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PubMed2006

Utility of computed tomography perfusion in detection of cerebral vasospasm in patients with subarachnoid hemorrhage.

OBJECT: Digital subtraction (DS) angiography is the gold standard for detecting cerebral vasospasm after subarachnoid hemorrhage (SAH). Computed tomography (CT) perfusion is a recently developed modality for the evaluation of cerebral hemodynamics. This study was conducted to evaluate the potential of using CT perfusion to detect vasospasm in patients with SAH. METHODS: Fourteen patients between the ages of 41 and 66 years with aneurysmal SAH underwent 23 CT perfusion scans for suspected vasospasm. All patients underwent DS angiography within 12 hours of the CT perfusion scans. The presence of vasospasm on CT perfusion images was determined based on qualitative reading using color maps of mean transit time, cerebral blood flow, and cerebral blood volume as criteria. The presence or absence of vasospasm as retrospectively determined using CT perfusion was compared with DS angiography findings. Of the 23 CT perfusion scans performed, 21 (91%) were concordant with angiography findings in predicting the presence or absence of vasospasm. In 15 of 23 scans, the presence of vasospasm was detected on CT perfusion scans and confirmed on DS angiography studies. In two cases, vasospasm was revealed on DS angiography but was not confirmed on CT perfusion. The degree of agreement between CT perfusion and DS angiography for detection of vasospasm was high (K = 0.8, p , 0.0001). CONCLUSIONS: Computed tomography perfusion is an accurate, reliable, and noninvasive method to detect the presence or absence of vasospasm. It can be used as a tool to help guide the decision to pursue DS angiography with the intent to treat vasospasm.

Adult↗
PubMed1976

[Asymmetric brain perfusion in the aged?].

Between 1971 and 1975 we performed 1580 dynamic perfusion studies in 1411 patients. The patients were admitted to the nuclear medicine department for brain scanning from the medical, neurological and neurosurgical departments as well as directly by private family physicians. For dynamic brain studies we used the scintillation camera (Searle Radiographics) and a bolus of 99mTc-pertechnetate intravenously injected. The polaroid frames were exposed at 4 second intervals The results of the dynamic brain study were divided into five categories: normal, moderately diminished perfusion of one hemisphere, severe perfusion defect of one hemisphere, focal or multifocal hypervascular areas ("hot areas") and stenosis or occlusion of the carotid artery. In 1009 cases we found a normal perfusion of the tracer material without any side difference between the brain hemispheres. In 68 patients with motoric hemisyndrome of the right side and in 89 patients with hemisyndrome of the left side we were able to demonstrate a diminished perfusion of the contralateral hemisphere. In 65 patients with confirmed primary or metastatic brain tumors we observed a perfusion deficiency in 39 cases and focal "hot" areas in 26 cases. In 24 epileptic patients we found asymmetrical perfusion of the brain. In 109 patients without any neurological signs or symptoms we registered a "false positive" dynamic perfusion study with an asymmetrical initial transition of the injected tracer material. The left hemisphere showed a diminished perfusion in 86 cases, the right in 23 cases. The asymmetrical brain perfusion was not observed in patients under the age of twenty years. The incidence of "false positive" dynamic brain studies was found to be dependent on the age of the investigeted patients with a maximum of asymmetrical brain perfusion scans in the age group between 61 and 70 years. At present time we are not able to explain the reason of the "false positive" results. Because of this reason the investigation will be continued together with the neurologists and radiologists to find out a possible correlation between our study, the EEG-curves and results of the morphological brain investigations such as pneumoencephalography or ACT-scans.

Adolescent↗
PubMed1999

Temperature effects on surface pressure-induced changes in rat skin perfusion: implications in pressure ulcer development.

