is a common and high-dose examination. Therefore, the aim of this work was to establish the DRL for Computed Tomography (CT) examinations of the spine in healthcare institutions across Jordan.

METHODS

Data was retrieved from the picture archiving and communications system (PACS), which included the CT Dose Index (CTDI (vol) ) and Dose Length Product (DLP). The median radiation dose values of the dosimetric indices were calculated for each site. DRL values were defined as the 75th percentile distribution of the median CTDI (vol)  and DLP values.

RESULTS

Data was collected from 659 CT examinations (316 cervical spine and 343 lumbar-sacral spine). Of the participants, 68% were males, and the patients' mean weight was 69.7 kg (minimum = 60; maximum = 80, SD = 8.9). The 75th percentile for the DLP of cervical and LS-spine CT scans in Jordan were 565.2 and 967.7 mGy.cm, respectively.

CONCLUSIONS

This research demonstrates a wide range of variability in CTDI (vol)  and DLP values for spinal CT examinations; these variations were associated with the acquisition protocol and highlight the need to optimize radiation dose in spinal CT examinations.

Establishing Protocol-based Dose Metrics for Common Abdomen and Pelvis Computed Tomography Protocols

BACKGROUND AND AIM

The majority of the existing diagnostic reference levels (DRLs) that have been established for computed tomography (CT) are based on various anatomical locations, such as the head, chest, abdomen, etc. However, DRLs are initiated to improve radiation protection by conducting a comparison of similar examinations with similar objectives. The aim of this study was to explore the feasibility of establishing dose baselines based on common CT protocols for patients who underwent enhanced CT abdomen and pelvis exams.

METHODS

Dose length product total (tDLPs), volumetric CT dose index (CTDIvol), size-specific dose estimate (SSDE), effective dose (E), and scan acquisition parameters for a total of 216 adult patients, who underwent an enhanced CT abdomen and pelvis exams over a one-year period, were obtained and retrospectively analyzed. Spearman coefficient and one-way ANOVA tests were used to check significant differences between dose metrics and the different CT protocols.

RESULTS

The data exhibited 9 different CT protocols to acquire an enhanced CT abdomen and pelvis exam at our institute. Out of these, 4 were found more common, i.e., CT protocols were acquired for a minimum of 10 cases. Triphasic liver demonstrated the highest mean and median tDLPs across all 4 CT protocols. Triphasic liver protocol registered the highest E followed by gastric sleeve protocol with a mean of 28.7 and 24.7 mSv, respectively. Significant differences (p < 0.0001) were found between the tDLPs of anatomical location and the CT protocol.

CONCLUSION

Evidently, wide variability exists across CT dose indices and patient dose metrics relying on anatomical-based dose baseline, i.e., DRLs. Patient dose optimizations require establishing dose baselines based on CT protocols rather than the anatomical location.

Surgical Sealant with Integrated Shape-Morphing Dual Modality Ultrasound and Computed Tomography Sensors for Gastric Leak Detection

Postoperative anastomotic leaks are the most feared complications after gastric surgery. For diagnostics clinicians mostly rely on clinical symptoms such as fever and tachycardia, often developing as a result of an already fully developed, i.e., symptomatic, surgical leak. A gastric fluid responsive, dual modality, electronic-free, leak sensor system integrable into surgical adhesive suture support materials is introduced. Leak sensors contain high atomic number carbonates embedded in a polyacrylamide matrix, that upon exposure to gastric fluid convert into gaseous carbon dioxide (CO2 ). CO2 bubbles remain entrapped in the hydrogel matrix, leading to a distinctly increased echogenic contrast detectable by a low-cost and portable ultrasound transducer, while the dissolution of the carbonate species and the resulting diffusion of the cation produces a markedly reduced contrast in computed tomography imaging. The sensing elements can be patterned into a variety of characteristic shapes and can be combined with nonreactive tantalum oxide reference elements, allowing the design of shape-morphing sensing elements visible to the naked eye as well as artificial intelligence-assisted automated detection. In summary, shape-morphing dual modality sensors for the early and robust detection of postoperative complications at deep tissue sites, opening new routes for postoperative patient surveillance using existing hospital infrastructure is reported.

Investigating CT head diagnostic reference levels based on indication-based protocols - a single site study

INTRODUCTION

This study aimed to provide clinically-relevant insights into establishing CT DRLs based on indication-based protocols in Ireland, focusing on CT head examinations performed at a neurology centre of excellence hospital.

METHODS

Dose data were collected retrospectively. Typical values for six CT head indication-based protocols were established using a sample size of 50 patients for each protocol. Typical values for each protocol were set as the median of the distribution curve. Dose distributions for each protocol were calculated and compared using non-parametric median test (k-samples) to ascertain significant dose differences between the typical values.

RESULTS

Most typical values pairings showed significant differences (p < 0.001) except between stroke/non-vascular brain, stroke/acute brain, and acute brain/non-vascular brain pairings. This was expected due to similar scan parameters. The typical value for stroke (3-phases angiogram) was 52% lower than the typical value for stroke. Dose levels of the male populations recorded were higher than female populations for all protocols. Statistical comparison showed significant differences for dose quantities and/or scan length between both genders in five protocols.

CONCLUSION

Proposed values for DLP were up to 63% and 69% lower than the EU and Irish national DRLs respectively. Establishment of CT stroke DRLs should be based on the scan performed instead of number of scan acquisitions. Lastly, gender-based CT DRLs for specific protocols within the head region require further investigation.

IMPLICATIONS FOR PRACTICE

With increasing CT examinations worldwide, radiation dose optimisation is key. The value of indication based DRLs is to enhance the required patient protection so image quality can be maintained, however with relevant DRLs for varying protocols. Establishment of CT typical values and site specific DRLs for procedures beyond the national DRLs can drive dose optimisation locally.

