Magnetic resonance findings in skeletal muscle tears

Magnetic resonance (MR) images of skeletal muscle tears can clearly delineate the severity of muscle injury. Although MR imaging is seldom necessary in patients with acute muscle trauma, it can be helpful in deciding on clinical management. The two major MR findings in acute muscle tears are deformity of the muscle and the presence of abnormal signal reflecting hemorrhage and edema. In acute tears, methemoglobin within the extravascular blood causes high-signal areas on both T1- and T2-weighted images. With partial tears, the blood may dissect in a distinctive linear pattern along the muscle bundles and fibers. As healing begins, the muscle signal diminishes, first on the T1-weighted images and then on the T2-weighted images. When there is residual abnormal signal on images obtained more than several months after the injury, it is presumed to represent hemorrhage from recurrent tears. In patients with a questionable history of a remote injury, the clinical presentation may be that of persistent pain or a soft tissue mass. In these cases MR imaging may identify the cause of the pain and can exclude a neoplasm by proving that the mass is a hypertrophied or retracted muscle. Thus, MR imaging has a limited, but occasionally important role in selected patients with skeletal muscle tears.     

Postoperative sella: evaluation with fast spin echo T2-weighted high-resolution imaging

OBJECTIVE: The purpose of this study was to investigate the magnetic resonance features of the postoperative sella with fast spin echo (FSE) T2-weighted high-resolution imaging and to evaluate the benefits of the sequence using a follow-up magnetic resonance imaging protocol after transsphenoidal surgery. METHODS: Coronal spin echo (SE) T1-weighted and FSE T2-weighted images were prospectively obtained in 24 patients after surgery for pituitary adenomas. We observed the signals and the contour of normal structures, fluid collection, implanted materials, and mass lesions, including granulation tissue and adenoma. RESULTS: The pituitary gland was delineated in 51 of 59 FSE T2-weighted images, 90.2% of which presented clear boundaries. Whereas the gland was detected in 49 of 58 SE T1-weighted images, only 20.4% showed the boundaries. A mass lesion was identified in each of 12 patients with good resolution on FSE T2-weighted images. SE T1-weighted images detected mass lesions in 7 of 12 patients without distinctive boundaries. Contrast enhancement had little advantage in clarifying the boundaries between normal and abnormal structures. For the detection of mass lesions in the sella, the kappa values for interobserver agreement were 0.8 for FSE T2-weighted images and 0.25 for SE T1-weighted images. CONCLUSION: FSE T2-weighted imaging is a reliable method with which to assess the sella with sufficient resolution after transsphenoidal surgery. The combination of unenhanced SE T1-weighted and FSE T2-weighted images may reduce the use of contrast material after pituitary surgery.     

Malignant lesions of the liver identified on T1- but not T2-weighted MR images at 1.5 T

The authors reviewed their 2 1/2-year experience with a magnetic resonance (MR) imaging protocol for a 1.5-T MR imager that included T2-weighted fat-suppressed spin-echo, T1-weighted breath-hold gradient-echo, and serial dynamic gadolinium-enhanced T1-weighted gradient-echo imaging to identify histologic types of malignant liver lesions more apparent on T1- than on T2-weighted images. MR images of 212 consecutive patients with malignant liver lesions were reviewed. T2-weighted, T1-weighted, and dynamic contrast-enhanced T1-weighted images were examined separately in a blinded fashion. Seven patients demonstrated liver lesions (lymphoma [two patients] and carcinoid, hepatocellular carcinoma, colon adenocarcinoma, transitional cell carcinoma, and melanoma [one patient each]) on T1-weighted images that were inconspicuous on T2-weighted images. In all cases, the lesions were most conspicuous on T1-weighted images obtained immediately after administration of contrast agent. Histologic confirmation was present for all seven patients. The consistent feature among these lesions was that they were hypovascular, due either to a fibrous stroma or to dense monoclonal cellularity. These results suggest that in some patients with hypovascular primary neoplasms, the lesions may be identified only on T1-weighted images, and that immediate postcontrast T1-weighted images are of particular value in demonstrating lesions.     

