Abstract: The adverse consequences of carotid atherosclerotic plaques are manifest through two effects on brain perfusion: 1) embolism from intimal ulcerations to the brain and eye, and 2) a reduction in hemispheric flow. The purpose of this chapter is to understand the local Doppler velocity signals and the local pressure-flow relationships associated with stenosis of the carotid arteries in order to quantitate the degree of carotid narrowing and its effect on brain perfusion.

Abstract: Quantitative perfusion imaging is critically important for the evaluation and management of medical therapy. Sonicated microbubble echo contrast agents make ultrasound perfusion imaging a real, and potentially more economic, alternative to more conventional techniques (X-ray angiography, cine-CT, radioisotopes, and Magnetic Resonance). Sonicated microbubbles are excellent ultrasound reflectors and they flow unimpeded through the capillary circulation (because of their uniformly small size). This paper reviews the major issues in the ongoing development of quantitative echo contrast perfusion imaging.

Abstract: The intracranial pressure of 31 patients with bacterial meningitis, in a comatose state and with a score lower than 6 on Glasgow's scale, was monitored by means of an extradural captor in order to detect intracranial hypertension and optimize its treatment All patients had intracranial hypertension during the first 48 hours Brain perfusion pressure was inferior to 50 mmHg in 5 cases Computed tomography of the brain showed cerebral oedema in 16 cases Twenty (64%) of the patient survived, 15 of them without sequelae Monitoring intracranial pressure in patients with bacterial meningitis and coma makes it possible to optimize treatment and shows that a less than 50 mmHg brain perfusion pressure is associated with a 100% death rate

Abstract: No attempt will be made to review all aspects of renal in vitro techniques. The focus will be on renal slices and perfusion techniques as they apply to toxicological problems. For broader coverage of in vitro procedures, especially physiological studies the reader is referred to several reviews1,2. In addition, extensive reviews of renal slices and renal perfusion and other techniques have been published3–5.

Abstract: A recently developed Tc-99m radiocompound, hexamethylpropyleneamine oxime (Tc-99m HM-PAO), exhibits favorable properties for regional cerebral blood flow study in man. The authors present a case of luxury perfusion syndrome observed in a 72-year-old patient with acute stroke and a right-sided hemiplegia, documented by planar scintigraphy and SPECT study in correlation with CT scan. The metabolic basis of this phenomenon is discussed and the usefulness of assessing regional brain perfusion by Tc-99m HM-PAO with conventional nuclear medicine equipment is underlined.

Abstract: The optimal strategy for diagnostic evaluation of patients with suspected pulmonary thromboembolism (PE) is subject of controversial and often conflicting opinions. If untreated, as many as 30% of patients with PE may die. Conversely, anticoagulant therapy significantly decreases mortality from PE, but bleeding complications occur. Underdiagnosis may result in a preventable death, and overdiagnosis may lead to significant hemorrhage from unnecessary anticoagulant therapy. This article outlines a practical guide for the use of pulmonary ventilation-perfusion (V-P) scintigraphy in patients with suspected PE. Perfusion imaging involves the intravenous injection of radiolabeled particles ranging from 10 to 60 ..mu..m in diameter (technetium Tc 99m macroaggregated albumin or technetium Tc 99m serum albumin microspheres); these particles are trapped in the capillaries and precapillary arterioles of the lung. The radiolabeled particles are distributed to the lungs in proportion to regional pulmonary blood flow. The correspondence of perfusion defects to bronchopulmonary segments is best appreciated in the posterior oblique views.

Abstract: 99mTc macroaggregated albumin lung perfusion scans were performed with assessment of pulmonary hemodynamics in 14 male patients with a centrally located lung tumor, subjected to pneumonectomy. In 7 patients perfusion of the affected lung was less than one third of total perfusion. However, all tumors were resectable. Results show that predictive value of the perfusion scan was significant (p<0.02) with regard to forced expiratory volume in the first second (FEV1, r=0.80). A fair but not significant correlation existed in the prediction of vital capacity (VC, r=0.64) and total lung capacity (TLC, r=0.71). No correlation was found between perioperative change in mean pulmonary artery pressure (MPAP) and either relative radionuclide uptake of the affected lung or predicted FEV1. So, the lung perfusion scan cannot be used in preoperative estimation of postoperative MPAP.