Establishment of national diagnostic dose reference levels (DRLs) for routine computed tomography examinations in Jordan

Background: Dose reference levels (DRLs) are used as indicators as well as guidance for dose optimization and to ensure justification of appropriate dose for a given clinical indication. The main aims of this study were to establish local DRLs for each CT imaging protocol as a reference point to evaluate the radiation dose indices and to compare our DRLs with those established in other countries and against the internationally reported guidelines.

Materials and methods: 2000 CT dose reports of different adult imaging protocols from January 2021 until April 2022 were collected retrospectively at different hospitals in Jordan. Data were collected from CT scans that were performed using different types and models of CT scanners and included four adult non-enhanced, helical CT imaging protocols; Head, Chest, Abdomen-Pelvis, and Chest-Abdomen-Pelvis.

Results: The average doses of CTDIvol, DLP, and effective dose were (65.11 mGy, 1232.71 mGy·cm, 2.83 mSv) for the head scan, (16.6 mGy, 586.6 mGy·cm, 8.21 mSv) for the chest scan, (17.91 mGy, 929.9 mGy·cm, 13.9 mSv) for the abdomen-pelvis scan, and (19.3 mGy, 1152 mGy·cm, 17.25 mSv) for the chest-abdomen-pelvis scan. In comparison with results from different international studies, DLP values measured in the present study were lower for the chest-abdomen-pelvis and abdomen-pelvis CT scans, and higher for the head CT and chest CT scans.

Conclusions: It is very important that each country establishes its own DRLs and compares them with those reported by other countries, especially the developed ones. It is also important that these levels are regularly updated.

Assessment of patients radiation doses associated with computed tomography coronary angiography

Computed tomography coronary angiography (CTCA) has generated tremendous interest over the past 20 years by using multidetector computed tomography (MDCT) because of its high diagnostic accuracy and efficacy in assessing patients with coronary artery disease. This technique is related to high radiation doses, which has raised serious concerns in the literature. Effective dose (E, mSv) may be a single parameter meant to reflect the relative risk from radiation exposure. Therefore, it is necessary to calculate this quantity to point to relative radiation risk. The objectives of this study are to evaluate patients' exposure during diagnostic CCTA procedures and to estimate the risks. Seven hundred ninety patients were estimated during three successive years. The patient's exposure was estimated based on a CT device's delivered radiation dose (Siemens Somatom Sensation 64 (64-MDCT)). The participating physicians obtained the parameters relevant to the radiation dose from the scan protocol generated by the CT system after each CCTA study. The parameters included the volume CT dose index (CTDIvol, mGy) and dose length product (DLP, mGy × cm). The mean and range of CTDIvol (mGy) and DLP (mGy × cm) for three respective year was (2018):10.8 (1.14-77.7) and 2369.8 ± 1231.4 (290.4-6188.9), (2019): 13.82 (1.13-348.5), and 2180.5 (501.8-9534.5) and (2020) 10.9 (0.7-52.9) and 1877.3 (149.4-5011.1), respectively. Patients' effective doses were higher compared to previous studies. Therefore, the CT acquisition parameter optimization is vital to reduce the dose to its minimal value.

ESTABLISHMENT OF REGIONAL DIAGNOSTIC REFERENCE LEVELS IN ADULT COMPUTED TOMOGRAPHY FOR FOUR AFRICAN COUNTRIES: A PRELIMINARY SURVEY

This preliminary study aims towards the establishment of regional diagnostic reference levels (DRLs) for routine adult computed tomography (CT) examinations. The study was performed on 54 CT facilities from four African countries (Ghana, Kenya, Namibia and Senegal) and the results compared with international DRLs. Data were collected from facilities using a structured questionnaire provided by the International Atomic Energy Agency. Dose descriptors (volume computed tomography dose index [CTDIvol] and dose length product [DLP]) evaluations were performed on CT head and body phantoms for head, chest and abdomen CT examination protocols using standard methods. The estimated dose indices were compared with console-displayed dose values. Experienced radiologists accepted the diagnostic image quality of the images as per departmental imaging requirements. Median CTDIvol and DLP data from each facility were compiled to estimate the typical dose in each country. National DRLs were established based on the 75th percentile of median values, whereas the regional DRLs were based on the median of the national DRLs. Comparison of measured CTDIvol with console values of all facilities in all four countries was within 20% as recommended. The established CTDIvol DRLs for head CT, chest CT and abdomen CT were 60.9 mGy, 15.2 mGy and 15.7 mGy, respectively. Similarly, that of DLP, DRLs were 1259 mGy.cm, 544 mGy.cm and 737 mGy.cm, respectively for head CT, chest CT and abdomen CT. The established DRLs from this study were comparable to DRLs from other countries with some variations. This study would serve as baseline for establishment of a more generalized regional adult CT DRLs for Africa.

Gender based lung cancer risks for symptomatic coronary artery disease patients undergone cardiac CT

We estimate the lifetime attributable risk (LAR) of lung cancer incidence in symptomatic Coronary Artery Disease (CAD) patients receiving enhanced Coronary Computed Tomography Angiography (CCTA) and the unenhanced Computed Tomography Calcium Scoring (CTCS) examination. Retrospective analysis has been made of CCTA and CTCS data collected for 87 confirmed CAD adult patients. Patient effective dose (E) and organ doses (ODs) were calculated using CT-EXPO. Statistical correlation and the differences between E and ODs in enhanced CCTA and unenhanced CTCS were calculated using the Pearson coefficient and Wilcoxon unpaired t-test. Following BEIR VII report guidance, organ-specific LARs for the cohort were estimated using the organ-equivalent dose-to-risk conversion factor for numbers of cases per 100,000 patients exposed to low doses of 0.1 Gy. Significant statistical difference (p<0.0001) is found between E obtained for CTCS and that of CCTA. The scan length was found to be greater in CCTA (17.5 ± 2.9 cm) compared to that for CTCS (15 ± 2 cm). More elevated values of dose were noted for the esophagus (4.2 ± 2.15 mSv) and thymus (9.6 ± 2.54 mSv) for both CTCS and CCTA. CTCS organ doses were lower than that of CCTA. Per 100,000 patients, female cumulative doses are seen to give rise to greater lung cancer LARs compared to that for males, albeit with risk varying significantly, noticeably greater for females, younger patients and combined CCTA and CTCS scans. While scan parameters and tube-modulation methods clearly contribute to patient dose, mAs offers by far the greater contribution.

