The aim of this study was to define the imaging characteristics of primary and recurrent gastrointestinal stromal tumors (GIST) in computed tomography with respect to the tumor size. Computed ...tomography was performed in 35 patients with histologically confirmed gastrointestinal stromal tumors and analyzed retrospectively by two experienced and independent radiologist. The following morphologic tumor characteristics of primary ( n=20) and ( n=16) recurrent tumors were evaluated according to tumor size, shape, homogeneity, density compared with liver, contrast enhancement, presence of calcifications, ulcerations, fistula or distant metastases and the anatomical relationship to the intestinal wall, and the infiltration of adjacent visceral organs. Small GIST (<5 cm) showed a sharp tumor margin with homogeneous density and structure on unenhanced and contrast-enhanced images, and were characterized by an intraluminal tumor growth. Intermediate sized GIST (>5-10 cm) demonstrated an irregular shape, inhomogeneous density on unenhanced and contrast-enhanced images, a combined intra- and extraluminal tumor growth with aggressive findings, and infiltration of adjacent organs in 9 primary diagnosed and 2 recurrent tumors. Large GIST (>10 cm), which were observed in 8 primary tumors and 11 recurrent tumors, showed an irregular margin with inhomogeneous density and aggressive findings, and were characterized by signs of malignancy such as distant and peritoneal metastases. Small recurrent tumors had a similar appearance as compared with large primary tumors. Computed tomography gives additional information with respect to the relationship of gastrointestinal stromal tumor to the gastrointestinal wall and surrounding organs, and it detects distant metastasis. Primary and recurrent GIST demonstrate characteristic CT imaging features which are related to tumor size. Aggressive findings and signs of malignancy are found in larger tumors and in recurrent disease. Computed tomography is useful in detection and characterization of primary and recurrent tumors with regard to tumor growth pattern, tumor size, and varied appearances of gastrointestinal stromal tumors, and indirectly gives hints regarding dignity and therefore prognostic outcome.
Between 1998 to 2000, the shoulders of 17 patients with rotator cuff tears were examined using magnetic resonance imaging preoperatively, and 6 and 12 months after open surgical repair. To assess the ...course of the supraspinatus muscle atrophy, the easily reproducible magnetic resonance imaging parameters occupation ratio and tangent sign in the Y-shaped view of the supraspinous fossa were evaluated and compared with the clinical examination. Occupation ratio is a quantitative parameter that reflects the area ratio, expressed as a percentage of the supraspinatus muscle belly to the supraspinous fossa. The tangent sign is a qualitative parameter that represents a line connecting the coracoid process and the apex of the scapular spine. Occupation ratio and tangent sign are reliable diagnostic tools in magnetic resonance imaging assessment of supraspinatus muscle atrophy. The sensitivity of the magnetic resonance imaging parameter occupation ratio is 75% and the specificity is 85%. The imaging parameter tangent sign has a sensitivity of 100% and a specificity of 85%. There is a significant relationship between occupation ratio, tangent sign, and improvement of strength and mobility registered in the score of Constant and Murley 12 months after surgery.
To evaluate whether time-resolved 3D MR-angiography at 3T with a net acceleration factor of eight is applicable in clinical routine and to evaluate whether good image quality and a low artifact level ...can be achieved with a temporal update rate that allows for additional information on pathologies.
Thirty-one consecutive patients underwent time-resolved 3D contrast-enhanced MR-angiography on a 3T system. Imaging consisted of accelerated 3D gradient echo sequences combining parallel imaging with an acceleration factor of four, partial Fourier acquisition along phase and slice encoding direction, and twofold temporal acceleration using view sharing. Data volumes representing the arterial and venous contrast phases were independently evaluated by two experienced radiologists by grading of image quality and artifact level on a 0-3 scale.
