Showing papers in "Journal of Computer Assisted Tomography in 1994"

Automatic 3D intersubject registration of MR volumetric data in standardized Talairach space

Abstract: Objective In both diagnostic and research applications, the interpretation of MR images of the human brain is facilitated when different data sets can be compared by visual inspection of equivalent anatomical planes. Quantitative analysis with predefined atlas templates often requires the initial alignment of atlas and image planes. Unfortunately, the axial planes acquired during separate scanning sessions are often different in their relative position and orientation, and these slices are not coplanar with those in the atlas. We have developed a completely automatic method to register a given volumetric data set with Talairach stereotaxic coordinate system. Materials and methods The registration method is based on multi-scale, three-dimensional (3D) cross-correlation with an average (n > 300) MR brain image volume aligned with the Talariach stereotaxic space. Once the data set is re-sampled by the transformation recovered by the algorithm, atlas slices can be directly superimposed on the corresponding slices of the re-sampled volume. the use of such a standardized space also allows the direct comparison, voxel to voxel, of two or more data sets brought into stereotaxic space. Results With use of a two-tailed Student t test for paired samples, there was no significant difference in the transformation parameters recovered by the automatic algorithm when compared with two manual landmark-based methods (p > 0.1 for all parameters except y-scale, where p > 0.05). Using root-mean-square difference between normalized voxel intensities as an unbiased measure of registration, we show that when estimated and averaged over 60 volumetric MR images in standard space, this measure was 30% lower for the automatic technique than the manual method, indicating better registrations. Likewise, the automatic method showed a 57% reduction in standard deviation, implying a more stable technique. The algorithm is able to recover the transformation even when data are missing from the top or bottom of the volume. Conclusion We present a fully automatic registration method to map volumetric data into stereotaxic space that yields results comparable with those of manually based techniques. The method requires no manual identification of points or contours and therefore does not suffer the drawbacks involved in user intervention such as reproducibility and interobserver variability.

The Ecat Exact Hr - Performance of a New High-resolution Positron Scanner

Abstract: Objective: The ECAT EXACT HR is a newly designed CTI-Siemens PET scanner with high spatial resolution. Its physical performance with respect to resolution, count rate efficiency, and scatter was investigated and evaluated with phantom studies. Materials and Methods: The new tomograph consists of three rings of 112 BGO block detectors (50 mm x 23 mm x 30 mm deep) each, covering an axial field of view of 15 cm with a patient port of 56 cm diameter. Each block is sawed into an 8 x 7 matrix giving 24 detector rings with 784 crystals each. Results: Total sensitivity for a 20 cm cylinder phantom is 177 kcps/mu Ci/ml in two-dimensional (2D) mode and increases to 1.46 Mcps/mu Ci/ml in 3D mode. Count rate performance was investigated for different low energy discriminator thresholds. Smaller detector blocks improve noise equivalent counts by similar to 50% compared with the EXACT system both in 2D and in 3D mode. Scatter fractions vary in 2D from 0.09 to 0.13 for energy thresholds from 450 to 250 keV for line sources in a 20 cm diameter phantom. In 3D mode an increase of scatter by a factor of 3 is observed. Transaxial spatial resolution varies from 3.6 mm full width at half-maximum (FWHM) at the center to 4.5 mm FWHM tangentially and 7.4 mm FWHM radially at R = 20 cm. Average axial resolution changes from 4.0 mm FWHM at center to 6.7 mm FWHM at R = 20 cm. Conclusion: Due to its special properties, the EXACT HR can be equally applied to routine clinical brain and whole-body imaging and to noninvasive experimental studies of regional tracer concentrations in medium-sized animals