T-shirt size as a classification for body habitus in computed tomography (CT) and development of size-based dose reference levels for different indications

PURPOSE

To examine the impact of patient size on dose indices and develop size-based reference levels (50th and 75th percentiles) for 20 body CT exams for routine and organ-specific clinical indications.

METHODS

Based on effective diameter estimated from adult body CT, each acquisition was classified into T-shirt size as XXS, XS, S, M, L, XL, and XXL. Radiation dose indices for each size and each exam type were correlated.

RESULTS

About 0.93 million CT exams from 256 CT facilities in the United States were analysed. Taking T-shirt size M as a reference, the CTDI_vol for other sizes were: XXS (∼60%), XS (∼65%), S (∼75%), L (∼130%), XL (∼165%), XXL (∼210%), or grossly small patients received about 60% of the dose as compared to M sized patients and XXL required doubling the dose. Taking ratio of the dose indices of the largest to smallest size, it was evident that SSDE variation was much less (about 50%) than that in CTDI_vol, but there was still nearly 40 to 220% variation in SSDE across the range of t-shirt sizes. The 50th and 75th percentile values are presented for CTDI_vol, SSDE and DLP for each of the 20 CT exams and for each of the seven T-shirt sizes.

CONCLUSIONS

A novel approach expressing body habitus in terms of T-shirt size is not only simple and intuitive, but it also provides a tool to have a perception of differences in dose metrices among patients of different body build.

Diagnostic reference levels and median doses for common clinical indications of CT: findings from an international registry

OB JECTIVES

The European Society of Radiology identified 10 common indications for computed tomography (CT) as part of the European Study on Clinical Diagnostic Reference Levels (DRLs, EUCLID), to help standardize radiation doses. The objective of this study is to generate DRLs and median doses for these indications using data from the UCSF CT International Dose Registry.

METHODS

Standardized data on 3.7 million CTs in adults were collected between 2016 and 2019 from 161 institutions across seven countries (United States of America (US), Switzerland, Netherlands, Germany, UK, Israel, Japan). DRLs (75th percentile) and median doses for volumetric CT-dose index (CTDIvol) and dose-length product (DLP) were assessed for each EUCLID category (chronic sinusitis, stroke, cervical spine trauma, coronary calcium scoring, lung cancer, pulmonary embolism, coronary CT angiography, hepatocellular carcinoma (HCC), colic/abdominal pain, appendicitis), and US radiation doses were compared with European.

RESULTS

The number of CT scans within EUCLID categories ranged from 8,933 (HCC) to over 1.2 million (stroke). There was greater variation in dose between categories than within categories (p < .001), and doses were significantly different between categories within anatomic areas. DRLs and median doses were assessed for all categories. DRLs were higher in the US for 9 of the 10 indications (except chronic sinusitis) than in Europe but with a significantly higher sample size in the US.

CONCLUSIONS

DRLs for CTDIvol and DLP for EUCLID clinical indications from diverse organizations were established and can contribute to dose optimization. These values were usually significantly higher in the US than in Europe.

KEY POINTS

• Registry data were used to create benchmarks for 10 common indications for CT identified by the European Society of Radiology. • Observed US radiation doses were higher than European for 9 of 10 indications (except chronic sinusitis). • The presented diagnostic reference levels and median doses highlight potentially unnecessary variation in radiation dose.

ESTIMATION OF PATIENT RADIATION DOSES FROM MULTI-DETECTOR COMPUTED TOMOGRAPHY ANGIOGRAPHY PROCEDURES IN TANZANIA

The aim of the present study was to estimate the volume CT dose index (CTDIvol), dose length product (DLP) and effective dose (ED) to patients from five multi-detector computed tomography angiography (MDCTA) procedures: brain, carotid, coronary, entire aorta and lower limb from four medical institutions in Tanzania; to compare these doses to those reported in the literature, and to compare the data obtained with ICRP 103 and Monte Carlo software. The radiation doses for 217 patients were estimated using patient demographics, patient-related exposure parameters, the geometry of examination and CT-Expo V 2.4 Monte Carlo-based software. The median values of the CTDIvol, DLP and ED for MDCTA procedures of the brain and carotids were 36.8 mGy, 1481.0 mGy∙cm and 5.2 mSv, and 15.9 mGy, 1224.0 mGy∙cm and 7.8 mSv, respectively; while for the coronary, entire aortic, and lower limbs were 49.4 mGy, 1493.0 mGy∙cm and 30.6 mSv; 16.2 mGy, 2287.0 mGy∙cm and 41.1 mSv; and 6.4 mGy, 1406.0 mGy∙cm and 10.5 mSv, respectively. The ratio of the maximum to minimum ED values to individual patients across the four medical centers were 41.4, 11.1, 4.6, 9.5 and 37.4, respectively, for the brain, carotid, coronary, entire aortic and lower limb CT angiography procedures. The mean values of CTDIvol, DLP and ED in the present study were typically higher than the values reported from Kenya, Korea and Saudi Arabia. The 75th percentile values of the DLP were above the preliminary diagnostic references levels proposed by Kenya, Switzerland and Korea. The observed wide range of examination scanning protocols and patient doses for similar MDCTA procedures within and across hospitals; and the observed relatively high patient doses compared to those reported in the literature, call for the need to standardize scanning protocols and optimise patient dose from MDCTA procedures.

