Regions Of High Signal Intensity Research Articles

Intramyocardial hemorrhage and microvascular obstruction after primary percutaneous coronary intervention

Reperfusion may cause intramyocardial hemorrhage (IMH) by extravasation of erythrocytes through severely damaged endothelial walls. The purpose of the study was to evaluate the clinical significance of IMH in relation to infarct size, microvascular obstruction (MVO) and function in patients after primary percutaneous intervention. Forty-five patients underwent cardiovascular MR imaging (CMR) 1 week and 4 months after primary stenting for a first acute myocardial infarction. T2-weighted spin-echo imaging (T2W) was used to assess infarct related edema and IMH, and delayed enhancement (DE) was used to assess infarct size and MVO. Cine CMR was used to assess left ventricular volumes and function at baseline and at 4 months follow-up. In 22 (49%) patients, IMH was detected as areas of attenuated signal in the core of the high signal intensity region on T2W images. Patients with IMH had larger infarcts, higher left ventricular volumes and lower ejection fraction. Contrast-to-noise ratio (CNR) between hyperintense periphery and the hypo-intense core of the T2W ischemic area correlated to peak CKMB, total infarct size and MVO size. Using univariable analysis, CNR predicted ejection fraction at baseline (β = −0.62, P = 0.003) and follow-up (β = −0.84, P < 0.001). However, after multivariable analysis, baseline ejection fraction and presence of MVO were the only parameters that predicted functional changes at follow-up. IMH was found in the majority of patients with MVO after reperfused myocardial infarction. It was closely related to markers of infarct size, MVO and function, but did not have prognostic significance beyond MVO.

Higher Lesion Detection by 3.0T MRI in Patient with Transient Global Amnesia

PurposeTransient global amnesia (TGA) patients were retrospectively reviewed to determine the usefulness of high-field strength MRI in detecting probable ischemic lesions in TGA.Materials and MethodsWe investigated the lesion detection rate in patients with TGA using 1.5T and 3.0T MRI. Acute probable ischemic lesions were defined as regions of high-signal intensity in diffusion weighted image with corresponding low-signal intensity in apparent diffusion coefficient map.Results3.0T MRI showed 11 out of 32 patients with probable ischemic lesions in the hippocampus with mean lesion size of 2.8 ± 0.6 mm, whereas 1.5T MRI detected no lesion in any of 11 patients. There were no significant differences in clinical characteristics between the groups of 1.5 and 3.0T MRI.ConclusionHigh-field strength MRI has a higher detection rate of probable ischemic lesions than low-field strength MRI in patients with TGA.

Deep Retroperitoneal Pelvic Endometriosis: MR Imaging Appearance with Laparoscopic Correlation

Deep pelvic endometriosis is defined as subperitoneal infiltration of endometrial implants in the uterosacral ligaments, rectum, rectovaginal septum, vagina, or bladder. It is responsible for severe pelvic pain. Accurate preoperative assessment of disease extension is required for planning complete surgical excision, but such assessment is difficult with physical examination. Various sonographic approaches (transvaginal, transrectal, endoscopic transrectal) have been used for this purpose but do not allow panoramic evaluation. Furthermore, exploratory laparoscopy has limitations in demonstrating deep endometriotic lesions hidden by adhesions or located in the subperitoneal space. Despite some limitations, magnetic resonance (MR) imaging is able to directly demonstrate deep pelvic endometriosis. The MR imaging features depend on the type of lesions: infiltrating small implants, solid deep lesions mainly located in the posterior cul-de-sac and involving the uterosacral ligaments and torus uterinus, or visceral endometriosis involving the bladder and rectal wall. Solid deep lesions have low to intermediate signal intensity with punctate regions of high signal intensity on T1-weighted images, show uniform low signal intensity on T2-weighted images, and can demonstrate enhancement on contrast-enhanced images. MR imaging is a useful adjunct to physical examination and transvaginal or transrectal sonography in evaluation of patients with deep infiltrating endometriosis.