MRI guided laser induced interstitial thermotherapy of cerebral neoplasms

Abstract: OBJECTIVE Laser-induced interstitial thermotherapy (LITT) using a neodymium:yttrium aluminum garnet (Nd: YAG) laser is a new therapeutic approach in the treatment of brain tumors. The purpose of our study was to determine the value of MRI in monitoring LITT. MATERIALS AND METHODS Eight patients with intracerebral tumors were treated with LITT. The light guide was inserted via an applicator sheath that was implanted stereotaxically with CT guidance. The laser irradiation was performed within the MR unit and monitored by repetitive measurements of a T1-weighted 2D-FLASH sequence. RESULTS During therapy in all patients, typical changes of signal intensity were seen. A gradually increasing central zone of high signal intensity was surrounded by an increasing peripheral area of reduced signal intensity. The diameter of an enhancing rim at the outer border of the peripheral area after Gd-DTPA was considered as the total lesion size. The lesion size as determined on 2D-FLASH scans during LITT accounted for 88-100% (mean 93.5%) of total lesion size on T1-weighted images after Gd-DTPA acquired immediately after therapy. On T2-weighted images the signal intensities of the two zones were vice versa. Follow-up studies showed a decrease of total lesion size (15-87%). CONCLUSION Our results demonstrate that MRI is feasible and effective in monitoring LITT. However, the role of LITT in the therapeutic workup of brain tumors still has to be defined in future clinical studies.

A comparison of conventional and spiral CT : an experimental study on the detection of spherical lesions

Abstract: Objective It is accepted that spiral CT scanning may offer significant advantages in a number of clinical applications. There is still some concern with respect to image quality, however, since slice sensitivity profiles are slightly broadened due to the table motion. We carried out theoretical analysis, phantom measurements, and computer simulations to evaluate and to compare contrast and spatial resolution for conventional and for spiral scanning. Special emphasis was put on the task of detecting spherical lesions. Materials and methods For standard test objects that measure only resolution in the scan plane, no significant difference between conventional and spiral scanning was observed. We therefore designed a phantom setup that allowed us to place spheres of arbitrary diameter and contrast in arbitrary positions to test three-dimensional (3D) resolution. Results For conventional CT, both lesion contrast and the degree of spatial separation of lesions observed depend on the relation of the start position of the scan series to the random location of a sphere or lesion. Spiral CT offers space-invariant resolution due to its continuous scanning. Small lesion contrast may be improved by up to a factor of 1.8 when compared with conventional CT since slices can be centered retrospectively. Measurements and simulations were in excellent agreement. Conclusion We conclude that spiral CT can offer improved 3D contrast and spatial resolution. To exploit these advantages, images should be reconstructed in spiral CT at increments of less than half the distance traveled during one 360 degrees tube rotation. With four to five images per such interval, usually equal to the slice width, results very close to the theoretical optimum are achieved. Many of the presented considerations and results apply to other slice imaging modalities like MRI in analogous fashion.

Quantitative comparisons of image registration techniques based on high-resolution MRI of the brain.

Abstract: Objective A variety of methods for matching intrasubject MRI-MRI, PET-PET, or MRI-PET image pairs have been proposed. Based on the rigid body transformations needed to align pairs of high-resolution MRI scans and/or simulated PET scans (derived from these MRI scans), we obtained general comparisons of four intrasubject image registration techniques: Talairach coordinates, head and hat, equivalent internal points, and ratio image uniformity. In addition, we obtained a comparison of stereotaxic Z frames with a customized head mold for MRI-MRI image pairs. Materials and methods and results Each technique was quantitatively evaluated using the mean and maximum voxel registration errors for matched voxel pairs within the brain volumes being registered. Conclusion We conclude that fiducial markers such as stereotaxic Z frames that are not rigidly fixed to a patient's skull are inaccurate compared with other registration techniques, Talairach coordinate transformations provide surprisingly good registration, and minimizing the variance of MRI-MRI, PET-PET, or MRI-PET ratio images provides significantly better registration than all other techniques tested. Registration optimization based on measurement of the similarity of spatial distributions of voxel values is superior to techniques that do not use such information.

Lung cyst formation in lymphocytic interstitial pneumonia: CT features.

Abstract: Objective We performed this study to identify and characterize the CT findings of lymphocytic interstitial pneumonia (LIP). Materials and methods The CT findings of two patients with LIP were reviewed and correlated with their histologic specimens. Results Chest CT of the two patients showed areas of increased attenuation in both lung fields which were associated with nodular and cystic lesions surrounding the peribronchovascular bundles. The most characteristic abnormality identified on CT was the presence of multiple cysts throughout both lungs. Macroscopic findings of lung biopsy specimens included multiple nodular and cystic lesions. Conclusion This description of multiple pulmonary cysts formation in LIP is new.

Quantitative metabolite patterns of human brain tumors: detection by 1H NMR spectroscopy in vivo and in vitro.