DIAGNOSTIC REFERENCE LEVELS OF CARDIAC COMPUTED TOMOGRAPHY ANGIOGRAPHY IN A SINGLE MEDICAL CENTER IN TAIWAN: A 3-Y ANALYSIS

This study aimed to establish the diagnostic reference levels (DRLs) for coronary computed tomography angiography (CCTA) and coronary arterial calcium score (CACS) owing to a large variability in patient radiation dose and the lack of dose recommendations in Taiwan. Volume computed tomography dose index (CTDIvol) and dose-length product (DLP) were obtained using CCTAs and the CACS of 445 patients over a 3-y period in a single medical center in Taiwan. CCTAs were performed using routine protocols and 256-detector CT scanners. Electrocardiogram gating was retrospective. The obtained data were analyzed using Prism 6 to determine the 25th, 50th (median) and 75th DRL percentiles for CTDIvol and DLP. These DRL results were compared with existing DRLs from seven countries. The DRLs for CCTA determined from this survey were similar to the existing data from other countries. Such DRLs could provide a useful tool for the optimization of radiation dose for CCTA in Taiwan.

PEDIATRIC REGIONAL DRL ASSESSMENT IN COMMON CT EXAMINATIONS FOR MEDICAL EXPOSURE OPTIMIZATION IN TEHRAN, IRAN

The main purpose of this pilot study was to assess the regional diagnostic reference level (RDRL) of computed tomography (CT) examinations to optimise medical exposure in five pediatric medical imaging centers in Tehran, Iran where the most frequent CT examinations were investigated. For each patient, CT volume dose indexes (CTDIvol) and dose length product (DLP) in each group were recorded and their third quartile was calculated and set as RDRL. Pediatrics were divided into four age groups (<1; 1-5; 5-10 and 10-15 years). Then, the third quartile values for head, chest and abdomen-pelvic CTs were, respectively, calculated for each group in terms of CTDIvol: 21.3, 24.4, 24.2 and 36.3 mGy; 2.9, 3.2, 3.7 and 5.7 mGy; 3.7, 5.7, 6.3 and 6.8 mGy; and in terms of DLP: 322.2, 390.1, 424.9 and 694.1 mGy.cm; 53.1, 115.2, 145.3 and 167.6 mGy.cm and 128.7, 317.7, 460.2 and 813.8 mGy.cm. Finally, RDRLs were compared with other countries and preceding data in Iran. As a result, CTDIVOL values were lower than other national and international studies except for chest and abdomen-pelvic values obtained in Europe. Moreover, this matter applied to DLP so that other formerly reported values were higher than the present study but European values for chest and abdomen-pelvic scans and also Tehran studies conducted in 2012. Variation of scan parameters (tube voltage (kVp), tube current (mAs) and scan length), CTDIvol and DLP of different procedures among different age groups were statistically significant (P-value < 0.05). The variations in dose between CT departments as well as between identical scanners suggest a large potential for optimization of examinations relative to which this study provides helpful data.

Towards establishment of diagnostic reference levels based on clinical indication in the state of Qatar

OBJECTIVES

The objectives of this study were to: 1) evaluate patient radiation exposure in CT and 2) establish CT Diagnostic Reference Levels (DRL)s based on clinical indication (CI) in Qatar.

MATERIALS AND METHODS

Patient data for 13 CIs were collected using specially designed collection forms from the dose management software (DMS) of Hamad Medical Corporation (HMC), the main Qatar healthcare provider. The methodology described in the International Commission on Radiological Protection (ICRP) Report 135 was followed to establish national clinical DRLs in terms of Volumetric Computed Tomography Dose Index (CTDIvol) and total Dose Length Product (DLPt). Effective dose (Ef) was estimated by DMS using DLPt and appropriate conversion factors and was analyzed for comparison purposes.

RESULTS

Data were retrospectively collected for 896 adult patients undergoing CT examinations in 4 hospitals and 7 CT scanners. CT for Diffuse infiltrative lung disease imparted the lowest radiation in terms of CTDIvol (5 mGy), DLPt (181 mGy.cm) and Ef (3.6 mSv). Total body CT for severe trauma imparted the highest DLPt (3137 mGy.cm) and Ef (38.6 mSv) of all CIs with a CTDIvol of 15 mGy. Rounded Third quartile CTDIvol and DLPt values were defined as the Qatar CT clinical DRLs. Comparison was limited due to sparse international literature. When this was possible data were lower or comparable with other studies.

CONCLUSIONS

This is the first study reporting national clinical DRLs in Asia and second one internationally after UK. For accurate comparison between studies, systemized CI nomenclature must be followed by researchers.

ADULT CT EXAMINATIONS IN ALGERIA: TOWARDS UPDATING NATIONAL DIAGNOSTIC REFERENCE LEVELS

A pilot study has concerned the most frequent computed tomography examinations (CT). This represents the first results based on actual survey for diagnostic reference levels (DRLs) establishment in Algeria. A total number of 2540 patients underwent this survey that has included the recording of CT parameters, computed tomography dose index (CTDIvol) and dose-length product of the head, thorax, abdomen, abdomen-pelvis (AP), lumbar spine (LS) and thorax-abdomen-pelvis (TAP) performed on standard patients. The proposed DRLs are 71 mGy/1282 mGy.cm for head, 16 mGy/555 mGy.cm for thorax, 18 mGy/671 mGy.cm for abdomen, 21 mGy/950 mGy.cm for AP, 36 mGy/957 mGy.cm for LS and 18 mGy/994 mGy.cm for TAP. The rounded 75th percentile seems to be higher in some examinations compared to the literature. Our findings confirm the need to optimise our practice. These results provide a starting point for institutional evaluation of CT radiation doses.

