C-arm flat-panel CT arthrography of the shoulder: Radiation dose considerations and preliminary data on diagnostic performance

Computed Tomography: State-of-the-Art Advancements in Musculoskeletal Imaging

ABSTRACT

Although musculoskeletal magnetic resonance imaging (MRI) plays a dominant role in characterizing abnormalities, novel computed tomography (CT) techniques have found an emerging niche in several scenarios such as trauma, gout, and the characterization of pathologic biomechanical states during motion and weight-bearing. Recent developments and advancements in the field of musculoskeletal CT include 4-dimensional, cone-beam (CB), and dual-energy (DE) CT. Four-dimensional CT has the potential to quantify biomechanical derangements of peripheral joints in different joint positions to diagnose and characterize patellofemoral instability, scapholunate ligamentous injuries, and syndesmotic injuries. Cone-beam CT provides an opportunity to image peripheral joints during weight-bearing, augmenting the diagnosis and characterization of disease processes. Emerging CBCT technologies improved spatial resolution for osseous microstructures in the quantitative analysis of osteoarthritis-related subchondral bone changes, trauma, and fracture healing. Dual-energy CT-based material decomposition visualizes and quantifies monosodium urate crystals in gout, bone marrow edema in traumatic and nontraumatic fractures, and neoplastic disease. Recently, DE techniques have been applied to CBCT, contributing to increased image quality in contrast-enhanced arthrography, bone densitometry, and bone marrow imaging. This review describes 4-dimensional CT, CBCT, and DECT advances, current logistical limitations, and prospects for each technique.

Evaluation of CT-Guided Ultra-Low-Dose Protocol for Injection Guidance in Preparation of MR-Arthrography of the Shoulder and Hip Joints in Comparison to Conventional and Low-Dose Protocols

To evaluate patients’ radiation exposure undergoing CT-guided joint injection in preparation of MR-arthrography. We developed a novel ultra-low-dose protocol utilizing tin-filtration, performed it in 60 patients and compared the radiation exposure (DLP) and success rate to conventional protocol (26 cases) and low-dose protocol (37 cases). We evaluated 123 patients’ radiation exposure undergoing CT-guided joint injection from 16 January–21 March. A total of 55 patients received CT-guided joint injections with various other examination protocols and were excluded from further investigation. In total, 56 patients received shoulder injection and 67 received hip injection with consecutive MR arthrography. The ultra-low-dose protocol was performed in 60 patients, the low-dose protocol in 37 patients and the conventional protocol in 26 patients. We compared the dose of the interventional scans for each protocol (DLP) and then evaluated success rate with MR-arthrography images as gold standard of intraarticular or extracapsular contrast injection. There were significant differences when comparing the DLP of the ultra-low-dose protocol (DLP 1.1 ± 0.39; p < 0.01) to the low dose protocol (DLP 5.3 ± 3.24; p < 0.01) as well as against the conventional protocol (DLP 22.9 ± 8.66; p < 0.01). The ultra-low-dose protocol exposed the patients to an average effective dose of 0.016 millisievert and resulted in a successful joint injection in all 60 patients. The low dose protocol as well as the conventional protocol were also successful in all patients. The presented ultra-low-dose CT-guided joint injection protocol for the preparation of MR-arthrography demonstrated to reduce patients’ radiation dose in a way that it was less than the equivalent of the natural radiation exposure in Germany over 3 days—and thereby, negligible to the patient.

Application of Multislice Spiral CT in Diagnosis of Ankle Joint Sports Injury

In recent years, with the continuous improvement of medical treatment at home and abroad, computerized tomography (CT) technology has developed rapidly. The market competition at home and abroad is becoming increasingly fierce. The manufacturing cost of CT machines is highly valued by manufacturers. Reducing the manufacturing costs of CT machines is of great significance to medical equipment companies. The CT host is composed of a fixed control system and a rotation control system. Based on the analysis of the existing CT host system structure, this paper designs and implements a set of low-cost asynchronous variable-frequency rotation control systems based on the unchanged control interface of the existing main rotation servo control system, improving the market competitiveness of the product. Based on the constant structure of the rotating machine of the CT machine, the simulation analysis of asynchronous variable frequency control is carried out. A set of asynchronous variable frequency control design schemes and multi-stage speed curve control methods compatible with the original system structure are obtained. The verification and analysis of the functions of acceleration and deceleration control, rotation positioning, fault protection, electromagnetic radiation and other functions at the highest speed meet the system’s main performance requirements, such as acceleration and deceleration time at the highest speed, positioning accuracy, and speed stability. Through internal system verification, testing and clinical verification, the control system designed in this paper meets the design requirements. According to experimental data, the system is fully compatible with a running accuracy of 0.3%. The main performance indicators such as acceleration time and positioning accuracy have been improved. The acceleration time from static acceleration to the maximum speed of 0.39 seconds per revolution increases from 21 seconds to 19.9 seconds, and the positioning accuracy was improved from 0.3° to 0.24°. Finally, this study explores the diagnostic value of multislice spiral CT (MSCT) in ankle trauma.