Abstract: Objective The aim of the present study was to investigate quantitative metabolite patterns in human brain tumors by 1H nuclear MR spectroscopy (1H MRS). Materials and methods Single voxel 1H MRS was used in studying metabolites in 23 primary brain tumors in vivo. The T2 relaxation times and saturation factors were determined for N-acetylaspartate (NAA), total creatine (Cr), choline-containing compounds (Cho), and water, which was used as an internal standard in computations of metabolite concentrations in vivo. Metabolites in biopsy specimens from 75 tumors were quantified by means of 1H MRS in vitro. Results The NAA concentrations were lower in brain tumors than in normal tissue in vitro and in vivo, irrespective of the histological type. The NAA was some threefold higher in vivo than in vitro, which could be due to partial volume effect and/or contributions from other metabolites to the peak at 2.02 ppm in vivo. Ratios of Cho to Cr concentrations were elevated in tumors relative to normal brain in vivo. Absolute Cho was some 50% higher in both benign astrocytomas and oligodendrogliomas in vivo than in normal brain. However, Cho concentration in vitro was significantly higher only in pituitary adenomas than in healthy white matter. Total creatine was approximately 50% lower in malignant astrocytomas and meningiomas than in normal brain. Conclusion It is concluded that absolute concentrations of metabolites in vivo yield a different picture of tumor metabolites than that derived from uncorrected metabolite ratios.

Assessment of cerebral blood volume with dynamic susceptibility contrast enhanced gradient-echo imaging.

Abstract: Objective Dynamic susceptibility contrast (DSC) enhanced MRI was used to study relative cerebral blood volume (rCBV). Materials and Methods We examined 15 healthy subjects and 47 patients with vascular stenosis or occlusion, with brain infarctions, and with cerebral neoplasms. During bolus injection of Gd-diethylenetriamine pentaacetic acid, a series of rapid T2*-weighted fast low angle shot two-dimensional images were recorded from the same slice. From these images, changes in signal intensity during bolus passage were computed pixel-by-pixel and converted into contrast agent concentration curves. Applying the principles of indicator dilution theory, images of rCBV were calculated. Results and Conclusion Regions of infarctions show almost zero rCBV. In patients with high-grade vascular stenosis or occlusion a bolus delay in comparison to the unaffected side and an increased mean transit time can be observed. Some of the affected areas show an increased rCBV, which is a well-known physiological mechanism that takes place to compensate for the reduced cerebral blood pressure. In brain tumors, rCBV imaging reveals focal or homogeneous areas of increased blood volume. This can even be observed in low-grade astrocytomas with unaffected blood-brain barrier. In CBV imaging, the effects of radiotherapy on tumor tissue can be monitored as a significant decrease of rCBV in tumor tissue after therapy.

Injection of alcohol into bone metastases under CT guidance.

Abstract: Objective Percutaneous injection of ethanol was evaluated in terminally ill cancer patients with painful osteolytic bone metastases treated previously without success by radiation or chemotherapy and conventional pain therapy. Methods and materials Twenty-five patients with 27 bone metastases in various locations underwent one to three instillations of 3-25 ml ethanol (95%) under CT guidance, which allowed precise needle positioning and control of the diffusion of alcohol thus minimizing the complications. Results Within 24 to 48 h 74% of the cases experienced a reduction of analgesic needs. Conclusion Percutaneous ethanol injection under CT guidance is useful in reducing pain and in improving the quality of life of patients with advanced stages of cancer and painful bone metastases.

Postcontrast MR arthrography in assessment of cartilage lesions

Abstract: OBJECTIVE Although MR has been proven effective in evaluating many components of the musculoskeletal system, including ligaments, fibrocartilage, muscle, and bone marrow, its role in the evaluation of articular cartilage remains controversial. Recent studies have demonstrated that intraarticular injection of Gd-DTPA [MR arthrography (MRA)] improves the detection of cartilage abnormalities in cadaveric specimens. The aim of this study was to determine the efficacy of MRA for the detection of naturally occurring cartilage lesions in a clinical population. MATERIALS AND METHODS Sixty knees of 58 patients were studied with a three-dimensional (3D) T2*-weighted GE sequence (FISP) both before and after and a T1-weighted (T1W) SE sequence after the intraarticular injection of a 2 mmol/L Gd-DTPA solution. All knees subsequently underwent arthroscopy or arthrotomy. RESULTS The MRA sequences performed significantly better (kappa = 0.85) than the routine FISP sequences (kappa = 0.39) in both the detection and the staging of cartilage abnormalities. The MRA FISP sequence (kappa = 0.91) performed slightly better than the MRA T1W sequence (kappa = 0.85), but there was no statistically significant difference between the two sequences. No complications from the intraarticular injection of contrast material occurred. CONCLUSION Therefore, MRA appears to be an effective and safe method for the evaluation of articular cartilage abnormalities.