Evaluation of Impact of Factors Affecting CT Radiation Dose for Optimizing Patient Dose Levels

The dose metrics and factors influencing radiation exposure for patients undergoing head, chest, and abdominal computed tomography (CT) scans were investigated for optimization of patient dose levels. The local diagnostic reference levels (DRLs) of adult CT scans performed in our hospital were established based on 28,147 consecutive examinations, including 5510 head scans, 9091 chest scans, and 13,526 abdominal scans. Among the six CT scanners used in our hospital, four of them are 64-slice multi-detector CT units (MDCT64), and the other two have detector slices higher than 64 (MDCTH). Multivariate analysis was conducted to evaluate the effects of body size, kVp, mAs, and pitch on volume CT dose index (CTDIvol). The local DRLs expressed in terms of the 75th percentile of CTDIvol for the head, chest, and abdominal scans performed on MDCT64 were 59.32, 9.24, and 10.64 mGy, respectively. The corresponding results for MDCTH were 57.90, 7.67, and 9.86 mGy. In regard to multivariate analysis, CTDIvol showed various dependence on the predictors investigated in this study. All regression relationships have coefficient of determination (R2) larger than 0.75, indicating a good fit to the data. Overall, the research results obtained through our workflow could facilitate the modification of CT imaging procedures once the local DRLs are unusually high compared to the national DRLs.

Computed tomography diagnostic reference levels for adult brain, chest and abdominal examinations: A systematic review

OBJECTIVES

Radiation dose variation within and among Computed Tomography (CT) centres is commonly reported. This work systematically reviewed published articles on adult Diagnostic Reference Levels (DRLs) for the brain, chest and abdomen to determine the causes and extent of variation. A systematic literature search and review was performed in selected databases containing leading journals in radiography, radiology and medical physics using carefully defined search terms related to CT and DRLs. The quality of the included articles was determined using the Effective Public Health Practise Project tool for quantitative studies.

KEY FINDINGS

The 54 articles reviewed include: 45 studies using human data, 8 studies using phantom data, and one study with both human and phantom data. The main comparator in between studies was the dose indices used in reporting DRLs. DRL variations of up to a factor of 2 for the same procedure were noted in phantom studies, and up to a factor of 3 in human studies. Sources of variation include the type of scanner, the age of the scanner, differences in protocols, variations in patients, as well as variations in study design. Different combinations of dose indices were reported: volume computed tomography dose index (CTDIvol) and dose length product (DLP) (59%); DLP only (11%); weighted computed tomography dose index (CTDIw) and DLP (9%); CTDIvol only (7%); CTDIvol, DLP and effective dose (ED) (6%); CTDIw only (4%); CTDIvol, DLP and size specific dose estimate (SSDE) (1%) and CTDIw, CTDIvol and DLP (1%). The use of different dose indices limited dose comparison between studies.

CONCLUSION

The study noted a 2-3 fold variation in DRLs between studies for the same procedure. The causes of variation are reported and include study design, scanner technology and the use of different dose indices.

IMPLICATIONS FOR PRACTICE

There is a need for standardisation of CT DRLs in line with the International Commission on Radiological Protection recommendations to reduce dose variation and facilitate dose comparison.

Radiation exposure of computed tomography imaging for the assessment of acute stroke

Purpose

To assess suspected acute stroke, the computed tomography (CT) protocol contains a non-contrast CT (NCCT), a CT angiography (CTA), and a CT perfusion (CTP). Due to assumably high radiation doses of the complete protocol, the aim of this study is to examine radiation exposure and to establish diagnostic reference levels (DRLs).

Methods

In this retrospective study, dose data of 921 patients with initial CT imaging for suspected acute stroke and dose monitoring with a DICOM header–based tracking and monitoring software were analyzed. Between June 2017 and January 2020, 1655 CT scans were included, which were performed on three different modern multi-slice CT scanners, including 921 NCCT, 465 CTA, and 269 CTP scans. Radiation exposure was reported for CT dose index (CTDI_vol) and dose-length product (DLP). DRLs were set at the 75th percentile of dose distribution.

Results

DRLs were assessed for each step (CTDI_vol/DLP): NCCT 33.9 mGy/527.8 mGy cm and CTA 13.7 mGy/478.3 mGy cm. Radiation exposure of CTP was invariable and depended on CT device and its protocol settings with CTDI_vol 124.9–258.2 mGy and DLP 1852.6–3044.3 mGy cm.

Conclusion

Performing complementary CT techniques such as CTA and CTP for the assessment of acute stroke increases total radiation exposure. Hence, the revised DRLs for the complete protocol are required, where our local DRLs may help as benchmarks.

A systematic review on the current status of adult diagnostic reference levels in head, chest and abdominopelvic Computed Tomography

Computed tomography (CT) is a routinely employed diagnostic tool for the detection and diagnosis of disease processes. Despite the primary focus of radiation dose reduction and improvements in CT scanners, radiation dose exposure remains an ever-increasing concern. Scanning protocol optimisation relative to body weight and scanner manufacturer still lags behind the diagnostic reference levels (DRLs) that are set on an international scale. The aim of this systematic review is to evaluate the current status of adult DRLs in head, chest and abdominopelvic CT over time on a global scale. A search was carried out in early 2019 using the Medline, PubMed, EMBASE, SCOPUS and manual databases. The reference lists of published articles were also assessed to identify further articles. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) methodology was employed to evaluate articles for relevance. Articles were included if they assessed the DRL in head, chest and abdominopelvic scans. The search resulted in 6079 articles, of which 67 were included after a thorough screening process. The literature demonstrates a wide dose variation in reported head, chest and abdominopelvic dose length product (DLP) DRL, ranging from 700-1359, 330-707 and 550-1486 mGy·cm, respectively. Where reported, the volumed CT dose index (CTDI_vol) DRL in the head, chest and abdominopelvic studies ranged from 30.4-85.5, 9-15 and 12.3-31 mGy·cm, respectively. The global means were shown to be slightly lower and significantly lower than the reported values of DLP and CTDI_vol values for the American College of Radiology and European Commission, respectively. This review emphasises the need for an international standardisation for head and body DRL establishment methods, to provide a more comparable global measurement of dose variations across CT sites as well as regular monitoring of delivered radiation dose to patients.