The effect of varying local skin temperature on surface pressure-induced changes in skin perfusion and deformation was determined in hairless fuzzy rats (13.5+/-3 mo, 474+/-25 g). Skin surface pressure was applied by a computer-controlled plunger with corresponding skin deformation measured by a linear variable differential transformer while a laser Doppler flowmeter measured skin perfusion. In Protocol I, skin surface perfusion was measured without heating (control, T=28 degrees C), with heating (T=36 degrees C), for control (probe just touching skin, 3.7 mmHg), and at two different skin surface pressures, 18 mmHg and 73 mmHg. Heating caused perfusion to increase at control and 18 mmHg pressure, but not at 73 mmHg. In Protocol II, skin perfusion was measured with and without heating as in Protocol I, but this time skin surface pressure was increased from 3.7 to 62 mmHg in increments of 3.7 mmHg. For unheated skin, perfusion increased as skin surface pressure increased from 3.7 to 18 mmHg. Further increases in surface pressure caused a decrease in perfusion until zero perfusion was reached for pressures over 55 mmHg. Heating increased skin perfusion for surface pressures from 3.7 to 18 mmHg, but not for pressures greater than 18 mmHg. After the release of surface pressure, the reactive hyperemia peak of perfusion increased with heating. In Protocol III, where skin deformation (creep and relaxation) was measured during the application of 3.7 and 18 mmHg, heating caused the tissue to be stiffer, allowing less deformation. It was found that for surface pressures below 18 mmHg, increasing skin temperature significantly increased skin perfusion and tissue stiffness. The clinical significance of these findings may have relevance in evaluating temperature and pressure effects on skin blood flow and deformation as well as the efficacy of using temperature as a therapeutic modality in the treatment of pressure ulcers.

Analysis of Variance↗
PubMed2000

The effect of short-term coronary perfusion using oxygenated diluted blood following cold storage for long-term heart preservation.

BACKGROUND: The aim of this study was to compare the results obtained from the use of both University of Wisconsin (UW) solution and diluted blood in short-term coronary perfusion following 12-hour cold storage. METHODS: Following coronary vascular washout of adult mongrel dogs with the UW solution, the heart was excised and immersed in a cold (4 degrees C) UW solution for 12 hours followed by 1-hour of coronary perfusion. Two different solutions were used for the coronary perfusion; a 4 degrees C oxygenated UW solution (Group U, n=7) and 15 degrees C oxygenated diluted blood (Group B, n=7). Myocardial high energy phosphate (HEP) levels, tissue water content (TWC), interstitial tissue space (ITS) rates and histological findings were evaluated at 0- and 12-hour cold storage and also following coronary perfusion. The preserved graft was then evaluated through orthotopic transplantation. The control group in this experiment consisted of seven hearts transplanted after 12-hour cold storage without coronary perfusion. RESULTS: Myocardial HEP levels significantly decreased after 12-hour cold storage. The recovery rate of myocardial HEP levels after coronary perfusion was significantly (p<0.05) higher in Group B than in Group U. The increase of myocardial TWC during coronary perfusion was significantly (p<0.01) higher in Group B than in Group U. After 1-hour coronary perfusion, the subendocardial ITS rate was significantly (p<0.01) higher compared with the value at 0-hour cold storage in Group U, whereas it demonstrated no significant change in Group B. PAS stain revealed the glycogen content of the subendocardial tissues was higher in Group B than in Group U. The recovery rate of hemodynamic parameters 2 hours after heart transplantation was higher in Group U and significantly (p<0.05) higher in Group B than in the control. CONCLUSIONS: Myocardial HEP levels recovered significantly after additional coronary perfusion. Though the UW solution prevented myocardial cellular edema, subendocardial perfusion was incomplete and the recovery rate of myocardial HEP levels was lower, suggesting that diluted blood may become the solution of choice as a perfusate.

Adenosine↗
PubMed2001

Quantitative assessment of motion artifacts and validation of a new motion-correction program for myocardial perfusion SPECT.