Myelination of the Pig’s Brain: A Correlated MRI and Histological Study

Minipigs, 2, 4, 6 months old, were used to evaluate the relationship between myelination in the fiber tracts of the central nervous system (CNS) of this animal during development. Histological results showed an increased density of the myelinated fibers as well as branching of these fibers in the areas studied, including the cortical white matter, olfactory tract, the corticospinal tract, the fasciculus cuneatus and the spinal V nucleus from 2 to 6 months old. By 6 months, the pig was sexually matured. Concomitantly, there was an increase in high signal-intensity regions (sites) in the magnetic resonance T₁-weighted images as myelination progressed. There is a good correlation between the histologically observed progress of myelination and the T₁-weighted images in the development of the CNS of the pig.

IGRT for cervical cancer: Is it less toxic than non IGRT

We have been used MR images for brachytherapy for cervical cancer with the purpose of getting more conformal dose distribution and also reducing late morbidity. We evaluate whether this technique is less toxic than our historical data using Manchester system. Between January 1995 and December 2000, 60 patients with histological confirmed squamous cell carcinoma of the uterine cervix (FIGO Stage Ib: 7, stage IIb: 25, stage IIIb: 20, stageIVb: 7) were treated with external irradiation and MR image guided intracavitary HDR brachytherapy. Average age of the patients was 61.3 years (range: 33–85 years). Median follow-up duration was 46 months (range: 5–103 months). All patients were treated 30Gy whole pelvic irradiation followed by 20Gy boost to parametrium. Both CT and MRI were performed at the first and third time of brachytherapy under CT-MR compatible applicator insertion. The GTV was defined as high signal intensity region obtained MRI. The PTV was defined as a volume, which include 1cm margin in cranio-caudal directions. We delivered 6Gy/fraction to the PTV, one fraction /week, to a total dose of 24Gy. Until 1994, 332 patients were treated with same external irradiation technique followed by Intracavitary brachytherapy using Manchester system optimization (6Gy /fraction to a total dose of 24Gy to Point A). The 5-year survival rates according to stage, average Point A dose, maximum rectal, bladder dose and late genitourinary morbidity rates were compared between the two groups. In IGRT group, ten patients have died of their cancer and two died of intercurrent disease without evidence of recurrence. The 5 year overall survival and RFS rates according to stage in IGRT group were as follows; stage Ib: 100%, 85.7%, stage IIb: 86.5%, 100%, stage IIIb: 67.5%, 78.3%, stage IVb: 50%, 44%, respectively. Average point A dose was 496cGy (ranged: 102–710cGy). The average maximum rectal dose was 549cGy ± 214cGy in IGRT group and 1000cGy ± 640cGy in non-IGRT group, respectively. The average maximum bladder dose was 594 ± 180cGy in IGRT group and 1210cGy in non-IGRT group. The 5 year overall survival rate according to stage in non-IGRT group were as follows; stage Ib: 90%, stage IIb: 75%, stage IIIb: 52.3%, respectively. Grade1 late morbidity of bladder was observed in 2/60. Grade 1 and 2 late rectal morbidity was observed in 10/60 and 2/60, respectively. No cases were observed greater than Grade 3 morbidity at 5 years in IGRT group, whereas late rectal morbidity in non IGRT group was as follows; Grade 1: 21% (70/332), Grade 2: 9.7% (32/332), Grade 3: 5.7% (19/332), respectively. We have shown that IGRT using MRI for cervical cancer is less toxic than non-IGRT technique and the survival rate using IGRT was equal to or better than non-IGRT

Localized nodular synovitis of the knee: MR imaging appearance and clinical correlates in 21 patients.