Diagnostic Reference Levels based on clinical indications in computed tomography: a literature review

BACKGROUND

In August 2017, the European Commission awarded the "European Study on Clinical Diagnostic Reference levels for X-ray Medical Imaging" project to the European Society of Radiology, to provide up-to-date Diagnostic Reference Levels based on clinical indications. The aim of this work was to conduct an extensive literature review by analysing the most recent studies published and the data provided by the National Competent Authorities, to understand the current situation regarding Diagnostic Reference Levels based on clinical indications for computed tomography.

RESULTS

The literature review has identified 23 papers with Diagnostic Reference Levels based on clinical indications for computed tomography from 15 countries; 12 of them from Europe. A total of 28 clinical indications for 6 anatomical areas (head, cervical spine/neck, chest, abdomen, abdomen-pelvis, chest-abdomen-pelvis) have been identified.

CONCLUSIONS

In all the six anatomical areas for which Diagnostic Reference Levels based on clinical indications were found, a huge variation of computed tomography dose descriptor values was identified, providing evidence for a need to develop strategies to standardise and optimise computed tomography protocols.

LOCAL DRLS FOR PAEDIATRIC CT EXAMINATIONS BASED ON SIZE-SPECIFIC DOSE ESTIMATES IN KERMANSHAH, IRAN

Due to the radiosensitivity of paediatric patients to X-ray, it is necessary to survey the paediatric DRLs using size-specific dose estimates (SSDE). In the present study, we determined the local diagnostic reference levels (DRLs) for paediatric chest, head and abdomen-pelvis CT examinations and their Surview scans in Kermanshah city, Iran. For ≤1 year, 1-5 years, 5-10 years and 10-15 years the DRLs (mGy) based on SSDE were determined N/A, 6.00, 6.25, 8.27 for abdomen-pelvis, and 8.74, 7.45, 11.15, 10.45 for chest and 19.05, 18.33, 18.22, 20.14 for head examinations, respectively. The differences between body size and default phantom defined in CT scanners are significant and should be considered when determining the DRLs. Based on our findings, use of CTDIv and SSDE parameters for determining DRLs leads to significant different results in children; thus SSDE is suggested as a more accurate index than CTDIV for establishing DRLs in paediatric CT examinations.

Machine Learning Techniques Applied to Dose Prediction in Computed Tomography Tests

Increasingly more patients exposed to radiation from computed axial tomography (CT) will have a greater risk of developing tumors or cancer that are caused by cell mutation in the future. A minor dose level would decrease the number of these possible cases. However, this framework can result in medical specialists (radiologists) not being able to detect anomalies or lesions. This work explores a way of addressing these concerns, achieving the reduction of unnecessary radiation without compromising the diagnosis. We contribute with a novel methodology in the CT area to predict the precise radiation that a patient should be given to accomplish this goal. Specifically, from a real dataset composed of the dose data of over fifty thousand patients that have been classified into standardized protocols (skull, abdomen, thorax, pelvis, etc.), we eliminate atypical information (outliers), to later generate regression curves employing diverse well-known Machine Learning techniques. As a result, we have chosen the best analytical technique per protocol; a selection that was thoroughly carried out according to traditional dosimetry parameters to accurately quantify the dose level that the radiologist should apply in each CT test.

Establishment of diagnostic reference levels in cardiac computed tomography

The aim of this study was to determine diagnostic reference levels (DRLs) for cardiac computed tomography (CCT) in Jordan. Volume computed tomography dose index (CTDI_vol) and dose–length product (DLP) were collected from 228 CCTs performed at seven Jordanian hospitals specialized in cardiac CT. DRLs for cardiac CT were defined at the 75th percentile of CTDI_vol and DLP. CTDI_vol and DLP were collected from 30 successive cardiac CT in each center except for one center (18 scans). The 75th percentile of the CTDI_vol and the DLP of the centers calculated from mixed retrospective and prospective gated modes were 47.74 milligray (mGy) and 1035 mGy/cm, respectively. This study demonstrated wide dose variations among the surveyed hospitals for cardiac CT scans; there was a 5.1‐fold difference between the highest and lowest median DLP with a range of 223.2–1146.7 mGy/cm. Differences were associated with variations in the mAs and kVp. This study confirmed large variability in CTDI_vol and DLP for cardiac CT scans; variation was associated with acquisition protocols and highlights the need for dose optimization. DRLs are proposed for CCT; there remains substantial potential for optimization of cardiac CT examinations for adults in Jordan.

Analysis of a multicentre cloud-based CT dosimetric database: preliminary results

BACKGROUND

To manage and analyse dosimetric data provided by computed tomography (CT) scanners from four Italian hospitals.

METHODS

A radiation dose index monitoring (RDIM) software was used to collect anonymised exams stored in a cloud server. Since hospitals use different names for the same procedure, digital imaging and communications in medicine (DICOM) tags more appropriate to describe exams were selected and associated to study common names (SCNs) from a radiology playbook according to scan region and use of contrast media. Retrospective analysis was carried out to describe population and to evaluate dosimetric indexes and inaccuracies associated with SCNs.

RESULTS

More than 400 procedures were clustered into 95 SCNs, but 78% of exams on adults were described with only 10 SCNs. Median values of dose-length product (DLP) and volumetric CT dose index (CTDI_vol) for three analysed SCNs were in agreement with those previously published. The percentage of inaccuracies does not heavily affect the dosimetric analysis on the whole cloud, since variations in median values reached at most 8%.