UNLABELLED: Patient motion during myocardial perfusion SPECT can produce images that show artifactual perfusion defects. The relationship between the degree of motion and the extent of artifactual perfusion defects is not clear for either single- or double-head detectors. Using both single- and double-head detectors and quantitative perfusion SPECT (QPS) software, we studied the pattern and extent of defects induced by simulated motion and validated a new automatic motion-correction program for myocardial perfusion SPECT. METHODS: Vertical motion was simulated by upward shifting of the raw projection datasets in a returning pattern (bounce) and in a nonreturning pattern at 3 different phases of the SPECT acquisition (early, middle, and late), whereas upward creep was simulated by uniform shifting throughout the acquisition. Lateral motion was similarly simulated by left shifting of the raw projection datasets in a returning pattern and in a nonreturning pattern. Simulations were performed using single- and double-head detectors, and simulated motion was applied to projection images from 8 patients who had normal 99mTc-sestamibi SPECT findings. Additionally, images from 130 patients with actual clinical motion were assessed before and after motion correction. The extent of perfusion defects was assessed by QPS, and a 20-segment, 5-point scoring system was used to assess the effect of motion on the presence and extent of perfusion defects. RESULTS: Of 12 bounce simulations, the bouncing motion failed to produce significant (>3%) perfusion defects with either the single- or the double-head detector. With the single-head detector, early shifting created the largest defect, whereas with the double-head detector, shifting during the middle of the acquisition created the largest defect. With regard to upward creep, defects were of larger extent with the double- than the single-head detector. With the single-head detector, 8 of 20 simulated motion patterns yielded significant perfusion defects of the left ventricle, 7 (88%) of which were significantly improved after motion correction. With the double-head detector, 12 of 20 patterns yielded significant defects, all of which improved significantly after correction. Of 2,600 segments in the 130 patients with actual clinical motion, only 1.3% (30/2,259) of segments that were considered normal (score = 0 or 1) changed to abnormal (score = 2-4) after motion correction, whereas 27% (92/341) of abnormal segments were reclassified as normal after motion correction. CONCLUSION: Artifactual perfusion defects created by simulated motion are a function of the time, degree, and type of motion and the number of camera detectors. Application of an automatic motion-correction algorithm effectively decreases motion artifacts on myocardial perfusion SPECT images.

Aged↗
PubMed2002

The effects of motion artifact and low perfusion on the performance of a new generation of pulse oximeters in volunteers undergoing hypoxemia.

INTRODUCTION: Motion artifact and low perfusion often lead to faulty or absent pulse oximetry readings in clinical practice. OBJECTIVE: Determine the impact of motion artifact and low perfusion on newly introduced pulse oximetry technologies during hypoxemic episodes in healthy volunteers. METHODS: Five different pulse oximeters from 4 manufacturers (the Datex Ohmeda 3900P; the Agilent; the Nellcor N-3000; the Nellcor N-395; and the Schiller OX-1, which is the European version of the Ivy SatGuard 2000 with Masimo SET) were compared with respect to their ability (separated or in combination) to provide accurate readings in the presence of motion artifact and low perfusion. Four of these oximeters represent the latest available oximetry technology, and one (the N-3000) represents a previous generation of oximeters. Oxygen saturation values (S(pO(2))) and pulse rate from the oximeters were recorded during episodes of induced hypoxemia in 10 healthy volunteers. Standardized and repeatable motion artifacts were generated by a motion machine and by having the test subject perform tapping and scratching motions. Perfusion to the finger was reduced by an inflatable balloon impinging on the brachial artery. The pulse oximetry readings from the test oximeters were compared to readings from control pulse oximeters on the unperturbed reference hand. The pulse rates from the test oximeters were compared to the electrocardiographically-measured heart rate. RESULTS: The frequency of faulty readings was increased by increasing motion interference and decreasing perfusion. The S(pO(2)) deviation was within +/- 3% of the reference reading > 95% of the time for all instruments during the control desaturation period in the absence of motion and with normal perfusion. With the combination of motion and low perfusion, the S(pO(2)) error was within +/- 3% less than 62% of the time for all oximeters tested. A significant difference in the frequency of large S(pO(2)) errors was observed only in the direct comparison of the N-395 and N-3000. The N-395 exhibited less frequent S(pO(2)) error exceeding 6% of S(pO(2)) in the combination of the most challenging situations (motion and motion with reduced perfusion). In the same situation the Datex-Ohmeda 3900P and Nellcor N-3000 showed significantly higher pulse rate errors than the other devices (Datex-Ohmeda 3900P 53% of the time and N-3000 37% of the time). CONCLUSIONS: The established model of creating motion artifact and low perfusion is capable of simulating a hierarchy of severe clinical situations. With solely motion or solely reduced perfusion the percentage of errors exceeding +/- 3% of S(pO(2)) increased by 20% and 10%, respectively, compared to the control period. Simultaneous presence of motion and reduced perfusion leads to a relative incidence of > 35% of errors > 3% of S(pO(2)) for the various oximeters. In this situation the N-3000 and the Datex-Ohmeda 3900P exhibited differences between estimated pulse rate and electrocardiographically-measured heart rate > 25 beats/min > 37% of the time.