Spiral CT of bronchial arteries in chronic thromboembolism.

Abstract: OBJECTIVE: Computed tomography study of bronchial artery anatomy and evaluation of dilatation and tortuousity as indicators for pulmonary hypertension and surgical risk in patients with chronic thromboembolism were performed. MATERIALS AND METHODS: We retrospectively reviewed contrast-enhanced, thin section spiral CT scans of 39 patients undergoing pulmonary thromboendarterectomy. Findings were compared with mean pulmonary artery (PA) pressure in all, postoperative mortality in 33, and postoperative CT in 5 patients. Twenty patients without pulmonary hypertension served as controls. RESULTS: In the pulmonary hypertension group, 50 bronchial arteries were observed in 30 of 39 patients. Their prevalence was significantly higher than in the control group (p or = 1.5 mm in 20 patients (51%); a tortuous course was found in 14 (36%). The correlation between total bronchial artery diameter and mean PA pressure was poor (r = 0.2). Patients with dilated bronchial arteries had a significantly lower risk for postoperative death than patients without (p < 0.05); positive predictive value was 100% and confidence interval 0.79-1.0. Despite normal postoperative PA pressures, bronchial arteries were still visible on follow-up studies. CONCLUSION: The CT depiction of bronchial arteries, dilatation, and tortuousity provides indicators for chronic thromboembolic pulmonary hypertension. Its degree cannot be estimated. Dilated bronchial arteries are a significant predictor for survival of pulmonary thromboendarterectomy.

CT and MR distinction of adenomas and nonadenomas of the adrenal gland.

Abstract: Objective Because the distinction between adenomas and nonadenomas of the adrenal gland is essential, we investigated which of the following parameters--size, CT attenuation values, MRI signal intensity ratios on T1- and T2-weighted sequences, calculated T2 relaxation times, or T2 relaxation time ratios--provides better discrimination. Materials and methods We compared these parameters in 44 adrenal masses of 37 patients by means of the Student t test and receiver operating characteristics (ROC) analyses. Results Only size, CT attenuation values, and signal intensity ratios on T2-weighted MR images of adenomas showed a significant difference from those of nonadenomas. With use of ROC analysis, CT demonstrated a significantly larger area under the curve compared to size and T2 signal intensity ratios, indicating superior performance. Conclusion We found attenuation values on non-contrast-enhanced CT to be the best method in discriminating adrenal adenomas from nonadenomas. Adrenal masses with CT attenuation values below 15 HU warrant no further investigations.

CT findings in groove pancreatitis: correlation with histopathological findings.

Abstract: OBJECTIVE To clarify the CT characteristics of groove pancreatitis, which is a segmental form of chronic pancreatitis. MATERIALS AND METHODS The CT findings in four patients with proved groove pancreatitis were reviewed retrospectively. The examinations consisted of plain CT, dynamic CT, and high dose enhancement CT in each patient. Correlation between the CT findings and the resected specimens was performed in three patients. RESULTS In every patient a mass was detected in the head of the pancreas that involved the duodenum. Dynamic CT demonstrated a poorly enhancing lesion extending between the pancreatic head and the duodenum. Cysts in the duodenal wall and/or the groove and duodenal stenosis due to wall thickening were seen in four and three patients, respectively. These CT findings reflect the histological characteristics of this disease. CONCLUSION Computed tomography, including dynamic study, can demonstrate the characteristic findings of groove pancreatitis and suggest the diagnosis.

Prototype breast coil for MR-guided needle localization.

