Image quality improvement in three-dimensional time-of-flight magnetic resonance angiography using the subtraction method for brain and temporal bone diseases.

BACKGROUND: Time-of-flight (TOF) magnetic resonance (MR) angiography is based on flow-related enhancement using the T1-weighted spoiled gradient echo, or the fast low-angle shot gradient echo sequence. However, materials with short T1 relaxation times may show hyperintensity signals and contaminate the TOF images. The objective of our study was to determine whether subtraction three-dimensional (3D) TOF MR angiography improves image quality in brain and temporal bone diseases with unwanted contaminations with short T1 relaxation times. METHODS: During the 12-month study period, patients who had masses with short T1 relaxation times noted on precontrast T1-weighted brain MR images and 24 healthy volunteers were scanned using conventional and subtraction 3D TOF MR angiography. The qualitative evaluation of each MR angiogram was based on signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and scores in three categories, namely, (1) presence of misregistration artifacts, (2) ability to display arterial anatomy selectively (without contamination by materials with short T1 relaxation times), and (3) arterial flow-related enhancement. RESULTS: We included 12 patients with intracranial hematomas, brain tumors, or middle-ear cholesterol granulomas. Subtraction 3D TOF MR angiography yielded higher CNRs between the area of the basilar artery (BA) and normal-appearing parenchyma of the brain and lower SNRs in the area of the BA compared with the conventional technique (147.7 ± 77.6 vs. 130.6 ± 54.2, p < 0.003 and 162.5 ± 79.9 vs. 194.3 ± 62.3, p < 0.001, respectively) in all 36 cases. The 3D subtraction angiography did not deteriorate image quality with misregistration artifacts and showed a better selective display of arteries (p < 0.0001) and arterial flow-related enhancement (p < 0.044) than the conventional method. CONCLUSION: Subtraction 3D TOF MR angiography is more appropriate than the conventional method in improving the image quality in brain and temporal bone diseases with unwanted contaminations with short T1 relaxation times.

In vivo and in vitro sonographic diagnosis of an encrusted nephrostomy catheter with color doppler twinkling artifact.

Encrustation is one of the most common complications that may develop with the use of a nephrostomy catheter. We used the color Doppler twinkling artifact to detect encrustation and obstruction of a nephrostomy catheter in vivo. This was confirmed by in vitro scanning of the catheter after analyzing the radiogram. Color Doppler twinkling artifact may provide useful information on the management of nephrostomy catheters.

Color Doppler twinkling artifact of calcified cardiac valves in vitro: a not well known phenomenon in echocardiography.

The color Doppler twinkling artifact manifests as a rapidly changing mixture of red and blue colors behind strongly reflective structures. The twinkling artifact occurs behind diseased cardiac valves, although the phenomenon is not well described. This study sought to determine the presence of the color Doppler twinkling artifact in calcified cardiac valves in vitro using soft tissue radiography for reference. Seventeen specimens of diseased cardiac valves from patients undergoing valve replacement surgery were studied. The overall sensitivity and specificity for the detection of calcifications using the presence of the twinkling artifact were 66.7% and 81.8%, respectively. If valves with only microcalcifications or smooth calcifications were eliminated from the analysis, all (100%) of the three valves with irregular macrocalcifications exhibited the twinkling artifact. It is important to recognize this artifact because it may lead to misdiagnosis of vascular flow in echocardiography.

A rare hernia of intra-abdominal fat in the thorax under an intact diaphragm: multidetector computed tomography.

Neither abdominal wall hernia nor diaphragmatic hernia is an unusual disease. But some may have difficulty diagnosing the presence of intra-abdominal fat in the thorax under an intact diaphragm. We report a case with an external compression of the right lower lung from intra-abdominal fat owing to a hernia through the right lateral abdominal wall and secondary through the ninth intercostal space of the chest wall to the right lower thorax without traumatic history. Multiple images, including multidetector row computed tomography, are reviewed.