Multicentric study of patients receiving 50 or 100 mSv in a single day through CT imaging-frequency determination and imaging protocols involved

Dose, dose, dose, but where is the patient dose?

The article reviews the historical developments in radiation dose metrices in medical imaging. It identifies the good, the bad, and the ugly aspects of current-day metrices. The actions on shifting focus from International Commission on Radiological Protection (ICRP) Reference-Man-based population-average phantoms to patient-specific computational phantoms have been proposed and discussed. Technological developments in recent years involving AI-based automatic organ segmentation and 'near real-time' Monte Carlo dose calculations suggest the feasibility and advantage of obtaining patient-specific organ doses. It appears that the time for ICRP and other international organizations to embrace 'patient-specific' dose quantity representing risk may have finally come. While the existing dose metrices meet specific demands, emphasis needs to be also placed on making radiation units understandable to the medical community.

Cumulative radiation exposure from multimodality recurrent imaging of CT, fluoroscopically guided intervention, and nuclear medicine

OBJECTIVES

To assess cumulative effective dose (CED) over a 4-year period in patients undergoing multimodality recurrent imaging at a major hospital in the USA.

METHODS

CED from CT, fluoroscopically guided intervention (FGI), and nuclear medicine was analyzed in consecutive exams in a tertiary care center in 2018-2021. Patients with CED ≥ 100 mSv were classified by age and body habitus (underweight, healthy weight, overweight, obese), as per body mass index percentiles < 5th, 5th to < 85th, 85th to < 95th, and ≥ 95th (age 2-19 years), and its ranges < 18.5, 18.5-24.9, 25-29.9, and ≥ 30 (≥ 20 years), respectively.

RESULTS

Among a total of 205,425 patients, 5.7% received CED ≥ 100 mSv (mean 184 mSv, maximum 1165 mSv) and their ages were mostly 50-64 years (34.1%), followed by 65-74 years (29.8%), ≥ 75 years (19.5%), 20-49 years (16.3%), and ≤ 19 years (0.29%). Body habitus in decreasing occurrence was obese (38.6%), overweight (31.9%), healthy weight (27.5%), and underweight (2.1%). Classification by dose indicated 172 patients (≥ 500 mSv) and 3 (≥ 1000 mSv). In comparison, 5.3% of 189,030 CT patients, 1.6% of 18,963 FGI patients, and 0.19% of 41,401 nuclear-medicine patients received CED ≥ 100 mSv from a single modality.

CONCLUSIONS

The study of total dose from CT, FGI, and nuclear medicine of patients with CED ≥ 100 mSv indicates major (89%) contribution of CT to CED with 70% of cohort being obese and overweight, and 64% of cohort aged 50-74 years.

CLINICAL RELEVANCE STATEMENT

Multimodality recurrent exams are common and there is a lack of information on patient cumulative radiation exposure. This study attempts to address this lacuna and has the potential to motivate actions to improve the justification process for enhancing patient safety.

KEY POINTS

• In total, 5.7% of patients undergoing multimodality recurrent imaging (CT, fluoroscopically guided intervention, nuclear medicine) incurred a dose of ≥ 100 mSv. • Mean dose was 184 mSv, with 15 to 18 times contribution from CT than that from fluoroscopically guided intervention or nuclear medicine. • In total, 70% of those who received ≥ 100mSv were either overweight or obese.

Evaluation of patient radiation dose and risk of cancer from CT examinations

Computed tomography (CT) examinations have been increasingly requested and become the major sources of patient exposure. The cancer risk from CT scans is contingent upon the amount of absorbed dose of organs. This study aims to determine the organ doses and risk of cancer incidence and mortality from CT examinations at high dose (cumulative effective dose, CED ≥ 100 mSv) in a single day to low dose (CED < 100 mSv) from common CT procedures. Data were gathered from two academic centers of patients aged 15 to 75 years old performed CT examinations during the period of 5 years. CED and organ dose were calculated using Monte Carlo simulation software. Lifetime attributable risk (LAR) was determined following Biological Effects of Ionizing Radiation (BEIR) VII report based on life table and baseline cancer rates of Thai population. At high dose, the highest LAR for breast cancer incidence in young female was 82 per 100,000 exposed patients with breast dose of 148 mGy (CT whole abdomen). The highest LAR for liver cancer incidence in male patient was 72 per 100,000 with liver dose of 133 mGy (multiple CT scans). At low dose, the highest average LAR for breast cancer incidence in young female was 23 per 100,000 while for liver cancer incidence in male patients was 22 per 100,000 (CTA whole aorta). Even though the LAR of cancer incidence and mortality was less than 100 per 100,000, they should not be neglected. The risk of cancer incidence may be increased in later life, particularly in young patients.