Abstract: OBJECTIVE Evaluation of breast lesions detected by MR alone is a problem: Preoperative MR-guided localization is difficult, since the breast is not accessible by a needle within the breast coil. Magnetic resonance-guided core biopsy and needle aspiration are impossible. Together with Siemens Erlangen, a prototype localization breast coil has been developed and tested. MATERIALS AND METHODS The device consists of a circular polarized coil, which contains two plates for mediolateral breast compression. They are perforated with numerous holes and thus allow access to the breast from both sides. By means of bushings, which fit into the holes, sterile needle insertion in a horizontal path is possible. RESULTS So far, precise needle insertion has been possible in 10 of 11 lesions, allowing exact needle insertion into 5 invasive carcinomas (1 MR-detected), 1 MR-detected additional focus, 2 in situ carcinomas (1 MR-detected), and 3 benign lesions. CONCLUSION Our studies show that MR-guided needle localization is possible.

US, CT, and MRI of primary and secondary liver lymphoma

Abstract: Objective To describe the imaging findings in patients with pathologically proven hepatic lymphoma. Materials and methods Ultrasound, CT, and MRI studies in 23 patients with primary (11 patients) or secondary (12 patients) liver lymphoma were retrospectively reviewed. All patients had proven non-Hodgkin lymphoma; all imaging studies were obtained within 3 weeks of biopsy. Results No finding or group of findings was specific for the diagnosis of hepatic lymphoma. In 7 of 11 cases of primary lymphoma, a single well-defined lesion was seen. Secondary liver lymphoma occurred as multiple (8 of 12) or diffusely infiltrating lesions (3 of 12) in most cases; it appeared as a solitary lesion in only 1 case. When discrete focal lesions were identified, the lesions were hypo- to anechoic on ultrasound, hypodense on CT, and had low and high signal intensity on TI- and T2-weighted MRI, respectively. Conclusion Although no one finding appears to be diagnostic of hepatic lymphoma, ultrasound that demonstrates a homogeneous, hypoechoic, through-transmitting lesion combined with CT that demonstrates a solid, low attenuation lesion is highly suggestive of primary liver lymphoma. Secondary liver lymphoma can have a greater variety of appearances and is more likely to be multiple or diffusely infiltrating lesions than a solitary lesion.

Gd-dtpa: An Alternative Contrast Medium for Ct

Abstract: Objective The purpose of this study was to demonstrate that gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) could be used as a contrast medium in CT as an alternative to iodine-based compounds. Materials and Methods Solutions of different concentrations of Gd-DTPA and iopromide were scanned in a tissue equivalent phantom and it was shown that Gd-DTPA caused 2.5 times the attenuation of an equimolar solution of iopromide. From these in vitro studies an in vivo dose of 0.5 mmol/kg Gd-DTPA was calculated to be equivalent to 50 ml iopromide 300. Results Pre- and postenhancement CT was performed in a volunteer using Gd-DTPA intravenously, and adequate enhancement occurred in intracranial vessels. Conclusion Gd-DTPA can be used to provide enhancement during CT and might be of value in iodine-sensitive patients.

Assessing myometrial invasion by endometrial carcinoma with dynamic MRI.

Abstract: OBJECTIVE Dynamic MRI was used to analyze patterns of contrast enhancement in muscle layers in the normal uterine body and to evaluate the depth of myometrial invasion by endometrial carcinoma. MATERIALS AND METHODS Dynamic MRI was performed in 18 normal volunteers and 22 patients with endometrial carcinoma. Eight of the 18 normal volunteers were of reproductive age, and 10 were postmenopausal. The dynamic study was performed immediately after the bolus administration of gadopentetate dimeglumine. Twelve consecutive images, including the early phase images, were obtained during the first 2 min. The delayed phase image was obtained subsequently. RESULTS An early enhancement zone of the inner muscle layer was demonstrated in 15 normal volunteers. In all patients in whom this early enhancement zone was preserved, the tumor was confined to < 50% of the muscle layer. In the evaluation of myometrial invasion, the accuracy of dynamic MRI was 91% compared with 77% on T2-weighted images. This improvement may be attributed to greater contrast and clearer demonstration of the border between tumor and myometrium in the early phase. CONCLUSION We consider the disruption of the early enhancement zone of the inner muscle layer to be an important indicator of myometrial invasion.

Red degeneration of uterine leiomyoma: MR appearance.

