# Diagnostic Performance of CT-like Images for Lumbar Pedicle Screw Planning and Spinal Canal Area Measurement: A Comparative Study with Conventional CT and MRI

## TL;DR

This study shows that CT-like images from MRI can reliably replace traditional CT scans for spine surgery planning, reducing radiation exposure and workload.

## Contribution

Demonstrates that CT-like images from MRI provide accurate measurements for spinal surgery comparable to conventional CT and MRI.

## Key findings

- CT-like images showed excellent agreement with CT for pedicle width and length measurements.
- CT-like images provided good to excellent agreement with MRI for spinal canal area assessment.
- The use of CT-like images could reduce the need for additional CT scans before spine surgery.

## Abstract

Computed tomography (CT) is often required before spine surgery to measure bone anatomy, even though magnetic resonance imaging (MRI) is already performed for nerve and soft-tissue evaluation. This leads to additional radiation exposure and increased clinical workloads. In this study, we evaluated whether CT-like images generated from MRI can provide measurements comparable to conventional CT for pedicle screw selection and assessing the spinal canal. Our results show that CT-like images offer reliable and clinically acceptable measurements. These findings suggest that a single MRI examination may support comprehensive preoperative spinal assessment, potentially reduce radiation exposure and improve clinical workflow.

Background: Although magnetic resonance imaging (MRI) provides excellent soft-tissue contrast for most spinal evaluations, computed tomography (CT) is still always required for preoperative planning to assess osseous anatomy and determine surgical device size, increasing the radiation exposure and workflow complexity. CT-like images enable visualization of precise bone morphology without ionizing radiation. In addition, these images often provide CT myelography-like contrasts, allowing the simultaneous depiction of the spinal canal area (SCA). This study aimed to evaluate whether CT-like images provide measurement accuracy equivalent to conventional CT and MRI for pedicle screw planning and spinal canal area assessment. Methods: We retrospectively analyzed paired lumbar CT and MRI datasets obtained within ≤1 month in 51 patients. Pedicle width and length were measured on CT and CT-like images, whereas SCA was measured on T2 weighed-images and CT-like images. A total of 224 vertebrae were analyzed. Annotated images were independently evaluated by two readers in a randomized order. Inter-modality agreement was assessed using intraclass correlation coefficients (ICCs) and a Bland–Altman analysis. Results: CT-like images demonstrated an excellent agreement with CT for pedicle measurements (ICCs: 0.968–0.985 for width; 0.922–0.966 for length). Mean differences were ≤0.1 mm for pedicle width and approximately 1 mm for pedicle length, which are unlikely to affect screw selection. The agreement with T2WI for SCA was good to excellent (ICCs: 0.766–0.945). Conclusions: CT-like images provide comparable performance for quantitative pedicle assessment and show high agreement for SCA evaluation, supporting comprehensive preoperative assessment with a single MRI examination.