Hypointense Areas Research Articles

MRI tracking of intravenously transplanted human neural stem cells in rat focal ischemia model

The present study investigated the ability of 1.5 T clinical magnetic resonance imaging (MRI) to detect ferumoxides- labeled human neural stem cells (NSCs) that had been intravenously (i.v.) injected into a rat model of focal cerebral ischemia. To detect transplanted cells, hNSCs were labeled with ferumoxide then followed by bromodeoxyuridine (BrdU) prior to transplantation. In the rat ischemia–human NSC group, human NSCs (4 × 10 6 cells in 5 ml PBS) were injected via tail vein 24 h after middle cerebral artery occlusion (MCAo), and the brains of the rats were scanned using a 1.5 T MRI unit over a period of 4 weeks (1 day before MCAo, then 1 and 3 days after cell injection, and weekly thereafter). In histologic sections, transplanted cells were identified by Prussian blue and anti-BrdU fluorescence staining. Regions with hypointense signals on T2-weighted and 3D gradient echo MR images corresponded with areas stained by Prussian blue, which suggested the presence of superparamagnetic iron oxide (SPIO) nanoparticles within the engrafted cells. Hypointense areas on MR images were observed in peri-infarct areas 3 days after cell injection. The findings indicate that 1.5 T MRI has sufficient sensitivity to track engrafted stem cells in vivo.

Embryonic Stem Cell Grafting in Normal and Infarcted Myocardium: Serial Assessment with MR Imaging and PET Dual Detection

To use magnetic resonance (MR) imaging and positron emission tomography (PET) dual detection of cardiac-grafted embryonic stem cells (ESCs) to examine (a) survival and proliferation of ESCs in normal and infarcted myocardium, (b) host macrophage versus grafted ESC contribution to serial MR imaging signal over time, and (c) cardiac function associated with the formation of grafts and whether improvement in cardiac function is related to cardiac differentiation of ESCs. All animal procedures were approved by the institutional animal care and use committee. Murine ESCs were stably transfected with a mutant version of herpes simplex virus type 1 thymidine kinase, HSV1-sr39tk, and also were labeled with superparamagnetic iron oxide (SPIO) particles. Cells were injected directly in the border zone of the infarcted heart or in corresponding regions of normal hearts in athymic rats. PET and MR imaging were performed longitudinally for 4 weeks in the same animals. ESCs survived and underwent proliferation in the infarcted and normal hearts, as demonstrated by serial increases in 9-(4-[(18)F]fluoro-3-hydroxymethylbutyl) guanine PET signals. In parallel, the hypointense areas on MR images at the injection sites decreased over time. Double staining for host macrophages and SPIO particles revealed that the majority of SPIO-containing cells were macrophages at week 4 after injection. Left ventricular ejection fraction increased in the ESC-treated rats but decreased in culture media-treated rats, and border-zone function was preserved in ESC-treated animals; however, cardiac differentiation of ESCs was less than 0.5%. Dual-modality imaging permits complementary information in regard to cell survival and proliferation, graft formation, and effects on cardiac function. http://radiology.rsnajnls.org/cgi/content/full/250/3/821/DC1.

Post-acute pathological changes in the thalamus and internal capsule in aged mice following controlled cortical impact injury: A magnetic resonance imaging, iron histochemical, and glial immunohistochemical study

Traumatic brain injury (TBI) is a major cause of neurological disability across all ages, but the elderly are particularly vulnerable and have a worse prognosis than younger individuals. To advance the understanding of long-term pathogenesis induced by TBI in the elderly, aged mice (21–24 months) were given a controlled cortical impact (CCI) injury to the sensorimotor cortex, and their brains were analyzed by MRI and histopathology at 1 and 2 months after CCI injury, a post-acute period. A T2 hypointensity was observed in the ipsilateral thalamus but not in the contralateral thalamus or in the thalamus of sham operated, control mice. The hypointensity was co-localized with increased histochemical staining of iron, a paramagnetic substance that causes a shortening of the T2 relaxation time. Since iron catalyzes reactions that lead to toxic free radicals, the deposition of iron in the thalamus raises the possibility that it promotes pathogenesis following TBI. Astrocyte gliosis and microgliosis were also observed in the ipsilateral thalamus in the post-acute period. The ipsilateral internal capsule displayed a trend for a T2 hypointensity, however, unlike the thalamus it did not have an increase of iron or GFAP staining, but it did have evidence of microgliosis. In summary, areas of T2 hypointensity were revealed in both the thalamus and internal capsule during the post-acute period following CCI injury, but the underlying pathology appeared to be distinct between these regions.

