Biomedical subjects
Publications and source records attributed to M R Williamson.
Magnetic resonance imaging was performed as a preoperative examination in three children with neurofibromatosis and soft-tissue plexiform neurofibromas. In all three patients, MRI showed more widespread soft tissue involvement than was suspected clinically including extension towards the spine in each case. Patient management was changed in each case after MRI was performed.
The diagnosis of infection in prosthetic vascular grafts is difficult clinically but very important due to the high associated morbidity and mortality. Various radiographic and imaging procedures have been used. 111In-labeled white cells have been used with a sensitivity approaching 100% and a specificity of approximately 90%. Computed tomography (CT) has also been advocated as a means of detecting these infections by some. Similarly, ultrasound has been used. More recently, magnetic resonance imaging (MRI) has been advocated in hopes that the signal of the infected graft would differ from that of the noninfected graft. This article reviews the data supporting each of these modalities.
A device was constructed to allow rapid adjustment of the position of a surface coil in magnetic resonance (MR) imaging of the spine. The device consists of two sheets of acrylic plastic and a movable sled. The surface coil is placed on the sled and can be precisely moved superiorly or inferiorly with a cord attached to the sled. The device can save approximately 30 minutes during MR imaging of the entire spine and increases patient comfort and cooperation.
The authors have tested four Greenfield filters for deflection in a 1.5 Tesla magnetic field and found large variations in the amount of deflection among filters. They also placed two filters in dogs and checked the filter for migration by taking radiographs before and after magnetic resonance imaging (MRI) scans. They found no evidence of migration. They conclude that, while most Greenfield filters respond to a magnetic field, the chance of migration of a filter because of an MRI scan is small. Therefore, MRI scanning of patients with Greenfield filters has little risk.
We performed magnetic resonance imaging on nine patients with nonarteritic ischemic optic neuropathy and 11 control patients with sensorineural hearing loss and suspected acoustic neuroma. We then counted the number of subcortical lesions in each patient, which may represent an index of generalized cerebral vascular disease. Although patients in the ischemic optic neuropathy group had an average of 3.2 subcortical lesions and those in the control group had an average of 0.9 lesions, this difference was not significant. Based on the presence of subcortical lesions, patients with nonarteritic ischemic optic neuropathy do not appear to have an increased incidence of generalized cerebral vascular disease.
Long-term dialysis patients frequently develop acquired renal cystic disease (ARCD). The discovery of ARCD and renal cell carcinoma in one of our hemodialysis patients led us to review the literature. ARCD has been described mainly in the maintenance hemodialysis (MH) population. Therefore, we investigated 20 peritoneal dialysis (PD) patients for ARCD using ultrasonography. Seven patients (35%) had detectable cysts and two patients (10%) had multiple bilateral cysts. One patient had a large asymptomatic complex cyst that proved to be an adenocarcinoma. Our study suggests that ARCD is relatively common in the PD population, and we speculate that it may be related more to length of time in end-stage renal disease (ESRD) than to the mode of dialysis. The potential for malignant change appears to justify a routine screening examination with ultrasonography and/or computerized tomography (CT) to detect this recently described and probably underrecognized entity.
Report is made of false-positive localization of In-111 leukocytes in the submandibular gland area in children. Possible mechanisms are discussed, but this may represent a normal finding in children.
Three pediatric cases are presented to demonstrate the value of bone scanning in this population to evaluate the fracture complications of nonunion and sequestrum formation.
Three cases are presented in which the intraperitoneal injection of radiopharmaceutical is used to assess diaphragmatic competency.
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Unexplained false-positive accumulation of In-111 leukocyte in the gastrointestinal tract has been reported previously. In a pediatric population, uptake in the submandibular gland was noted in 19 of 42 children. This is believed to be a normal finding in children that is not seen in adults. In some of these 19 children, unexplained gastrointestinal activity was also noted. Saliva from a patient with false-positive gastrointestinal uptake and positive submandibular activity was positive for In-111. One suggested cause of unexplained gut activity may be secondary to swallowed activity in the saliva from the normal submandibular activity in children.
Indium-111 leukocyte scanning is a reliable means of locating acute infection in adults, but its use in the pediatric population has not been extensively documented. The results of scans on 30 children retrospectively reviewed are presented. Acute infections were detected in 15 of 16 patients (94% sensitivity) with one false negative scan. There were 8 truly negative and 6 falsely positive studies (57% specificity).
An asymptomatic thyroid nodule that appeared cystic on ultrasound was seen in a 14-year-old girl. Tc-99m pertechnetate thyroid imaging was expected to show a cold nodule, but surprisingly revealed a hyperfunctioning nodule. A partial thyroidectomy revealed an hemorrhagic cystic adenoma. The occurrence of a cystic nodule, which continued to show hyperfunction, is unusual.
The nuclear medicine bleeding scan is frequently insufficient to locate sites of bleeding precisely, in spite of its great sensitivity. A small, hand-held Geiger-Müller counter, placed directly on exposed intestine in the operating room, enables precise location of the probable bleeding site. In three patients, the technique allowed a minimal amount of intestine to be resected, distinguished between large- and small-intestinal hemorrhage, and eliminated other foci as sites of bleeding.
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Making a clinical diagnosis of infection in prosthetic vascular grafts is difficult but when undiagnosed, this condition has a high mortality rate. Using Indium-111-labeled white-blood cells, 30 scans were performed in 21 patients suspected of having a prosthetic graft infection. The diagnosis of infected graft was confirmed by surgery in all cases, and lack of infection was established by resolution of symptoms with conservative therapy. Twenty-four hour scans of autologous Indium-111 leukocytes were obtained, and correlative CT studies were done in 11 cases. There were 13 infected grafts at surgery (purulent material present), and scans were positive in all (100% sensitivity); of 17 scans, there were 15 true negatives and two false positives (88% specificity). Using the criteria of gas or fluid around the graft, the sensitivity of CT was only 37% in a small subset of these patients. One-half of the cases in which infection was suspected clinically had no infection and had negative scans. Various types of grafts and graft materials were used, and there was no correlation with presence or absence of infection on the basis of the type of graft. Extragraft infection sites were found in five patients. In conclusion, use of Indium-111 leukocytes has been found to be an accurate and valuable diagnostic method for evaluation of suspected prosthetic vascular graft infection, and to have higher diagnostic accuracy than CT.
Previous reports have indicated an accuracy of nearly 100% for LeVeen shunt studies. A case is presented that fulfills the criteria for proper function, but the LeVeen shunt tube was poorly functioning with its tip partially extravascular.
Ultrasound is currently the modality of choice for examination of the fetus in pregnancy. Pregnancy is felt to be a possible risk factor for the development of gallstones. The purpose of this study was to determine whether obstetric patients sent for ultrasonic evaluation should have a simultaneous ultrasonic examination of the gallbladder to detect asymptomatic gallstones. In this study, 11.3 per cent of 142 patients were found to have gallstones. The authors conclude that cholecystosonography should be performed on pregnant patients sent for ultrasonic examination.