Posterior hip dislocations: a cadaveric angiographic study.

Avascular necrosis (AVN) of the femoral head after a traumatic posterior hip dislocation (Thompson and Epstein type I) has been hypothesized to occur due to changes in blood flow. However, to the best of our knowledge of the English literature, a human cadaveric angiographic study has never been performed to delineate these vascular changes. Six fresh frozen human cadavers were used to examine the effects of posterior hip dislocation on the extraosseous and intraosseous blood supply to the femoral head and neck. After a forceful posterior hip dislocation was performed on the cadavers, the proximal vessels were injected with a radioopaque colored latex liquid polymer (Microfil) and examined under cinefluoroscopy. The contra lateral hips were used as controls and were examined in a similar manner. Both hips of the cadavers were harvested, and a macroscopic and microscopic examination was performed. The cine-fluoroscopic examination delineated the dynamic effects of posterior dislocation on the surrounding vasculature. Filling defects were most notable at the junction of the external iliac and common femoral arteries. Filling defects were also present in the circumflex vessels. Compared to controls, the common femoral and circumflex vessel filling defects were statistically significant (p < 0.004). These defects were secondary to an apparent stretching and twisting of the artery caused by the pull and rotation of the dislocated hip. A number of collateral vessels from the gluteal arteries were also demonstrated on fluoroscopic examination. The macro and microscopic examination did not show a qualitative or a quantitative difference in the amount of latex present in the dislocated and control groups. Based on the results of this study, changes in the extraosseous blood flow to the dislocated hip do occur. The vessels that appear to be most affected by the dislocation are the common femoral and circumflex vessels. However, these extraosseous changes do not consistently result in changes in the intraosseous blood flow possibly due to collateral circulation. Relocating the femoral head in a traumatic posterior hip dislocation may provide earlier blood flow to the femoral head by relieving tension across the femoral and circumflex vessels. Delayed relocation could contribute to the development of AVN in the femoral head by not only inducing immediate ischemia at the time of injury but by also producing a progressive and delayed form of arterial damage in the femoral and circumflex vessels. AVN may not be an absolute outcome of posterior hip dislocations due to preexisting collateral circulation and/or the preservation of the femoral circumflex vessels.

Pneumomediastinum associated with cocaine abuse: a case report and review of the literature.

A case of pneumomediastinum following inhalation of cocaine alkaloid (free-base) is reported. This is the third reported case in the literature. The presumed mechanism is barotrauma secondary to vigorous inhalation for valsalva maneuvers.

CT and MR imaging in staging bladder neoplasms.

Thirteen patients with bladder carcinoma were examined by magnetic resonance (MR) imaging and CT to determine the relative accuracy of the modalities in staging bladder carcinoma. Magnetic resonance correctly identified the presence or absence of extravesical spread of carcinoma in 10 of 13 patients (77%). Two patients were understaged and one was overstaged. Computed tomography correctly staged nine of 13 patients (69%), with three patients understaged and one patient overstaged. Neither MR nor CT was able to determine depth of invasion of the bladder wall in the absence of extravesical spread.

Magnetic resonance imaging of the genitourinary tract.

MRI is in its infancy as a clinical imaging tool. It is undergoing intensive investigation in various areas of the body. Evaluation of the brain and spine is superb, and in some areas of the brain, like the posterior fossa, it is thought to be superior to CT. Evolving indications for body scanning include staging of pelvic malignancies, evaluation of liver malignancy, evaluation and staging of musculoskeletal problems, and, to a lesser degree, staging of renal malignancies and evaluation of vascular disease. The main problem in body imaging stems from image degradation because of respiratory motion that is transmitted to upper abdominal organs. Respiratory gating of image acquisition or utilization of short heavily T1-weighted pulse sequences will likely overcome this problem in due time. Minimizing motion artifact will make MR images comparable to, if not better than, CT images with regard to transverse anatomic display, and MR images have the added advantage of multiplanar scanning, which can be done directly, without need of additional computer reconstruction time and without having to move the patient. The second major problem in MRI is the lack of understanding of equipment potential. Unlike conventional radiography and CT, in which the behavior of the X-ray beam is understood with regard to image formation, in MRI new parameters are used to generate images. As stated earlier, MR signal intensity is due to hydrogen concentration, T1 and T2 relaxation times of the tissue, and flow of protons through the imaged volume. How these factors are weighted depends on pulse sequence selection, and thus image contrast and information content of the scans change. On the surface, these images display anatomic information as do other imaging modalities, but manipulation of pulse sequences may ultimately lead to the ability to demonstrate physiologic and chemical parameters previously unavailable in imaging. Current research is geared to help extract this data by testing new pulse sequences, using different types of receiver RF coils, and using MR-specific contrast materials. Minor MRI problems such as long scan times are being dealt with to decrease time to an acceptable length. The nonvisualization of soft tissue calcifications will probably remain a problem that may have to be weighed against other known advantages. At this time further research and clinical experience are the key to what is needed in MRI, to gain further knowledge with regard to imaging physiologic phenomena, such as flow and spectroscopy, and possibly to monitor the chemical basis of disease.(ABSTRACT TRUNCATED AT 400 WORDS)

Magnetic resonance imaging of the prostate.

