MR findings of renal cortical necrosis

PURPOSE: Evaluating the MR findings of renal cortical necrosis was the purpose of this study. METHOD: Eight series of T1-/T2-weighted (n = 8) and contrast-enhanced T1-weighted (n = 4) MR images in six patients with renal cortical necrosis diagnosed by renal biopsy (n = 4) or on clinical grounds (n = 2) were reviewed. In those who had follow-up MRI (n = 2) or comparable CT (n = 3), interval changes of MR findings and comparison with CT images were done. RESULTS: Swollen kidney with dark signal intensity rim involving the inner cortex and column of Bertin was noted on T2-and T1-weighted images. It was more conspicuous on T2-weighted images. The lesion did not enhance and was differentiated from uninvolved renal parenchyma. In the follow-up MRI, thickened dark signal intensity was more prominent and proved to be calcification or fibrosis. CONCLUSION: MRI, especially T2-weighted and contrast-enhanced T1-weighted imaging, was helpful in evaluating renal cortical necrosis.     

MRI findings in renal transplant recipients with hip and knee pain

Purpose

To evaluate and demonstrate the MRI findings of renal transplant recipients with hip and knee pain and to investigate the most common etiology of pain.

Materials and methods

69 hip MRIs of 57 patients with hip pain and 30 knee MRIs of 24 patients with knee pain with no history of trauma were retrospectively evaluated by two radiologists.

Results

In the evaluation of hip MRIs, 24 patients had avascular necrosis and effusion, 2 patients had bone marrow edema consistent with early stage of avascular necrosis. 18 patients had only intraarticular effusion, 6 patients had tendinitis, 6 patients had bursitis and 1 patient had soft tissue abscess. Five patients had muscle edema and five patients had muscle atrophy as additional findings to the primary pathologies. Among patients with knee pain, nine patients had degenerative joint disease. Seven patients had chondromalacia, five had bone marrow edema, six had meniscal tear, six had ligament rupture and two had bone infarct. Three of the patients had muscle edema accompanying to other pathologies.

Conclusion

The most common etiology of hip pain in renal transplant recipients is avascular necrosis as expected, intraarticular effusion is found to be the second reason for pain. However, knee pain is explained by ligament pathology, meniscal tear, chondromalacia or degenerative joint disease rather than osteonecrosis.     

Gd-DOTA-enhanced MR imaging and color Doppler US of renal allograft necrosis.

In 21 recipients of renal transplants suspected of allograft necrosis, the authors correlated the results of imaging to pathologic and histologic data in order to describe the magnetic resonance (MR) imaging and color Doppler ultrasonographic (US) characteristics of infarction. All patients underwent MR imaging performed with and without gadolinium tetraazacyclododecanetetraacetic acid (DOTA) and color Doppler US. Nonenhanced T1-weighted images showed no obvious changes, whereas nonenhanced T2-weighted images demonstrated a slight increase in signal intensity in areas of ischemic necrosis and low or heterogeneous signal intensity in areas of hemorrhagic necrosis. Gd-DOTA-enhanced MR images showed no contrast material uptake in infarcted areas. Color Doppler US characteristics of infarction included absence of Doppler signal and alteration of the cortical echogenic structure, particularly in cases of ischemic necrosis. Color Doppler US allows measurement of vascular resistance and assessment of intrarenal vasculature and the renal pedicle. Gd-DOTA-enhanced MR imaging is useful in confirming the diagnosis of infarction and provides an accurate evaluation of the extent of the infarct.     