Localized nodular synovitis of the knee and pigmented villonodular synovitis are similar histologically. The purpose of this study was to evaluate the MR imaging appearance and clinical findings of localized nodular synovitis of the knee and to differentiate this condition from pigmented villonodular synovitis. A retrospective review of MR imaging of the knee was performed in 21 patients with histologically confirmed localized nodular synovitis. Surgical excision of the lesion was performed in all patients. The MR imaging appearances of the lesions were defined, and the clinical and surgical findings were reviewed. All lesions presented as a solitary intraarticular mass. The mass originated from the synovial lining in different locations including the infrapatellar fat pad (n = 14), suprapatellar pouch (n = 5), and posterior aspect of the intercondylar notch (n = 2). A small (2.0-3.5 cm; mean diameter, 2.7 cm) ovoid mass (n = 13) was more common than a large (5.0-9.0 cm; mean diameter, 6.5 cm) polylobulated mass (n = 8). At surgery, a long pedicle attached the mass to the adjacent synovium in two patients, but this was observed on MR imaging in only one patient. The lesions showed intermediate (n = 15) or hyperintense (n = 6) signal intensity on T1-weighted images and heterogeneously high (n = 13) or low (n = 8) signal intensity with variable circular foci of low signal intensity on T2-weighted images. On T2-weighted images, linear regions of high signal intensity within the mass were seen in seven lesions. Prominent enhancement of the lesion with IV contrast administration was shown in all patients who were given contrast material (n = 10). Knee pain, joint swelling, and a palpable mass were the most frequent clinical manifestations. An acutely painful knee was noted in one patient who presented with torsion of an infrapatellar pedicle. Five patients complained of locking of the knee, but at physical examination, restricted terminal knee extension was noted in nine patients. Localized nodular synovitis of the knee predominantly involves the infrapatellar fat pad. It may produce symptoms related to mechanical derangement of the knee. Although there is no typical MR appearance for this lesion, many features help to differentiate it from pigmented villonodular synovitis.

Evolution of T1 black holes in patients with multiple sclerosis imaged monthly for 4 years.

T1 black holes (BHs) on MRIs may represent either areas of oedema or axonal loss in patients with multiple sclerosis. BHs begin as contrast enhancing lesions (CELs) and evolve differently from patient to patient, and within the same patient over time. We analysed BHs formation over a 4-year period. Forty-eight monthly MRIs of nine non-treated multiple sclerosis patients were evaluated for numbers of CELs and BHs. A BH was defined as a hypointense lesion on a T1 pre-contrast image that coincided with a region of high signal intensity on the T2-weighted images. A BH was considered as acute (ABH) when it occurred coincidently with the presence of enhancement and as persisting (PBH) when present after the cessation of enhancement. The present study aimed to analyse: (i) the incidence of CELs and new PBHs, and the accumulation of PBHs; (ii) the relationship between the quantity of the CELs in a given month and the likelihood of accumulating PBHs in the subsequent month; and (iii) the relationship between the duration of CELs and PBHs. Pitman's correlation test evaluated the effect of time on either the increase of CELs and new PBHs or the accumulation of PBHs, while a multiple logistic regression analysis evaluated the relationship between progression of time and CELs, and the increase of PBHs in a multivariate model. The relationship between the enhancing lesions duration and the PBHs duration, or the time to revert back to an isointense lesion was analysed using Kaplan-Meier survival models. PBHs accumulated (P < 0.001) in all patients, but the formation of new PBHs increased in four patients (P < or = 0.007) in conjunction with an increase in either the quantity of CELs (P < 0.001, for two patients) or the proportion of CELs turning into PBHs (P < or = 0.02, for two patients). Logistic regression analysis showed that neither progression of time nor the number of CELs in a given month were able to predict the probability of increasing the number of PBHs in the subsequent month in any patient. Out of 397 ABHs, 55.7% evolved to a PBH. The duration of PBHs correlated with the duration of enhancement. PBHs preceded by CELs observable on a single MRI persisted for a shorter time (P < 0.002) than those preceded by CELs visible on > or =2 monthly MRIs. The formation of a new PBH was found to be related to CELs activity; however, duration of PBHs is most likely a consequence of the duration of the enhancement.

