Helical CT with variable target noise levels for dose reduction in chest, abdomen and pelvis CT
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To evaluate a contiguous helical CT protocol with two different target noise levels in chest/abdomen/pelvis CT.
41 patients (study group) underwent a helical scan (P1) with two different target noise levels (SDs), SD = 16 for chest and SD = 13 for abdomen/pelvis. Two further protocols were planned but not executed: a single helical scan with only one SD (SD = 13) for the entire scan range (P2), and two separate helical scans overlapping over the liver and same SD settings as for P1 (P3). All DLPs were recorded. Image quality was assessed qualitatively and quantitatively on all scans. The control group consisted of 40 patients, was scanned with protocol P3 and analysed using the same metrics.
DLPs (mean/SD) for P1, P2 and P3 were 859.5/392.9, 1040.2/510.5 and 1027.4/469.4, respectively. P1 offered a mean dose reduction of 17.4% compared to P2, and 16.3% compared to P3 (both p < 0.001). There were no differences in image quality between both patient groups (p > 0.3).
Contiguous helical scanning of the chest/abdomen/pelvis with variable target noise levels results in approximately 17% dose reduction if compared to a single acquisition with only abdominal dose settings or two separate acquisitions of the chest and abdomen/pelvis.
• Low dose chest and standard abdomen CTs can be combined.
• Variable SD CT scanning allows for radiation dose reduction.
• Variable SD CT scanning maintains image quality.
KeywordsWhole body CT Dose reduction Dose modulation Image quality CT technique
Automatic exposure control
Exposure direction for the scout view, anteroposterior
Body mass index
Dose length product measured in mGy cm
Tube current measured in milliampere
Maximum intensity projection
Region of interest
Standard deviation of image noise expressed in Hounsfield units
Compliance with ethical standards
The scientific guarantor of this publication is Patrik Rogalla.
Conflict of interest
The authors of this manuscript declare relationships with the following companies: Toshiba Medical Systems, Canon Group.
Statistics and biometry
No complex statistical methods were necessary for this paper.
Written informed consent was obtained from all subjects (patients) in this study.
Institutional review board approval was obtained.
• diagnostic or prognostic study
• performed at one institution
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