Lattice engineering for stabilized black FAPbI3 perovskite single crystals for high-resolution x-ray imaging at the lowest dose

Preliminary theoretical analyses indicate that lattice relaxation may be used to release lattice strain in the FAPbI3 perovskite to warrant both high x-ray detection performance and improved stability. Herein, we demonstrate stable black α-phase FAPbI3 single crystals (SCs) realized by lattice engineering via annealing in the ambient atmosphere. The engineered α-FAPbI3 SC detector shows almost all the best figures of merit including a high sensitivity of 4.15 × 105 μC Gyair-1 cm-2, a low detection limit of 1.1 nGyair s-1, a high resolution of 15.9 lp mm-1, and a short response time of 214 μs. We further demonstrate high-definition x-ray imaging at a dose rate below 10 nGyair s-1 on the FAPbI3 SC, indicating a minimal dose-area product of 0.048 mGyair cm2 to the patient for one-time posteroanterior chest diagnosis, which is more than 3000 times lower than the international reference level of 150 mGyair cm2. In addition, the robust long-term stability enables the FAPbI3 SC x-ray detector to work steadily for more than 40 years.

Radiation dose management system in computed tomography procedures: a systematic review

A systematic literature review was carried out to explore articles that reported the use of radiation dose management systems (RDMSs) in computed tomography (CT). The preferred reporting items for systematic review and meta-analysis flow chart were used to screen articles in PubMed, EBSCOhost, Web of Science, SCOPUS and Cochrane Library. A total of 1041 articles were retrieved and screened. After evaluation against criteria, 38 articles were selected and synthesised narratively. The results revealed that several RDMSs have been used in CT. The review also indicated that the use of RDMSs has promoted the implementation of diagnostic reference levels for dose optimisation. A RDMS, such as DoseWatch, is associated with compatibility challenges and failure in data transmission, while manual RDMSs are cumbersome and prone to data entry errors. Thus, a robust automated RDMS that is compatible with the different CT systems would provide efficient CT dose management.

Assessment of cumulative cancer risk attributable to diagnostic X-ray radiation: a large cohort study

OBJECTIVE

To assess the risk of cancer induced by diagnostic X-ray exposure in multiple radiological examinations and to explore the relevant influences to provide a reference for rational usage of X-ray examinations.

METHODS

Data for all adult patients who underwent X-ray examinations from August 2004 to April 2020 in a general hospital was collected, including sex, age, primary diagnosis, and X-ray examination. Based on the Biological Effects of Ionizing Radiations report, age and sex and effective dose for a single X-ray examination were used to calculate the lifetime attributable risk (LAR). Patients whose cancer LAR values were in the top 5% were considered to have a high cancer risk; the factors influencing this status were explored by using multivariate logistic regression analyses.

RESULTS

In total, 1,143,413 patients with 3,301,286 X-ray examinations were included. LARs of cancer incidence and death were < 0.2% and < 0.13% among 95% of patients and they were > 1% among 0.21% and 0.07% of patients. High risks of incidence and death were significantly associated with corrected exposure frequency (odds ratio [OR], 1.080 and 1.080), sex (OR, male vs. female, 0.421 and 0.372), and year of birth (OR, 1.088 and 1.054), with all p values < 0.001. Among 20 disease categories, congenital disease (OR, 3.792 and 4.024), genitourinary disease (OR, 3.608 and 3.202), digestive disease (OR, 3.247 and 3.272), and tumor disease (OR, 2.706 and 2.767) had the strongest associations with high risks of incidence and death (all p values < 0.001).

CONCLUSIONS

Cancer risk induced by diagnostic X-ray examinations can be considered acceptable clinically. Patients having certain diseases are potentially at a relative higher risk due to recurrent examinations.

KEY POINTS

• It was the first large-scale investigation of cumulative X-ray exposure in China, involving more than 3.3 million X-ray scans of all types of diagnostic X-ray examinations for about 1.1 million patients during the past 16 years. • The study revealed that the incidence risk of cancer induced by X-ray-related examinations was 0.01% on average, which was substantially lower than that of cancer induced by non-X-ray radiation. The risk could be considered acceptable clinically. • Patients having certain diseases were potentially at a relatively higher cancer risk due to recurrent X-ray examinations. The cumulative effect of X-ray exposure could not be ignored and was worthy of attention.

Accounting for radiation exposure from previous CT exams while deciding on the next exam: What do referring clinicians think?