The prostate was examined by magnetic resonance imaging (MRI) in 33 subjects, including five normal volunteers, 18 with prostatic carcinomas, seven with benign nodular hyperplasias, two cases of acute prostatitis, and one case of chronic prostatitis. Of 18 prostatic carcinomas, 16 produced an inhomogeneous signal intensity, with areas of diminished signal on T1-weighted scans and usually increased signal on T2-weighted images relative to the rest of the prostate. However, a similar appearance was also seen in five cases of benign nodular hyperplasia. It is doubtful at present whether MRI is able to reliably differentiate benign from malignant prostatic disease. Extraprostatic tumor extension and pelvic adenopathy was well shown, and MRI is very promising as a method for the preoperative staging of known prostatic carcinomas.

Magnetic resonance imaging of the abnormal female pelvis.

Twenty-three women with 27 instances of pelvic pathology were evaluated by magnetic resonance imaging (MRI). Different pulse sequences were used, which varied the dependence of the images on T1 and T2. Sonography was performed on 22 of the 23 patients. Five patients had CT examinations, including the patient who did not have sonography. MRI was also done in four normal volunteers. The spatial resolution of the MRI scans with short TR and TE intervals approached that of CT. There was overlap of MRI signal characteristics between various pathologic entities and also within the same entity (e.g., cystadenomas and endometriomas).

Magnetic resonance imaging of the kidney.

In this article, the principles of MR renal evaluation are reviewed. Techniques and pulse sequences used for evaluation are described. The author presents his experience with MRI in the evaluation of normal anatomy of the kidney, renal masses (cystic and solid), renal medical diseases, and renal transplants and compares this technique with conventional imaging modalities.

Magnetic resonance imaging of the pelvis.

Magnetic resonance imaging (MRI) is a very promising modality for evaluation of the pelvis. Its major role appears likely to be the staging of known malignancies. In this article, the appearance of normal pelvic anatomy on MR scans is presented, as well as a discussion of the use of MRI in the detection and evaluation of pathologic conditions and a comparison of MRI with CT.

Percutaneous nephrostomy in neonates and infants.

A total of 8 patients between 2 days and 2 years old underwent 13 percutaneous nephrostomies for treatment of hydronephrosis. No significant complications were encountered.

CT-guided liver biopsies: eight years' experience. Work in progress.

In the past eight years 180 patients with liver abnormalities demonstrated on computed tomography (CT) underwent CT-guided biopsies with 22-guage Madayag, 14-gauge Travenol, or 18-gauge Menghini needles used singly or in combination. Cytologic and pathologic results were tabulated and correlated with the subsequent surgical or autopsy findings and with clinical follow-up ranging from three months to three years. Complications of the procedures were also recorded. It is concluded that cutting needle biopsies provide a higher yield of diagnostic tissue compared with aspiration biopsies (89.9% versus 65%) without a significant increase in complications (1.44% versus 0.83%). The techniques utilized, risk of complications, and the indications for biopsy are discussed.

Magnetic resonance imaging of the breast. Work in progress.

Ten normal volunteers and 45 patients with breast abnormalities were examined with magnetic resonance (MR), utilizing a 0.3-tesla superconducting magnet. In all patients, MR detected an abnormality that corresponded to the area of pathology seen on either a mammogram or computed tomographic (CT) scan. An appreciable advantage of MR over mammography was observed in patients with cysts and in those with areas of asymmetric dysplastic breast tissue. Abnormalities on MR images appeared as areas of low signal intensity relative to adjacent normal ductal and fatty tissue. The configuration of a lesion on MR permitted distinction between a benign and a malignant process.

Nuclear magnetic resonance imaging of the mediastinum and hili: early impressions of its efficacy.

Nuclear magnetic resonance (NMR) scans of the mediastinum and/or hili were obtained in 22 of 25 patients selected on the basis of an abnormal CT scan. All patients had proven disease; 19 malignant and four benign processes were studied successfully. The high contrast resolution of NMR in the mediastinum allowed clear definition of disease in all cases. In six, NMR showed a greater extent of disease than CT. The ability of NMR to perform sagittal and coronal images also aided in disease analysis. In this preliminary study, NMR proved to be as useful as CT, or more so, in the evaluation of malignant disease of the hili and mediastinum.

NMR scanning of the pelvis: initial experience with a 0.3 T system.

Pelvic NMR scans were obtained on 29 patients using a 0.3 T superconducting magnet system. Pathologies studied included four bladder carcinomas, four prostatic carcinomas, four ovarian dermoid cysts, three ovarian cysts, three endometrial carcinomas, two endometriomas, and one each of serous cystadenoma of the ovary, benign prostatic hypertrophy, pelvic hematoma, and undifferentiated sarcoma. NMR is a very promising method for characterizing pelvic masses and in staging pelvic malignancies. It can show primary tumors of the prostate, bladder, and uterus and reveals tumor extension into pelvic fat. The pelvis is particularly well suited to NMR scanning because of the abundant natural contrast provided by pelvic fat and by urine in the bladder and gas in the bowel. There is also less motion blurring than in the upper abdomen and chest because there is relatively little respiratory motion of pelvic organs. Various pulse sequences were used in scanning the pelvis; their relative merits are discussed.