Time-resolved MR-angiography was successfully performed in all subjects without the need for contrast agent bolus timing. Excellent arterial (average score = 2.65 +/- 0.32) and good venous (average score = 2.56 +/- 0.28) diagnostic image quality and little image degrading due to artifacts (average score = 2.20 +/- 0.16) were confirmed by both independent readers (agreement in 65.2% of all evaluations). In 14 patients vascular pathologies were identified in the arterial phases. In eight examinations temporal resolution and depiction of contrast agent dynamics provided additional information about pathology.
Without the necessity for additional bolus timing, time-resolved 3D contrast-enhanced MR-angiography with imaging acceleration along both the spatial encoding direction and temporal domain revealed excellent diagnostic image quality in neurovascular and thoracic imaging. Despite the limited spatial resolution as compared to high-resolution imaging of the carotid artery bifurcation, the results demonstrate the applicability of contrast-enhanced MR-angiography in thoracic and abdominal MRA as well as cervical imaging with a temporal update rate allowing for additional information on pathologies. Future studies may include an evaluation of optimal trade-offs between spatial and temporal resolution, different acceleration factors and a comparison to the gold-standard for accuracy.
Abstract Purpose To evaluate image quality of dose-reduced CT of the paranasal-sinus using an iterative reconstruction technique. Methods In this study 80 patients (mean age: 46.9 ± 18 years) ...underwent CT of the paranasalsinus (Siemens Definition, Forchheim, Germany), with either standard settings (A: 120 kV, 60 mAs) reconstructed with conventional filtered back projection (FBP) or with tube current–time product lowering of 20%, 40% and 60% (B: 48 mAs, C: 36 mAs and D: 24 mAs) using iterative reconstruction ( n = 20 each). Subjective image quality was independently assessed by four blinded observers using a semiquantitative five-point grading scale (1 = poor, 5 = excellent). Effective dose was calculated from the dose-length product. Mann–Whitney- U -test was used for statistical analysis. Results Mean effective dose was 0.28 ± 0.03 mSv(A), 0.23 ± 0.02 mSv(B), 0.17 ± 0.02 mSv(C) and 0.11 ± 0.01 mSv(D) resulting in a maximum dose reduction of 60% with iterative reconstruction technique as compared to the standard low-dose CT. Best image quality was observed at 48 mAs (mean 4.8; p < 0.05), whereas standard low-dose CT (A) and maximum dose reduced scans (D) showed no significant difference in subjective image quality (mean 4.37 (A) and 4.31 (B); p = 0.72). Interobserver agreement was excellent ( κ values 0.79–0.93). Conclusion As compared to filtered back projection, the iterative reconstruction technique allows for significant dose reduction of up to 60% for paranasal-sinus CT without impairing the diagnostic image quality.
Pulmonary sequestration is a relatively rare but clinically significant congenital anomaly. This disease is a spectrum of disorders involving the pulmonary airways, the arterial supply to the lungs, ...the lung parenchyma and its venous drainage. Traditionally, the diagnosis of pulmonary sequestration has been made definitively with arterial angiography. It is imperative for the preoperative evaluation that the arterial supply and venous drainage of the sequestered segment is identified. Several cases of MR diagnosis and preoperative evaluation of pulmonary sequestration and blood supply have been reported. In this case, MR imaging was able to provide important information about systemic blood supply via intercostal arteries and regular venous drainage. Furthermore this imaging technique revealed a second pulmonary sequestration in the dorsal phrenicocostal sinus that was not diagnosed before.
About 20 years ago, a theory was put forward that neurovascular contact of the root entry zone (REZ) of the ninth and 10th cranial nerve is responsible for elevated blood pressure in patients with ...essential hypertension. To test this hypothesis, we used MR tomography and MR angiography to evaluate the presence and degree of neurovascular contact of the REZ of the ninth and 10th cranial nerves in patients with essential hypertension as compared with patients with renal parenchymal hypertension and normotensive healthy volunteers.