Adult↗
PubMed2002

Incremental value of assessment of regional wall motion for detection of multivessel coronary artery disease in exercise (201)Tl gated myocardial perfusion imaging.

UNLABELLED: Assessment of reversible perfusion defects in exercise (201)Tl perfusion SPECT has low sensitivity and high specificity for detection of multivessel coronary artery disease (CAD). The goal of this study was to evaluate whether worsening of left ventricular regional wall motion assessed by an automated algorithm in exercise (201)Tl electrocardiography-gated SPECT had incremental diagnostic value over perfusion data for detection of multivessel CAD. METHODS: Two hundred one patients underwent exercise (201)Tl gated SPECT. Software that automatically analyzes left ventricular function was used to assess exercise and rest regional wall motion. Regional wall motion on initial images was compared with that on rest images, that is, delayed images for patients without reinjection images and reinjection images for patients with reinjection images. The left ventricle was divided into 9 segments, with individual segments assigned to 3 coronary territories. Worsening of wall motion was defined as worsening in any segment on initial images compared with rest images. RESULTS: Of 73 patients with multivessel CAD, 20 (27.4%) had reversible perfusion defects in multiple coronary territories, 26 (35.6%) exhibited worsening of regional wall motion in multiple territories, and 37 (50.7%) had reversible perfusion defects or worsening of regional wall motion in multiple territories. The sensitivity of the combination of reversible perfusion defect and worsening of regional wall motion was significantly higher than that of reversible perfusion defect alone for detection of multivessel CAD (50.7% vs. 27.4%, P < 0.05). The specificity of the combination of reversible perfusion defect and worsening of regional wall motion for detecting multivessel CAD did not differ from that of reversible perfusion defect alone and that of worsening of regional wall motion alone (94.5% vs. 99.2% and 97.7%, respectively, P = not statistically significant). CONCLUSION: Combined assessment of worsening of left ventricular regional wall motion by exercise and perfusion data in exercise (201)Tl gated myocardial SPECT was more sensitive, with acceptable specificity, than was assessment with perfusion data alone for detection of multivessel CAD.

Coronary Angiography↗
PubMed2004

Pulmonary functional MRI: an animal model study of oxygen-enhanced ventilation combined with Gd-DTPA-enhanced perfusion.

BACKGROUND: The assessment of regional pulmonary ventilation and perfusion is essential for the evaluation of a variety of lung disorders. Pulmonary ventilation MRI using inhaled oxygen as a contrast medium can be obtained with a clinical MR scanner, without additional equipment, and has been demonstrated to be a feasible means of assessing ventilation in animal models and some clinical patients. However, few studies have reported on MR ventilation-perfusion imaging. In this study, we evaluated the usefulness of oxygen-enhanced ventilation in combination with first-pass Gd-DTPA-enhanced perfusion MRI in a canine model of pulmonary embolism and airway obstruction. METHODS: Peripheral pulmonary embolisms were produced in eight dogs by intravenous injection of gelfoam strips at the pulmonary segmental arterial level, and airway obstructions were created in five of the dogs by inserting a self-designed balloon catheter into a secondary bronchus. Oxygen-enhanced MR ventilation images were produced by subtracting images from before and after inhalation of pure oxygen. Pulmonary perfusion MR images were acquired with a dynamic three-dimensional fast gradient-echo sequence. MR ventilation and perfusion images were read and contrasted with results from general examinations of pathological anatomy, ventilation-perfusion scintigraphy, and pulmonary angiography. RESULTS: Regions identified as having airway obstructions matched using both MR ventilation and perfusion imaging, but regions of pulmonary embolisms were mismatched. The area of airway obstruction defects was smaller using MR ventilation imagery than that using ventilation scintigraphy. Abnormal perfusion regions due to pulmonary embolisms were divided into defective regions and reduced regions based on the time course of signal intensity changes. In the diagnosis of pulmonary embolisms with the technique of ventilation and perfusion MRI, sensitivity and specificity were 75.0% and 98.1%, respectively, and the diagnostic results of this MRI technique were in agreement with the results of ventilation-perfusion scintigraphy and pulmonary angiography (K: 0.899, 0.743). CONCLUSIONS: Oxygen-enhanced ventilation in combination with pulmonary perfusion MRI can be used to diagnose abnormalities of airways and blood vessels in the lungs, and can provide regional functional information with high spatial and temporal resolution. This method possesses great potential value for clinical applications.

