IntroductionThe aim of this study was to establish institutional diagnostic reference levels (DRLs) by summarising doses collected across the five computed tomography (CT) system in our institution.Methods CT dose data of 15940 patients were collected retrospectively from May 2015 to October 2015 in five institutional scanners. The mean, 75th percentile and 90th percentile of the dose spread were calculated according to anatomic region. The common CT examinations such as head, chest, combined abdomen/pelvis (A/P), and combined chest/abdomen/pelvis (C/A/P) were reviewed. Distribution of CT dose index (CTDIvol), dose‐length product (DLP) and effective dose (ED) were extracted from the data for single‐phasic and multiphasic examinations.ResultsThe institutional DRL for our CT units were established as mean (50th percentile) of CTDIvol (mGy), DLP (mGy.cm) and ED (mSv) for single and multiphasic studies using the dose‐tracking software. In single phasic examination, Head: (49.0 mGy), (978.0 mGy.cm), (2.4 mSv) respectively; Chest: (6.0 mGy), (254.0 mGy.cm), (4.9 mSv) respectively; CT A/P (10.0 mGy), (514.0 mGy.cm), (8.9 mSv) respectively; CT C/A/P (10.0 mGy), (674.0 mGy.cm), (11.8 mSv) respectively. In multiphasic studies: Head (45.0 mGy), (1822.0 mGy.cm), (5.0 mSv) respectively; Chest (8.0 mGy), (577.0 mGy.cm), (10.0 mSv) respectively; CT A/P: (10.0 mGy), (1153.0 mGy.cm), (20.2 mSv) respectively; CT C/A/P: (11.0 mGy), (1090.0 mGy.cm), (19.2 mSv) respectively.ConclusionsThe reported metrics offer a variety of information that institutions can use for quality improvement activities. The variations in dose between scanners suggest a large potential for optimisation of radiation dose.

Patients and clinicians often raise concerns about radiation exposure to various organs during computerized tomography-based imaging. We evaluated radiation exposure during standard and low-dose imaging protocols for non-contrast computerized tomography, computerized tomography angiography and computerized tomography perfusion of the head. Whether reducing the radiation dose affected the image quality was also evaluated. Radiation data were retrieved for computerized tomography-based imaging studies performed for acute ischemic stroke patients during 2015. The volume-weighted computerized tomography dose index, dose-length product, scan length, effective dose and whole-body integral dose for brain, skin, eye, thyroid and red bone marrow were extracted from dose-tracking software. Dose metrics for low-dose protocols data were compared with standard protocols. The calculated effective doses for noncontrast computerized tomography, computerized tomography angiography and computerized tomography perfusion were 2.56 ± 0.67 mSv, 4.45 ± 2.5 mSv, and 4.47 ± 0.85 mSv, respectively for 391 acute ischemic stroke patients. Corresponding radiation exposures for lowdose protocol (n = 31) were non-contrast computerized tomography (2.36 ± 0.65 mSv), computerized tomography angiography (1.57 ± 0.74 mSv) and computerized tomography perfusion (2.20 ± 0.55 mSv). Overall, the effective dose for one complete stroke imaging protocol (non-contrast computerized tomography + computerized tomography angiography + computerized tomography perfusion) for the standard-dose protocol was 11.48 mSv, which was reduced to 6.13 mSv (46.6% reduction) using a low-dose protocol (p < 0.001). Reduced radiation exposure was noted for other radiosensitive organs. Radiation exposures of sensitive organs are within acceptable limits with standard neuroimaging protocols for acute ischemic stroke. Lower-dose computerized tomography imaging protocols reduced the radiation doses without appreciable deterioration in image quality.

No abstract

Background and aims: Recently, safety concerns were raised about the radiation dose for acute ischemic stroke (AIS) patients undergoing computed tomography (CT), CT angiography (CTA) and CT perfusion (CTP). We evaluated precise radiation dose to the brain during various imaging studies in our AIS patients. Methods: Brain imaging was performed with 64-detector row CT scanner (Phillips-iCT256) using standard protocols recommended by American Association of Physicist in Medicine. For each procedure, volume weighted CT dose index (CTDIvol, mGy) and dose-length product DLP (mGy.cm) were obtained from dose reports generated at the time of acquisition. Organ specific dose to brain, eye, bone marrow and thyroid were also obtained. The estimates of cancer risk were interpolated. Results: In this prospective study, a total of 18 patients who underwent CT, CTA as well as CTP were included. Mean DLP for non-enhanced CT, CTA and CTP were 1068.25, 1150 and 1197 mGy.cm, respectively. Corresponding whole body effective dose for the CT, CTA and CTP were calculated as 2.57, 2.6, 2.4 mSv, respectively. Cumulative doses to the brain, eyes, bone marrow and thyroid gland were 33.81, 32.8, 1.21 and 1.31 mGy for the non-contrast brain CT. CTDIvol measurements for different protocols tested by the phantom were in agreement with values given in dose reports. Conclusions: The effective radiation doses are less than previously reported and much below the radiation threshold level for deterministic effects for brain and optic lens (500-2000mGy). Estimated life-time attributable cancer risks are very low with the current radiation doses.