Abstract: A recently developed 99mTc radiocompound, hexamethyl-propyleneamine oxime (99mTc-HM-PAO) exhibits favorable properties for regional cerebral tomograms in man utilizing conventional instrumentation (SPECT). Planar and tomographic studies using a rotating gamma camera equipped with a high sensitivity, low energy, collimator were performed in 5 normal subjects and 20 patients suffering from different cerebral diseases. SPECT abnormalities observed in patients with CVD, brain tumors and hydrocephalus were compared with results from X-ray CT. Our preliminary study demonstrates the feasibility of assessing regional brain perfusion using SPECT and a 99mTc radiopharmaceutical which is lipid soluble and has a high extraction fraction in the brain.

Abstract: 99mTc-TBI myocardial perfusion imaging has been studied in 7 normal subjects and 24 patients with coronary artery disease Scintigraphic data revealed that 99mTc-TBI myocardial perfusion imaging is more sensitive than ECG in detecting myocardial infarction In comparing 99mTc-TBI imaging with contrast angiography, its' sensitivity for the diagnosis of coronary artery disease was 917%

Abstract: Perfusion scanning of the lung is the method of choice in assessing preoperative pulmonary partial function and predicting functional operability. In addition, the quantitative perfusion scan gives an estimation of the extent of surgery. If perfusion in the tumor-affected lung is less than 30% of the total pulmonary blood flow, pneumonectomy has to be anticipated. With a perfusion of less than 10%, technical and prognostic inoperability is predicted. In M-staging, bone scanning is still the most sensitive technique available and should be used for preoperative screening, while other imaging techniques-like sonography and CT scanning-have replaced liver and brain scanning. Nuclear medicine techniques using tumoraffin substances have not achieved wide clinical application, but tumor scintigraphy with radiolabeled monoclonal tumor markers may become an important tool in the management of bronchogenic carcinoma in the near future.

Abstract: The discrepancy between three methods for cerebral perfusion imagings in the case of a man with meningioma is presented. Imaging with N-isopropyl-P-(I-123) iodoamphetamine (IMP) showed no activity in the tumor. Imaging with Tc-99m hexamethylpropyleneamine oxime (HM-PAO) and the local cerebral blood flow (LCBF) image with Xe-133 inhalation showed high tumor activity. IMP is a more accurate method for imaging the brain tissue blood flow.

Abstract: A rare case of benign cardiac fibroma causing a focal defect on Tl-201 imaging in an adult patient is presented. The abnormalities on the Tl-201 scan are correlated with other studies performed on the same patient. The usefulness of the Tl-201 myocardial perfusion scan as an early, noninvasive test in cardiac workup is stressed.

Abstract: Recent interest has evolved to expand the use of 2D-echocardiography (2DE) from measurements of left ventricular (LV) regional and global myocardial function to the study of myocardial perfusion using contrast 2DE [1–5]. Although the first initial reports [6–11] have stimulated great interest to develop a method serving the purpose of measurement of myocardial perfusion, numerous problems since then have arisen. It is the purpose of this report to critically discuss current available litterature and experience in studying myocardial perfusion by contrast 2DE and furthermore evaluate current and future research opportunities to develop an echocontrast method for measuring myocardial perfusion.

Abstract: Two scintigraphic methods, resting dipyridamole and exercise thallium-201 myocardial perfusion imaging, to detect and localize coronary artery stenosis were compared in 32 patients suffering from coronary artery disease. The sensitivity of detecting a greater than 50% coronary stenosis was 94% for exercise thallium-201 perfusion imaging and 88% for dipyridamole thallium-201 perfusion imaging. The overall sensitivity and specificity of localizing a greater than 50% coronary stenosis by the two methods were also not significantly different. The results of the two scintigraphic methods were independent of the severity of coronary artery disease. Dipyridamole thallium-201 myocardial perfusion imaging provides a useful and safe alternative test for detecting and localizing coronary artery stenosis in patients unable to perform maximal exercise.