MR of osteochondritis dissecans and avascular necrosis of the mandibular condyle

We studied 40 patients exhibiting radiologic changes of either osteochondritis dissecans (OCD) or avascular necrosis (AVN) involving the mandibular condyle to evaluate the structural changes associated with these lesions when using high-field-strength MR imaging. Various clinical indications for imaging each patient with routine radiography, tomography, and surface-coil MR included headache, temporomandibular joint (TMJ) and/or ilsilateral facial pain, joint crepitus, clicking, locking, and either recently acquired or changing (unstable) occlusal disorder. Radiologic findings included alterations in condyle morphology and MR signal characteristics compatible with either OCD or AVN or, in some cases, both. Previous nonsurgical mandibular trauma was temporally related to the onset of symptoms in eight patients. Five patients exhibiting either unilateral or bilateral AVN involving the condyles and condylar necks had undergone previous orthognathic surgery, including sagittal split mandibular osteotomies followed by intermaxillary fixation. One patient exhibiting condylar AVN with articular surface collapse and osseous destruction had undergone previous TMJ meniscectomy followed by insertion of a permanent Proplast implant. Thirty-one of 34 patients with no prior surgery and MR changes of condylar OCD/AVN had associated internal derangement of the TMJ meniscus. There was surgical confirmation of findings in 10 joints. We assert that OCD and AVN are relatively common, clinically significant lesions of the mandibular condyle often associated with preexisting internal derangement of the temporomandibular joint.     

Femoral head avascular necrosis: correlation of MR imaging, radiographic staging, radionuclide imaging, and clinical findings

To better correlate the appearance of avascular necrosis (AVN) of the femoral head on magnetic resonance (MR) images with the stage of disease, MR images of 56 proved AVN lesions were compared with staging from corresponding radiographs (n = 56), Tc-99m scans (n = 41), and grade of symptoms (n = 28). Fractures complicating AVN were seen in 28 (50%) of 56 radiographs (radiographic stages III-V). With long repetition (TR) and echo delay (TE) times, a characteristic "double line sign" consisting of high signal intensity inside a low-intensity peripheral rim was seen in 45 lesions (80%). The central region within the rim was isointense with marrow fat on both short and long TR and TE images in 20 (71%) of 28 lesions uncomplicated by fracture (stages I-II) but in only four (14%) of 28 stage III-V lesions (P less than .001). Symptoms were least severe in lesions isointense with fat and most severe in lesions with low-signal central regions at short and long TRs and TEs. The peripheral double line sign on long TR/TE images may add specificity to the diagnosis of AVN by MR imaging. A chronologic pattern of central MR signal features is presented which may allow staging of AVN by MR imaging.     

Screening for avascular necrosis of the hip with rapid MRI: preliminary experience

PURPOSE: The purpose of this work was to compare rapidly acquired MR images with routinely employed SE and turbo SE (TSE) images in screening for hip avascular necrosis (AVN). METHOD: Twelve patients with findings suspicious for radiographically occult AVN of one or both hips were studied with our routine screening protocol (imaging time >7 min) and similarly weighted, rapidly acquired MR sequences (imaging time <1 min). RESULTS: The rapidly acquired MR images were judged to be similar to the routine protocol in demonstrating marrow edema, irregular lines within the femoral head characteristic of AVN, and osteoarthritis. CONCLUSION: The rapidly acquired MR sequences that we studied reliably revealed the presence or absence of AVN, marrow edema, and osteoarthritis of the hip in our sample population when compared with SE and TSE sequences that we routinely perform. Further investigation of rapidly acquired MR sequences is warranted, as imaging time may be dramatically reduced and patient throughput increased.     

The role of MR imaging in avascular necrosis of the femoral head

Due to the pattern of its blood supply, the femoral head is particularly vulnerable to avascular necrosis (AVN). Nontraumatic AVN is a devastating disorder affecting young patients, and despite treatment it normally follows a progressive course toward a destructive osteoarthropathy. Magnetic resonance (MR) imaging is currently used in major classification systems solely for early detection of femoral head AVN when plain radiographs are normal. More recent data have shown that MR imaging may improve staging, investigate radiologically occult collapse, depict other causes of disability and pain, assess prognosis, and evaluate treatment. This article reviews the established and evolving role of MR imaging in patients at risk or with known femoral head AVN.     

