Epithelioid hemangioendothelioma mimicking a nerve sheath tumor clinically and on MR imaging.

Epithelioid hemangioendothelioma is a tumor of the soft tissues arising from the vascular endothelium. It is considered an intermediate grade malignancy. A 42-year-old female patient presented with pain and tingling down her right arm and a mass at the right medial upper extremity. MRI revealed an oblong mass along the course of the neurovascular bundle. Given the clinical and MR findings, a nerve sheath tumor was suspected. At surgery, the mass was adherent to both the brachial artery medially and the median nerve posteriorly. Pathology revealed epithelioid hemangioendothelioma. The imaging characteristics of epithelioid hemangioendothelioma on ultrasound, CT, and MRI are reviewed. Epithelioid hemangioendothelioma can mimic a nerve sheath tumor clinically and radiologically and should be considered in the differential diagnosis of tumors involving or adjacent to a neurovascular bundle.

Cardiac arrest: abdominal CT imaging features.

We report computed tomographic findings of two unusual cases of sudden cardiac arrest. The imaging features documented include reflux of contrast into the abdomen as indicated by opacification of renal veins, hepatic veins, inferior vena cava, and hepatic and renal parenchyma. The reflux of contrast into the portal vein in one patient has not been described in the literature. The thoracic findings were reflux of contrast into the coronary sinus, nonopacificaton of the left ventricle with intravenous contrast, and lack of cardiac motion artifact.

Breath-hold 3D MR angiography of the renal vasculature using a contrast-enhanced multiecho gradient-echo technique.

OBJECTIVE: Significant evolution of contrast-enhanced MR angiography for evaluating vascular diseases in the abdomen has occurred during the past several years. The state-of-the-art gradient-echo imaging technique employs a short echo time (TE) and a short repetition time (TR) for rapid vascular imaging with contrast-enhanced MR angiography. However, because of the short TR (< or = 3-8 msec), the background stationary tissue becomes saturated, with resultant poor contrast resolution of visceral organs. The authors present a new approach to vascular imaging using a multiecho gradient-echo technique with a TR sufficiently long (41 msec) to image the renal vasculature and parenchyma without background tissue suppression. METHODS: Twenty-four partitions (3D slab thickness = 72 mm) with an in-plane resolution of 224 x 256 were obtained in 21 seconds. Three measurements were performed with an interscan delay of 8 seconds. In the pulse sequence, the partition loop is defined as the innermost loop, in which Kz views are acquired centrically for a fixed Ky, followed by Ky views in a conventional linear or sequential order. The partition encodings are segmented to permit multiple encodings in which two TR loops were used to span a total of 24 echoes with 12 along the positive and 12 along the negative direction in k space. A large bandwidth of 650 Hz/pixel was used to keep the echo train length short, with an echo spacing of 1.86 msec. A frequency-selective fat saturation pulse was placed before slab-selective excitation. The other parameters in the pulse sequence were TR/TE/flip = 41/2.2/45; the field of view was 360 to 390 mm. Maximum intensity projections of each 3D contrast-enhanced measurement were performed. The vascular-to-background contrast, bowel-related magnetic susceptibility artifact, and background stationary signals were subjectively graded. The authors examined the utility of this technique in 16 randomly selected patients (3 normal, 13 abnormal) with varied renal vasculature and parenchymal abnormalities. Results were confirmed with conventional x-ray angiography, surgery, or clinical follow-up. RESULTS: Vascular-to-background contrast was graded as very good (grade III/III) in all cases. The bowel-related magnetic susceptibility artifacts were not considered significant. Background visceral organ soft tissue contrast was not suppressed and was graded as good (grade III/III) in all cases. Eight hemodynamically significant (> 50% diameter) stenoses in seven patients were accurately assessed (one with fibromuscular dysplasia). Three patients with renal masses (two with renal cell carcinoma and one with renal lymphoma) were accurately assessed for arterial anatomy and venous extension. Other renal venous abnormalities seen were retroaortic renal vein (n = 1), chronic occlusion (n = 1), and accessories (total of five) (n = 1). CONCLUSIONS: Rapid breath-hold contrast-enhanced MR angiography of the renal vasculature with a multiecho gradient-echo using a long TR depicted the renal vasculature with high vessel-to-background contrast without significant bowel-related susceptibility artifact and without background visceral organ tissue signal suppression, resulting in high background soft tissue contrast resolution.