CONCLUSIONS

Implementation of a cloud-based RDIM software and related issues were described, showing the strength of the chosen playbook-based clustering and its usefulness for homogeneous data analysis. This approach may allow for optimisation actions, accurate assessment of the risk associated with radiation exposure, comparison of different facilities, and, last but not least, collection of information for the implementation of the 2013/59 Euratom Directive.

Studying the lung dose uncertainty during chest CT scans using phantoms with statistical lung volumes and shapes

In recent years, there has been increasing interest in constructing a series of deformable phantoms which follow the statistical distributions of some anatomical variations, known as 'statistical phantoms'. The main purpose of this study was to develop statistical phantoms by considering the variations in lung volume and shape, in order to evaluate the lung dose uncertainty for individuals undergoing chest computed tomography. Calculations were performed for 100 statistical lung volume phantoms and 70 statistical lung shape phantoms at tube voltages of 80 and 120 kVp, with the use of Monte Carlo MCNP code. The obtained results indicate that dose fluctuations for low tube voltage (80 kVp) are higher than those at 120 kVp. Moreover, it shows that the impact of statistical variations in lung volume on dose discrepancy (5% to 7%) is higher than the impact of statistical lung shape variations (around 2%).

Local clinical diagnostic reference levels for chest and abdomen CT examinations in adults as a function of body mass index and clinical indication: a prospective multicenter study

OBJECTIVES

To compare institutional dose levels based on clinical indication and BMI class to anatomy-based national DRLs (NDRLs) in chest and abdomen CT examinations and to assess local clinical diagnostic reference levels (LCDRLs).

METHODS

From February 2017 to June 2018, after protocol optimization according to clinical indication and body mass index (BMI) class (< 25; ≥ 25), 5310 abdomen and 1058 chest CT series were collected from 5 CT scanners in a Swiss multicenter group. Clinical indication-based institutional dose levels were compared to the Swiss anatomy-based NDRLs. Statistical significance was assessed (p < 0.05). LCDRLs were calculated as the third quartile of the median dose values for each CT scanner.

RESULTS

For chest examinations, dose metrics based on clinical indication were always below P75 NDRL for CTDI_vol (range 3.9-6.4 vs. 7.0 mGy) and DLP (164.0-211.2 vs. 250 mGycm) in all BMI classes except for DLP in BMI ≥ 25 (248.8-255.4 vs. 250.0 mGycm). For abdomen examinations, they were significantly lower or not different than P50 NDRLs for all BMI classes (3.8-9.0 vs. 10.0 mGy and 192.9-446.8 vs. 470mGycm). The estimated LCDRLs show a drop in CTDI_vol (21% for chest and 32% for abdomen, on average) with respect to current DRLs. When considering BMI stratification, the largest LCDRL difference within the same clinical indication is for renal tumor (4.6 mGy for BMI < 25 vs. 10.0 mGy for BMI ≥ 25; - 117%).

CONCLUSION

The results suggest the necessity of estimating clinical indication-based DRLs, especially for abdomen examinations. Stratifying per BMI class allows further optimization of the CT doses.

KEY POINTS

• Our data show that clinical indication-based DRLs might be more appropriate than anatomy-based DRLs and might help in reducing large variations in dose levels for the same type of examinations. • Stratifying the data per patient-size subgroups (non-overweight, overweight) allows a better optimization of CT doses and therefore the possibility to set LCDRLs based on BMI class. • Institutions who are fostering continuous dose optimization and LDRLs should consider defining protocols based on clinical indication and BMI group, to achieve ALARA.

Radiation Dose Associated With Over Scanning in Neck CT

The increasing utilization of computed tomography scans exposes patients to significant amounts of radiation. One of the factors that can result in unnecessary radiation dose is scanning beyond the clinically indicated anatomical region. This study aims to assess the optimization in overscan frequency, scan length, and radiation dose following targeted educational talks aimed to address a routinely over scanned protocol; the computed tomography Neck. A targeted radiation awareness talk regarding scan adherence as a method of radiation dose optimization was delivered to all medical imaging technologists employed at a large teaching hospital. An audit of the radiation dose associated with computed tomography Neck protocols was conducted in the month before, a month after and 1 year after the awareness talk. Results show that following the radiation awareness talks there was a 15% reduction in overscan frequency, an average over scan length reduction of 33% and a 20% reduction in overall radiation dose. The targeted nature of the talk, explicitly addressing scan range in the neck region, significantly reduced radiation dose to the patients. The results of this study are effective in illustrating the potential clinical radiation dose saving from strict adherence to scan range.

Patient dose evaluation in computed tomography: A French national study based on clinical indications

PURPOSE

A national survey was performed to assess patient dose indicators based on clinical indication and on patient morphology for most common adult computed tomography (CT) examinations in France.

METHODS

Seventeen groups of clinical indications (GCIs) for diagnostic CT in adult patients were considered based on their frequency and on image quality requirements. Data was collected for 15-30 consecutive examinations performed between 2015 and 2017, per CT scanner and GCI. Distributions of total examination Dose-Length Product (DLP) and Volume CT Dose Index (CTDI_vol) were assessed for each GCI as a function of patient gender or patient Body Mass Index (BMI) for head/neck and trunk examinations, respectively.

RESULTS

6610 examinations were analysed. Median total exam DLP values were higher for men compared to women patients for head and neck examinations: difference ranged from 6% for ear trauma indication (577 vs 543 mGy·cm, p = 0.01) to 35% for brain tumour GCI (1472 vs 1093 mGy·cm, p < 0.01). For trunk examinations, total exam DLP increased consistently with patient's BMI. For normal-BMI patients, median CTDI_vol and DLP differed significantly between different GCIs for single-phase CT of the chest (3 mGy and 112 mGy·cm, respectively, for chronic obstructive pulmonary disease group vs 5.8 mGy and 207 mGy·cm for pulmonary embolism group, p < 0.05) and of the abdomen-pelvis (5.6 mGy and 284 mGy·cm, respectively, in renal colic group vs 9.5 mGy and 463 mGy·cm in occlusive syndrome group, p < 0.05).