Abstract: Perfusion scintigraphy of the testicles has still its place, in addition to scrotal ultrasound imaging, in the investigation of the "acute scrotum". It reveals scintigraphic patterns typical for twisted testicle and acute or subacute epididymitis. Especially in the Bundeswehr, with its large number of young men, this method enhances the diagnostic spectrum and helps in making surgical decisions. However, in the examination of scrotal masses, ultrasound imaging or surgery is to be preferred.

Abstract: • Conjunctival oxygen tension (Pcjo2) was measured continuously during carotid endarterectomy in 15 patients to evaluate its sensitivity in patients receiving shunts. These studies suggest that Pcjo2tracks brain perfusion during periods of carotid artery occlusion. Reduced Pcjo2was clearly demonstrated with systemic hypotension, carotid artery clamping, and carotid shunt obstruction and clamping. Monitoring of Pcjo2is noninvasive, easy to perform, offers no danger to the patient, and allows real-time assessment of the local tissue perfusion. It provides valuable information on the effectiveness of carotid oxygen transport and, in conjunction with arterial blood gas values, expresses carotid artery perfusion relative to systemic oxygen transport. Further investigations using the Pcjo2sensor may define criteria for intraoperative carotid arterial shunting in patients with tenuous cerebral perfusion, and for prompt intervention in patients with deteriorating perfusion prior to the onset of life-threatening cerebral ischemia. (Arch Surg1986;121:914-917)

Abstract: Two cases are presented in which patients with obstructive lung disease were considered to have a pulmonary embolism (PE). Emergency lung perfusion scans supported the diagnosis of PE in both cases. However, rapid resolution of the symptoms and perfusion defects by repeat ventilation-perfusion scanning at 24 hr suggested that PE was unlikely. In selected cases of wheezing patients, repeat perfusion scans may obviate the need for pulmonary angiography. The authors report two cases in which repeat perfusion scans almost normalized by 24 hr. Review of the literature indicates that the rate of resolution of perfusion defects would have been much slower had pulmonary embolism occurred.

Abstract: Noninvasive cardiac imaging withechocardiography or thallium-201 scintigraphy utilizing pharmacologic agents asalternatives toexerciseisgaining popularity. We investigated the physiologic rationale underlying theoptimal choice ofpharmacologic stressforfunctional versus perfusion imaging. Withtheuseofanopen-chest dogmodel, acritical stenosis oftheleft circumflex coronaryartery was produced withtotal ablation ofhyperemic responsetoa 15secperiod ofcomplete occlusion. Regional left ventricular wallthickening was assessed byquantitative two-dimensional echocardiography. Regional myocardial bloodflowwas determined bymicrospheres inboththe flow-restricted left circumflex areaandthecontrol areasupplied bytheleft anterior descending artery. Eight dogsreceived 15,ug/kg/min dobutamine intravenously for10min, andninedogsreceived 0.14 mg/kg/min dipyridamole intravenously for4min.Dobutamine induced wallthickening abnormalities inalldogswhile dipyridamole induced dysfunction inonly55%oftheanimals studied (p< .01). Subendocardial bloodflowtotheleft circumflex areawas unchanged after bothdobutamine and dipyridamole whencompared withbaseline blood flow. However, subendocardial blood flowincreased markedly after dipyridamole inthecontrol area.Regional subendocardial blood flowratio (left anterior descending/left circumflex) was 3.74 0.09(mean+ SEM)after dipyridamole versus1.27+ 0.09 after dobutamine (p< .001). Subendocardial bloodflowintheleft circumflex areadecreased sig- nificantly inthesubgroup ofdogsthat developed regional dysfunction on dipyridamole (0.73 + 0.14 vs 1.26+ 0.18ml/min/g, p < 0.05, n = 5),while itremained unchanged inthesubgroup that did notshowdysfunction (1.82 + 0.17 vs 1.57+ 0.12ml/min/g; p = NS,n = 4).We conclude that: (1)Dobutamine ismore effective ininducing regional myocardial dysfunction thandipyridamole for similar coronarylesions. Thus,forimaging modalities that rely on functional assessment, such as echocardiography, dobutamine may beasuperior agent. (2)Dipyridamole induces greater blood flow heterogeneity thandobutamine. Hence, forperfusion imaging, suchasthallium-201 scintigraphy, dipyridamole may bethepharmacologic agentofchoice. (3)Dipyridamole-induced regional myo- cardial dysfunction occurswhenthere isan absolute decrease insubendocardial bloodflowduring vasodilatation. Circulation 76,No.4,943-951, 1987. THE USEFULNESSofexercise stress testing inthe evaluation ofcoronary artery disease hasexpanded withthedevelopment ofnoninvasive cardiac imaging techniques. Inconjunction withperfusion imaging FromtheDivisions ofCardiology andNuclear Medicine, Department ofInternal Medicine, andDepartments ofSurgery andPhysiology,