The use of recombinant human bone morphogenetic protein 2 (rhBMP-2) to promote spinal fusion in a nonhuman primate anterior interbody fusion model.

STUDY DESIGN: A study on the efficacy of recombinant human bone morphogenetic protein 2 (rhBMP-2) in a nonhuman primate anterior interbody fusion model. OBJECTIVES: To investigate the efficacy of rhBMP-2 with an absorbable collagen sponge carrier to promote spinal fusion in a nonhuman primate anterior interbody fusion model. SUMMARY OF BACKGROUND DATA: RhBMP-2 is an osteoinductive growth factor capable of inducing new bone formation in vivo. Although dosage studies using rhBMP-2 have been performed on species of lower phylogenetic level, they cannot be extrapolated to the primate. Dosage studies on nonhuman primates are essential before proceeding with human primate application. METHODS: Six female adult Macaca mulatta (rhesus macaque) monkeys underwent an anterior L7-S1 interbody lumbar fusion. All six sites were assigned randomly to one of two fusion methods: 1) autogenous bone graft within a single freeze-dried smooth cortical dowel allograft cylinder (control) or 2) rhBMP-2-soaked absorbable collagen sponges within a single freeze-dried smooth cortical dowel allograft cylinder also soaked in rhBMP-2. The animals underwent a baseline computed tomography scan followed by 3- and 6-month postoperation scans. Anteroposterior and lateral radiographs of the lumbosacral spine were performed monthly. After the monkeys were killed, the lumbar spine fusion sites were evaluated. Histologic evaluation of all fusion sites was performed. RESULTS: The three monkeys receiving rhBMP-2-soaked collagen sponges with a freeze-dried allograft demonstrated radiographic signs of fusion as early as 8 weeks. The control animals were slower to reveal new bone formation. The computed tomography scans revealed extensive fusion of the L7-S1 lumbar vertebrae in the group with rhBMP-2. A pseudarthrosis was present in two of the control animals. CONCLUSIONS: This study was able to document the efficacy of rhBMP-2 with an absorbable collagen sponge carrier and a cortical dowel allograft to promote anterior interbody fusion in a nonhuman primate model at a dose of 0.4 mg per implant site (1.5 mg/mL concentration). The late of new bone formation and fusion with the use of rhBMP-2 and cortical dowel allograft appears to be far superior to that of autogenous cancellous iliac crest graft with cortical dowel allograft.

Contrast-enhanced MR angiography of the mesenteric circulation: a pictorial essay.

Outstanding results have been achieved with magnetic resonance (MR) angiography, which has become competitive with conventional angiography as a vascular imaging technique. With the advances in gradient technology and the capability of imaging vessels in a single breath hold, one can track an intravenous bolus of paramagnetic contrast agent and evaluate the entire mesenteric circulation. Use of a breath-hold technique obviates the problem of motion artifact. Use of targeted maximum-intensity projection images from the three-dimensional (3D) volume data allows evaluation of the vascular anatomy at different phases (arterial and venous) of contrast enhancement. MR angiography performed with a contrast-enhanced breath-hold fat-suppressed 3D technique allows visualization of the superior mesenteric vessels, celiac artery, and portal vein in healthy subjects. Pathologic conditions of the mesenteric vessels that can be identified with this technique include stenosis or occlusion of the superior mesenteric artery, celiac artery aneurysm, thrombosis of the superior mesenteric vein, portal hypertension with varices, and vascular invasion by pancreatic carcinoma.

Contrast-enhanced 3D MRA with centric ordering in k space: a preliminary clinical experience in imaging the abdominal aorta and renal and peripheral arterial vasculature.