PURPOSE

To obtain clinicians' views of the need to account for radiation exposure from previous CT scans and the advisability of a regulatory mechanism to control the number of CT scans for an individual patient.

METHODS

A convenience survey was conducted by emailing a link to a three-question electronic survey to clinicians in many countries, mostly through radiology and radiation protection contacts.

RESULTS

505 responses were received from 24 countries. 293 respondents (58%) understand that current regulations do not limit the number of CT scans that can be prescribed for a single patient in a year. When asked whether there should be a regulation to limit the number of CT scans that can be prescribed for a single patient in one year, only a small fraction (143, 28%) answered 'No', 182 (36%) answered 'Maybe' and 166 (33%) answered 'Yes'. Most respondents (337; 67%) think that radiation risk should form part of the consideration when deciding whether to request a CT exam. A minority (138; 27%) think the decision should be based only on the medical indication for the CT exam. Comparison among the 4 countries (South Korea, Hungary, USA and Canada) with the largest number of respondents indicated wide variations in responses.

CONCLUSIONS

A majority of the surveyed clinicians consider radiation risk, in addition to clinical factors, when prescribing CT exams. Most respondents are in favor of, or would consider, regulation to control the number of CT scans that could be performed on a patient annually.

Comparison of patient effective doses from multiple CT examinations based on different calculation methods

The aim of this study is to compare effective dose (E) estimations based on different methods for patients with recurrent computed tomography (CT) examinations. Seventeen methods were used to determine the E of each phase as well as the total E of the CT examination. These included three groups of estimations: based on the use of published E, calculated from typical or patient-specific values of volume computed tomography dose index (CTDI_vol) and dose-length product (DLP) multiplied by conversion coefficients, and based on patient-specific calculations with use of software. The E from a single phase of the examination varied with a ratio from 1.3 to 6.8 for small size patients, from 1.2 to 6.5 for normal size patients, and from 1.7 up to 18.1 for large size patients, depending on the calculation method used. The cumulative effective dose (CED) ratio per patient for the different size groups varied as follows: from 1.4 to 2.5 (small), from 1.7 to 4.3 (normal), and from 2.2 up to 6.3 (large). The minimum CED across patients varied from 38 up to 200 mSv, while the variation of maximum CED was from 122 up to 538 mSv. Although E is recommended for population estimations, it is sometimes needed and used for individual patients in clinical practice. Its value is highly dependent on the method applied. Individual estimations of E can vary up to 18.1 times and CED estimations can differ up to 6 times. The related large uncertainties should always be taken into account.

Establishment of national diagnostic reference levels for percutaneous coronary interventions (PCIs) in Thailand

PURPOSE

To establish national diagnostic reference levels (DRLs) for percutaneous coronary intervention (PCI) in Thailand for lesions of different complexity.

METHODS

Radiation dose quantity as kerma-area-product (KAP) and cumulative air-kerma at reference point (CAK) from 76 catheterization labs in 38 hospitals in PCI registry of Thailand was transferred online to central data management. Sixteen months data (May 2018 to August 2019) was analyzed. We also investigated role of different factors that influence radiation dose the most.

RESULTS

Analysis of 22,737 PCIs resulted in national DRLs for PCI of 91.3 Gy.cm² (KAP) and 1360 mGy (CAK). The NDRLs for KAP for type C, B2, B1 and A lesions were 106.8, 82.6, 67.9, and 45.3 Gy.cm² respectively and for CAK, 1705, 1247, 962, and 790 mGy respectively. Thus, as compared to lesion A, lesion C had more than double the dose and B2 had nearly 1.6 times and B1 had 1.2 times CAK. Our DRL values are lower than other Asian countries like Japan and Korea and are in the middle range of Western countries. University hospital had significantly higher dose than private or public hospital possibly because of higher load of complex procedures in university hospitals and trainees performing the procedures. Transradial approach showed lower doses than transfemoral approach.

CONCLUSIONS

This large multi-centric study established DRLs for PCIs which can act as reference for future studies. A hallmark of our study is establishment of reference levels for coronary lesions classified as per ACC/AHA and thus for different complexities.

Strategies for Dose Optimization: Views From Health Care Systems

BACKGROUND

Advances in CT have facilitated widespread use of medical imaging while increasing patient lifetime exposure to ionizing radiation.

PURPOSE

To describe dose optimization strategies used by health care organizations to optimize radiation dose and image quality.

MATERIALS AND METHODS

A qualitative study of semistructured interviews conducted with 26 leaders from 19 health care systems in the United States, Europe, and Japan. Interviews focused on strategies that were used to optimize radiation dose at the organizational level. A directed content analysis approach was used in data analysis.

