Abstract
PurposeFeasibility of a highly reduced-dose lumbar spine CT protocol using iterative reconstruction (IR) in a human cadaver model.Materials and methodsThe lumbar spine of 20 human cadavers was repeatedly examined using three different reduced-dose protocols (RDCT) with decreasing reference tube current-exposure time products (RDCT-1: 50 mAs; RDCT-2: 30 mAs; RDCT-3: 10 mAs) at a constant tube voltage of 140 kV. A clinical standard-dose protocol (SDCT) served as the reference (reference tube current–exposure time product: 70 mAs; tube voltage: 140 kV). Images were reconstructed using filtered back projection (FBP) and two increasing levels of IR: IRL4 and IRL6. A five-point scale was used by two observers to assess the diagnostic quality of anatomical structures (cortical and trabecular bone, intervertebral foramina, pedicles and intervertebral joints, spinous and transverse processes). Objective image noise (OIN) was measured. Results were interpreted using a linear mixed-effects regression model.ResultsRDCT-2 with IRL6 (1.2 ± 0.5mSv) was the lowest reduced-dose protocol which provided diagnostically acceptable and equivalent image quality compared to the SDCT (2.3 ± 1.1mSV) with FBP (p > 0.05). All RDCT protocols achieved a significant reduction of the mean (±SD) effective radiation doses (RDCT-1: 1.7±0.9mSv; RDCT-2: 1.2±0.5mSv; RDCT-3: 0.4±0.2mSv; p < 0.05) compared to SDCT. OIN was lower in all RDCT protocols with the application of IRL4 and IRL6, compared to the SDCT with FBP (p < 0.05).ConclusionHighly reduced-dose lumbar spine CT providing diagnostically acceptable image quality is feasible using IR in this cadaver model and may be transferred into a clinical setting.
Highlights
Plain radiography of the skeleton, including the lumbar spine, is commonly performed, accounting for nearly 30% of all radiographic exams ordered in Germany [1,2,3]
All reduced-dose protocols (RDCT) protocols achieved a significant reduction of the mean (±standard deviation (SD)) effective radiation doses (RDCT-1: 1.7±0.9mSv; RDCT-2: 1.2±0.5mSv; RDCT3: 0.4±0.2mSv; p < 0.05) compared to standard dose CT (SDCT)
Objective image noise (OIN) was lower in all RDCT protocols with the application of IRL4 and IRL6, compared to the SDCT with filtered back projection (FBP) (p < 0.05)
Summary
Plain radiography of the skeleton, including the lumbar spine, is commonly performed, accounting for nearly 30% of all radiographic exams ordered in Germany [1,2,3]. The radiation dose of a two-view radiograph of the lumbar spine is reported to be around 1.1 mSv [1]. Lumbar spine CT exposes patients to high doses of ionizing radiation, with reported values up to 19 mSv [8,9]. Following the ALARAprinciples (as low as reasonably achievable), a reduction of ionizing radiation in standard dose CT (SDCT), without compromising image quality, is required [12]. Dose reduction alone is associated with increasing image noise, resulting in impaired image quality
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