The objective of this study was to determine the clinical utility of a contrast-enhanced, centric reordered, three-dimensional (3D) MR angiography (MRA) pulse sequence in imaging the abdominal aorta and renal and peripheral lower extremity arteries. Twenty-eight MRA studies were performed on 23 patients and four volunteers at 1.5 T using a 3D contrast-enhanced, centric reordered pulse sequence. In 20 patients, the abdominal aorta and renal arteries were imaged, and in seven patients, the lower extremity arteries were imaged. In 19 patients, a total of 51 renal vessels were evaluated (33 renal arteries using .1 mmol/kg of gadopentetate dimeglumine and 18 renal arteries using .2 mmol/kg of gadoteridol). A total of 70 peripheral arterial segments were assessed using .2 mmol/kg of gadoteridol. Correlation with conventional angiography was made for the following 14 cases: renal artery stenosis (four cases), abdominal aortic stenosis (one case), arteriovenous fistula in a transplant kidney (one case), renal arteriovenous malformation (one case), common iliac artery aneurysms (one case), and peripheral lower extremity (six cases). Of the 70 peripheral arterial segments evaluated, in 35, there was correlation with x-ray angiography. The mean percent of aortic signal enhancement was significantly higher in the .2 mmol/kg dose group (370.8 +/- 190.3) than in the .1 mmol/kg dose group (184.5 +/- 128.9) (P = .02). However, there was no apparent difference between the two doses for visualization of the renal and accessory renal arteries. There was concordance between the contrast-enhanced 3D MRA studies and conventional angiography in all cases of renal artery and peripheral arterial stenoses and occlusions, including visualization of reconstituted peripheral arterial segments. There was no evidence of spin dephasing effects at sites of stenoses on the 3D contrast-enhanced MRA studies. Contrast-enhanced, centric reordered, 3D MRA can rapidly image the abdominal aorta and renal and accessory renal arteries, as well as peripheral lower extremity arteries, with high resolution. Accurate depiction of the vascular lumen at sites of stenosis is made because of the lack of spin dephasing effects, even with hemodynamically significant stenoses. Additional larger clinical trials are required with this promising technique.

3D breath-hold contrast-enhanced MRA: a preliminary experience in aorta and iliac vascular disease.

PURPOSE: Our goal was to describe a 3D breath-hold (3D BH) contrast-enhanced MRA technique and apply the technique to patients with known or suspected aortic and iliac artery disease. METHOD: A fat-suppressed 3D GRE pulse sequence was designed with a total of 16 partition encodings. This took < 24 s for data acquisition in the abdomen and pelvis and was easily achieved during a single breath-hold. The technique was applied to 26 patients who presented with either known or suspected abdominal aortic or iliac vascular diseases. For comparison, in 19 patients a 2D TOF MRA pulse sequence with a traveling saturation band was used. Angiographic correlation was made in 18 studies. RESULTS: The 3D BH MRA was easily applicable in the evaluation of vascular anatomy and pathology. In three cases, it was superior to 2D TOF and conventional angiography for visualizing clot within the wall of an aneurysm in the abdominal aorta. In 20 cases, both MRA techniques overestimated the degree of stenosis in the lower peripheral vessels; however, this was more pronounced on 2D TOF. In five cases, the aneurysm wall was clearly defined by 3D BH MRA, whereas there was considerable signal loss in 2D TOF due to complex flow. With 3D BH MRA, the entire vessel territory both in abdominal aorta and in iliac vessels was visualized in all cases without signal falloff in the FOV. Breath-holding provided static images of the vessels that were free of blurring due to respiratory motion. CONCLUSION: Preliminary experience suggests that 3D BH with its distinct advantage of speed may serve as a useful screening tool for patients who cannot have conventional angiography or tolerate a lengthy MR examination of the abdominal aorta and iliac arteries.

Gradient-echo perfusion imaging of musculoskeletal abnormalities with contrast-enhanced two-dimensional fat-saturation FLASH.

The objective of this study was to evaluate the utility of MR perfusion imaging of various musculoskeletal lesions with a contrast-enhanced two-dimensional fat saturation fast low angle shot (FLASH) sequence and to assess the potential of this technique for distinguishing malignant from benign conditions. Thirty-six musculoskeletal lesions were studied at 1.5 T. The signal intensity of the lesions, adjacent artery, muscle, bone marrow, and fat were plotted against time. The time to peak enhancement, time to maximum signal intensity, percent enhancement, rate of peak enhancement, and rate of enhancement parameters were calculated. Because of a significant overlap between malignant and benign conditions, accuracy rates were lower than reported previously. The best parameter based on these values was the rate of peak enhancement (sensitivity, 84.6%; specificity, 65.2-66.6%; positive predictive value, 57.8-68.7%). Fat saturation gradient-echo MR perfusion imaging allows for a rapid assessment of the vascularity of musculoskeletal pathology; however, a significant overlap persists between malignant neoplasms and several benign conditions.

