SYSTEMATIC EVALUATION OF LOW-DOSE IMAGING FOR CT-GUIDED PERIRADICULAR INFILTRATIONS

Background: Periradicular infiltrations are frequently performed in neuroradiological routine and are planned and guided by multi-detector computed tomography (MDCT). The objective of this study was to evaluate image quality and confidence for planning of periradicular infiltrations using virtually lowered tube currents and iterative reconstruction (IR). Methods: Twenty patients (age: 54.9 [+ or -] 13.1 years) underwent MDCT for planning purposes of periradicular infiltrations at the level of the lumbosacral spine using a standard imaging protocol provided by the MDCT vendor. Planning scans were simulated as if they were made at 50% (D50), 10% (D10), 5% (D5), and 1% (D1) of the original tube current. Image reconstruction was achieved with two levels of IR (A: similar to clinical reconstructions, B: ten times stronger regularization). Two readers (R1 and R2) performed qualitative image evaluation considering overall image quality and artifacts, image contrast, determination of nerve roots (scoring: 1--possible, 2--unclear, and 3--not possible), and confidence for intervention planning (scoring: 1--high, 2--medium, and 3--low confidence). Result: Level A of IR was favorable regarding overall image quality, artifacts, and image contrast according to both readers, with preserved very good to excellent scores for D10. Similarly, level A of IR led to better scores for determination of nerve roots, with D10 still allowing for clear nerve root depiction in the majority of patients (D10 A: R1: 1.4 [+ or -] 0.5 vs. R2: 1.5 [+ or -] 0.5, p> 0.05). The confidence for intervention planning remained high for tube currents virtually lowered down to 5% of the original dose (D5 A: 1.4 [+ or -] 0.5 vs. R2: 1.4 [+ or -] 0.5, p > 0.05). Inter-reader agreement of confidence for intervention planning was good to excellent (weighted Cohen's kappa > 0.60). Conclusion: MDCT for planning purposes of lumbosacral periradicular infiltrations may be conducted with tube currents lowered down to 5% of standard imaging without restrictions in intervention planning confidence. Thus, radiation exposure could be decreased considerably.