Indikationen der MR- und CT-Arthrografie – Empfehlungen der AG Muskuloskelettale Radiologie der DRG

High-resolution flat panel CT versus 3-T MR arthrography of the wrist: initial results in vivo

OBJECTIVES

The objective of this study was to compare the diagnostic performance of direct C-arm flat panel computed tomography arthrography (FPCT-A) with direct magnetic resonance arthrography (MR-A) of the wrist in patients with clinically suspected pathologies.

METHODS

Forty-nine patients underwent tri-compartmental wrist arthrography. FPCT-A was acquired using a high-resolution acquisition mode, followed by a 3-T MR exam using a dedicated wrist coil. Image quality and artifacts of FPCT-A and MR-A were evaluated with regard to the depictability of anatomical structures. The time stamps for the different image acquisitions were recorded for workflow assessment.

RESULTS

Image quality was rated significantly superior for all structures for FPCT-A (p < 0.001) as compared to MR-A including intrinsic ligaments, TFCC, cartilage, subchondral bone, and trabeculae. The differences in image quality were highest for cartilage (2.0) and lowest for TFCC (0.9). The artifacts were rated lower in MR-A than in FPCT-A (p < 0.001). The procedure was more time-efficient in FPCT-A than in MR-A.

CONCLUSIONS

FPCT-A of the wrist provides superior image quality and optimized workflow as compared to MR-A. Therefore, FPCT-A should be considered in patients scheduled for dedicated imaging of the intrinsic structures of the wrist.

KEY POINTS

• FPCT arthrography allows high-resolution imaging of the intrinsic wrist structures. • The image quality is superior as compared to MR arthrography. • The procedure is more time-efficient than MR arthrography.

Ultra-high resolution C-Arm CT arthrography of the wrist: Radiation dose and image quality compared to conventional multidetector computed tomography

OBJECTIVE

Objective of this phantom and cadaveric study was to compare the effective radiation dose (ED) and image quality (IQ) between C-arm computed tomography (CACT) using an ultra-high resolution 1×1 binning with a standard 16-slice CT (MDCT) arthrography of the wrist.

METHODS

ED was determined with thermoluminescence dosimetry using an anthropomorphic phantom and different patient positions. Imaging was conducted in 10 human cadaveric wrists after tri-compartmental injection of diluted iodinated contrast material and a wire phantom. IQ of MDCT was compared with CACT reconstructed with a soft (CACT1) and sharp (CACT2) kernel. High and low contrast resolution was determined. Three radiologists assessed IQ of wrist structures and occurrence of image artifacts using a 5-point Likert scale.

RESULTS

ED of MDCT was comparable to standard CACT (4.3μSv/3.7μSv). High contrast resolution was best for CACT2, decreased to CACT1 and MDCT. Low contrast resolution increased between CACT2 and MDCT (P<0.001). IQ was best for CACT2 (1.3±0.5), decreased to CACT1 (1.9±0.6) and MDCT (3.5±0.6). Non-compromising artifacts were only reported for CACT.

CONCLUSIONS

The results of this phantom and cadaveric study indicate that ultra-high resolution C-Arm CT arthrography of the wrist bears the potential to outperform MDCT arthrography in terms of image quality and workflow at the cost of mildly increasing image artifacts while radiation dose to the patient is comparably low for both, MDCT and C-Arm CT.

[Systematics of shoulder instability]

Shoulder instability is defined as a symptomatic abnormal motion of the humeral head relative to the glenoid during active shoulder motion. Glenohumeral instabilities are classified according to the causative factors as the pathogenesis of instability plays an important role with respect to treatment options. Instabilities are classified into traumatic and atraumatic instabilities as part of a multidirectional instability syndrome and into microtraumatic instabilities.For diagnostics plain radiographs ("trauma series") are performed to document shoulder dislocation and its successful repositioning. Direct magnetic resonance (MR) arthrography is the most important imaging modality for delineation of the different injury patterns of the labral-ligamentous complex and bony structures. Monocontrast computed tomography (CT) arthrography with the use of multidetector CT scanners represents an alternative imaging modality; however, MR imaging should be preferred in the work-up of shoulder instabilities due to the mostly younger age of patients.

C-arm flat-panel CT arthrography of the wrist and elbow: first experiences in human cadavers

OBJECTIVE

To determine the optimal intra-articular iodine concentration for C-arm flat-panel computed tomography (FPCT) arthrography using advanced joint phantoms and to evaluate its application in human cadaveric wrists and elbows. Multi-detector (MD) CT served as the standard of reference.

MATERIALS AND METHODS

Joint phantoms and 10 human cadaveric wrist and elbow joints were scanned with C-arm FPCT (5-s, 8-s, and 20-s runs) and standard MDCT using different and optimal concentrations of iodinated contrast material. CT numbers of contrast material, tissue, and noise were measured and contrast-to-noise ratios (CNR) calculated for quantitative analysis. Image and depiction of cartilage, bone, and soft tissues were rated. Radiation doses were compared.

RESULTS

In FPCT, iodine concentrations positively correlated with CT numbers and noise of contrast material and with radiation dose (r = 0.713-0.996, p < 0.05 each). At an iodine concentration of 45 mg/ml, CNR of cartilage and soft tissues were highest for all FPCT acquisitions and higher than in MDCT. The 20-s FPCT run performed best for image quality and depiction of anatomical structures and was rated overall equal to MDCT (p = 0.857).

CONCLUSION

The optimal iodine concentration for C-arm FPCT arthrography in this study is 45 mg/ml, leading to superior CNR and image quality for an optimal FPCT protocol compared with standard MDCT arthrography in human cadaveric joints.