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Biomedical subjects

W R Brody

Publications and source records attributed to W R Brody.

At least 55 records · Page 3Linked to original sources
PubMed1981

Acute myocardial ischemia detected in vivo by computed tomography.

Normal and acutely ischemic myocardium was imaged by dynamic computed transmission tomography (CT) in dogs during injection of contrast material. The rotary fan-beam CT scanner used could obtain 16 sequential, ungated, 3.0-second scans at 13-20-second intervals. Time-attenuation curves of myocardial enhancement, which were constructed from serial CT images of normally functioning anterior and lateral left ventricular myocardium, demonstrated mean +/- SEM baseline values: 37 +/- 3.3 and 32 +/- 4.0 CT#s; mean +/- SEM peak enhancement: 72 +/- 4.1 and 73 +/- 3.9 CT#s; and decay in enhancement having mean +/- SD time constants: 3.12 +/- 0.27 and 3.17 +/- 0.22 minutes. Regions of acutely ischemic myocardium demonstrated lower but not significantly different baseline values (mean +/- SEM = 25 +/- 4.3 CT#s) from normal (mean +/- sEM = 37 +/- 3.3 CT#s), without a peak and decay in enhancement. The authors conclude that regions of experimentally-produced acute ischemia are readily detected in vivo by dynamic CT imaging as absent or markedly reduced myocardial contrast enhancement.

Acute Disease↗
PubMed1981

Dynamics of myocardial contrast enhancement: an in vivo computed-tomographic study.

Enhancement of normal functioning myocardium was quantitated in 15 dogs by serial computed transmission tomographic (CT) images during the bolus (10 ml/sec.) or slow (1 ml/sec.) intravenous injection of diatrizoate contrast media (1 ml/kg body weight) in concentrations of 37, 18.5, or 9.25 g iodine (I)/dl. Homogenous images of myocardial enhancement were obtained. However, major streak artifacts were observed frequently when contrast material was injected as a bolus, and myocardial edges were not defined clearly when contrast material with a concentration of 9.25 g I/dl was injected slowly. Time-attenuation curves of normal myocardial enhancement constructed from serial CT images demonstrated a peak in contrast enhancement (delta Hounsfield units, 22-45) followed by a period of deterioration that lasted two to three minutes. These results can be applied to make optimal use of both single (static) and serial (dynamic) myocardial CT images.

Animals↗
PubMed1981

Intravenous arteriography using scanned projection radiography.

Visualization of arteries using intravenous injections of contrast material requires an imaging system capable of (a) excellent sensitivity to dilute concentrations of contrast media and (b) adequate temporal resolution to minimize the effects of motion during the exposure. A line-scanned radiography system based on a CT fan-beam detector (high-pressure xenon ionization chamber) was used for phantom and animal studies of intravenous arteriography to demonstrate the potential advantages of this method. Even though line-scanned systems require long scan times compared to existing radiographic methods, they are capable of showing rapidly moving arteries without blurring. Concentrations of 3 mg/ml of iodine could be seen in vessels 2 mm in diameter. Phantom studies using kVp switching showed that bone or soft tissue could be selectively cancelled.

Angiography↗
PubMed1981

Hybrid subtraction for improved arteriography.

A hybrid subtraction method to reduce the motion sensitivity of temporal subtraction for intravenous arteriography is described. Hybrid subtraction uses dual-energy scanned projection radiography to provide pre- and post-contrast images with the soft tissues subtracted. These pre- and post-contrast soft-tissue-cancelled images are then subtracted. Because involuntary motion (such as swallowing or bowel peristalsis) often affects soft tissues primarily, this hybrid technique provides better visualization of carotid and abdominal arteries than temporal or dual-energy subtraction alone.

Angiography↗
PubMed1980

The use of computed tomography in the diagnosis of coronary artery bypass graft patency.

In a preliminary evaluation of the use of dynamic computed tomography (CT) for the detection of patent aortocoronary bypass grafts, 30 patients were scanned either during the early postoperative period or after graft patency was determined by angiography. To visualize the proximal grafts, CT scans were taken through the aortic root following an intravenous bolus injection of contrast medium. Patent bypass grafts to the left anterior descending and right coronary arteries were demonstrated in 77.5%, while posterior grafts to the circumflex and obtuse marginal coronary arteries were detected in 40%. With its potential for extracting dynamic events, CT scanning provides a new, noninvasive modality for the diagnosis of patent bypass grafts, which heretofore have only been visualized by selective angiography.

Adult↗
PubMed1980

Gated cardiac computed tomography with a motion phantom.

CT images of the heart are significantly degraded by the effects of motion during the scanning interval. The use of electrocardiographic (ECG) gating to provide "stop-action" cardiac images remains limited by artifacts. A motion phantom has been constructed to allow systematic study of the artifact structure of ECG-gated images and to isolate the origins of these artifacts. "Stop-action" reconstructed images are presented demonstrating two classes of artifacts: (a) pinwheel artifacts that appear at the edges of high-contrast moving objects; and (b) linear streaks occurring in relation to missing views when an incomplete angular set of projections is used for image reconstruction with the convolution back-projection algorithm. These results underscore the use of the motion phantom for the analysis of image artifacts and stress the need for new CT reconstruction algorithms which are optmized for "stop-action" scanning.