Hyperparathyroidism--comparison of flash imaging with spin echo MR imaging

MR images of the neck were prospectively studied in 19 patients with hyperparathyroidism. Fast low angle shot (FLASH) sequence was performed in addition to T1- and T2-weighted spin echo (SE) sequences. FLASH images were obtained with 320/12/20 degrees (TR/TE/flip angle) using presaturation technique. TE of 12 ms was chosen to eliminate high signal of fat tissue. In the evaluation of detectability, a combination of T1-weighted SE and FLASH images (T1WI + FLASH) was compared with a combination of T1- and T2-weighted SE images (T1WI + T2WI). MR imaging correctly depicted 20 of 30 abnormal glands on both T1WI + FLASH and T1WI + T2WI. FLASH imaging effectively eliminated high signal of fat tissue. Nineteen abnormal glands demonstrated higher signal than surrounding tissues on FLASH images, whereas 12 glands were high-intense on T2-weighted SE images. We conclude that FLASH imaging provides improved tissue contrast and anatomic delineation and, thus, may replace T2-weighted SE imaging in the neck.     

Amyloid arthropathy of the hip joint: MR demonstration of presumed amyloid lesions in 152 patients with long-term hemodialysis

The aim of this study was to determine the spectrum of MR findings of presumed amyloid arthropathy of the hip joints in patients on long-term hemodialysis. We prospectively performed T1- and T2-weighted spin-echo imaging on 152 consecutive patients on hemodialysis. The duration of hemodialysis ranged from 5 months to 24 years, 2 months (mean: 8 years, 8 months). The frequency, location, and signal intensity of bone lesions were assessed. In 12 cases with contrast-enhanced MR examination, enhancement pattern of bone lesions, synovial lesions, and intra-articular lesions were characterized. Bone lesions presumed to be amyloid deposits were identified in 60 patients (39%). Magnetic resonance imaging revealed that amyloid lesions were more extensive than anticipated by plain radiographs. All bone lesions showed decreased signal intensity on T1-weighted images. On T2-weighted images, bone lesions showed increased signal intensity in 32 patients (54%), decreased signal intensity in 11 patients (18%), and both increased and decreased signal intensity in 17 patients (28%). Following intravenous injection of gadolinium-based contrast, all bone lesions showed moderate enhancement. Synovial thickening could not be identified on T1- and T2-weighted images. However, contrast-enhanced images showed thickened synovial membrane, which could be differentiated from joint fluid. Intra-articular nodules showed decreased or intermediate signal intensity on T1-weighted images and decreased signal intensity on T2-weighted images; the intra-articular nodules were contiguous with subchondral bone lesions. Magnetic resonance imaging is useful for evaluating the distribution and extent of amyloidosis of the hip joints in patients undergoing long-term hemodialysis.     

Non-communicating intramuscular ganglia

Intramuscular ganglia are rare. Most of the previously reported cases were connected with an adjacent joint. We present the imaging findings in three patients who had intramuscular ganglia that were not connected with a joint. Magnetic resonance showed a septated, encapsulated mass that was isoor hypointense to muscle on T1-weighted and hyperintense on T2-weighted images. A post-contrast T1-weighted scan in one patient showed minimal capsular enhancement. Ultrasound performed in one case showed an encapsulated, anechoic mass.     

Preoperative staging of endometrial carcinoma: diagnostic effect of T2-weighted fast spin-echo MR imaging

PURPOSE: To evaluate the usefulness of T2-weighted fast spin-echo magnetic resonance (MR) imaging with a 512 x 256 matrix for assessment of the preoperative stage of endometrial carcinoma. MATERIALS AND METHODS: Twenty-eight women with histopathologically proved endometrial carcinoma underwent preoperative T2-weighted fast spin-echo, dynamic T1-weighted fast spin-echo, and postcontrast T1-weighted spin-echo MR imaging with a phased-array surface coil. The uterine long-axis planes in each sequence were reviewed at separate sessions by three radiologists blinded to the histopathologic data. RESULTS: For the diagnosis of myometrial invasion, no statistically significant differences were found among T2-weighted imaging, dynamic imaging, and postcontrast T1-weighted imaging. For the diagnosis of deep myometrial invasion, T2-weighted and dynamic images showed higher specificity than postcontrast T1-weighted images (T2-weighted, 89%; dynamic, 88%; and postcontrast T1-weighted, 80%). For cervical invasion, T2-weighted and dynamic images showed larger areas under receiver operating characteristic curves than did postcontrast T1-weighted images (T2-weighted, 0.78; dynamic, 0.71; and postcontrast T1-weighted, 0.67). CONCLUSION: T2-weighted imaging is useful for identifying the stage of endometrial carcinoma.     

