Failure of regression of atherosclerosis in dogs with moderate cholesterolemia.

Controversy exists as to whether regression occurs in atherosclerotic plaques in response to serum cholesterol reduction. In the present study, using sequential observation of canine atherosclerosis, we attempted regression in hypothyroid dogs. Animals with established lesions prior to a regression attempt were placed on a 0.05% cholesterol diet and observed up to 60 months. Weighted average cholesterols ranged from 235 to 587 mg/100 ml during the regression attempt. A control fed for the entire period of the experiment, 75 months, had an average weighted cholesterol of 435 mg/100 ml. We failed to obtain regression of atherosclerotic plaques in spite of reduction of serum cholesterol from high to moderate levels. The lesions in the experimental animals contained less lipid and more collagen and calcium than occurred in the control. Complicated plaques with aneurysm formation, stenosis of the distal aorta, and gangrene of the tail were also noted.

Xe-133 rebreathing system for ventilation studies on ventilator-assisted patients.

We describe a manually operated system, simple to assemble, that will enable xenon-133 lung ventilation studies to be performed on ventilator-assisted patients. It can be constructed from items readily available. Radiation exposure levels to the operator were measured and are reported.

Regression of atherosclerotic plaques in rhesus monkeys. Angiographic, morphologic, and angiochemical changes.

On a diet with high levels of cholesterol and sucrose, a beta-lipoproteinemia developed in rhesus monkeys that is similar to type II human hyperlipidemia. Lesion regression appeared in response to drastic lowering of serum cholesterol (SC) levels. This experiment analyzed angiochemical responses on the addition of a bile-acid sequestrant to continued atherogenic feeding, which resulted in ranges of moderate cholesterolemia that mimick those that occur in man. After two years of atherogenic diet, fatty fibrous plaques were demonstrated in ten monkeys; then cholestyramine resin, 1.5 g/100 g of the atherosclerotic diet, was added to the food of eight monkeys, whereas two served as controls during a 12-month regression period. Six adult control monkeys that did not receive the atherosclerotic diet were also killed. Seven experimental animals overall showed plaque regression when SC level fell from 400 +/- 130 to 237 +/- 74 mg/dL; one animal showed angiographic combinations of progression and regression. Angiochemical evaluation demonstrated discordant data with instances of decreased plaque cholesterol content and increased levels of collagen. On the average, plaque regression and final composition were related to absolute levels of SC reduction induced by cholestyramine. Regression required that the threshold levels of cholesterol be below 200 mg/dL. Plaques regressed mainly by lipid absorption; in this experiment and, in particular, arterial segments, collagen content sometimes increased.

Diagnosis of ruptured intracranial dermoid cyst: value MR over CT.

The CT and MR findings of seven patients with pathologically proved ruptured dermoid cysts were reviewed to analyze the MR characteristics and to see if MR evaluation had significant advantages over CT. In six cases, both CT and MR identified fatty material in the CSF spaces. Hemorrhage complicated preoperative diagnosis in one case. Patterns of extraaxial fat distribution were as follows: intraventricular fat/CSF levels (three patients), generalized subarachnoid spread (six patients), and localized subarachnoid spread with sulcal widening (one patient). There was no correlation between fat distribution and clinical symptoms. MR showed the vascular involvement better than CT did in five of seven cases, and showed extension of the cysts into the skull base in two cases. Signal intensity of the solid mass was low on T1-weighted MR images and inhomogeneously high on T2-weighted images, which correlated pathologically with the presence of crystal cholesterol, hair, sebaceous glands, and epithelial cells in all cases. On MR, brain parenchyma showed little edema or other reaction to the masses, which were typically large. The value of MR over CT in the examination of ruptured dermoid cysts is the conspicuity of the extent of subarachnoid spread, involvement of the extraaxial structures, and evidence of vascular compromise, which can obviate angiography. MR had no advantage over CT in making the initial diagnosis of ruptured dermoid, but it would be the preferred preoperative study.

Magnetic resonance imaging of a third trimester abdominal pregnancy.

Abdominal pregnancies are rare, representing 1% of all ectopic pregnancies. Early and accurate diagnosis is essential in order to avoid the serious complications associated with the condition, including catastrophic hemorrhage secondary to placental separation. The clinical presentation of abdominal pregnancy is extremely variable and physical examination by itself may be insufficient for diagnosis. Ultrasound (US) is currently the imaging method of choice for establishing gestational location, but sonographic interpretation may be difficult due to gas within the gastrointestinal tract and distorted pelvic anatomy. The use of magnetic resonance imaging (MRI) in obstetric diagnosis, including abdominal pregnancy, has been described. We report a case of an abdominal pregnancy of 32 wk gestation diagnosed by MRI.

The value of quantitative sacroiliac scintigraphy in detection of sacroiliitis.