Abstract: Objective Red degeneration (hemorrhagic infarction) of uterine leiomyoma can cause acute abdominal pain. This study was undertaken to identify MR features useful in diagnosing this rare complication of uterine leiomyoma. Materials and methods Magnetic resonance imaging from five patients symptomatic for 7 to 20 days with pathologic confirmation of red degeneration was retrospectively evaluated and correlated with histopathologic findings. Results The lesions had a common MRI appearance: hyperintense rim on T1-weighted imaging (WI) and hypointense rim on T2-WI. These findings corresponded with numerous dilated vessels filled with red blood cells at the periphery of the lesion. The signal characteristics of the rim are best explained as an effect of abundant intracellular methemoglobin in these vessels. Conclusion Recognition of these characteristics may help radiologists differentiate symptomatic red degeneration from other clinical conditions that need surgical interventions.

Visualization of flow by vector analysis of multidirectional cine MR velocity mapping.

Abstract: OBJECTIVE We describe a noninvasive method for visualization of flow and demonstrate its application in a flow phantom and in the great vessels of healthy volunteers and patients with aortic and pulmonary arterial disease. The technique uses multidirectional MR velocity mapping acquired in selected planes. Maps of orthogonal velocity components were then processed into a graphic form immediately recognizable as flow. MATERIALS AND METHODS Cine MR velocity maps of orthogonal velocity components in selected planes were acquired in a flow phantom, 10 healthy volunteers, and 13 patients with dilated great vessels. Velocities were presented by multiple computer-generated streaks whose orientation, length, and movement corresponded to velocity vectors in the chosen plane. RESULTS The velocity vector maps allowed visualization of complex patterns of primary and secondary flow in the thoracic aorta and pulmonary arteries. The technique revealed coherent, helical forward blood movements in the normal thoracic aorta during midsystole and a reverse flow during early diastole. Abnormal flow patterns with secondary vortices were seen in patients with dilated arteries. CONCLUSION The potential of MR velocity vector mapping for in vitro and in vivo visualization of flow patterns is demonstrated. Although this study was limited to two-directional flow in a single anatomical plane, the method provides information that might advance our understanding of the human vascular system in health and disease. Further developments to reduce the acquisition time and the handling and presenting of three-directional velocity data are required to enhance the capability of this method.

MR evaluation of clinically suspected adnexal masses.

Abstract: Objective Our goal was to determine the sensitivity, specificity, predictive value, and accuracy of pelvic MRI in the prospective evaluation of women with a clinically suspected pelvic mass. Materials and methods One-hundred three patients with clinically suspected pelvic masses were prospectively evaluated by pelvic MRI. Masses were analyzed for size, location, morphological characteristics, and signal behavior. Masses were classified as benign, malignant, or indeterminate and in every case an attempt was made to generate a specific diagnosis according to previously reported characteristic MR appearances. Surgical follow-up was obtained within 3 months of MRI examination for all patients, excepting 11 patients with typically appearing leiomyomas. Results One hundred twenty pelvic masses were confirmed. Magnetic resonance was 100% sensitive and 99% specific in prospectively diagnosing dermoids, 96% sensitive and 100% specific in diagnosing subserosal leiomyomas, and 92% sensitive and 91% specific in diagnosing endometriomas. Conclusion When physical examination or ultrasound examination is inconclusive, pelvic MRI can aid in the evaluation of women with a suspected pelvic mass. By identifying these common benign gynecologic conditions, unnecessary surgery can be avoided.

Enhancement of liver hemangiomas on T1-weighted MR SE images by superparamagnetic iron oxide particles.

Abstract: OBJECTIVE Superparamagnetic iron oxide (SPIO) particles are phagocytosed by cells of the macrophage-monocytic phagocytic system. They are usually used in MRI as a negative contrast agent, because of their strong T2* effect, to improve detection of tumors in the liver and spleen. However, they also have a potent T1 relaxivity. In the current study, we describe this T1 effect in liver hemangiomas. MATERIALS AND METHODS Twelve patients (nine women and three men, aged from 38 to 76 years) with liver hemangiomas were examined by means of MRI at 1.5 T before and after intravenous administration of SPIO particles at a dose of 15 mumol Fe/kg body wt. Signal intensity was measured from regions of interest. RESULTS Whereas on postcontrast T2-weighted SE images the hemangiomas showed on average a signal drop of 20% (p = 0.011) and 49% (p = 0.001) (first and second echo, respectively), their signal increased by 106% (p = 0.001) on postcontrast T1-weighted SE images. CONCLUSION The T1 effect (signal enhancement) we observed in liver hemangiomas after infusion of SPIO particles could prove to be a useful new diagnostic feature that would help characterize these common lesions and differentiate them from other liver tumors.