Detection of lymph node metastases by contrast-enhanced MRI in an experimental model.

Lymph node size, the accumulation of a nodal lymphotrophic contrast agent (LCDIO), and MRI were compared as methods for detecting nodal metastases in an experimental murine model. Lymph node metastases (B16-F1 melanoma expressing green fluorescent protein (GFP) and C57BL/6 mice) were generated to obtain a wide spectrum of nodes, including normal nodes and nodes bearing micrometastases, small metastases, or large metastases. Nodal uptake of LCDIO was measured using (111)Indium-labeled LCDIO and was found to be lower in micrometastastic nodes (4.20 +/- 1.4%ID/gm) than in normal nodes (8.60 +/- 0.22% ID dose/gram, P < 0.005). Nodal tumor burden was quantified from the amount of GFP present in nodes measured using the Western blot method, and was found to correlate with the decrease of LCDIO uptake. By MRI, nodes bearing small and large metastases contained regions of high signal intensity (SI) that corresponded to the visual pattern of tumor in nodes. Micrometastatic nodes were distinguishable from normal nodes based on a diffuse pattern of inhomogeneous SI. The signal-to-background ratio (SBR) of normal nodes (0.0112 +/- 0.0061) was different from micrometastatic nodes (0.179 +/- 0.080, P < 0.00046) and nodes bearing small metastases (0.723 +/- 0.269, P < 0.00013), with high degrees of significance.

CNS expression of diacylglycerol kinase iota and L18A mRNAs

The diacylglycerol kinases family shows a high degree of molecular diversity and distinct expression patterns in thebrain, suggesting an importance of these enzymes for brain function. A likely mechanism of action is the regulationof protein kinase C (PKC) pathways. The expression of one diacylglycerol kinase isoform, iota, is increased in thecortex of AA rats bred for high alcohol preference. The autoradiogram shows the expression of this isoform in therat brain mapped by in situhybridization. Regions of high signal intensity are coded in red colors and of low intensityin blue. For further information on this topic, see the article by W Sommer et alon pages 103–108.

Treatable chondral injuries in the knee: frequency of associated focal subchondral edema.

In the knee, chondral flaps and fractures are radiographically occult articular cartilage injuries that can mimic meniscal tears clinically; once correctly diagnosed, these injuries can be treated surgically. We investigated an associated MR imaging finding--focal subchondral bone edema--in a series of surgically proven lesions. Two musculoskeletal radiologists retrospectively reviewed the MR studies of 18 knees with arthroscopically proven treatable cartilage infractions, noting articular surface defects and associated subchondral bone edema; subchondral edema was defined as focal regions of high signal intensity in the bone immediately underlying an articular surface defect on a T2-weighted or short inversion time inversion recovery (STIR) image. The first observer saw focal subchondral edema deep relative to a cartilage surface defect in 15 (83%) of the 18 cases; in two additional cases a surface defect was seen without underlying edema. The second observer identified 13 knees (72%) with surface defects and associated subchondral edema and three with chondral surface defects and no associated edema. Subchondral edema was seen more frequently on fat-suppressed images and on STIR images than non-fat-suppressed images. Focal subchondral edema is commonly visible on MR images of treatable, traumatic cartilage defects in the knee; this MR finding may prove to be an important clue to assist in the detection of these traumatic chondral lesions.

Peripheral focal low signal intensity areas in the degenerated annulus fibrosus on T2-weighted fast spin echo MR images: correlation with macroscopic and microscopic findings in elderly cadavers.

