Radiation risk issues in recurrent imaging

Abstract

Millions of patients benefit from medical imaging every single day. However, we have entered an unprecedented era in imaging practices wherein 1 out of 125 patients can be exposed to effective dose >50 mSv from a single CT exam and 3 out of 10,000 patients undergoing CT exams could potentially receive cumulative effective doses > 100 mSv in a single day. Recurrent imaging with CT, fluoroscopically guided interventions, and hybrid imaging modalities such as positron emission tomography/computed tomography (PET/CT) is more prevalent today than ever before. Presently, we do not know the cumulative doses that patients may be receiving across all imaging modalities combined. Furthermore, patients with diseases with longer life expectancies are being exposed to high doses of radiation enabling radiation effects to manifest over a longer time period. The emphasis in the past on improving justification of imaging and optimization of technique and practice has proved useful. While that must continue, the current situation requires imaging device manufacturers to urgently develop imaging technologies that are safer for patients as high doses have been observed in patients where imaging has been justified through clinical decision-support and optimized by keeping doses below the national benchmark doses. There is a need to have a critical look at the fundamental principles of radiation protection as cumulative doses are likely to increase in the coming years.

Patients undergoing multiple 18F-FDG PET/CT scans: frequency, clinical indications, and cumulative dose

“…The important findings of this largest ever 11-year study covering 55,424 18 FDG-PET/CT exams in 32,658 patients for assessing the frequency of patients with multiple exams include: 24.2% patients scanned 2-5 times in a year, 16.7% of them being unique patients (not counted as a separate patient in multiple years); the maximum number of PET/CT scans in a year of 5; 82% of the patient cohort with malignant disease; 2.4% of the patients with ≥ 2 18 F-FDG PET/CT scans in a year were with non-malignant indications; 1.4% patients received a total effective dose above 100 mSv in one year from multiple 18 F -FDG PET/CT scans and 0.8% of them received ≥ 100 mSv in a year more than one time; the CED of 27.8% (9087 patients) who underwent 2 to 23 18 F -FDG PET/CT scans over 11 years ranged 38 to 575 mSv (median: 271 mSv). It must be noted that 100 mSv is neither a dose limit nor threshold for radiation effect, but a number of organizations including UNSCEAR [13] have mentioned a low dose as dose below 100 mSv and it has been used in recent years as a level in many recent studies to draw attention to high doses [10,14,15]. This comprehensive study is the largest study, to the best of our knowledge, and that too from a country where tools for radiation dose assessment, such as commercial dose management systems are hardly available.…”

Patients Undergoing Multiple 18F-FDG PET/CT Scans: 11-Year Study At A High-Capacity Center

“…Thus, modern dose management systems do not typically provide dose from radiopharmaceutical part just as they do for CT part [20]. Despite limitations of E, it has not been replaced and in fact for multiple exams of a single patient covering different body parts, it remains the only dose quantity and as a result it has been used increasingly [21,22]. ICRP in its recent report has clari ed use of E that allows use of this dose quantity albeit with understanding for situations where there were doubts of its use [19,22].…”

How should radiation exposure be handled in fluoroscopy‐guided endoscopic procedures in the field of gastroenterology?

“…As the latest review described, the current consensus requires imaging device manufacturers to urgently develop imaging technologies that are safer for patients 56 …”

“…As the latest review described, the current consensus requires imaging device manufacturers to urgently develop imaging technologies that are safer for patients. 56 The grid-controlled pulsed fluoroscopy unit has been reported to achieve significantly lower patient doses without the loss of diagnostic accuracy for various abdominal and pelvic fluoroscopic examinations. 57 The image processing technique of frame rate conversion (FRC) can provide images at a frame rate twice the X-ray pulse rate by interpolating from two consecutive fluoroscopic images.…”