Abstract: To the Editor .—The article by Kram et al 1 claims that by measuring transconjunctival oxygen tension (Pcjo 2 ) one can assess adequacy of brain perfusion during carotid endarterectomy. This conclusion is drawn without the authors having actually evaluated simultaneous brain perfusion using any currently accepted method, such as electroencephalography or monitoring of regional cerebral blood flow (rCBF) and stump pressure. My colleagues and I 2 compared Pcjo 2 measurements with continuous 16-channel electroencephalograms (EEGs) and rCBF measurements using Xenon Xe 133 in 18 patients undergoing carotid endarterectomy. As in the study by Kram and coworkers, the Pcjo 2 value fell in all patients following occlusion of the carotid artery. However, only five of the 18 patients had any evidence of central nervous system ischemia, as detected by electroencephalography. The degree of Pcjo 2 change did not bear any correlation with rCBF or identify those patients whose rCBF fell below

Abstract: Unidirectional L-phenylalanine transport into six brain regions of pentobarbital-anesthetized rats was studied using the in situ brain perfusion technique. This technique allows both accurate measurements of cerebrovascular amino acid transport and complete control of perfusate amino acid composition. L-Phenylalanine influx into the brain was sodium independent and could be described by a model with a saturable and a nonsaturable component. Best-fit values for the kinetic constants in the parietal cortex equaled 6.9 X 10(-4) mumol/s/g for Vmax, 0.011 mumol/ml for Km, and 1.8 X 10(-4) ml/s/g for KD during perfusion with fluid that did not contain competing amino acids. D-Phenylalanine competitively inhibited L-phenylalanine transport with a Ki approximately 10-fold greater than the Km for L-phenylalanine. There were no significant regional differences in Km, KD, or Ki, whereas Vmax was significantly greater in the cortical lobes than in the other brain regions. L-Phenylalanine influx during plasma perfusion was only 30% of that predicted in the absence of competing amino acids. Competitive inhibition increased the apparent Km during plasma perfusion by approximately 20-fold, to 0.21 mumol/ml. These data provide accurate new estimates of the kinetic constants that describe L-phenylalanine transport across the blood-brain barrier. In addition, they indicate that the cerebrovascular transfer site affinity (1/Km) for L-phenylalanine is three- to 12-fold greater than previously estimated in either awake or anesthetized animals.

Abstract: Pulmonary embolism (PE) is difficult to diagnose. The clinical signs and symptoms of the disorder are nonspecific, and the results of laboratory tests are undependable. Accordingly, imaging studies have played a major role in evaluation of patients with suspected PE. Chest radiography is an essential part of this imaging evaluation, but is neither sensitive nor specific, per se. The radiograph is used primarily to provide a regional comparison for ventilation-perfusion (V-P) scintigraphy. V-P scintigraphy typically is the pivotal noninvasive approach to diagnosis of PE. Multi-view perfusion scintigraphy is a sensitive means for detecting the multiple, wedge-shaped defects characteristic of PE. The perfusion scan's inherent nonspecificity is improved by the ventilation study, which reveals abnormalities of ventilation that account for perfusion defects not caused by PE. Multi-view ventilation imaging with either the xenon gases, Kr-81m or radioaerosols is useful for comparison with perfusion scans. When performed properly and interpreted within the guidelines of current diagnostic schemes for scintigraphy, V-P studies provide approximately 90% reliability for the diagnosis of PE. When used alone or in conjunction with noninvasive studies of deep venous thrombosis, they provide an excellent basis for selection of certain patients for pulmonary angiography, and for other decisions about the clinical management of patients with suspected PE.