Arthroscopic management and platelet-rich plasma therapy for avascular necrosis of the hip

Purpose  

The purpose is to describe a noninvasive arthroscopic procedure as an alternative to open surgery for avascular necrosis of the hip.     

Rapidly destructive osteoarthritis of the hip: MR imaging findings

OBJECTIVE: The purpose of our study was to use an artificial neural network to differentiate benign from malignant pulmonary nodules on high-resolution CT findings and to evaluate the effect of artificial neural network output on the performance of radiologists using receiver operating characteristic analysis. MATERIALS AND METHODS: We selected 155 cases with pulmonary nodules less than 3 cm (99 malignant nodules and 56 benign nodules). An artificial neural network was used to distinguish benign from malignant nodules on the basis of seven clinical parameters and 16 radiologic findings that were extracted by attending radiologists using subjective rating scales. In the observer test, 12 radiologists (four attending radiologists, four radiology fellows, and four radiology residents) were presented with high-resolution CT images, first without and then with the artificial neural network output. Observer performance was evaluated by means of receiver operating characteristic analysis using a continuous rating scale. RESULTS: The artificial neural network showed a high performance in differentiating benign from malignant pulmonary nodules (A(z) = 0.951). The average A(z) value for all radiologists increased by a statistically significant level, from 0.831 to 0.959, with the use of the artificial neural network output. CONCLUSION: Our computerized scheme using the artificial neural network can improve the diagnostic accuracy of radiologists who are differentiating benign from malignant pulmonary nodules on high-resolution CT.     

MR imaging of iliopsoas bursitis and concurrent avascular necrosis of the femoral head

The magnetic resonance (MR) features of iliopsoas bursitis secondary to an inflammatory arthropathy of the hip are described in a patient with concurrent avascular necrosis of the femoral heads. The MR findings of avascular necrosis were demonstrated on one side where radiography, bone scan, and CT were negative.     

MR imaging findings in transient osteoporosis of the hip

Purpose: The authors sought to describe the magnetic resonance (MR) imaging findings including perfusion imaging, in association with the course of acute bone marrow oedema syndrome (aBMEs), in a group of patients with acute hip pain and a final diagnosis of transient osteoporosis of the hip (TOH). Materials and methods: From 217 patients referred with a probable diagnosis of avascular necrosis (AVN) of the femoral head, we identified 42 patients who had clinical and radiographic findings not relevant to AVN. MR imaging examinations were performed on a 1.0T scanner. Perfusion imaging was performed in 20 patients. The bone marrow oedema (BME) was classified in four stages. In addition, the presence or absence of oedema in the subchondral area and the presence of other subchondral lesions were recorded. Acetabular bone marrow was also assessed for the presence of oedema. The quantitative measurements included: maximum size of the effusion, percentage of enhancement (PE) and time of peak enhancement of abnormal marrow compared to the first pass, on the perfusion images. Results: Osteopenia was present on plain radiographs in 87% of cases. The most common pattern of BME was extending to the femoral head and neck. Acetabulum was involved in 16.6%. In 22.6% the BME spared the subchondral region of the femoral head. There were two cases (4.7%) with subchondral changes. A joint effusion was noted in 33 of the 42 patients. On perfusion imaging, a delayed peak enhancement was noted in 20 patients between 40 and 65 s after the first pass of contrast. No patient had any evidence of femoral head collapse or change in sphericity on follow-up MRI. None of the patients developed avascular necrosis in a time frame of 18 months from the onset of the acute hip pain. Conclusion: The aBMEs MR imaging pattern varies and is most commonly appearing on X-rays as osteopenia. Absence of subcondral lesions, delayed peak enhancement of the abnormal marrow on perfusion images, and sparing of subchondral zone from marrow oedema are MR imaging findings highly correlated to TOH.     