MR cholangiopancreatography (MRCP).

Magnetic resonance cholangiopancreatography (MRCP) is an evolving new technique for noninvasive imaging of diseases of the biliary tree and pancreatic duct. The advantage of this method is that one can obtain maximum intensity projection (MIP) images of the pancreatico-biliary system similar to those obtained with endoscopic retrograde cholangiopancreatography (ERCP) without the need of administration of intravenous or oral contrast. Heavily T2-weighted sequences are used that render the bile and the intraductal pancreatic fluid bright against a dark background.

Mesenteric circulation: three-dimensional MR angiography with a gadolinium-enhanced multiecho gradient-echo technique.

To evaluate the mesenteric circulation with magnetic resonance (MR) angiography, the authors examined 16 individuals (12 patients, four volunteers) with a gadolinium-enhanced, breath-hold, fat-saturated, multiecho, three-dimensional, gradient-echo sequence. Twenty examinations were performed. Grades of 3 or 4 (on a five-point scale [4 = best seen, 0 = not seen]) were applicable to 17 (85%) of 20 MR angiograms obtained in superior mesenteric artery trunks, 15 (75%) in celiac arteries, five (25%) in inferior mesenteric arteries; 15 (75%) of first-order branching, 12 (60%) of second-order branching, and 10 (50%) of third-order branching; 17 (85%) in superior mesenteric veins; and 17 (85%) in portal veins. MR angiography with this technique depicted the mesenteric arterial and venous circulation and the portal vein with excellent resolution in a short time.

Augmentation of autograft using rhBMP-2 and different carrier media in the canine spinal fusion model.

This study evaluated the use of recombinant human bone morphogenetic protein (rhBMP-2) with various types of carrier media, and the effect of rhBMP-2 as an adjunct to autogenous iliac crest bone graft in the canine spinal fusion model. BMP induces mesenchymal cells to differentiate into cartilage and bone. The recent availability of rhBMP-2 has created the opportunity to evaluate this material's properties in augmenting autogenous bone graft in spinal fusion. Currently, the most appropriate type of carrier media for rhBMP-2 is undetermined. Bilateral intertransverse spinal fusions were performed on six canine lumbar spines at L1-L2, L3-L4, and L5-L6, using autogenous posterior iliac crest bone graft at each level, creating a total of 18 segmental fusion sites. All 18 sites were then randomly assigned to one of six fusion methods: autogenous bone graft (ABG) alone, ABG + rhBMP-2, ABG + collagen (Helistat) "sandwich" + rhBMP-2, ABG + collagen (Helistat) morsels + rhBMP-2, ABG + polylactic/glycolic acid sponge (PLGA) sandwich + rhBMP-2, and ABG + open-pore polylactic acid morsels + rhBMP-2. Each material was evaluated for ease of handling and application at the index surgery. The animals underwent computed tomography (CT) scanning of the lumbar fusion sites after 8 weeks. Volumetric measurements of total fusion mass at each level were performed using two-dimensional CT scan slices and a volumetric program supplied by the Siemens Medical System. The animals were killed after imaging studies. The lumbar spine fusion sites were evaluated for integrity of the fusion mass, both visually and with manual mechanical stressing. Crossover of the fusion mass to adjoining levels was also evaluated. Histologic evaluation of all fusion sites was performed. The addition of rhBMP-2 significantly increased bone graft volume as noted on CT scan. Carrier that could be mixed with morselized bone graft offered easier handling and application and all spine segments fused. Polylactic/glycolic acid (PLGA) sites were associated with a greater incidence of voids within the fusion mass. No significant difference in carrier media for rhBMP-2 could be determined. However, PLGA was associated with a higher rate of fusion mass void formation. rhBMP-2, when added to autograft, significantly increased the volume and the maturity of the resulting fusion mass.

