Abstract
The aim of this study was to evaluate the implications of low radiation dose in abdominal computed tomography (CT) when combined with noise reduction filters and to see if this approach can overcome the challenges that arise while scanning obese patients. Anthropomorphic phantoms layered with and without 3-cm-thick circumferential animal fat packs to simulate different sized patients were scanned using a 128-slice multidetector CT (MDCT) scanner. Abdominal protocols (n = 12) were applied using various tube currents (150, 200, 250, and 300 mA) and tube voltages (100, 120, and 140 kVp). MOSFET dosimeters measured the internal organ dose. All images were reconstructed with filtered back projection (FBP) and different iterative reconstruction (IR) strengths (SAFIRE 3, SAFIRE 4, and SAFIRE 5) techniques and objective noise was measured within three regions of interests (ROIs) at the level of L4–L5. Organ doses varied from 0.34–56.2 mGy; the colon received the highest doses for both phantom sizes. Compared to the normal-weighted phantom, the obese phantom was associated with an approximately 20% decrease in effective dose. The 100 kVp procedure resulted in a 40% lower effective dose (p < 0.05) compared to at 120 kVp and the associated noise increase was improved by increasing the IR (5) use, which resulted in a 60% noise reduction compared to when using FBP (p < 0.05). When combined with iterative reconstruction, the low-kVp approach is feasible for obese patients in order to optimize radiation dose and maintain objective image quality.
Highlights
The prevalence of obese patients undergoing computed tomography (CT) continues to increase
Significant reductions in CTDIvol, dose length product (DLP)(mGy·cm), and effective dose were seen when the tube potential was reduced from 120 to 100 kVp and an approximately 56% reduction was seen when the 140 kVp strength was reduced to 100 (p < 0.05)
Our findings showed up to a 40% dose reduction with a comparable noise level for the obese condition when iterative reconstruction (IR) was used for the protocol at 100 kVp compared to the protocols using 120 kVp and filtered back projection (FBP) for the matched tube current values
Summary
The prevalence of obese patients undergoing computed tomography (CT) continues to increase. Bariatric imaging is associated with both technical limitations and potentially compromised image quality in CT [1,2,3,4], as increased radiation output is required to compensate for the additional absorption of the X-ray beams and the reduction of signals reaching the CT detector. This results in higher patient doses, depending on patient shape, size, and composition [5]. Development of a CT dose reduction protocol is recommended to avoid unnecessary radiation risk
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