To correlate the peripheral focal low signal intensity areas in the degenerated annulus fibrosus on T2-weighted fast spin echo MR images with the macroscopic and microscopic findings in cadavers derived from elderly subjects. Twenty-eight intervertebral disks (16 lumbar and 12 cervical) derived from four nonembalmed cadavers were examined with T1-weighted spin echo and proton density-weighted and T2-weighted fast spin echo MR imaging. The signal intensities of the annulus fibrosus were evaluated on sagittal MR images and correlated with the findings on corresponding sagittal anatomic sections. The MR imaging-histologic correlation was then studied. Peripheral focal low signal intensity areas and adjacent regions of high signal intensity were found in five lumbar intervertebral disks. Peripheral focal low signal intensity regions consisted of disorganized compact annular fibers, tiny fissures, and dense fibrosis. The high signal intensity regions, adjacent to the areas of low signal intensity, consisted of mucoid degeneration, tiny fissures, and chondroid metaplasia. Awareness of the histologic findings in regions that reveal peripheral focal low signal intensity with adjacent regions of high signal intensity in the degenerated annulus fibrosus on T2-weighted images may facilitate effective interpretation of clinical MR images of the spine.

MRI of the cartilaginous epiphysis of the femoral head in the piglet hip after ischemic damage.

MRI of the cartilaginous epiphysis (CE) of piglet femoral head was performed after ischemic damage to study the changes in the CE found on MRI and to correlate these changes with histologic findings. Avascular necrosis of the femoral head was induced with a suture ligature in nine piglets; one piglet was killed postoperatively on day 3 and on weeks 1, 2, 3, 4, 6, 7, and 8 (two piglets were killed on week 3). MRI of the ischemic and contralateral nonischemic hip joints were obtained with a 60-mm field of view (low resolution MRI). Biopsy cores of the femoral heads were imaged with a 15-mm field of view (high resolution MRI) and correlated with histologic sections. The CE for all operated hips, except for the 3-day postoperative specimen, showed evidence of ischemic changes on histologic assessment; the severity of damage increased with time. The MRI appearance of ischemic and nonischemic CE was clearly different by 2 weeks after the operation. No trilaminar signal pattern was evident in the high resolution T2-weighted (T2W) imaging of the ischemic CE from 2 weeks after the operation. In the 3- to 8-week postoperative specimens, focal areas of low signal intensity on high resolution T1-weighted (T1W) and T2W imaging corresponded to the areas of chondronecrosis found on histologic assessment. The regions of high signal intensity on T2W imaging corresponded to the areas of chondrocyte clusters with increased safranin-O staining. High resolution MRI can demonstrate changes in the CE associated with ischemic injury and may have a role in the assessment of the CE and its development after ischemic injury.

Calcific tendinitis of the longus colli muscle: Case report

Background To the best of our knowledge, only one patient with calcium hydroxyapatite deposition disease (CHADD) of the longus colli muscle has been reported in the otolaryngology literature. Methods Clinical findings and results of imaging studies in such a patient are reported. Results Two particular imaging findings of this disorder are discussed. First, disappearance of calcifications over the short time frame of a week, accompanied by the resolution of clinical symptoms. Second, the presence of an extensive region of high signal intensity extending from the skull base to the lower border of C5, on T2-weighted spin-echo magnetic resonance (MR) images. Conclusions Knowledge of the characteristic clinical spectrum and imaging features of this disorder are crucial for a correct diagnosis of this uncommon cause of odynophagia and dysphagia. © 1997 John Wiley & Sons, Inc. Head Neck 19:545–548, 1997.

Renal cell cancer: incidence of hemorrhage on MR images in patients with chronic renal insufficiency.