RESULTS

Analysis identified seven organizational strategies used by these leaders for optimizing CT dose: (1) engaging radiologists and technologists, (2) establishing a CT dose committee, (3) managing organizational change, (4) providing leadership and support, (5) monitoring and benchmarking, (6) modifying CT protocols, and (7) changes in equipment and work rules.

CONCLUSIONS

Leaders in these health systems engaged in specific strategies to optimize CT dose within their organizations. The strategies address challenges health systems encounter in optimizing CT dose at the organizational level and offer an evolving framework for consideration in dose optimization efforts for enhancing safety and use of medical imaging.

Referring physician perspective on how to handle frequent use of CT imaging

The increasing use of computed tomography (CT) and other relatively high radiation dose exams in a recurrent manner result in radiation risks to individual patients. Recent studies have provided alarming information not only to the radiological community but also to referring physicians. We, as referring physicians, are often implicated in the overuse of imaging. However, a recent paper rightfully summarized the situation that despite the best use of available clinical decision support system for prescribing an imaging exam at a major hospital in the USA, many patients were found to have high cumulative doses. Motivated by the cue provided by the paper in this very journal, we decided to come forward with a possible solution taking the example of the drug prescription system that we routinely use. We provide a template to translate prescription drug monitoring program to ionising radiation imaging. We suggest that all body CT exams should be monitored at an individual, prescriber, and institution level for frequency of use. Furthermore, there should be radiation risk stratification of an individual patient based on the cumulative radiation burden in recent years. Further, an individual's radiation risk-stratified in different risk levels should be available for use by the referring/ordering clinicians at the point of care. Finally, we feel distanced by the use of multiple scary radiation dose quantities in different imaging modalities and would prefer as simple a metric as 'milligram.'

Assessment of patients' cumulative doses in one year and collective dose to population through CT examinations

PURPOSE

To estimate percentage of patients undergoing multiple CT exams leading to cumulative effective dose (CED) of more than 25, 50, 75 and 100 mSv in one year and assess per capita and the collective effective dose.

METHODS

Data from a regional hospital network was collected retrospectively using radiation dose monitoring system at 6 facilities with 8 CT scanners. The data was analyzed to find number of patients in different dose groups, their age, gender, number of CT exams and exams needed to reach 100 mSv based on age groups.

RESULTS

In one year 43,010 patients underwent 75,252 CT examinations. The number of exams per 1000 population was 153. Further 27% of the patients were younger than 55- years and 15.9% of them were younger than 45-year-old. A total of 0.67% of patients received a CED > 100 mSv; 3.5% had CED > 50 mSv, 11.9% with CED > 25 mSv and the maximum CED was 529 mSv. The minimum time to reach 100 mSv was a single CT exam. Seven patients received > 100 mSv in a single CT exam. 0.36% of patients had 10 or more CT exams in one year and 3.8% had 5 or more CT exams. The mean CED was 12.3 mSv, the average individual effective dose was 1.1 mSv and the collective effective dose was 521.3 person-Sv.

CONCLUSIONS

The alarming high CED received by large number of patients and with high collective dose to population requires urgent actions by all stake holders in the best interest of patient radiation safety.

Old enemy, new threat: you can't solve today's problems with yesterday's solution

The radiation protection principles of justification, optimization, and dose limitation as enumerated by the International Commission on Radiological Protection have been guiding light for the profession for over three decades. The dose limitation does not apply to medical exposure but keeping patients' doses low is achieved through optimization, particularly by developing and using diagnostic reference levels (DRLs). There are new findings that demonstrate that despite using the best possible approaches to justification and optimization including as well use of DRLs, a very large number of patients are receiving doses in excess of 100 mSv of effective dose or organ doses exceeding 100 mGy. A non-ignorable fraction of patients is receiving such high doses in a single day. The magnitude of such patients creates the need for a relook into the principles with the intent to understand what can be done to attend to today's problems. A look at other areas such as approaches, and principles used in the pharmaceutical industry and in traffic management throws some light into what can be learnt from these examples. It appears that the system needs to be enriched to deal with the protection of the individual patient. The currently available approaches and even the principles are largely based on the protection of the population or group of patients. The third level of justification for individual needs further refinement to take into account series of imaging many patients are needing, and cumulative radiation doses involved, many of which happen in a short duration of 1 to 5 years. There is every likelihood of patient radiation doses continuing to increase further that underscores the need for timely attention. This paper provides several suggestions to deal with the situation.