Evaluation of RARE-MR urography in the assessment of ureterohydronephrosis.

Abstract: Objective The goal of this prospective study was to evaluate the value of the fast imaging sequence called RARE-MR urography (RMU) for the diagnosis of ureterohydronephrosis. Materials and Methods Sixty-nine patients underwent this procedure. The results were compared with those obtained by intravenous urography (IVU) and ultrasonography (US). Results The accuracy of RMU in the detection of urinary tract dilatation and the localization of the level of obstruction was excellent (100%). The determination of the type of obstruction, intrinsic versus extrinsic, was 80% by IVU and 60% for RMU. The RMU sequence alone could not specify the nature of the obstruction. Functional information about the obstructed collecting system could not be obtained. Conclusion The RMU technique may be considered in the following circumstances: contraindications to IVU (allergy to contrast medium, severe renal failure), impairment of renal excretion, and failure to locate the level of obstruction by US. The absence of ionizing radiations favors the promotion of this procedure to study ureterohydronephrosis during pregnancy.

CT in adnexal torsion with emphasis on tubal findings: correlation with US.

Abstract: OBJECTIVE Our goal was to determine the CT and US aspects of the fallopian tube in adnexal torsion MATERIALS AND METHODS The CT scans and US studies of 10 patients with surgically proven unilateral torsion of the adnexa were reviewed RESULTS On CT the fallopian tube on the involved side was identified in eight cases as an almost tubular or comma-shaped structure extending from the uterine cornua and covering partially the adnexal mass This tube was significantly thickened and measured 20-40 mm Hemorrhage (density > or = 50 HU on precontrast CT scans) was present in the tube in six patients A heterogeneous contrast agent uptake was detected in the tube in five patients An adnexal mass was visualized on the involved side in all patients, with hemorrhage in the mass in four patients Peritoneal fluid and/or ileus were present in six patients On US an echogenic structure that corresponded to the enlarged tube visualized on CT was detected in three cases and an adnexal mass in all cases CONCLUSION Thickening of the fallopian tube with hemorrhage could be detected by CT and is suggestive of torsion especially if associated with an adnexal mass

Ct and Mri of Gorham Syndrome

Abstract: Gorham syndrome, also known as massive osteolysis or vanishing bone, is a rare disorder (135 cases reported) leading to extensive loss of bony matrix, replaced by proliferating thin-walled vascular channels Three histologically proven cases of the disease are reported, including the clinical presentation and modern imaging features with CT (with 3D reconstruction) as well as T1- and T2-weighted MRI Two cases in young women were located in the pelvis with extensive osteolysis reaching to the acetabulum The third case in a 2-month-old boy is the youngest case ever reported and involved the humerus The radiological appearance of the disease is discussed and the importance of the modern imaging methods debated

CT demonstration of calcification in carcinoma of the lung

Abstract: ObjectiveOur goal was to assess the diagnostic significance of calcification in carcinoma of the lung, as seen on CT.Materials and MethodsWe prospectively identified 500 consecutive patients with the provisional clinical diagnosis of lung cancer, who underwent CT examination of the chest from 1987 t

US and CT imaging features of intrapancreatic metastases.

Abstract: Objective Twenty-four patients with intrapancreatic metastases were retrospectively studied to identify diagnostic criteria on cross-sectional imaging. Materials and Methods Ultrasound and CT of the pancreas were reexamined by two radiologists who specified morphologic patterns. Results Metastases of the pancreas were found more often solitary (14 cases) than multiple (10 cases) and as homogeneous nodules hypoechoic on US (15 cases), hypodense on CT (11 cases), sometimes hypervascular (6 cases) or pseudocystic (4 cases). Dynamic contrast-enhanced CT demonstrated small lesions 10 mm in diameter (three cases), not seen on US, and was highly suggestive when it showed several nodules in the gland. We identified some other criteria of intrapancreatic metastatic disease: two or more locations in the pancreas, nonobliteration of the retropancreatic fat regardless of the size of the lesion, nondilated biliary tree in the case of a large tumor of the pancreatic head, and a hypervascular mass without endocrine syndrome. Percutaneous puncture assessed the diagnosis (10 cases) and differentiated metastases from a primary ductal adenocarcinoma of the pancreas. Conclusion Detection and identification of suggestive features of pancreatic metastases may be obtained by examination of the pancreas with dynamic CT.