Patients with essential hypertension (group 1; n = 33), renal parenchymal hypertension (group 2; n = 30), and normotensive healthy volunteers (group 3; n = 25) underwent high-resolution (axial and coronal) brain stem MR imaging and MR angiography. The images were interpreted consensually by two radiologists who were blinded to the patients' hypertensive status. Neurovascular contact was graded as vessel contact without associated brain stem deformity (grade I), vessel contact with associated brain stem deformity (grade II), or vessel contact with associated deformity and displacement of the brain stem (grade III).
Neurovascular contact of the REZ of the ninth and 10th cranial nerve on the left side was found in 48.5% in group 1, in 26.7% in group 2, and in 48.0% in group 3. The rate of neurovascular contact on the right side was 24.2%, 13.3%, and 40.0%, respectively. chi(2) analysis showed no statistical difference between the groups.
Neurovascular contact is not more frequent in patients with essential hypertension than in normotensive control subjects or in those with secondary hypertension; therefore, MR imaging cannot aid patient selection for neurosurgical vascular decompression.
To evaluate the quality of chest radiographs after 32:1 compression/decompression with different image compression algorithms.
Ten digital (Thoravison) radiographs of an anthropomorphic chest phantom ...with superimposed simulated nodular lesions (NL) and linear reticular lesions (LL) were obtained. Each radiograph was subdivided into 15 fields; they contained the lesions with a probability of 0.5. The radiographs were compressed and decompressed by using JPEG, fractal and wavelet algorithms at a compression rate of 32:1. Five radiologists evaluated the images. Data were analyzed with the receiver operating characteristic (ROC) method (comparison of area under curve).
At 32:1 JPEG or wavelet compression, no statistically significant difference was observed for both NL and LL when compared with the original images. The fractal algorithm performed significantly lower for both NL and LL when compared with the original radiographs.
The JPEG and wavelet image compression does not result in loss of relevant information for chest x-rays at a compression rate of 32:1.
To prospectively investigate the feasibility, image quality, and radiation dose for prospective electrocardiographically (ECG) triggered sequential dual-source computed tomographic (CT) angiography ...of the thoracic aorta in comparison to retrospective ECG-gated helical dual-source CT angiography.
This study was approved by the institutional review board; informed consent was obtained. One hundred thirty-nine patients referred for ECG-assisted dual-source CT angiography of the thoracic aorta were prospectively enrolled. Inclusion criteria were stable sinus rhythm and heart rate of 80 beats per minute or less. Tube voltage was adjusted to body mass index (< 25.0 kg/m(2), 100 kV, n = 58; > or = 25.0 kg/m(2), 120 kV, n = 81). In both cohorts, patients were randomly assigned to prospective or retrospective ECG-assisted data acquisition. In both groups, tube current (250 mAs per rotation) was centered at 70% of the R-R cycle. The presence of motion or stair-step artifacts of the thoracic aorta was independently assessed by two readers. Effective radiation dose was calculated from the dose-length product.
Subjective scoring of motion and stair-step artifacts was equivalent for both techniques. Scan length was not significantly different (23.8 cm +/- 2.4 standard deviation vs 23.7 cm +/- 2.5 for prospective and retrospective ECG-triggered CT angiography, respectively; P = .54). Scanning time was significantly longer for prospective ECG-triggered CT angiography (18.8 seconds +/- 3.4 vs 16.4 seconds +/- 3.3, P < .001). Mean estimated effective dose was significantly lower for prospective data acquisition (100 kV, 1.9 mSv +/- 0.5 vs 4.1 mSv +/- 0.7, P < .001; 120 kV, 5.3 mSv +/- 1.1 vs 9.5 mSv +/- 3.0, P < .001).
Prospective ECG-gated sequential dual-source CT angiography of the thoracic aorta is feasible, despite the slightly longer acquisition time. Thus, motion-free imaging of the thoracic aorta is possible at significantly lower radiation exposure than retrospective ECG-gated helical dual-source CT angiography in certain patients with a regular heart rate.
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