Detection of hepatic tumors: arterial-phase MR imaging versus spiral CT arteriography

BACKGROUND: Distinction between uncomplicated infective fasciitis and early necrotizing fasciitis can be extremely difficult without operation, yet the management and prognosis of both conditions depend greatly on early recognition and assessment of the extent of involvement. STUDY DESIGN: This was a prospective review of the utility of magnetic resonance imaging (MRI) in nine patients with suspected infective or necrotizing fasciitis treated at an academic medical center or a Veterans Administration hospital. RESULTS: Magnetic resonance imaging documented fascial inflammation, characterized by low intensity on T1-weighted images and high intensity on T2-weighted images, in all nine patients. Absence of gadolinium contrast enhancement on T1-weighted images reliably detected fascial necrosis in all six patients who required operative debridement. Magnetic resonance imaging was extremely useful in defining the extent of fasciitis and was more accurate in predicting necrosis or pyomyositis than was myoglobinuria or elevation of serum creatine kinase or lactate dehydrogenase. Operation was avoided in two patients without evidence of necrosis on MRI. One patient without evidence of necrosis, explored because of contradictory clinical findings, was confirmed at operation to have cellulitis without necrosis. CONCLUSIONS: Magnetic resonance imaging with gadolinium contrast accurately determines the presence of necrosis and the need for operation in patients with fasciitis of the lower extremity. Preoperative determination of the extent of involvement facilitates operative planning.     

Ethnic variation of twinning rates in Malawi

To examine the usefulness of magnetic resonance imaging (MRI) in the preoperative determination of cancerous invasion, we examined 39 patients with advanced colorectal cancer with 0.5T MRI. We employed short inversion time inversion recovery (STIR) sequences, in addition to ordinary spin echo sequences for T1- and T2-weighted images. Preoperatively, the estimated depth of tumor invasion was classified into three grades according to MRI findings, and confirmed on the basis of surgical and histopathologic results. The depth of tumor invasion estimated preoperatively using STIR sequences corresponded well with the surgical and histopathologic results in 85% of the cases. In contrast, assessments based on T1-weighted images corresponded well in only 62% of the cases and T2-weighted images corresponded well in only 64%.     

Focal malignant hepatic lesions: MR imaging enhanced with gadolinium benzyloxypropionictetra-acetate (BOPTA)--preliminary results of phase II clinical application

PURPOSE: To investigate enhancement with gadolinium benzyloxypropionictetraacetate (BOPTA) at magnetic resonance (MR) imaging to detect focal malignant hepatic lesions. MATERIALS AND METHODS: A phase II trial was performed in 34 patients. Gd-BOPTA-enhanced spin-echo (SE) and gradient-recalled-echo (GRE) T1-weighted MR imaging were performed at 40 and 90 minutes after intravenous injection of 0.05 and 0.10 mmol/kg Gd-BOPTA. RESULTS: The percentage of enhancement in liver parenchyma was significantly (P<.05) increased on GRE T1-weighted compared with SE T1-weighted images at 40 and 90 minutes after injection of the higher dose and compared with SE and GRE T1-weighted images obtained with the lower dose. The contrast-to-noise ratio of metastases was significantly increased on GRE T1-weighted images (0.10 mmol/kg) at 90 minutes compared with precontrast images. Significantly more small primary metastases were detected on GRE T1-weighted images (0.10 mmol/kg) at 90 minutes compared with precontrast SE T1-weighted images. CONCLUSION: Gd-BOPTA is a safe hepatobiliary contrast agent that helps detection of small metastases.     