This study describes the occurrence of hemorrhage in renal cancer in patients with chronic renal insufficiency as shown on MR images. Thirteen consecutive patients with chronic renal insufficiency who had histologically proven renal cancer and underwent MRI at 1.5 T were entered in the study. MR examinations included spoiled gradient echo (SGE) and T1-weighted fat-suppressed imaging pre- and postgadolinium administration. All renal cancers were well shown on MR images and were most clearly depicted on postgadolinium T1-weighted fat-suppressed images. Tumors in 12 of 13 patients had regions of high signal intensity on precontrast T1-weighted images. Histology demonstrated intratumoral hemorrhage in all 12 of these patients. Four hemorrhagic tumors were largely cystic on imaging studies. One of these cancers altered in appearance from largely cystic with extensive hemorrhage to largely solid with substantial enhancement after a 2.5-year interval. Renal cancers demonstrated minimal enhancement (11 patients) on early postgadolinium images and were minimally enhanced on delayed images in 10 of 13 tumors. Two renal cancers demonstrated intense enhancement. Renal cancers are well shown on MR images in patients with chronic renal insufficiency. Because of the common occurrence of hemorrhage into renal cancers in patients with renal insufficiency, caution should be exercised when evaluating hemorrhagic cystic lesions in these patients.

Quantification of the extent of area at risk with fast contrast-enhanced magnetic resonance imaging in experimental coronary artery stenosis

Fast magnetic resonance (MR) imaging techniques have the capability of demonstrating regions of ischemia caused by stenosis. The size of the potentially ischemic area determines the importance of the stenosis. The purpose of this study was to determine the relative values of relaxivity-enhancing and magnetic-susceptibility MR contrast media in detecting and sizing the area at risk in dogs. Eight dogs were subjected to critical left circumflex coronary artery (LCX) stenosis. Sixty sequential inversion-recovery— and driven-equilibrium—prepared fast gradient recalled echo images were acquired during bolus administration of 0.03 mmol/kg gadodiamide or 0.4 mmol/kg sprodiamide in basal and vasodilated (dipyridamole-stress) states. The size of the area at risk was measured and compared with that measured post mortem. In the basal state, gadodiamide and sprodiamide equivalently altered the signal intensities of nonischemic myocardium and the territory of stenosed coronary artery. Dipyridamole produced a significant increase in left anterior descending coronary artery flow with a decrease in LCX flow. The hypoperfused region was observed as a low— and high—signal intensity region after administration of gadodiamide and sprodiamide, respectively. The size of the hypoperfused region was slightly smaller with gadodiamide (37.4% ± 2.8%) and sprodiamide (34.0% ± 2.2%) than the true area at risk measured post mortem (41.8% ± 2.2%; p < 0.05). Dipyridamole perfusion MR imaging with relaxivity or susceptibility contrast media is a noninvasive method to identify and quantify the area at risk in the territory of a stenotic coronary artery. Changes in myocardial signal intensity on fast gradient recalled echo images reflect the augmentation of flow and volume induced with dipyridamole and are consistent with the “steal phenomenon.”

Correlation of magnetic resonance imaging and surgical findings in patients with temporomandibular joint disorders

Purpose: This study compared the magnetic resonance imaging (MRI) and surgical findings in patients with temporomandibular joint disorders. Materials and Methods: Forty-three patients and 30 asymptomatic volunteers underwent MRI using the three-dimensional (3D) FISP acquisition technique. The 43 patients (43 joints) then underwent discectomy, and the surgical and MRI findings were correlated. Results: In 28 joints (28 patients), splits surrounded by regions of high-signal intensity were seen in the discs and retrodiscal tissues on MRI. Surgically, a tear was confirmed in 26 (93%) of these joints. Histologically, these areas showed severe myxomatous degeneration. Disc deformity was visualized by MRI in all patients and increases in signal intensity were found in some discs. High-signal intensities also were observed in 30 joint spaces, in which serous joint effusion was confirmed surgically. Conclusion: Pathologic intracapsular changes are accurately depicted by FISP-3D, and this method is particularly useful for diagnosing changes in the disc and retrodiscal tissues.

