Evidence-based recommendations for musculoskeletal kinematic 4D-CT studies using wide area-detector scanners: a phantom study with cadaveric correlation.

PROPOSE: To establish evidence-based recommendations for musculoskeletal kinematic 4D-CT on wide area-detector CT. MATERIALS AND METHODS: In order to assess factors influencing image quality in kinematic CT studies, a phantom consisting of a polymethylmethacrylate rotating disk with round wells of different sizes was imaged with various acquisition protocols. Cadaveric acquisitions were performed on the ankle joint during motion in two different axes and at different speeds to allow validation of phantom data. Images were acquired with a 320 detector-row CT scanner and were evaluated by two readers. RESULTS: Motion artefacts were significantly correlated with various parameters (movement axis, distance to centre, rotation speed and volume acquisition speed) (p < 0.0001). The relation between motion artefacts and distance to motion fulcrum was exponential (R2 0.99). Half reconstruction led to a 23 % increase in image noise and a 40 % decrease in motion artefacts. Cadaveric acquisitions confirmed phantom data. Based on these findings, high tube rotation speed and half reconstruction are recommended for kinematic CT. The axis of motion significantly influences image artefacts and should be considered in patient training and evaluation of acquisition protocol suitability. CONCLUSION: This study provides evidence-based recommendations for musculoskeletal kinematic 4D-CT. KEY POINTS: • Motion artefacts can hamper the quality and interpretation of dynamic joint studies • The recommendations presented here help increase image quality • Patient training and preparation can be improved • The artefact-free distance concept helps protocol adaptation and comparison.

Vascular renal anatomy and the ureteropelvic junction: preoperative multidetector CT scanning with split-bolus injection as a predictor of laparoscopic findings.

PURPOSE: To compare multidetector CT scan (MDCT) results with intraoperative findings in the detection of an inferior-pole pedicle crossing the ureteropelvic junction. PATIENTS AND METHODS: Over the 2-year study period, 35 patients receiving laparoscopic pyeloplasty underwent preoperative investigation with a novel MDCT protocol in order to detect crossing vessels. Postprocessing, including maximum intensity projection, volume-rendering technique, and multiplanar reconstruction, was used in addition to standard axial views. RESULTS: All the arteries found during laparoscopic surgery were detected by MDCT, but one radiologic false-positive was noted at the beginning of the series. Seven veins were not detected with MDCT. In the only case featuring an isolated inferior-pole vein, the aberrant vessel was identified by MDCT. CONCLUSION: Multidetector CT scanning is a highly accurate way of providing all the information necessary preoperatively concerning renal parenchymal anomalies, urinary stones, and collecting system and vessel anatomy. It helps physicians make appropriate therapeutic decisions and gives surgeons information about what they can expect during laparoscopic procedures.

Assessment of the use of a saline chaser to reduce the volume of contrast medium in abdominal CT.

OBJECTIVE: The purpose of this study was to investigate, first, the effect on enhancement of the liver and aorta during abdominal CT of the use of saline solution as a partial substitute for or in addition to contrast medium when the dose of medium is determined by the patient's body weight and, second, whether use of a saline chaser allows a decrease in the dose of contrast medium to less than 1.5 mL/kg. SUBJECTS AND METHODS: We enrolled 407 patients undergoing abdominal exploration on MDCT, including an early arterial phase and a portal phase. Group 1 received contrast medium at a dose of 1.5 mL/kg. Group 2 received contrast medium at a dose of 1.5 mL/kg less 20 mL of iodine followed by 30 mL of saline solution. Group 3 received the full 1.5 mL/kg dose of medium followed by a 30-mL saline chaser. Attenuation values were obtained from the aorta in the arterial phase and from the liver in the portal phase. RESULTS: The groups were comparable in mean body weight and heart rate. None of the differences between them in aortic enhancement in the early arterial phase were statistically significant (group 1, 206 +/- 3 H; group 2, 204 +/- 3 H; group 3, 209 +/- 4 H). There was a negative correlation between weight and aortic enhancement (r = -0.42, p < 0.0001) and a positive correlation between weight and hepatic enhancement (r = 0.19, p < 0.0001). A significant reduction (p = 0.0002) in hepatic enhancement was observed in group 2 (group 1, 53 H; group 2, 46 H; group 3, 54 H). Hepatic enhancement greater than 45 H was observed in all groups except for the group 2 subgroup of patients weighing less than 55 kg. CONCLUSION: In MDCT, reducing the amount of contrast medium does not affect aortic enhancement in the early arterial phase but decreases hepatic enhancement at the portal phase. The saline chaser technique had no influence on the phases studied. Greater than 1.5 mL/kg reduction in the dose of contrast medium followed by saline flushing may not be advisable for liver CT in low- and medium-weight patients.

Pathologic conditions of the hypothenar eminence: evaluation with multidetector CT and MR imaging.

Pain, weakness, and sensory loss occur frequently in the hypothenar eminence. However, clinical examination is difficult and nonspecific, and the prescribed imaging technique may be inadequate, or images may be misinterpreted. Different imaging modalities have various degrees of usefulness for the diagnosis of painful pathologic conditions of the hypothenar eminence. Radiography, multidetector computed tomography (CT), multidetector CT arthrography, and magnetic resonance (MR) imaging of the wrist are useful for surveying the anatomy of the hypothenar eminence, the Guyon canal, and the ulnar nerve and artery and for determining the cause of pain or other symptoms. A fracture of the pisiform bone or the hook of the hamate bone, osteoarthritis or osteochondromatosis of the pisotriquetral joint, Guyon canal syndrome, hypothenar hammer syndrome, tendinopathy of the flexor carpi ulnaris, an anomalous muscle, a ganglion cyst, or a tumor may be responsible for ulnar neuropathy. Specific radiographic views, such as the semisupinated oblique view and the lateral view with the hand radially deviated and the thumb abducted, often provide a sufficient basis for the diagnosis of acute fracture of the hook of the hamate or the pisiform bone. Multidetector CT angiography is an efficient method for diagnosing hypothenar hammer syndrome, and multidetector CT arthrography is well suited for evaluation of the pisotriquetral joint. MR imaging is the modality of choice for depiction of the ulnar nerve.

Current multiplanar imaging of the stapes.

PURPOSE: CT analysis of the stapes is difficult in the axial plane (AP), because of its oblique orientation. Oblique axial reformations could provide a more precise analysis of the stapes in normal and pathologic conditions. MATERIALS AND METHODS: CT of the temporal bone was performed in 31 patients. Only the normal side was examined in the AP and oblique axial plane (OAP), in the plane of the stapes superstructure. Conspicuousness of each stapes component was evaluated in both planes by 2 independent readers. Reproducibility between the 2 readers (R1 and R2) and comparison of conspicuousness between the AP and the OAP in the analysis of the stapes crura were evaluated. The normal position of the stapes arch in relationship to the footplate was determined in the OAP by using biometric landmarks. RESULTS: Conspicuousness of the stapes crura was increased by using OAP. The conspicuousness of the anterior crus was enhanced in 38% with the OAP according to R1 (P < .05) and 32% according to R2 (P < .05). The conspicuousness of the posterior crus was enhanced in 35% with the OAP according to R1 (P < .05), but not significantly enhanced in 22% with the OAP according to R2 (P = .095). Analysis of conspicuousness of the stapes crura was reproducible according to the kappa test. A perpendicular line to the footplate intersecting its midportion crosses the stapes head and the long process of the incus in the OAP in normal patients. CONCLUSION: OAP could enhance the CT analysis of the stapes and provide useful biometric landmarks in pathologic conditions.