AJR. American journal of roentgenology
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AJR Am J Roentgenol · Nov 1990
Soft-tissue tumors of the foot: value of MR imaging for specific diagnosis.
We reviewed MR imaging findings in 14 patients with primary soft-tissue tumors of the foot and compared them with surgical and pathologic findings to determine the value of MR imaging in anatomic localization, delineation, and characterization of such lesions. Nine tumors (64%) were benign, and five (36%) were malignant. The anatomic location (compartment, space, relation to specific tendon) and extent of all tumors were accurately shown by MR imaging. ⋯ MR imaging of the foot is accurate in showing the extent of soft-tissue tumors, which is helpful for surgical planning. Determination of their specific anatomic location may help characterize some tumors. Although our series is small, it appears that MR imaging often suggests a specific diagnosis in certain benign soft-tissue tumors of the foot and may often correctly distinguish benign from malignant tumors.
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The objective of this study was to provide a worst-case estimate of thermal effects of MR imaging by subjecting anesthetized unshorn sheep to power deposition at specific absorption rates (SARs) well above approved standards for periods of time in excess of normal clinical imaging protocols. A control period with no RF power was followed by 20-105 min of RF power application. Afterward, there was a 20-min or longer recovery period with no RF power. ⋯ MR power deposition at SAR levels well above typical clinical imaging protocols caused body temperature to increase. For exposure periods in excess of standard clinical imaging protocols the temperature increase was insufficient to cause adverse thermal effects. Studies in healthy humans are needed to determine whether enhanced heat-loss effector mechanisms are likely to cause deep-body temperatures to plateau at an acceptable level, and to elucidate mechanisms that determine subcutaneous temperature.
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AJR Am J Roentgenol · Nov 1990
Carcinoma of the prostate: value of transrectal sonography in detecting extension into the neurovascular bundle.
Detection of involvement of the neurovascular bundles (NVB) by tumor is important in deciding whether sexual function can be preserved in patients undergoing radical prostatectomy for prostatic cancer. The nerve branches innervating the corpora cavernosa have a rather constant association with the capsular arteries and veins of the prostate, forming the periprostatic neurovascular bundle, which can be identified intraoperatively and spared during radical surgery, thus preserving potency. We examined 160 patients with biopsy-proved clinical stage A or B adenocarcinoma with transrectal sonography before radical prostatectomy to determine how useful the procedure is for predicting tumor extension into the NVB. ⋯ The sensitivity of sonography for predicting invasion of the NVB was 66%, with a specificity of 78% and an accuracy of 75%. Positive predictive values and negative predictive values were 51% and 86%, respectively. We conclude that transrectal sonography currently suffers from lack of sufficient spatial resolution to detect accurately invasion of the NVB.
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AJR Am J Roentgenol · Nov 1990
Case ReportsDiffusion-weighted MR imaging of the brain: value of differentiating between extraaxial cysts and epidermoid tumors.
This study demonstrates the use of diffusion-weighted MR imaging in improving the specificity of the diagnosis of extraaxial brain tumors. Three surgically proved lesions (one arachnoid cyst and two epidermoid tumors) and two nonsurgically proved lesions (arachnoid and ependymal cysts) were evaluated with T1- and T2-weighted spin-echo studies followed by intravoxel incoherent motion (IVIM) MR imaging. The IVIM images of the lesions were displayed as an apparent diffusion coefficient (ADC) image obtained at 0.65 G/cm (maximum gradient b value = 100 sec/mm2) and compared with external oil and water phantoms. ⋯ Cisternal CSF demonstrated uniformly high ADC, primarily because of bulk flow, which enhanced image contrast. Improved delineation of postsurgical changes was also possible. Our preliminary results show that diffusion-weighted MR imaging can be useful in distinguishing between arachnoid cysts and epidermoid tumors.