Giant cell tumor of the tendon sheath in the ankle: MRI with pathologic correlation.

We report a case of Giant cell tumor of the tendon sheath involving the ankle, wherein spin-echo (T1- and T2-weighted), gradient-echo, and dynamic contrast-enhanced sequences were performed, and the tumor was noted to be very vascular. To the best of our knowledge, the use of gradient-echo sequences and the pattern of enhancement by time-intensity curves has not been reported earlier.

Imaging features of splenic epidermoid cyst with pathologic correlation.

The spleen can be involved in a variety of cystic lesions ranging from cystic neoplasms and parasitic cysts to "true" and "false" cysts. Epidermoid splenic cyst is a rare true cyst that is developmental in origin. We present two young patients with such a cyst and illustrate their features on ultrasound, CT, and MRI with pathologic correlation.

MR imaging of myositis ossificans: variable patterns at different stages.

Five patients with a palpable mass at presentation underwent magnetic resonance (MR) imaging. The final diagnosis was myositis ossificans (MO). MR imaging features, particularly after injection of gadopentetate dimeglumine, mimicked those of an inflammatory mass or neoplasm. The lesions were excised in three patients, and the images were correlated with histologic findings. Three different appearances were noted on MR images, corresponding to the stages of maturation of MO. Two cases involved early-stage lesions, and T1-weighted MR images showed a mass with homogeneous intermediate signal intensity. Both lesions showed rim enhancement after contrast agent injection and high signal intensity on T2-weighted images. Pathologic specimens demonstrated stroma with masses of spindle cells in which osteoid production was interspersed. The enhanced rim of the lesion mimicked the expected MR appearance of an abscess or necrotic tumor. Areas of enhancement in adjacent muscle were also seen on postcontrast T1-weighted images. Intermediate-stage MO was present in one case; there was evidence of a thin rim of calcification on plain radiographs and fatty changes in the lesion on T1-weighted images, corresponding with histologic findings. One case of a mature lesion showed a considerable degree of peripheral calcification both on MR images and at histology. MR imaging is nonspecific in the diagnosis of early-stage MO.

Hepatic focal nodular hyperplasia: CT and sonographic spectrum.

Fifteen patients with pathologically proven focal nodular hyperplasia (FNH) of the liver had abdominal computed tomography (CT) (15) and ultrasound (11). In seven patients, the lesions were incidentally found during gallbladder or renal examination, whereas the other eight had a primary neoplasm and the liver was studied for possible metastasis. In 11 unenhanced CT scans, the ratio of isodense to hypodense lesions was 8 to 3. In 15 contrast-enhanced CT scans, seven were isodense, six were hypodense, and in two, the lesion enhanced (hyperdense). In seven patients a hypodense lesion on unenhanced CT became isodense with contrast injection. Delayed images in three showed the lesions appearing as hypodense in two and displaying a rim of enhancement in one. In one case, unenhanced CT was normal and only enhanced CT showed an area of homogeneous increased density. Ultrasound was done in 11 patients, the lesion was hypoechoic to the liver in five, echogenic in four, and isoechoic in two. Findings of central scar were seen on CT and ultrasound in three cases. Pathologic diagnosis was available in all cases, seven by needle aspiration and eight by surgical resection. In our experience, FNH has many CT and sonographic features that can mimic hemangioma or metastasis. While the presence of a central scar increases the specificity, in a cancer patient, the findings should be interpreted with caution and needle aspiration should be obtained.

Morphologic changes of the liver following chemotherapy for metastatic breast carcinoma: CT findings.

Thirty patients with metastatic breast carcinoma to the liver underwent systemic chemotherapy. Twenty-four of these patients also received hepatic arterial infusion chemotherapy, three in conjunction with hepatic artery embolization. The morphologic changes of the liver believed to be due to chemotoxic effect of treatment occurred in 27 patients, and were evaluated by serial computed tomography (CT) examinations. These included fatty changes in seven patients, severe cirrhotic changes in four, localized atrophy with regional contour changes in three, and areas of low density in the regions of previously treated metastases in 13. The CT features of cirrhosis included density changes along with nodular irregularity of the hepatic borders with marked decrease in liver size and development of ascites.