Usefulness of magnetic resonance imaging for detecting intrasubstance tear and/or degeneration of lateral discoid meniscus

In order to determine the usefulness of magnetic resonance imaging (MRI) for detection of intrasubstance tears or degeneration of the lateral discoid meniscus, we compared findings obtained with MRI with those of histological examination. Sixty-four symptomatic lateral discoid menisci were studied using MRI before surgical treatment. Of these, 18 (28%) met the criteria that MRI signals did not extend to the surface and that no visible tears were observable at arthroscopy. Findings of intrameniscal regions of high signal intensity and flattening in shape on MR images were found to represent intrasubstance tears or degeneration not detected at arthroscopy. Our findings thus demonstrate that MRI is more sensitive than arthroscopy in the detection of intrasubstance pathologies of the lateral discoid menisci.

Acute stroke in cats: comparison of dynamic susceptibility-contrast MR imaging with T2- and diffusion-weighted MR imaging.

To evaluate the hemodynamics of acute stroke in cats by means of dynamic susceptibility-contrast magnetic resonance (MR) imaging compared with standard T2- and diffusion-weighted MR imaging. Unilateral permanent occlusion of the middle cerebral artery was performed in 18 cats. MR imaging was performed with each method 2 hours (n = 2), 6 hours (n = 10), and 24 hours (n = 11) after occlusion. At every time point, dynamic MR images clearly showed ischemic regions of steady-state signal hyperintensity and areas of less dynamic decrease in signal intensity that corresponded closely to those seen on diffusion-weighted MR images. T2-weighted MR images did not reveal regions of high signal intensity 2 hours after occlusion. The measurements of relative blood volume obtained with the dynamic method were significantly lower in steady-state hyperintense ischemic areas of the affected side than those in the contralateral normal areas at 6 and 24 hours (P < .001). This dynamic method can advance the time of detection of early ischemia in comparison with T2-weighted MR imaging and provides functional information about hemodynamics not provided by other methods of MR imaging.

MR detection of degenerating uterine leiomyomas.

Gonadotropin-releasing hormone (GnRH) analogues have been advocated for the conservative management of uterine leiomyoma. These drugs induce a hypoestrogenic state and affect undegenerated myoma cells. Therefore, we evaluated the usefulness of MRI for distinguishing undegenerated and degenerated leiomyomas. Twenty lesions were studied in 16 patients with surgically resected leiomyoma. A 1.5 T unit was used to obtain T1- and T2-weighted images and Gd-DTPA-enhanced T1-weighted images. Signal intensity maps were made for each pulse sequence, and detailed histological maps were also made in the same plane as the MR images. Then the MR maps were compared with the histological maps of the resected specimens. Interstitial edema, the initial sign of degeneration, was detected as a high signal intensity region on T2-weighted images and showed enhancement with Gd-DTPA. Hyaline degeneration could not be distinguished from smooth muscle whorls on T1- and T2-weighted images. However, undegenerated leiomyoma could be distinguished from hyaline degeneration, because the former was slightly enhanced by Gd-DTPA but the latter was not. These findings showed that Gd-DTPA-enhanced MRI can distinguish undegenerated leiomyomas from degenerated leiomyomas and suggest that MRI may be useful for predicting the response of this tumor to GnRH analogue therapy.

Lumbar facet joint capsule: appearance at MR imaging and CT.

The joint spaces and synovium of the lumbar facet joints extend beyond the articular surfaces of the joint in the majority of adults. The authors correlated magnetic resonance (MR) imaging, computed tomographic (CT), and axial cryomicrotome sections of 66 facet joints in nine cadavers. Extensions of the synovium and joint space along the superior and inferior articular processes, under the ligamentum flavum, and into the ligamentum flavum could be recognized with use of MR and, less successfully, CT. The injection of a paramagnetic contrast medium into the facet joint facilitated visualization of the capsule on MR images. On the ventral aspect of the lumbar facet joint, MR images showed regions of high signal intensity where the joint space extended into the ligamentum flavum or between the ligamentum flavum and lamina. On the dorsal aspect of the joint, MR demonstrated prominence of the fibrous joint capsule where the joint space extended under it along the inferior articular process or along the superior articular process. The variable appearance of the ventral and dorsal aspects of the lumbar facet joint on CT and MR images is due to extension of the synovium and joint space.