Airway Obstruction↗
PubMed2005

Effects of carotid or vertebrobasilar stent placement on cerebral perfusion and cognition.

INTRODUCTION: There are no well-established physiologic or neuropsychological criteria for identifying which patients with stenosis of the cervicocerebral vessels are at high risk of stroke or cognitive impairment. Our purpose was to evaluate changes in cognitive performance and cerebral perfusion associated with endovascular stent placement of the cervicocerebral vessels. METHODS: A consecutive series of 20 patients, 31-88 years of age, who underwent 21 stent procedures for arterial stenosis (10 extracranial carotid stents [ECS], four intracranial carotid stents [ICS], and seven extra- or intracranial vertebrobasilar stents [VBS]) was investigated retrospectively. All patients were evaluated with CT or MR perfusion studies both before and after stent placement. Cognitive response after stent placement was evaluated by using an informant questionnaire. RESULTS: In patients with anterior circulation stenoses (ECS and ICS group), 11 of 14 (79%) had a baseline perfusion abnormality and all 11 patients showed improved perfusion after stent placement. Four of seven (57%) patients with posterior circulation stenoses (VBS group) had a baseline perfusion abnormality and two of the four patients showed improved perfusion after stent placement. Degree of stenosis was the strongest predictor of the presence of a baseline perfusion abnormality (P = .03). Fifteen of 19 (79%) of the patients showed improved cognitive scores after stent placement. Among patients with improvement in perfusion after stent placement, 11 of 13 (85%) had improved cognitive scores. Improved perfusion after stent placement was a significant predictor of cognitive improvement (P = .04). Patients who were stented on an elective basis demonstrated greater improvement in cognition as compared with patients stented urgently (P = .01). CONCLUSION: Endovascular stent placement of the cervicocerebral vessels can safely and effectively resolve cerebral perfusion abnormalities. Improvement in perfusion parameters is associated with cognitive improvement. Larger, blinded, prospective studies are needed to confirm these preliminary observations.

Adult↗
PubMed2005

Association of ischemia on stress (99m)Tc-tetrofosmin myocardial perfusion imaging with all-cause mortality in patients with diabetes mellitus.

UNLABELLED: Stress myocardial perfusion imaging is a useful method for evaluation of coronary artery disease (CAD) in patients with diabetes mellitus. However, its role in predicting all-cause mortality is not well defined. The aim of this study was to determine whether myocardial ischemia on stress myocardial perfusion imaging can predict all causes of death in patients with diabetes mellitus. METHODS: We studied 297 patients with diabetes mellitus and known or suspected CAD by exercise or dobutamine stress (99m)Tc-tetrofosmin myocardial perfusion tomographic imaging. Ischemia was defined as reversible perfusion abnormalities. The endpoints were death from any cause and hard cardiac events (cardiac death and nonfatal myocardial infarction). RESULTS: An abnormal scan was detected in 179 (60%) patients. Myocardial perfusion abnormalities were fixed in 76 (26%) patients and were reversible in 103 (35%) patients. During a mean follow-up of 6 +/- 2.1 y, 80 (27%) patients died. Nonfatal myocardial infarction occurred in 14 (5%) patients. The annual mortality rate was 2.5% in patients with normal perfusion, 4.5% in patients with fixed defects, and 6% in patients with ischemia. The annual cardiac death rate was 4.2% in patients with ischemia and 2.6% in patients with fixed defects. In patients with normal perfusion, the annual cardiac death rate was 0.9% during the 5 y after the stress test. In a Cox multivariate analysis model, predictors of death were age, history of heart failure, peripheral vascular disease, and reversible perfusion defects. CONCLUSION: Myocardial ischemia on stress (99m)Tc-tetrofosmin myocardial perfusion imaging is associated with an increased risk of all-cause mortality during long-term follow-up among patients with diabetes mellitus. Patients with normal perfusion have a lower mortality rate and may require less frequent follow-up stress perfusion imaging.

Cause of Death↗
PubMed2005

[Systolic and diastolic left ventricle function assessment by tissue Doppler echocardiography in patients with perfusion defects in SPECT study].