A Rare Case of a Giant Pelvic Retroperitoneal Epidermoid Cyst

To The Editor: Epidermoid cyst is a frequent benign cutaneous tumor that could occur in any part of the human body. The pelvic cysts are uncommon and only a few cases are described in the literature. The following is a report of a rare case of a pelvic epidermoid cyst. A seventy year old multiparus lady presented with progressive swelling in the abdomen. Clinical examination confirmed a large mass in the abdomin. The ultrasound showed a giant 35 cm abdomino-pelvic echogene mass, extending from the pubis symphysis to the epigastric region, displacing the liver, spleen and the urinary bladder. The computed tomography showed similar finding (figure 1). A giant ovarian cyst was diagnosed. Median laparotomy was performed and a 30 cm retroperitoneal cyst was found. Ovaries and uterus were normal. Uneventful cyst cleavage was performed after liberation of some intestinal and epiploic adherences (figure 2). The cyst contained sebaceous matter and histological examination shows that the cystic wall was lined with flattened squamous epithelia with a distinguished granular layer. The cystic space was filled with a large amount of keratinized material. The histology was compatible with an epidermoid cyst. The post operative course was uneventful and the patient was doing well at the 5 months follow-up visit. Figure 1 Reconstruction of the image with CT scan, giant intra-abdominal mass. Figure 2 Image of the cyst after excision, size > 30cm Epidermoid cyst is a frequent benign cutaneous tumor, usually present in patients with an age range of 19 to 45 years. In children it is associated with a Gardner syndrome in 50% of cases [1]. It was described in various parts of the body including penis, spleen and brain [2–4]. It is the most frequent cutaneous cyst in the head and neck (49%) [5]. Only three cases of pelvic epidermoid cyst were reported in the literature, one was retroperitoneal [1] and the other two were retro-rectal [6, 7]. Concerning pathogenic theories, the epidermal cyst could be congenital, or post traumatic [8]. Epidermoid cysts are benign tumors with no risk of malignant transformation, but they may grow insidiously to reach a considerable sizes displacing or damaging other tissues and organs [9]. Pre-operatively, diagnosis of pelvic epidermoid cyst is difficult. Ultrasound and computed tomography often lead to a diagnosis of ovarian cyst. Magnetic resonance imaging (MRI) is more specific, as it shows epidermoid cyst as hypointense area on T1-weighted imaging and hyperintense on T2 weighted imaging without enhancement at contrast injection [10]. MRI could also help in confirming retroperitoneal localization; unfortunately it was not performed in our patient's case. The treatment of the pelvic epidermoid cyst is a surgical ablation using a cleavage to avoid any organ damage. However, in dealing with retroperitoneal space it could be difficult to avoid damaging iliac vessels and nerves [11] and if that is the case then the cyst must be punctured and drained before it is dissected. Precaution should be taken to avoid spillage of the contents out. A successful laparoscopic excision of a retro-rectal epidermoid cyst was described [7]. In conclusion, this report described a patient with a giant retroperitoneal pelvic epidermoid cyst which was successfully treated surgically. Although the pelvic epidermoid cysts are rare and difficult to diagnose pre-operatively, it should be considered in the differential diagnosis of ovarian tumors.

