Abstract
PurposeTo evaluate dual-energy CT (DE) and dedicated metal artifact reduction algorithms (iMAR) during CT-guided biopsy in comparison to single-energy CT (SE).MethodsA trocar was placed in the liver of six pigs. CT acquisitions were performed with SE and dose equivalent DE at four dose levels(1.7–13.5mGy). Iterative reconstructions were performed with and without iMAR. ROIs were placed in four positions e.g. at the trocar tip(TROCAR) and liver parenchyma adjacent to the trocar tip(LIVER-1) by two independent observers for quantitative analysis using CT numbers, noise, SNR and CNR. Qualitative image analysis was performed regarding overall image quality and artifacts generated by iMAR.ResultsThere were no significant differences in CT numbers between DE and SE at TROCAR and LIVER-1 irrespective of iMAR. iMAR significantly reduced metal artifacts at LIVER-1 for all exposure settings for DE and SE(p = 0.02-0.04), but not at TROCAR. SNR, CNR and noise were comparable for DE and SE. SNR was best for high dose levels of 6.7/13.5mGy. Mean difference in the Blant-Altman analysis was -8.43 to 0.36. Cohen’s kappa for qualitative interreader-agreement was 0.901.ConclusionsiMAR independently reduced metal artifacts more effectively and efficiently than CT acquisition in DE at any dose setting and its application is feasible during CT-guided liver biopsy.
Highlights
CT-guided biopsy enables accurate tumor localization, intraprocedural monitoring and confirmation of needle position directly before obtainment of histological samples with a reported accuracy of 86% - 98% [1,2,3]
There were no significant differences in CT numbers between dual-energy CT (DE) and single-energy CT (SE) at TROCAR and LIVER-1 irrespective of iterative Metal Artifact Reduction (iMAR). iMAR significantly reduced metal artifacts at LIVER-1 for all exposure settings for DE and SE(p = 0.02-0.04), but not at TROCAR
signal-to-noise ratio (SNR), CNR and noise were comparable for DE and SE
Summary
CT-guided biopsy enables accurate tumor localization, intraprocedural monitoring and confirmation of needle position directly before obtainment of histological samples with a reported accuracy of 86% - 98% [1,2,3]. CT scans with contrast agent did not achieve better biopsy results compared to non-contrast CT [1]. The visibility of liver lesions during CT-guided biopsy is significantly reduced by metal artifacts caused by the biopsy needle, leading to insufficient visualization especially for small lesions with diameters less than 3 cm or when using an intercostal or subcostal access [1]. As shown by Stattaus et al, the insufficient visualization of small lesions leads to an increased rate of false-negative biopsy results of 12.8% in comparison to lesions with good visibility. While changing window settings can reduce metal artifacts induced by the biopsy needle, at the same time the soft tissue contrast and the visibility of the liver lesion is reduced. Removing the canulae inside the trocar and using a smaller-gauge guide can reduce needle artifacts significantly [4]
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