INTRODUCTION: Tissue Doppler imaging (TDI) facilitates the quantitative assessment of the regional systolic and diastolic left ventricle function. Heart scintigraphy (SPECT) facilitates the assessment of regional perfusion of the myocardium. The aim of the study was the evaluation of the correlation between the regional myocardial perfusion defects observed in the SPECT study and the regional systolic and diastolic left ventricle function observed in TDI examination in the ischaemic heart disease patients. MATERIAL AND METHODS: In 40 patients (33 men and 7 women) aged 43-74 years (mean age 56 years) diagnosed of ischaemic heart disease on the basis of coronary angiography, rest TDI examination was performed. Maximal systolic and maximal early-diastolic myocardial velocities were assessed in 13 myocardial segments of the left ventricle, supplied by respective coronary arteries (left anterior descending artery--LAD, circumflex artery--Cx, right coronary artery--RCA). During rest and exercise perfusion scintigraphy of the heart (Tc99 MIBI SPECT) myocardial perfusion was evaluated in the segments analysed previously during TDI study. On the basis of the SPECT examination results the patients were divided into three groups: group I) patients with fixed perfusion defects, group II) patients with exercise-induced perfusion defects and normal rest perfusion, group III) patients with normal perfusion during rest and exercise. RESULTS: Systolic and diastolic myocardial velocity in LAD and Cx supplied segments were significantly higher in group II and group III as compared with group I. Systolic and diastolic velocities of myocardium supplied by LAD were significantly lower in group II as compared with group III. In Cx supplied region the diastolic myocardial velocity was significantly lower in group II as compared with group Ill. CONCLUSIONS: In the left ventricle myocardial regions with fixed perfusion defects, statistically significant decrease of systolic and diastolic myocardial velocities was observed. Moreover, the decrease of diastolic myocardial velocity in the rest TDI examination was found in patients with normal rest perfusion and exercise-induced perfusion defects.

Adult↗
PubMed2006

[Diagnosis of coronary artery disease with 99Tcm-N-NOET myocardial perfusion imaging].

OBJECTIVE: To evaluate the sensitivity and specificity of (99)Tc(m)-N-NOET myocardial perfusion tomographic imaging (MPI) for the diagnosis of coronary artery disease (CAD). METHODS: Coronary angiography and (99)Tc(m)-N-NOET myocardial perfusion tomographic imaging were performed in the patients hospitalized in the Department of Cardiology, Peking Union Medical College Hospital, from June to December 2005 with known or suspected diagnosis of CAD. Adenosine was infused intravenously at a rate of 140 microg x kg(-1)min(-1) for 6 minutes. At the third minute of adenosine infusion, 740 MBq (20 mCi) (99)Tc(m)-N-NOET was injected intravenously. MPI was obtained 15 minutes after the (99)Tc(m)-N-NOET infusion. If the result was abnormal, rest myocardial perfusion imaging would be performed 2 hours later. Coronary angiography was performed in all patients within one week after the myocardial perfusion imaging. RESULTS: Myocardial perfusion imaging was performed in 53 cases, 36 males and 17 females, aged 56 +/- 10, who underwent coronary angiography, among which 31 had > or = 50% stenosis of coronary artery and 23 had normal coronary artery. All of the patients with stenosis of coronary artery had positive (99)Tc(m)-N-NOET adenosine stress myocardial perfusion imaging. Nineteen out of the 29 cases without stenosis of coronary artery had negative adenosine myocardial perfusion imaging. The sensitivity and specificity of (99)Tc(m)-N-NOET adenosine myocardial perfusion imaging were 100% and 73% respectively in the detection of stenosis of coronary arteries. Seven cases got percutaneous coronary intervention and 2 got coronary artery bypass graft. Six of the 9 patients undergoing revascularization had stenosis of stents or grafts, 5 of which had positive myocardial perfusion imaging. 3 cases hadn't restenosis and their results of myocardial perfusion imaging were negative. CONCLUSION: (99)Tc(m)-N-NOET myocardial perfusion imaging is a useful non-interventional method for detecting coronary artery stenosis.

Aged↗
PubMed1994

Concepts of myocardial perfusion imaging in magnetic resonance imaging.