Magnetic resonance imaging study on the results of surgery for cervical compression myelopathy

The morphologic changes and signal intensity of the spinal cord on preoperative magnetic resonance images were correlated with postoperative outcomes in 74 patients undergoing decompressive cervical surgery for compressive myelopathy. The transverse area of the spinal cord on T1-weighted images at the level of maximum compression was closely correlated with the severity of myelopathy, duration of disease, and recovery rate as determined by the Japanese Orthopaedic Association score. In patients with ossification of the posterior longitudinal ligament or cervical spondylotic myelopathy, the increased intramedullary T2-weighted magnetic resonance imaging signal at the site of maximal cord compression and duration of disease significantly influenced the rate of recovery. A multiple regression equation was then developed with these three variables to predict surgical outcomes.     

Islet cell tumors: comparison of dynamic contrast-enhanced CT and MR imaging with dynamic gadolinium enhancement and fat suppression

Ten patients with 11 islet cell tumors underwent dynamic contrast material-enhanced computed tomography (CT) and magnetic resonance (MR) imaging within a 1-month period. MR imaging depicted all 11 tumors, and CT depicted seven of the 11 tumors. CT did not depict four of seven tumors that measured 2.5 cm in diameter or less. Islet cell tumors had low signal intensity on T1-weighted fat-suppressed MR images, and gastrinomas were best shown with this technique. Two of three insulinomas less than 1.5 cm in diameter were best shown on dynamic contrast-enhanced fast low-angle shot (FLASH) images as uniform areas of high signal intensity. Hepatic metastases were seen in five patients and showed peripheral ringlike enhancement best demonstrated on dynamic gadolinium-enhanced FLASH images. Hepatic lesions were most conspicuous on T2-weighted fat-suppressed spin-echo images. MR imaging with dynamic gadolinium enhancement and fat suppression is a promising tool in the investigation of islet cell tumors.     

Vascular lesions in children: percutaneous MR imaging-guided interstitial Nd:YAG laser therapy--preliminary experience

PURPOSE: To investigate the use of magnetic resonance (MR) imaging to guide interstitial laser therapy of deep hemangiomas and vascular malformations in children. MATERIALS AND METHODS: Sixteen children aged 3 months to 16 years with symptomatic vascular lesions underwent percutaneous laser treatment. MR imaging guidance of the laser applicator and online thermomonitoring with MR imaging were performed with a 0.2-T open MR system. Follow-up studies were performed 2 days and 6 weeks after thermotherapy. RESULTS: Interactive positioning of the laser applicator was possible in all patients. Online thermomonitoring was possible in 122 of 137 therapy spots (89%). There was a good correlation between volumes of coagulated tissue on intraprocedural T1-weighted images and volumes of coagulated tissue on follow-up T2-weighted images. At 6-week follow-up, MR imaging demonstrated a reduction in lesion size in 10 patients (mean reduction, 72%) and an increase in lesion size in two patients (mean increase, 134%). Clinical symptoms improved in 14 of 16 patients (88%). CONCLUSION: MR imaging-guided laser therapy appears to be a safe and potentially effective minimally invasive treatment for selected children with vascular lesions.     

Differential expression of DNA topoisomerase II alpha and II beta genes between small cell and non-small cell lung cancer

The purpose of this study is to describe the appearance of bowel-related abscesses on magnetic resonance (MR) images. Sixteen consecutive patients who had bowel-related abscesses underwent MR examination at 1.5T. MR sequences included T1-weighted fat-suppressed imaging pre- and post-intravenous gadolinium chelate administration (all patients) and breathing-independent single-shot T2-weighted half Fourier turbo (fast) spin echo (6 patients). Patients with pelvic abscesses also underwent sagittal imaging with post-gadolinium T1-weighted images (9 patients) and T2-weighted turbo (fast) spin echo (8 patients). Abscesses were confirmed by open surgery or surgical drainage (6 patients), percutaneous drainage (8 patients), or combined physical examination, fluoroscopic fistulogram, and clinical follow-up (2 patients). Oval-shaped fluid collections were identified in all of the patients, which ranged in diameter from 2 cm to 18 cm, mean: 8 cm. Abscesses were low to intermediate in signal on T1-weighted images, heterogenous and moderately high signal on T2-weighted images, and low signal on post-gadolinium images. A layering effect of lower signal material in the dependent portion of the abscess was noted in abscesses in 6 of 14 patients on T2-weighted images. Post-gadolinium images demonstrated a definable 3- to 7-mm thick abscess wall, which enhanced substantially with contrast. Definition of the wall was best shown on fat-suppressed images post-gadolinium. Substantial enhancement of surrounding periabscess tissues was demonstrated in all cases and was most clearly defined on fat-suppressed images. Image acquisition in two orthogonal planes was of value to demonstrate that fluid collections were oval, and separate from bowel. Image acquisition in the sagittal plane was useful in the evaluation of pelvic abscesses. The results from this preliminary study show that bowel-related abscesses are demonstrable on MR images using gadolinium-enhanced fat-suppressed T1-weighted and turbo (fast) spin-echo T2-weighted sequences. The presence of a thickened, enhancing lesion wall and enhancement of perilesional tissues on T1-weighted fat-suppressed images were observed in all abscesses. A layering effect of low signal intensity material in the dependent portion of the abscess was an important ancillary feature.     

