Ocular and orbital lesions: surface coil MR imaging

Nine lesions, four ocular (three melanomas, one hemangioma) and five orbital (two perioptic meningiomas, one hemangioma, one pseudotumor, one mucocele), were evaluated by magnetic resonance surface coil imaging at 1.5 T. Small ocular lesions with 3.9-4.5-mm-elevation were demonstrated. The use of two different pulse sequences resulted in separation of melanoma from adjacent retinal detachment. Contrast obtained between orbital lesions and the adjacent normal structures was better than that demonstrated with high-resolution computed tomography.     

Evaluation of abdominal trauma by computed tomography

Computed tomography (CT) was used in the evaluation of 100 patients suffering abdominal trauma. The type of trauma was blunt in 78 patients, penetrating in eight, and iatrogenic in 14. Forty per cent of cases had normal CT scans, while 60% showed substantial abdominal or retroperitoneal injuries. Surgery, clinical follow-up, and repeated radiologic examinations confirmed the accuracy of CT, and there were no cases in which medical or surgical management was inappropriately guided by CT. A wide variety of injuries was detected, including 19 splenic, eight hepatic, six pancreatic, 13 renal, 13 retroperitoneal or abdominal wall, and one intraperitoneal. CT has major advantages over plain radiography, radionuclide imaging, and angiography in assessment of trauma-induced injuries.     

Practical considerations in using calculated healthy-tissue complication probabilities for treatment-plan optimization

PURPOSE: Healthy and neoplastic tissues are generally exposed nonuniformly to ionizing radiation. It is thus useful to develop algorithms that predict the probability of tumor control or normal tissue complication probability (NTCP) for any given spatial pattern of dose delivery. The questions addressed here concern: (a) the sensitivity of the NTCP predictions to the actual model used for extrapolation from uniform irradiation (where some clinical data exist) to nonuniform exposures, (b) its dependence on tissue type, and (c) consequences for treatment-plan optimization. METHODS AND MATERIALS: Two (of several possible) NTCP formulations are used here: the Lyman model and a binomial equation. The effective volume-reduction scheme of Kutcher and Burman is used to obtain the NTCP for an arbitrary distribution of dose. NTCP was calculated for seven organs by postulating a dose distribution of maximum nonuniformity. RESULTS: Both models fit available NTCP data well, but have very different extrapolations for exposures of small tissue volumes and very low values of NTCP (e.g., < 5%) where no data exist. Organs with pronounced volume effects (lung, kidneys) show substantial NTCP differences between the two models. Even in organs where the volume effect is small (e.g., spinal cord, brain), differences in NTCP due to the model selected may still have serious clinical consequences, as an actual example (for the spinal cord) indicates. CONCLUSIONS: NTCP calculations based on extrapolations to volume fractions and/or NTCP levels for which reliable data do not exist depend on the model used to fit the data and the degree of dose nonuniformity. If NTCP is to be used in treatment-plan optimization, the prudent approach is to design plans that reproduce the conditions under which available dose-volume data were taken (e. g., uniform dose distributions).