Paralabral cysts in the hip joint: findings at MR arthrography

Purpose

The purpose of this research was to retrospectively characterize paralabral cysts of the hip as seen at MR arthrography.

Materials and methods

After Institutional Review Board approval, 704 patients who had MR arthrography were identified over a 3-year period and 40 patients were identified as having a cyst or fluid collection at the hip by MR report. MR images from these 40 patients were retrospectively reviewed by three radiologists where 18 were found to have a paralabral cyst, which were characterized as follows: location, configuration, contrast filling, size of the cyst, extent, direction, and whether associated osseous changes were present. In addition, the acetabular labrum was assessed for tears and, if present, the location and pattern were characterized.

Results

Paralabral cysts were located anterosuperiorly in 56%, anteriorly in 22%, posterosuperiorly in 17%, and anteroinferiorly in 6% of cases. The vast majority (94%) were multilocular and filled with intra-articular contrast medium. The average dimensions were 8?×?7?×?11?mm. The paralabral cyst demonstrated extracapsular extension in 72% of cases, with 39% located between the ilium and gluteus minimus, and 22% between the ilium and iliopsoas. Remodeling of the ilium adjacent to the cyst was observed in 50% of these cases. A labral tear was at the base of the labrum adjacent to the cyst in 78% of cases, while the tear was isolated to the body of the labrum in 22%. Tears were most commonly anterosuperior (55%) or anterior (28%) in location.

Conclusion

Our results show that paralabral cysts of the hip are most commonly located anterosuperiorly, are multilocular, fill with intra-articular contrast medium, have average dimensions up to 11?mm, and often extend extracapsularly between muscle and bone where they may remodel the adjacent ilium.     

Segmental patterns of avascular necrosis of the femoral heads: early detection with MR imaging

Thirty-two patients (64 hips) in whom avascular necrosis (AVN) of the femoral heads was highly suspected clinically were studied by magnetic resonance (MR) imaging, radionuclide bone scintigraphy, and conventional radiography. MR studies were positive for AVN in 37 hips, compared with 30 positive scintigraphic studies. In all cases in which scintigraphy and radiography were positive, MR imaging demonstrated decreased signal from the affected femoral heads, indicative of bone marrow disease. Imaging results were confirmed by biopsy or subsequent imaging appearances. In patients with negative initial scintigraphic and radiographic studies, the MR imaging criterion for a positive study was a moderately decreased bone marrow signal displaying segmental patterns within an otherwise normal-appearing femoral head on relatively T1-weighted images. In this series of high-risk patients, radionuclide scintigraphy had a sensitivity of 81%, compared with 100% for MR imaging. MR imaging should be the imaging modality of choice for early evaluation of bone marrow changes indicative of AVN.     

Magnetic resonance imaging criteria of successful core decompression in avascular necrosis of the hip

To identify imaging criteria that determine the outcome of core decompression (CD) in femoral-head avascular necrosis (AVN). Radiographs and magnetic resonance imaging (MRI) of 65 hips with early stage AVN treated by core decompression between January 1990 and December 2000 for AVN were reviewed. All hips were categorized into two groups according to the result of CD using total hip arthroplasty (THA) as an end point. Hips that had no THA at follow-up were allocated to group I; those treated with a THA were allocated to group II. CD results were calculated for each group using THA as an end point. The parameters analyzed were the presence or absence of edema associated with the double-line sign on the preoperative MRI, the type of epiphyseal scar (ES) according to Jing, and the type of necrosis according to Mitchell. On follow-up, 45 hips had no THA (group I); 20 patients had a THA (group II). Patients with a radiographic crescent sign and those with edema associated with the double-line sign progressed to THA significantly more frequently. The extent of the necrosis had less discriminatory effect between the two groups. ES and necrotic tissue types had no prognostic value. In regard to the success of CD, it is important to differentiate on MRI between a double line sign plus bone marrow edema and a double-line sign only.