Imaging of renal leiomyomas

Renal leiomyomas are rare benign tumors of the kidney which can be found at autopsy as small capsular nodules in about 5% of cases. The clinical incidence of such lesions is much smaller, and only case reports or small series have been reported in the imaging literature. To describe the imaging characteristics observed in a series of eight patients with pathology-proven asymptomatic leiomyomas of the kidney. We reviewed the imaging findings observed in eight patients with pathologically proven asymptomatic renal leiomyomas discovered during studies performed for reasons unrelated to the kidney. All patients had undergone computed tomography (CT), two ultrasonography, and one magnetic resonance imaging (MRI). Lesions ranged in size from 1.2 to 13 cm. Six were at the periphery of the kidney, compressed its outer surface, but did not cause disruption of the cortex; two involved the renal cortex. All had regular outer margins. A cleavage plane between the tumor and the kidney was revealed at CT and/or ultrasonography in three of the cases located at the periphery. At ultrasonography, leiomyomas appeared hypoechogenic. At CT, they were slightly hyperdense before contrast medium injection; all were hypodense to the renal cortex after contrast medium. Four were homogeneous, two were slightly heterogeneous, and the remaining two were frankly heterogeneous. The lesion studied by MRI, which was homogeneous at the postcontrast CT study, had a heterogeneous structure on both T1- and T2-weighted images, with internal areas of hypointensity on T1. There are some imaging findings that can help to suggest the diagnosis of renal leiomyomas. First, their density: all tumors examined before contrast were hyperdense to the kidney, with density similar to that of muscles, and all had lower enhancement than the adjacent renal parenchyma. Second, the location and margins of the tumors: most were peripheral, without involvement of the renal cortex and with well-defined margins. Although not pathognomonic for a renal leiomyoma, the combination of these findings should include leiomyoma in the list of differential diagnoses.

MR Arthrography of Acetabular Cartilage Delamination in Femoroacetabular Cam Impingement1

To retrospectively assess the frequency and performance of magnetic resonance (MR) arthrography to help diagnose acetabular cartilage delamination in femoroacetabular impingement (FAI). Institutional review board approval and informed consent were waived for this retrospective study. Forty-four consecutive patients with FAI of the cam type were included (mean age, 30.7 years; range, 16-49 years), including 30 men (mean age, 30.5 years; range, 16-49 years) and 14 women (mean age, 31.4 years; range, 18-48 years). The inclusion criteria were no previous surgery, surgery within 3 months after MR imaging, and availability of a detailed surgical report with acetabular cartilage findings. MR arthrographic findings were assessed independently by two blinded readers. Findings at surgery served as reference standard. Sensitivity, specificity, accuracy, and kappa statistics for interobserver agreement were calculated. At surgery, acetabular cartilage delamination was seen in 23 (52%) of 44 patients (mean size of cartilage flap from acetabular rim, 7.6 mm; range, 2-30 mm). At MR, patients with fluid signal intensity under the cartilage delamination had a respective sensitivity, specificity, and accuracy of 22%, 95%, and 57% for reader 1 and 30%, 95%, and 61% for reader 2. A hypointense line in the acetabular cartilage on sagittal three-dimensional double-echo steady-state images with water excitation demonstrated moderate diagnostic performance (respective sensitivity, specificity, and accuracy were 70%, 57%, and 64% for reader 1 and 70%, 62%, and 66% for reader 2). Hypointense areas in the acetabular cartilage were quite specific on both coronal intermediate-weighted fat-saturated images (respective sensitivity, specificity, and accuracy were 52%, 90%, and 70% for reader 1 and 74%, 90%, and 82% for reader 2) and coronal T1-weighted images (respective sensitivity, specificity, and accuracy were 35%, 90%, and 61% for reader 1 and 61%, 95%, and 77% for reader 2). Cartilage delamination is common in patients undergoing surgery for FAI. Fluid under the cartilage delamination is a specific but rare finding. Hypointense areas in the acetabular cartilage seen on intermediate-weighted fat-saturated or T1-weighted images appear to be helpful diagnostic criteria.

Carcinosarcoma of the uterus: radiologic–pathologic correlations with magnetic resonance imaging including diffusion-weighted imaging

The authors describe the MRI findings, including diffusion-weighted imaging findings, of histopathologically proven uterine carcinosarcoma in four postmenopausal women. In three of four patients, diffusion-weighted images clearly revealed hypointense areas corresponding to hypocellular regions caused by intratumoral necrosis, and apparent diffusion coefficient (ADC) mapping images indicated that necrotic areas had high ADC values. In the remaining patient, diffusion-weighted and ADC mapping images clearly distinguished components of adenocarcinoma from sarcoma. In all patients, diffusion-weighted and ADC mapping images precisely reflected histopathological findings. Diffusion-weighted images were found to demonstrate complicated tissue components in carcinosarcomas of the uterus, and thus, which may be useful for the diagnosis of this disease.