Serial MR imaging of intracranial metastases after radiosurgery

PURPOSE: To evaluate the spatiotemporal evolution of radiosurgical induced changes both in metastases and in normal brain tissue adjacent to the lesions by serial magnetic resonance (MR) imaging. METHODS AND MATERIALS: Thirty-five intracranial metastases of different primaries were treated in 25 patients by single high-dose radiosurgery. MR images acquired before radiosurgery were available in all patients. Sixty-three follow-up MR studies were performed in these patients including T2- and contrast-enhanced T1-weighted MR images. The average follow-up time was 9 +/- 5 months (mean +/- standard deviation [SD]). Based on contrast-enhanced T1-weighted MR images, tumor response was radiologically classified in the following four groups: stable disease was assumed if the average tumor diameter after treatment did not show a tumor shrinkage of more than 50% and an increase of more than 25%, partial remission as a shrinkage of tumor size of more than 50%, a disappearance of contrast-enhancing tumor as a complete remission, and an increase of tumor diameter of more than 25% as tumor progress. Moreover, we analysed signal changes on T2-weighted images in brain parenchyma adjacent to the enhancing metastases. RESULTS: The overall mean survival time was 10.5 +/- 7 months, with a 1-year actuarial survival rate of 40%. Stable disease, partial or complete remission of the metastatic tumor was observed in 22 patients (88%). Central or homogeneous loss of contrast enhancement appeared to be a good prognostic sign for stable disease or partial remission. This association was statistically significant (p < 0.05). Three patients (12%) suffered from tumor progression. In eight patients (32%) with stable disease or partial remission, signal changes on T2-weighted images were observed in tissue adjacent to the contrast enhancing lesions. A progression of the high signal on T2-weighted images was seen in seven of the eight patients between 3 and 6 months after therapy, followed by a signal regression 6-18 months after irradiation. CONCLUSION: MR imaging is a sensitive imaging tool to evaluate tumor response as well as the presence or absence of adjacent parenchymal changes following radiosurgery. Loss of homogeneous or central contrast enhancement on Gd-enhanced MR images appeared to be a good prognostic sign for tumor response. Tumor shrinkage seems not to be dependent on time. In addition, most cases of radiation induced changes in normal brain parenchyma observed on T2-weighted images seem to be self limited.     

Evaluation of the prostate and prostatic carcinoma with gadolinium-enhanced endorectal coil MR imaging

Thirteen patients who underwent subsequent radical prostatectomy for prostate cancer were studied with spin-density-T2-weighted and gadolinium-enhanced and unenhanced T1-weighted magnetic resonance (MR) imaging performed with an endorectal surface coil. With gadopentetate dimeglumine, the central gland showed inhomogeneous enhancement due to benign hyperplasia, whereas the peripheral zone demonstrated more uniform and less intense enhancement. With the T1-weighted sequence, depiction of the zonal anatomy, prostate capsule, surgical capsule, fibromuscular stroma, and periprostatic venous plexus was better with contrast enhancement, but these were best demonstrated on T2-weighted images. The trend was similar for prostatic tumor extent and capsular integrity. The seminal vesicles had a septal enhancement pattern and in several patients were best evaluated with enhanced T1-weighted images. These findings suggest that gadopentetate dimeglumine is not warranted for routine use in endorectal MR imaging of the prostate but may be useful for evaluation of the seminal vesicles in selected patients.     