Heart↗
PubMed1978

Ejection fraction by count rate from gated images.

Left-ventricular (LV) ejection fraction (EF) was determined from ECG-gated images of the cardiac blood pool, by computing the relative change in net LV counts occurring in these images during systole. EFs obtained with this method gave satisfactory interobserver agreement in 20 studies reviewed by three independent observers (average r = 0.95) and also compared favorably with EFs obtained by contrast ventriculography in 39 patients (r = 0.92). The technique appears suitable for use in the evaluation of systolic function in patients with heart disease.

Coronary Circulation↗
PubMed1977

Effects of dipyridamol and methylprednisolone on intimal thickening in vein grafts.

Fibrous intimal proliferation severe enough to produce occlusion has been observed in vein segments used for aorta-coronary bypass grafts. In an attempt to improve graft patency and decrease intimal fibrous thickening, animals with vein grafts were treated with dipyridamole or methylprednisolone for 8 to 12 weeks. Femoral vein segments were used to bypass the femoral artery in 36 dogs. Thirty-four of these grafts were patent at 8 weeks, with no statistically significant differences between control and drug treatment groups. Intimal thickness measurements were taken at three different points along the graft: proximal (upstream end), middle,and distal (downstream end). Dogs treated with methylprednisolone had significantly less intimal thickening (214 versus 125 mu, p less than 0.05) than did control animals in the middle of the veins but there was no difference in thickness measurements at the proximal and distal ends. Dipyridamole-treated animals did not differ from control dogs. Although these data show decreasing intimal thickening in the middle of grafts with methylprednisolone therapy, the intimal thickness was still considerably greater than normal. The lack of response near the anastomotic sites suggests that clinical application of either agent to improve long-term patency is unwarranted.

Animals↗
PubMed1977

The variable roentgen appearance of traumatic diaphragmatic hernia.

Alteration of the diaphragmatic contour should be added to the list of radiographic signs of traumatic diaphragmatic hernia (TDH). Such changes may sometimes be appreciated prior to gross herniation of abdominal viscera into the hemithorax. Alterations of the hemidiaphragmatic contour are non-specific, but suggestive of TDH in the appropriate clinical setting.

Diaphragm↗
PubMed1975

Topical hypothermic protection of the myocardium.

Profound topical hypothermia for intraoperative protection of the heart has been employed as an alternative to selective coronary perfusion with excellent clinical results. Based upon observations that hypothermia decreases cellular metabolism and prevents cellular damage from anoxia, topical hypothermia has been employed to provide protection for anoxic intervals exceeding 60 minutes. Additional advantages of this technique include a bloodless operative field with a flaccid myocardium. A continuous infusion of saline at 4 degrees C provides a simple and effective method of creating myocardial hypothermia. While topical hypothermia has been used successfully with anoxic intervals of 120 minutes, recent evidence indicates that in patients with combined coronary disease and ventricular hypertrophy, the degree of protection is inadequate after 70 minutes. Further investigation is needed to define more completely the degree and length of protection and to identify those situations in which the protection becomes inadequate.

Heart Arrest, Induced↗
PubMed1975

Long-term morphologic and hemodynamic evaluation of the left ventricle after cardiopulmonary bypass. A comparison of normothermic anoxic arrest, coronary artery perfusion, and profound topical cardiac hypothermia.

In order to assess the long-term effects of cardiopulmonary bypass (CPB) in combination with pupular methods of myocardial protection, 37 dogs were placed on CPB for 100 minutes with the use of a bubble oxygenator without hemodilution. A separate group (I) of eight normal dogs served as a control for assessment of hemodynamic changes. The operative groups were as follows: II, continuous coronary perfusion with an empty, beating heart for 60 minutes at 35 degrees C.; III, hypothermic anoxic arrest (aortic occlusion) for 60 minutes with topical cold saline lavage (4 degrees C.); IV, anoxic arrest for 60 minutes at 35 degrees C. Subgroups of Groups III and IV received intracoronary perfusion with Ringer's lactate or Sacks' solution during aortic occlusion and were compared with those animals receiving no perfusion. Survival in Groups II and III was significantly better than in Group IV (82 and 92 per cent vs. 45 per cent). Coronary perfusion with Ringer's lactate or Sack's solution did not influence survival. The 23 survivors from all groups underwent left heart catheterization and LV cineangiography 5 months after operation. All three operative groups had significant elevation of LVEDP and depression of maximum developed dp/dt when compared with normal dogs. Ejection fraction was significantly depressed in Groups III and IV, and there was evidence of left ventricular hypokinesia and/or akinesia in all three operative groups. Differences in function between Groups II, III, and IV were not significant. The use of intracoronary solutions during anoxic arrest did not significantly influence these functional alterations. Evidence of subendocardial fibrosis was found in each of the operative groups, with the most marked changes found in the normothermic arrest group. Moderate fibrosis was present, however, in some survivors in both the continuous coronary perfusion and topical hypothermic arrest groups. These data indicate that although survival is greatly enhanced when coronary artery perfusion or topical hypothermia is used, neither method prevents chronic deterioration in ventricular function nor the development of subendocardial fibrosis.

Animals↗