Lung RFA: Long-term results in a single-center experience

7528 Background: Radiofrequency ablation (RFA) is an advanced, minimally invasive technique used to treat several types of neoplasm. Its application in the treatment of lung tumors has received considerable interest. Long-term results on patients treated with lung RFA in a single center experience are reported. Methods: From February 2002 to December 2007, 79 patients with unresectable primary and secondary lung neoplasms underwent percutaneous CT-guided RFA. Treatment’s adequacy was assessed by CT scan detecting hypodensity of treated lesion, without contrast-enhancement, and by NMR showing an hypointense area without changes after gadolinium injection. Results: A total of 131 lung neoplasms underwent 93 sessions of RFA. In 2 cases a spiral, 19 Gauge needle, was used, and in 5 cases a bipolar 15 Gauge, cooled-tip needle, whereas in the 124 remaining nodules a monopolar, cooled-tip needle was used. With a median follow-up of 22 months (range 3–63), the rate of complete necrosis was 95%, while pneumothorax requiring pleural drainage occurred in 10.7% of sessions. Conclusions: Percutaneous lung RFA has confirmed to be a safe and feasible procedure to treat lung malignancies. CT scan and MRI with gadolinium have shown to be accurate in the response assessment. The procedure is well tolerated and could be a very attractive option in patients considered unfit for surgery. In addition, this minimally invasive ablative technique could be combined with systemic treatments. These long-term data provide meaningful results with respect to the efficacy of the technique, thus further investigation could define the optimal role of lung RFA in the multidisciplinary therapy of lung malignancies. No significant financial relationships to disclose.

Evaluation of the role of magnetization transfer imaging in prostate: a preliminary study

Results of the preliminary study on the evaluation of the role of magnetization transfer imaging (MTI) of prostate in men who had raised prostate-specific antigen (PSA) (>4 ng/ml) or abnormal digital rectal examination (DRE) are reported. MT ratio (MTR) was calculated for 20 patients from the hyper- (normal) and hypo-intense regions (area suspicious of malignancy as seen on T2-weighted MRI) of the peripheral zone (PZ) and the central gland (CG) at 1.5 T. In addition, MTR was calculated for three healthy controls. Mean MTR was also calculated for the whole of the PZ (including hyper- and hypo-intense area) in all patients. Out of 20 patients, biopsy revealed malignancy in 12 patients. Mean MTR value (8.29+/-3.49) for the whole of the PZ of patients who were positive for malignancy on biopsy was statically higher than that observed for patients who were negative for malignancy (6.18+/-3.15). The mean MTR for the whole of the PZ of controls was 6.18+/-1.63 and is similar to that of patients who were negative for malignancy. Furthermore, for patients who showed hyper- (normal portion) and hypo-intense (region suspicious of malignancy) regions of the PZ, the MTR was statistically significantly different. These preliminary results reveal the potential role of MT imaging in the evaluation of prostate cancer.

A case of intraosseous arteriovenous malformation with unusual radiological presentation of low blood flow

We report a case of intraosseous arteriovenous malformation (AVM) arising in the diaphysis of the tibia. The patient was a 15-year-old boy who presented with pain in the right lower leg for 3 years. Plain radiographs displayed honeycomb lytic lesions in the right tibial shaft, with slight expansion of the bone and cortical thinning. The lesion was isointense to the muscle on T1-weighted images, and hyperintense on T2-weighted images. An admixture of hypointense small nodular or linear areas on both T1- and T2-weighted images was present within the lesion. Post contrast fat-suppressed T1-images demonstrated a mild heterogeneous increase in signal intensity throughout the tumor. Angiographs showed only faint staining in the lesion. Curettage of the lesion was carried out, and the histological diagnosis of AVM was made. In the context of this patient's lesion, it should be noted that AVM rarely presents as an intraosseous lesion with low blood flow.

