AJR. American journal of roentgenology
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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
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.
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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 · Oct 1990
ReviewGunshot wounds: 1. Bullets, ballistics, and mechanisms of injury.
The nature and severity of a bullet wound depend on the characteristics of the bullet and of the tissues through which it travels. In addition to the mass and velocity of the bullet, its orientation and whether it fragments or deforms affect the nature of the wound. Two major mechanisms of wounding are described: crushing and stretching of tissue. Understanding the mechanisms by which bullets disrupt tissue can help physicians to evaluate and treat wounds.
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AJR Am J Roentgenol · Sep 1990
ReviewRadiology of the cervical spine in trauma patients: practice pitfalls and recommendations for improving efficiency and communication.
Trauma constitutes a significant portion of emergency department practice. Such patients often have suspected cervical spine injury necessitating cervical spine radiographs. The importance of detecting cervical spine injury is obvious because failure to do so can lead to tragic consequences for patient and physician alike. ⋯ Overreliance on the initial radiologic examination may lead to inappropriate haste in the evaluation of suspected cervical region injury as exemplified by the commonly voiced mandate to "clear the cervical spine" of injury. This approach is discouraged in patients with significant trauma in favor of a careful, progressive evaluation of the potentially injured cervical spine. Periodic review of these complex issues and close cooperation between clinical services are emphasized.