Flat-panel CT arthrography for cartilage defect detection in the ankle joint: first results in vivo

OBJECTIVES

The purpose of this study was to compare the diagnostic performance of flat-panel computed tomography (FPCT) arthrography for cartilage defect detection in the ankle joint to direct magnetic resonance (MR) arthrography using multidetector computed tomography (MDCT) arthrography as the reference standard.

METHODS

Twenty-seven patients with specific suspicion of articular cartilage lesion underwent ankle arthrography with injection of a mixture of diluted gadolinium and iobitridol and were examined consecutively with the use of FPCT, MDCT, and 1.5 T MR imaging. FPCT, MDCT, and MR arthrography examinations were blinded and randomly evaluated by two musculoskeletal radiologists in consensus. In each ankle, eight articular cartilage areas were assessed separately: medial talar surface, medial talar trochlea, lateral talar trochlea, lateral talar surface, tibial malleolus, medial tibial plafond, lateral tibial plafond, and fibular malleolus. Findings at FPCT and MR were compared with MDCT assessments in 216 cartilage areas.

RESULTS

For the detection of cartilage defects, FPCT demonstrated a sensitivity of 97%, specificity of 95%, and accuracy of 96%; and MR arthrography showed a sensitivity of 69%, specificity of 94%, and accuracy of 87%. FPCT and MR arthrography presented almost perfect agreement (κ = 0.87) and moderate agreement (κ = 0.60), respectively, with MDCT arthrography. Mean diagnostic confidence was higher for FPCT (2.9/3) than for MR (2.3/3) and MDCT (2.7/3) arthrography.

CONCLUSIONS

FPCT demonstrated better accuracy than did 1.5 T MR arthrography for cartilage defect detection in the ankle joint. Therefore, FPCT should be considered in patients scheduled for dedicated imaging of ankle articular cartilage.

Optimizing radiation dose parameters in MDCT arthrography of the shoulder: illustration of basic concepts in a cadaveric study

OBJECTIVE

To determine in a cadaveric study the lowest achievable radiation dose and optimal tube potential generating diagnostic image quality in multidetector computed tomography (MDCT) arthrography of the shoulder.

MATERIALS AND METHODS

Six shoulders from three human cadavers were scanned using a 256-MDCT system after intra-articular injection of diluted iodinated contrast material. Using six decreasing radiation dose levels (CTDI_vol: 20, 15, 10, 8, 6, and 4 mGy) and for each dose level, four decreasing tube potentials (140, 120, 100, and 80 kVp), image noise and contrast-to-noise ratio (CNR) were measured. Two independent and blinded observers assessed the overall diagnostic image quality, subjective amount of noise, and severity of artifacts according to a four-point scale. Influence of those MDCT data acquisition parameters on objective and subjective image quality was analyzed using the Kruskal-Wallis and Wilcoxon signed-rank tests, and pairwise comparisons were performed.

RESULTS

Multidetector CT protocols with radiation doses of 15 mGy or higher, combined with tube potentials of 100 kVp or higher, were equivalent in CNR to the reference 20 mGy-140 kVp protocol (all p ≥ 0.054). Above a CTDI_vol of 10 mGy and a tube potential of 120 kVp, all protocols generated diagnostic image quality and subjective noise equivalent to the 20 mGy-140 kVp protocol (all p ≥ 0.22).

CONCLUSIONS

Diagnostic image quality in MDCT arthrography of the shoulder can be obtained with a radiation dose of 10 mGy at an optimal tube potential of 120 kVp, corresponding to a reduction of up to 50% compared with standard-dose protocols, and as high as 500% compared with reported protocols in the literature.

Clinical role of guidance by C-arm CT for 125I brachytherapy on pulmonary tumors

PURPOSE

To evaluate the clinical value of C-arm CT (CACT)-guided interstitial iodine-125 (¹²⁵I) brachytherapy on pulmonary tumors.

MATERIALS AND METHODS

30 patients with 40 solid pulmonary tumors were enrolled to undergo CACT-guided interstitial ¹²⁵I brachytherapy between November 2011 and November 2014. The needle path was planned on a CACT virtual navigation and real-time fluoroscopy system. Technical success, puncture score, procedure time, local control rate (LCR), radiation exposure, complications and survival were investigated.

RESULTS

The technical success of interstitial ¹²⁵I brachytherapy under CACT guidance was 40/40 (100%). The performance score was 4.7 ± 0.5 with a mean total procedure time of 17.7 ± 5.6 min. LCR in small (≤2.0 cm), intermediate (2.1-4.9 cm) and large (≥5.0 cm) pulmonary tumors was 100, 89.5 and 72.7% at the 4-month follow-up, respectively. The mean effective dose was 10.1 ± 2.8 mSv. Major complications occurred in four patients (13.3%). The mean survival time was 28.4 ± 2.3 months.

CONCLUSION

CACT can provide virtual navigation and real-time fluoroscopy synchronously for interstitial ¹²⁵I seed implantation on pulmonary tumors.