Comparison of diffuse hepatocellular carcinoma and intrahepatic cholangiocarcinoma using sequentially acquired gadolinium-enhanced and Resovist-enhanced MRI

Purpose The purpose of this study was to compare MRI findings of diffuse hepatocellular carcinoma (D-HCC) and intrahepatic cholangiocarcinoma (IHC) to identify characteristics of each. Materials and methods We retrospectively analyzed MRI that consisted of unenhanced T1- and T2-weighted image, gadolinium (Gd)-enhanced dynamic image, and sequentially acquired Resovist-enhanced image from 29 patients with D-HCCs and 32 patients with IHC. Results On T2-weighted imaging, D-HCCs usually appeared as poorly defined, infiltrative mildly hyperintense masses, whereas IHC appeared as well-defined, lobulated mildly hyperintense masses with areas of strong hyperintensity and hypointensity. On dynamic- and Resovist-enhanced T1-weighted MRIs, D-HCCs appeared as hypovascular and homogeneously hypointense or isointense masses with internal reticulation, whereas IHD appeared as centripetal enhancing masses with or without delayed central hyperintensity. Biliary dilatation was predominantly observed in the area adjacent to the IHC and in the intratumoral area of D-HCC. Portal venous tumor thrombus was observed in most of the D-HCC, and portal vein encasement was seen in 17 of the IHC. Conclusion D-HCC and IHC exhibited characteristics of each at T1- and T2-weighted imaging, Gd-enhanced dynamic imaging, and sequentially acquired Resovist-enhanced T1-weighted imaging.

Poly(l-lysine)-Modified Iron Oxide Nanoparticles for Stem Cell Labeling

New surface-modified iron oxide nanoparticles were developed by precipitation of Fe(II) and Fe(III) salts with ammonium hydroxide and oxidation of the resulting magnetite with sodium hypochlorite, followed by the addition of poly( L-lysine) (PLL) solution. PLL of several molecular weights ranging from 146 ( L-lysine) to 579 000 was tested as a coating to boost the intracellular uptake of the nanoparticles. The nanoparticles were characterized by TEM, dynamic light scattering, FTIR, and ultrasonic spectrometry. TEM revealed that the particles were ca. 6 nm in diameter, while FTIR showed that their surfaces were well-coated with PLL. The interaction of PLL-modified iron oxide nanoparticles with DMEM culture medium was verified by UV-vis spectroscopy. Rat bone marrow stromal cells (rMSCs) and human mesenchymal stem cells (hMSC) were labeled with PLL-modified iron oxide nanoparticles or with Endorem (control). Optical microscopy and TEM confirmed the presence of PLL-modified iron oxide nanoparticles inside the cells. Cellular uptake was very high (more than 92%) for PLL-modified nanoparticles that were coated with PLL (molecular weight 388 00) at a concentration of 0.02 mg PLL per milliliter of colloid. The cellular uptake of PLL-modified iron oxide was facilitated by its interaction with the negatively charged cell surface and subsequent endosomolytic uptake. The relaxivity of rMSCs labeled with PLL-modified iron oxide and the amount of iron in the cells were determined. PLL-modified iron oxide-labeled rMSCs were imaged in vitro and in vivo after intracerebral grafting into the contralateral hemisphere of the adult rat brain. The implanted cells were visible on magnetic resonance (MR) images as a hypointense area at the injection site and in the lesion. In comparison with Endorem, nanoparticles modified with PLL of an optimum molecular weight demonstrated a higher efficiency of intracellular uptake by MSC cells.

Area of paradoxical signal drop after the administration of superparamagnetic iron oxide on the T2-weighted image of a patient with lymphangitic metastasis of the liver

We report a geographic area of prominent hypointensity in T2-weighted images vs. normal adjacent liver parenchyma in a patient with cholangiocarcinoma and lymphangitic metastasis of the liver after superparamagnetic iron oxide (SPIO) administration. The area showing this prominent signal drop showed Kupffer cell proliferation and lymphangitic metastasis during a pathologic examination.

