Use of lumbar run-up technique for cervical myelography.

Cervical myelography by lumbar run-up produces excellent radiologic studies in most cases. Use of this technique avoids the hazards and pitfalls associated with a lateral cervical puncture. We discuss 92 cases, with excellent or good results in 98% and nondiagnostic studies in only 2%. Both of the poor technical studies were followed by computed tomographic myelography to produce diagnostic examinations in all cases. There were no serious complications.

Renal stone disease treated with extracorporeal shock wave lithotripsy: short-term observations in 100 patients.

The immediate posttreatment findings are described for 100 patients who underwent extracorporeal shock wave lithotripsy (ESWL) for renal stone disease. Excretory urography was performed both before and 24-72 hours after ESWL. In 21 patients, stones were completely disintegrated, and stone fragments were passed rapidly. Stones were fragmented but not passed entirely within 24-72 hours in 76 patients. There was no appreciable effect on stones in three patients. In nine of 27 patients who had mild to severe ureteral obstruction caused by stone fragments, relief procedures (retrograde ureteral manipulation or percutaneous stone extraction) were necessary. Overall, 70 patients experienced successful stone disintegration without complications. Continued investigation is needed to determine prevalence of residual calculi, reversibility of acute effects of ESWL on the kidney, and possible development of late hypertension.

Renal morphology and function immediately after extracorporeal shock-wave lithotripsy.

The acute effects of extracorporeal shock-wave lithotripsy (ESWL) on morphology and function of the kidney were evaluated by excretory urography, quantitative radionuclide renography (QRR), and magnetic resonance imaging (MRI) in 33 consecutive patients. Excretory urograms demonstrated an enlarged kidney in seven (18%) of 41 treatments and partial or complete obstruction of the ureter by stone fragments after 15 (37%) of 41 treatments. Total effective renal plasma flow (ERPF) was not changed after ESWL, but the percentage ERPF of the treated kidney was decreased by more than 5% in 10 (30%) of 33 cases. QRR images showed partial parenchymal obstruction in 10 (25%) of 41 treated kidneys and total parenchymal obstruction in 9 (22%). MRI disclosed one or more of the following abnormalities in 24 (63%) of 38 treated kidneys: (1) loss of corticomedullary differentiation, (2) perirenal fluid, (3) subcapsular hematoma, (4) hemorrhage into a renal cyst, and (5) unexplained abnormalities. Treated kidneys were normal by all three imaging methods in 26% and abnormal by one or more tests in 74% of cases. The morphologic and functional changes are attributed to renal contusion resulting in edema and extravasation of urine and blood into the interstitial, subcapsular, and perirenal spaces.

Extraction of information from CT scans at different energies.

The image displayed in computed tomography is a scaled representation of attenuation coefficients within the patient's body. A number of authors have presented methods by which additional information (such as electron density, effective atomic number, and extrapolated attenuation coefficients for therapy applications) can be extracted from CT scans carried out at different energies. In the present paper, the dual-energy method described by Rutherford has been used to produce complete images of effective atomic number and electron density of a known phantom (the AAPM phantom) in order to investigate the usefulness of applying this method to current commercial scanners.

Determination of effective energies in CT calibration.

The effective energy of a polychromatic beam for a Computed Tomography (CT) scanner can be measured directly only with difficulty. However, a linear relationship exists between the measured CT numbers and corresponding attenuation coefficients of known materials at the effective energy of the x-ray beam. The effective energy can then be determined by searching all energies for the best linear correlation between the CT numbers and the attenuation coefficients. This can be performed by two methods: graphically, by means of choosing visually the straightest of the fitted lines or, mathematically, by maximizing the correlation coefficient. The energy corresponding to the optimal fit is therefore selected as the effective energy. The latter method was implemented by computer and demonstrated by scanning the AAPM phantom, which contained known materials, and determining the effective energies and the relationship between the linear attenuation coefficients and CT numbers for three commercial units.