From the Department of Diagnostic and Interventional Radiology and Neuroradiology, German Armed Forces Hospital Ulm, Ulm.
Department of Radiology, University Hospital of Ulm, Ulm, Germany.
Invest Radiol. 2022 Dec 1;57(12):789-801. doi: 10.1097/RLI.0000000000000898. Epub 2022 Jun 30.
Low-dose (LD) computed tomography (CT) is still rarely used in musculoskeletal (MSK) radiology. This study evaluates the potentials of LD CT for follow-up pelvic imaging with special focus on tin filtration (Sn) technology for normal and obese patients with and without metal implants.
In a phantom study, 5 different LD and normal-dose (ND) CT protocols with and without tin filtration were tested using a normal and an obese phantom. Iterative reconstruction (IR) and filtered back projection (FBP) were used for CT image reconstruction. In a subsequent retrospective patient study, ND CT images of 45 patients were compared with follow-up tin-filtered LD CT images with a 90% dose reduction. Sixty-four percent of patients contained metal implants at the follow-up examination. Computed tomography images were objectively (image noise, contrast-to-noise ratio [CNR], dose-normalized contrast-to-noise ratio [CNRD]) and subjectively, using a 6-point Likert score, evaluated. In addition, the figure of merit was calculated. For group comparisons, paired t tests, Wilcoxon signed rank test, analysis of variance, or Kruskal-Wallis tests were used, where applicable.
The LD Sn protocol with 67% dose reduction resulted in equal values in qualitative (Likert score) and quantitative image analysis (image noise) compared with the ND protocol in the phantom study. For follow-up examinations, dose could be reduced up to 90% by using Sn LD CT scans without impairment in the clinical study. However, metal implants resulted in a mild impairment of Sn LD as well as ND CT images. Cancellous bone ( P < 0.001) was assessed worse and cortical bone ( P = 0.063) equally in Sn LD CT images compared with ND CT images. Figure of merit values were significant ( P ≤ 0.02) lower and hence better in Sn LD as in ND protocols. Obese patients benefited in particular from tin filtration in LD MSK imaging in terms of image noise and CNR ( P ≤ 0.05).
Low-dose CT scans with tin filtration allow maximum dose reduction while maintaining high image quality for certain clinical purposes, for example, follow-up examinations, especially metal implant position, material loosening, and consolidation controls. Overweight patients benefit particularly from tin filter technology. Although metal implants decrease image quality in ND as well as in Sn LD CT images, this is not a relevant limitation for assessability.
低剂量（LD）计算机断层扫描（CT）在肌肉骨骼（MSK）放射学中仍很少使用。本研究评估了 LD CT 用于骨盆随访成像的潜力，特别关注锡滤过（Sn）技术在有和没有金属植入物的正常和肥胖患者中的应用。
在一项体模研究中，使用正常体模和肥胖体模测试了 5 种不同的 LD 和正常剂量（ND）CT 方案，包括有和没有锡滤过的方案。迭代重建（IR）和滤波反投影（FBP）用于 CT 图像重建。在随后的回顾性患者研究中，将 45 例患者的 ND CT 图像与随访的 90%剂量降低的锡滤过 LD CT 图像进行比较。64%的患者在随访检查时存在金属植入物。使用 6 分李克特量表对 CT 图像进行客观（图像噪声、对比噪声比[CNR]、剂量归一化对比噪声比[CNRD]）和主观评估。此外，还计算了优值。对于组间比较，在适用的情况下使用配对 t 检验、Wilcoxon 符号秩检验、方差分析或 Kruskal-Wallis 检验。
在体模研究中，与 ND 方案相比，LD Sn 方案（剂量降低 67%）在定性（李克特评分）和定量图像分析（图像噪声）方面产生了等效值。对于随访检查，通过使用 Sn LD CT 扫描，可以将剂量降低高达 90%，而不会影响临床研究。然而，金属植入物会导致 Sn LD 和 ND CT 图像的轻微损害。与 ND CT 图像相比，松质骨（P<0.001）的评估较差，皮质骨（P=0.063）的评估相同。优值在 Sn LD 中显著（P≤0.02）较低，因此优于 ND 方案。肥胖患者特别受益于 LD MSK 成像中的锡滤过技术，在图像噪声和 CNR 方面（P≤0.05）。
对于某些临床目的，例如随访检查，特别是金属植入物位置、材料松动和骨愈合监测，具有锡滤过的 LD CT 扫描可以在保持高图像质量的同时最大程度地降低剂量。超重患者特别受益于锡滤过技术。尽管金属植入物会降低 ND 和 Sn LD CT 图像的质量，但这不是可评估性的相关限制。