Intramuscular hemangioma of masseter muscle with prominent formation of phleboliths: A case report

A 14-year-old girl was referred for evaluation and management of progressive, painful swelling of the right cheek. Swelling had been present since 3-year old and had gradually increased in size. Magnetic resonance imaging (MRI) revealed a well-circumscribed, brighter mass in the right masseter muscle with numerous rounded areas of signal hypointensity. Preoperative diagnosis was intramuscular hemangioma of the masseter muscle and surgery was performed. The tumor was completely removed except for a few, small phleboliths. Pathological examination of resected tissue led to a high suspicion of cavernous hemangioma with phlebolithiasis. Nine months postoperatively, the patient developed another painful mass in the right masseter muscle. MRI indicated recurrent hemangioma and further surgery was performed. Careful exploration resulted in completely removal of residual phleboliths accompanied with fibroadipose tissue. Part of the buccal branch of the facial nerve was excised to achieve complete resection of the lesion. Histological examination revealed distinct venous formation in phleboliths adjacent to fibroadipose tissue, demonstrating that both phleboliths and feeding vessels had been left by the previous operation. The present report reviews the literature on intramuscular hemangiomas of the masseter muscle, and discusses diagnostic methods and optimal surgical treatment.

A case of primary malignant fibrous histiocytoma of the pancreas: CT and MRI findings

Primary malignant fibrous histiocytoma (MFH) of the pancreas is rare and a distinct clinical entity. We report a case of recurrence of pancreatic MFH with computed tomography (CT) and magnetic resonance imaging (MRI) findings. A 67-year-old man presented with a history of decreased body weight over the past 6 mo. Abdominal CT revealed a large, multilocular cystic mass in the head of the pancreas with obvious atrophy in the body and tail of the pancreas. After 6 mo postoperatively, MRI demonstrated a recurrent large mass in the primary area of the head of the pancreas. The lesion was heterogeneous, hypointense to the liver on T1-weighted imaging, and heterogeneously hyperintense to the liver with a hypointense area in the central part of the tumor on fat-saturated T2-weighted imaging. Contrast-enhanced T1-weighted imaging demonstrated a large multilocular cystic mass with a cystic wall, fibrous septa and enhancement of solid components. To the best of our knowledge, this is the first report on recurrence of primary MFH of the pancreas, and the first with MRI findings.

Imaging findings of liver involvement of Wilson's disease

Purpose The major purpose of this paper is to outline and correlate US, CT and MR imaging findings of liver in patients with Wilson's disease. Materials and methods Twenty-eight patients (10 male, 18 female, median age 16) with Wilson's disease were examined with US, CT and MRI. Liver echogenicity, echo pattern, contour irregularity, periportal thickness, perihepatic fat layer thickness, the presence of focal parenchymal lesion, and other associated findings were recorded by US in every patient. CT and MRI were done in 20 and 12 patients, respectively. Results Contour irregularity was observed in 24 patients and heterogeneous parenchymal echo pattern was seen in 26 patients with US. The presence of increased perihepatic fat layer was observed in eight patients. Severe parenchymal atrophy was seen in all lobes of the liver including caudate in contrast to post-viral chronic liver disease. Nineteen patients had periportal thickening. US showed multiple hyper and/or hypoechoic nodules smaller than 1 cm in 13 patients. MRI demonstrated small nodular hypointense areas on T2-weighted images in five patients. In only one patient these nodules showed contrast enhancement in CT and MR and pathologically proved to be dysplastic nodule. Conclusion Wilson's disease involving the liver has several unique radiological findings in comparison to other types of cirrhosis. These specific features include multiple nodular lesions in the liver, presence of perihepatic fat layer and normal caudate lobe which is contrary to other types cirrhosis. Liver injury in the Wilson's disease can be defined by imaging modalities, especially by US which we think is the most precise imaging modality to detect early parenchymal changes in the progress of the disease.

