Radiation Dose Reduction in CT Torsion Measurement of the Lower Limb: Introduction of a New Ultra-Low Dose Protocol

Abstract

This study analyzed the radiation exposure of a new ultra-low dose (ULD) protocol compared to a high-quality (HQ) protocol for CT-torsion measurement of the lower limb. The analyzed patients (n = 60) were examined in the period March to October 2019. In total, 30 consecutive patients were examined with the HQ and 30 consecutive patients with the new ULD protocol comprising automatic tube voltage selection, automatic exposure control, and iterative image reconstruction algorithms. Radiation dose parameters as well as the contrast-to-noise ratio (CNR) and diagnostic confidence (DC; rated by two radiologists) were analyzed and potential predictor variables, such as body mass index and body volume, were assessed. The new ULD protocol resulted in significantly lower radiation dose parameters, with a reduction of the median total dose equivalent to 0.17 mSv in the ULD protocol compared to 4.37 mSv in the HQ protocol (p < 0.001). Both groups showed no significant differences in regard to other parameters (p = 0.344–0.923). CNR was 12.2% lower using the new ULD protocol (p = 0.033). DC was rated best by both readers in every HQ CT and in every ULD CT. The new ULD protocol for CT-torsion measurement of the lower limb resulted in a 96% decrease of radiation exposure down to the level of a single pelvic radiograph while maintaining good image quality.

Ultra-low dose CT for scaphoid fracture detection—a simulational approach to quantify the capability of radiation exposure reduction without diagnostic limitation

“…At the wrist, Neubauer et al (28) were able to show that a dose optimization has even greater potential in multi-detector CT imaging in comparison to cone beam CT, which permits a detailed bony architecture but is limited due to a smaller FOV and increased scattered radiation (29). More recently, an excellent cortical outline of bone structures in simulated ULD-CT imaging was achieved in torsion measurements of the lower limbs and the results were confirmed in real ULD-CT imaging (14,15). These findings are consistent with the results of our study indicating that ULD-CT imaging could be as accurate as high quality CT imaging of the wrist.…”

“…ULD-CT simulations were generated using the raw CT data sets from the initial high quality CT with the dedicated software package ReconCT (Version 14.2.0.40998, Siemens Healthineers) similar to previous studies (14)(15)(16)(17). Simulations were made at 20%, 10%, and 5% of the original dosage and were then compared to the original data sets (100% dose level).…”

“…A reduction of radiation dosage according to the ALARA principle ("as low as reasonably achievable) is essential in CT imaging whilst maintaining an acceptable image quality for the assessment of osseous structures. To generally reduce the radiation, scan parameters have been altered or postprocessing software used (12)(13)(14)(15). The aim of this study was to evaluate the effect of simulation of dose reduction on fracture detection and classification at the scaphoid, and diagnostic confidence (DC), whilst correlating this to the readers' experience in MSK radiology.…”

Ultra-low-dose CT is feasible for torsion measurement of the lower limb in patients with metal implants

“…In recent studies, we developed a new ultra-low dose CT (ULD-CT) protocol with the assistance of automated tube voltage and tube current time product modulation 10,11 for patients without metal implants. Since patients who need torsion measurements of the lower limb often have metal implants, the now presented study aims to analyze the feasibility of such a ULD-CT protocol and the radiation exposure in a patient group with metal implants in the lower limb.…”

SIZE-specific dose estimate for lower-limb CT

“…However, CT examinations for deep vein thrombosis and lower limb arteriosclerosis obliterans may involve a scan ranging from the torso to the lower limbs. In this case, the CTDI vol (z), Dose Length Product (DLP), and effective dose have been used as patient dose indices [9][10][11][12]. The f-factor (DLP to effective dose conversion factor) for the lower limbs is not expressed in the International Commission on Radiological Protection (ICRP) publication 102 [13], but several studies have been reported [14,15].…”