MR appearance of umbilical endometriosis.

Abstract: Objective: We describe the MR appearance of endometriosis involving the umbilicus in two patients. One patient had a history of laparoscopy performed through the umbilicus; the other had an umbilical hernia. Materials and Methods: MR imaging was performed using both a body coil and a spine coil (with the patient lying prone on the spine coil). The lesions were surgically removed and their MR appearance was correlated with the results of histologic analysis. Results: The lesions were well delineated on MRI and showed evidence of prior hemorrhage consistent with endometriosis. Both lesions were shown to be endometriosis at surgical pathology. Conclusion: MR imaging was useful for delineating the size and location of the lesions and excluding intraabdominal extension

CT vs MRI in diagnosis of recurrent rectosigmoid carcinoma

Abstract: Objective Our goal was to compare the relative values of MRI vs. CT in diagnosing recurrent rectosigmoid cancer. Materials and methods We conducted a retrospective review of 18 patients who had surgical resection of primary rectosigmoid carcinoma and suspected recurrence. They were studied with CT and MR and followed for up to 4 years. Results At the time of the initial imaging, 10 patients had recurrent tumor and 4 of the remaining 8 patients later demonstrated local recurrence. Magnetic resonance demonstrated 91% sensitivity, 100% specificity, a positive predictive value (PPV) of 100%, and a negative predictive value (NPV) of 89% with a 95% accuracy. Computed tomography demonstrated a sensitivity of 82% and a specificity of 50% with a PPV of 69% and an NPV of 67% with an accuracy of 68%. In three cases interpreted on CT as presacral masses, all were shown on MR to represent displaced but normal pelvic structures. In four cases MR revealed tumor involving the sacrum and sacral nerves not apparent on CT. Conclusion Magnetic resonance showed superior sensitivity, specificity, and accuracy to CT and better definition of the extent of tumor.

MRI of complicated anal fistulae: comparison with digital examination.

Abstract: Objectives: The assessment of complicated anal fistulae is based on digital examination. Our objective was to study the potential role of MRI in this setting by comparing preoperative digital examination with MRI. Materials and Methods: Digital examination and MRI were prospectively and blindly interpreted in 13 patients with complicated anal fistulae. Surgical findings were used as standard. Results: Complete agreement between the results of digital examination and the surgical findings was observed in 8 patients and between the results of MRI and the surgical findings in 12 patients. Digital examination misclassified two low transsphincteric fistulae as high transsphincteric and missed high secondary extensions or abscesses in three other patients. Magnetic resonance misclassified only one suprasphincteric fistula as low transsphincteric and did not overlook high secondary extensions or abscesses. Conclusion: These findings suggest that MRI may show abnormalities not detected by preoperative digital examination.

Cervical tuberculous lymphadenitis: CT findings.

Abstract: Objective Cervical tuberculous lymphadenitis (CTBL) is still an important cause of neck mass in many countries. The purpose of this study is to analyze the CT findings of CTBL and compare them with those of malignant lymphadenopathies and pyogenic abscesses in the neck. Materials and methods We retrospectively reviewed the CT scans of 32 CTBLs, 25 malignant lymphadenopathies, and 12 pyogenic abscesses in the neck. Attenuation value, enhancement pattern, and surrounding fat plane were evaluated. Results The CT findings of CTBL were classified into four types: type 1, homogeneous soft tissue density; type 2, central low density and peripheral rim enhancement with relative preservation of surrounding fat planes; type 3, multilocular central low densities and peripheral rim enhancement with obliteration of surrounding fat planes; and type 4, large confluent low density with peripheral rim enhancement and loss of lymph node architecture. Among the 32 cases of CTBL, type 3 was most frequently noted (59.4%) followed by type 2 (21.9%), type 4 (15.6%), and type 1 (12.5%). The enhancing rim of CTBL was usually thick and irregular in contrast to some malignant lymph nodes showing thin and regular rim enhancement. The degree of surrounding fat plane obliteration was less in type 4 CTBL than in pyogenic cervical abscess. Conclusion Cervical tuberculous lymphadenitis usually shows a central low density and peripheral rim enhancement that tends to be thick and irregular compared with a malignant lymphadenopathy. Multilocular low densities with peripheral enhancement and a large confluent low density with less degree of fat plane obliteration than a pyogenic abscess are suggestive features of advanced CTBL.