Acute Astrocyte Activation in Brain Detected by Mri: New Insights into T1 Hypointensity

Increases in the T(1) of brain tissue, which give rise to dark or hypointense areas on T(1)-weighted images using magnetic resonance imaging (MRI), are common to a number of neuropathologies including multiple sclerosis (MS) and ischaemia. However, the biologic significance of T(1) increases remains unclear. Using a multiparametric MRI approach and well-defined experimental models, we have experimentally induced increases in tissue T(1) to determine the underlying cellular basis of such changes. We have shown that a rapid acute increase in T(1) relaxation in the brain occurs in experimental models of both low-flow ischaemia induced by intrastriatal injection of endothelin-1 (ET-1), and excitotoxicity induced by intrastriatal injection of N-methyl-D-aspartate (NMDA). However, there appears to be no consistent correlation between increases in T(1) relaxation and changes in other MRI parameters (apparent diffusion coefficient, T(2) relaxation, or magnetisation transfer ratio of tissue water). Immunohistochemically, one common morphologic feature shared by the ET-1 and NMDA models is acute astrocyte activation, which was detectable within 2 h of intracerebral ET-1 injection. Pretreatment with an inhibitor of astrocyte activation, arundic acid, significantly reduced the spatial extent of the T(1) signal change induced by intrastriatal ET-1 injection. These findings suggest that an increase in T(1) relaxation may identify the acute development of reactive astrocytes within a central nervous system lesion. Early changes in T(1) may, therefore, provide insight into acute and reversible injury processes in neurologic patients, such as those observed before contrast enhancement in MS.

Diffusion‐weighted imaging in brain aspergillosis

Brain aspergillosis is a rare pathology, occurring mainly in immunocompromised patients, responsible for multiple cerebral septic infarctions. Some researchers have described magnetic resonance (MR) findings in cerebral invasive aspergillosis, but diffusion-weighted imaging (DWI) has rarely been reported, especially in typical non-enhancing lesions, while it may be helpful for early differential diagnosis and may allow earlier antifungal treatment. We describe three cases of patients presenting brain aspergillosis, with MR imaging including diffusion-weighted sequences and apparent diffusion coefficient (ADC) cartography. The three patients described in this study presented a total of 23 circular lesions, and one patient presented an infarction area in the territory of the right middle cerebral artery. Lesions were ring-enhancing for one patient, and presented no enhancement for the other two. Eleven lesions were very bright on DWI, with reduced ADC values. Twelve lesions, either enhancing or not enhancing, presented a 'target-like' aspect with central and peripheral hypointense areas on DWI, corresponding to higher ADC value areas, and intermediate marked hypersignal on DWI. This typical aspect of aspergillosis lesions on DWI may allow early diagnosis and treatment of cerebral aspergillosis, and is helpful for differentiating aspergillosis lesions from other infectious or malignant lesions affecting immunocompromised patients.

Massive ovarian edema with torsion: unusual hemorrhage and the recovery of contrast enhancement

We report a case of massive ovarian edema due to left adnexal torsion. On initial magnetic resonance (MR), unusual hemorrhages were demonstrated as several hypointense areas on T2-weighted images. The lack of contrast enhancement was also observed in the left adnexa. Abdominal pain resolved spontaneously, and then follow-up MR demonstrated the recovery of enhancement and hemorrhages as hyperintense signals on T1-weighted images.

Imaging findings of soft tissue infections in AIDS ( report of 3 cases)

Objective To evaluate X-ray,CT and MRI findings of soft tissue infections in AIDS. Methods Three cases of soft tissue infections with AIDS were retrospectively analyzed by comparing the imaging findings with pathological results.All patients were performed MRI,X-ray was in 1 case,CT was in 1 case.Results Cellulitis was in 1 case:MRI showed extended thickening of subcutaneous tissues, ill-defined hypointense areas on T_1WI and hyperintensity on T_2WI,and reticular pattern on GRE. Necrotizing fasciitis was in 1 case:MRI showed obvious thickening of subcutaneous tissues and deep fasciae, abnormally increased signal intensity on T_1 and T_2WI.Fluid collections were within muscles and muscles interval on fat-suppressed T2 WI.Tuberculosis was in 1 case:CT demonstrated multiple low density areas in the subcutaneous tissues and clear peripheral rim enhancement.MRI appeared hypointense on T_1WI and hyperintensity on T_2WI,and peripheral rim enhancement following gadolinium injection.Conclusion Infections of soft tissue are common complication in patients with AIDS,radiology is important in early diagnosis and treatment planning in this population.