Circadian-time rhythm of hepatic protein kinase C of rats pretreated with phenobarbital

The magnetic resonance imaging (MRI) differential diagnosis of intrahepatic biloma from intrahepatic subacute hematoma has been reported in two cases. The biloma was heterogenously intense on T1-weighted images and homogenously hyperintense on T2-weighted images. The hematoma was hyperintense on the both T1- and T2-weighted MR images. The clinical significance of this MRI difference is that intrahepatic biloma needs drainage, whereas intrahepatic hematoma can heal spontaneously.     

Magnetic resonance imaging of renal lymphoma with computed tomography correlation

The magnetic resonance (MR) imaging and computed tomography (CT) findings in four patients (five kidneys) with non-Hodgkin's lymphoma involving the kidneys and perirenal spaces are presented. The patterns of disease in each case were as follows: bilateral renal nodules, infiltration in the perirenal space, infiltration in the perirenal space with renal involvement, and direct invasion from contiguous retroperitoneum. On plain CT, the lesions showed slight hyperdensity (three kidneys) and isodensity (two kidneys) as compared with normal renal parenchyma. But all lesions appeared as hypodense masses with more definite margins after contrast enhancement. MR imaging findings showed iso- or slight hypointense masses on T1-weighted images and definite hypointense masses on T2-weighted images as compared with the signal intensity of the renal cortex. Dynamic imaging and conventional delayed T1-weighted imaging following Gd-DTPA injection showed no significant enhancement of the lesions. In comparison with contrast enhanced CT, despite its poorer resolution, T2-weighted MR imaging showed nearly the same accuracy in the evaluation of number and extent of the lesions without contrast medium administration. MR imaging was also useful to evaluate the patency of vessel lumen surrounded by tumor mass and to determine the location and extent of huge lesions by its multiplanar imaging capabilities.     

Fast spin-echo MR imaging of the eye

Magnetic resonance imaging of the eye usually includes T2-weighted images both for screening purposes and for characterization of melanoma. Conventional T2-weighted spin-echo (SE) imaging suffers both from long acquisition times and incomplete recovery of the vitreous' signal. A fast SE sequence was therefore compared prospectively with conventional sequences in 29 consecutive patients with lesions of the eye. Fast SE images delineated melanoma and other lesions of the eye from vitreous better than conventional T2-weighted images. Image quality and lesion conspicuity were improved on the fast sequence. Whereas melanoma appeared hypointense to vitreous on both types of images, subretinal effusion was hypointense on fast images and hyperintense on conventional T2-weighted images. Ghosting of the globe, which, however, did not decrease diagnostic value, was more pronounced on fast images. Conventional T2-weighted images may be replaced by fast SE images in MR studies of the eye with a gain in lesion conspicuity and significant time saving.     

Catheter ablation of ventricular tachycardia associated with remote myocardial infarction: utility of the atrial transseptal approach

BACKGROUND: To determine the magnetic resonance (MR) imaging features of hepatic metastases from leiomyosarcoma and determine the pathologic basis for the MR appearance of these neoplasms. METHODS: MR examinations of eight patients with a total of 16 hepatic metastases from leiomyosarcoma were retrospectively reviewed. Hepatic metastases originated from a primary gastrointestinal (n = 6), uterine (n = 1), or retroperitoneal (n = 1) leiomyosarcoma. Correlation between MR features and pathologic findings was performed in 11 metastases from which histologic material was obtained. RESULTS: Among the 10 metastases seen on T1-weighted MR images, nine were homogeneous and one was heterogeneous. The latter contained areas of necrosis and hemorrhage on pathologic examination. Among the 16 metastases seen on T2-weighted MR images, 12 were well delineated and completely homogeneous, with a marked hyperintense signal ("hemangiomalike" pattern). These neoplasms were composed of smooth fibrous tissue without macroscopically visible areas of necrosis on pathologic examination. The remaining four metastases were heterogeneous and contained varying degrees of necrosis and hemorrhage or gelatinous tissue. CONCLUSION: A hemangiomalike pattern is the most common feature on T2-weighted MR images. We found that homogeneous hyperintensity of hepatic metastases from leiomyosarcoma on T2-weighted MR image does not reflect cystic changes.