CONCLUSION

This study provides morphological- and clinical-based patient dose indicators in CT as a practical tool for clinical practices optimisation.

Establishment of diagnostic reference levels arising from common CT examinations in Semnan County, Iran

Objective: The literature has approved that the use of the concept of diagnostic reference level (DRL) as a part of an optimization process could help to reduce patient doses in diagnostic radiology comprising the Computed Tomography (CT) examinations. There are four public/governmental CT centers in the province (Semnan, Iran) and, to our knowledge, after about 12 years since the launch of the first CT scanner in the province there is no dosimetry information on those CT scanners. The aim of this study was to evaluate CT dose indices with the aim of the establishment of the DRL for head, chest, cervical spine, and abdomen-pelvis examinations.

Methods: Scan parameters of 381 patients were collected during two months from 4 CT scanners. The CT dose index (CTDI) was measured using a calibrated ionization chamber on two cylindrical poly methyl methacrylate (PMMA) phantoms. For each sequences, weighted CTDI (CTDIw), volumetric CTDI (CTDIv) and dose length product (DLP) were calculated. The 75th percentile was proposed as the criterion for DRL values.

Results: Proposed DRL (CTDIw, CTDIv, DLP) for the head, chest, cervical spine, and abdomen-pelvis were (46.1 mGy, 46.1 mGy, 723 mGy × cm), (13.8 mGy, 12.0 mGy, 377 mGy × cm), (40.0 mGy, 40.0 mGy, 572 mGy × cm) and (14.9 mGy, 12.1 mGy, 524 mGy × cm), respectively.

Conclusion: Comparison with the others results from the other countries indicates that the head, chest and abdomen-pelvis scans in our region are lower or in the range of the other studies investigated in terms of dose. In the case of cervical spine scanning it’s necessary to review and regulate scan protocols to reach acceptable dose levels.

International variation in radiation dose for computed tomography examinations: prospective cohort study

OBJECTIVE

To determine patient, institution, and machine characteristics that contribute to variation in radiation doses used for computed tomography (CT).

DESIGN

Prospective cohort study.

SETTING

Data were assembled and analyzed from the University of California San Francisco CT International Dose Registry.

PARTICIPANTS

Standardized data from over 2.0 million CT examinations of adults who underwent CT between November 2015 and August 2017 from 151 institutions, across seven countries (Switzerland, Netherlands, Germany, United Kingdom, United States, Israel, and Japan).

MAIN OUTCOME MEASURES

Mean effective doses and proportions of high dose examinations for abdomen, chest, combined chest and abdomen, and head CT were determined by patient characteristics (sex, age, and size), type of institution (trauma center, care provision 24 hours per day and seven days per week, academic, private), institutional practice volume, machine factors (manufacturer, model), country, and how scanners were used, before and after adjustment for patient characteristics, using hierarchical linear and logistic regression. High dose examinations were defined as CT scans with doses above the 75th percentile defined during a baseline period.

RESULTS

The mean effective dose and proportion of high dose examinations varied substantially across institutions. The doses varied modestly (10-30%) by type of institution and machine characteristics after adjusting for patient characteristics. By contrast, even after adjusting for patient characteristics, wide variations in radiation doses across countries persisted, with a fourfold range in mean effective dose for abdomen CT examinations (7.0-25.7 mSv) and a 17-fold range in proportion of high dose examinations (4-69%). Similar variation across countries was observed for chest (mean effective dose 1.7-6.4 mSv, proportion of high dose examinations 1-26%) and combined chest and abdomen CT (10.0-37.9 mSv, 2-78%). Doses for head CT varied less (1.4-1.9 mSv, 8-27%). In multivariable models, the dose variation across countries was primarily attributable to institutional decisions regarding technical parameters (that is, how the scanners were used).

CONCLUSIONS

CT protocols and radiation doses vary greatly across countries and are primarily attributable to local choices regarding technical parameters, rather than patient, institution, or machine characteristics. These findings suggest that the optimization of doses to a consistent standard should be possible.

STUDY REGISTRATION

Clinicaltrials.gov NCT03000751.

Optimization of CT protocols using cause-and-effect analysis of outliers

The aim of this study was to implement an outlier marking and analysis methodology to optimize CT examination protocols. CT Head examination data, including dose metrics along with technical parameters, were stored in an automatic dose registry system. Reference dose metrics distribution was obtained throughout a 1-year period. Outlier thresholds were calculated taking into account the specific shape of the distribution, by using a robust measure of the skewness; the medcouple parameter. Subsequently, outliers from a 4-month period were marked and Cause-and-Effect analysis was carried out by a multidisciplinary dose committee. Reference Dose metrics distributions were obtained from 3690 CT Head examinations. Both CTDIvol and DLP showed a certain degree of skewness, with a medcouple value of 0.05 and 0.11, respectively. All of the upper-outliers fell within 3 identifiable groups of causes, ordered by relative importance: i) inadequate protocol selection, ii) arms or objects in the field-of-view, and iii) abnormal scanning region diameter. Regarding the lower-outliers, 90% were attributable to the inclusion of additional series in the original head protocol and the remaining 10% to unknown causes. Also, a general Cause-and-Effect diagram for outliers was elaborated. While the Dose Reference Level method applies to the general performance of a CT protocol and allows comparison with other centers, the outlier method represents a step further in the optimization process. The proposed method focuses on detecting incorrect utilization of the CT, which mainly arises from inadequate knowledge of CT technology.