To evaluate clinical usefulness of quantitative sacroiliac scintigraphy (QSS) in detecting sacroiliitis, we used a modified, pixel by pixel technique for calculating sacroiliac joint/sacrum uptake ratios (sacroiliac joint index - SII). We studied 90 controls, 18 selected patients with active sacroiliitis, 2 ankylosing spondylitis patients with completely ankylosed sacroiliac joints, 14 patients with nonspecific low back pain and 5 patients with rheumatoid arthritis. In the controls, we found that the SII decreases with increasing age (P less than 0.001) and is higher in males than in females (P less than 0.005). In the patients with active sacroiliitis, 9 out of 14 older than 30 had an abnormal SII; 3 of these patients showed no radiographic or CT abnormalities of the sacroiliac joints. None of the 4 patients with sacroiliitis under 30 years of age had values which fell out of the normal range for their age and sex. Only 1 of the 14 patients with non-inflammatory low back pain had an abnormally high SII. A borderline SII was found in 1 of the 5 patients with rheumatoid arthritis. QSS may be useful in detecting active sacroiliitis, sometimes even before the occurrence of radiologic abnormalities. However, because of its low sensitivity, its clinical usefulness is limited, especially in patients under 30 years of age.

Middle meningeal artery trauma.

We present the case of a patient who had the symptoms of a subarachnoid hemorrhage but was subsequently found to have an unusual combination of a separate traumatic pseudoaneurysm and a traumatic arteriovenous fistula of the middle meningeal artery. A review of the literature revealed a difference in the clinical course of patients with traumatic pseudoaneurysms compared to that of patients with arteriovenous fistulas. Patients who were found to have traumatic pseudoaneurysms of the middle meningeal artery frequently manifested signs of delayed hemorrhage. This mechanism may account for the prolonged lucid intervals exhibited in some patients subsequently found to have epidural hematomas.

CT demonstration of brain infarcts due to deep venous thrombosis in systemic lupus erythematosus.

Rapid development of low density bilateral lesions in the brain due to deep venous thrombosis in Systemic Lupus Erythematosis is described. To the best of our knowledge, this type of symmetry, distribution and appearance of brain infarcts in CT due to deep venous thrombosis has not been reported previously.

Generation of parametric images during routine Tc-99m PYP inhalation/Tc-99m MAA perfusion lung scintigraphy. Technical note.

A simple technique is described for generating ventilation/perfusion ratio and perfusion/ventilation ratio images from the posterior Tc-99m PYP aerosol inhalation and Tc-99m MAA perfusion images obtained during routine lung scintigraphy. These images highlight areas of ventilation/perfusion incongruence--mismatch or reverse mismatch--that may sometimes be difficult to detect on conventional images.

Use of Tc-99m sestamibi infusion for detection of hibernating myocardium. A preliminary report.

To evaluate whether a prolonged infusion of Tc-99m sestamibi allows for visualization of viable myocardium in areas of hypoperfused myocardium, 25 patients were prospectively studied. Each patient was imaged four times in two consecutive days in the following manner: day 1:1) immediately after injection of Tl-201 at rest, 2) 1 hour after a bolus injection of Tc-99m sestamibi at rest; and day 2: 1) imaging in the Tl-201 window for 24 hour redistribution, 2) imaging after a 1-hour infusion of Tc-99m sestamibi. The two Tc-99m sestamibi and two Tl-201 studies were evaluated for presence of redistribution. This was present both on the Tl-201 and Tc-99m sestamibi studies (concordant) in 13 cases, and absent on both the Tl-201 and Tc-99m sestamibi studies (concordant) in 9 cases. In two cases redistribution was seen on the Tl-201 images only, and in one case it was seen on the Tc-99m sestamibi images only (discordant). Tc-99m sestamibi infusion may provide information about the presence of viable myocardium which is similar to that provided by Tl-201 24-hour imaging.

A geometric method of measuring the left ventricular ejection fraction on gated Tc-99m sestamibi myocardial imaging.

Geometric measurements of the left ventricular diameters as used in biplane angiocardiography and echocardiography were applied to gated SPECT Tc-99m sestamibi myocardial scintigrams in order to calculate the left ventricular ejection fraction. These measurements take no longer than 5 minutes and require no additional computer software. In a review of 79 examinations, the left ventricular ejection fraction calculated using these measurements correlated well with the echocardiographically estimated ejection fraction (r = 0.78, P < 0.0001). The technique is highly reproducible with an intraobserver correlation of r = 0.94 and interobserver correlation of r = 0.93.

Preliminary imaging results using In-111 labeled CYT-356 (Prostascint) in the detection of recurrent prostate cancer.

To evaluate whether In-111 capromab pendetide (an antibody conjugate directed to a glycoprotein found primarily on the cell membrane of prostate tissue) radioimmunoscintigraphy can localize residual or metastatic prostatic carcinoma in 15 patients after prostatectomy and lymphadenectomy for prostatic carcinoma with rising serum prostate-specific antigen. One patient with 0.6 ng/ml serum prostate-specific antigen had normal imaging results and 14 patients had scintigraphic evidence of residual prostatic bed or metastatic prostatic carcinoma. Two patients with borderline abnormal bone scans had abnormal activity in the same regions on In-111 capromab pendetide images. All patients had negative radiographic abdominal and pelvic cross-sectional prestudy images, and there were no adverse effects related to In-111 capromab pendetide infusion and little human antimouse antibody response.