Based on the major innovations in ultrafast magnetic resonance (MR) imaging in recent years, myocardial perfusion imaging with MR has become the focus of many investigators. Two major approaches to myocardial perfusion imaging involve either exogenous or endogenous contrast agents. For the first category of perfusion experiments, we review the characteristics of the common contrast agents and MR techniques for experimental and clinical first-pass studies and in particular address the question of extracting quantitative estimates for myocardial blood flow (milliliters per minute per gram) and volume (milliliters per gram). We demonstrated quantitative perfusion analysis using intravascular relaxation agents and heavily T1-weighted ultrafast gradient echo sequences. Signal time curves need to be transformed to content time curves and the resulting residue functions were analyzed with a multiple-pathway, axially distributed perfusion model. These preliminary results suggest that quantitative assessment of myocardial perfusion is feasible, but additional studies should provide further confidence for this novel MR approach. The exact sensitivity and specificity of MR first-pass imaging in conjunction with extracellular contrast agents in patient studies and its diagnostic accuracy as judged against coronary angiography and scintigraphic perfusion imaging remain yet undefined. The second category of perfusion experiments does not require exogenous contrast agents and has not yet been tested in patient studies. Progress is reported on several MR perfusion-sensitive methods that use the tissue water as an endogenous contrast agent in combination with magnetization transfer techniques as well as paramagnetic deoxyhemoglobin for measuring tissue oxygenation using heavily T2*-weighted sequences for blood oxygen-level-dependent contrast. Possible future directions and developments toward further improvements for MR myocardial perfusion measurements and contraction-perfusion matching are also addressed.

Blood Volume↗
PubMed1993

Cerebral metabolism and function during normothermic retrograde cerebral perfusion.

Retrograde cerebral perfusion through a superior vena cava (SVC) cannula is a new technique used to protect the brain during circulatory arrest. Cerebral blood flow, oxygen consumption, blood sugar consumption and auditory brain stem responses were measured at various rates (100, 200 and 300 ml min-1) of retrograde cerebral perfusion in normothermic mongrel dogs (n = 12, body-weight 13-15 kg). During perfusion about 20% of the perfusate from the SVC was returned via the aorta, while the rest drained into the inferior vena cava. External jugular venous pressure increased as the perfusion rate increased (mean(s.d.) 26.0(6.4) mmHg at a rate of perfusion of 300 ml min-1). Oxygen and blood sugar consumption also increased as the rate of perfusion increased. Retrograde cerebral perfusion at 300 ml min-1 provided half of the cerebral blood flow (mean(s.d.) 14.7(6.4) versus 34.3(7.8)ml min-1) of antegrade cardiopulmonary bypass (CPB). Analysis of the blood returned through the aorta during perfusion at a rate of 300 ml min-1 showed that mean(s.d.) oxygen consumption was about one-third (4.4(2.1) versus 12.3(7.1) ml min-1) and blood sugar consumption about 15% (17(22) versus 114(54)mg min-1) of that seen in blood returned through the SVC during CPB. Auditory brain stem responses disappeared immediately when perfusion was started but recovered completely as soon as CPB was resumed. Although the oxygen provided by perfusion was not sufficient to maintain cerebral function, it should help protect the brain during circulatory arrest.

Animals↗
PubMed1993

Validation of measurement of regional myocardial perfusion in humans by ultrafast x-ray computed tomography.

The objective was to validate the measurement of myocardial perfusion in humans by ultrafast computed tomography (CT), by comparing measurements with those from single photon emission computed tomography (SPECT). Measurement of myocardial perfusion with high spatial resolution (including the differentiation of subendocardial and subepicardial perfusion) may be possible by ultrafast CT in humans. Although there are encouraging data from experiments with dogs, the technique has not been validated in humans. In 11 patients, ultrafast CT measurement of regional perfusion in a single short-axis slice was compared with that obtained by SPECT, and in 14, reproducibility of ultrafast CT was evaluated. The ultrafast CT scanner was set to acquire 20 images, gated to end-diastole. The images were divided into 32 equal segments, and the time course and extent of opacification of the left ventricular cavity and myocardium were analyzed to calculate absolute perfusion. The thallium tomograms were also divided into 32 segments for comparison. The pattern of relative perfusion by segment was represented as a curve. In 18 of 22 paired scans, the mean difference of the position of the minimum and maximum points of the curves was less than 4, indicating close agreement between the two techniques. When scoring segmental perfusion as normal or abnormal, there was agreement between the methods in 129 of 176 segments ([symbol: see text] 0.41). Reproducibility (mean difference +/- 1 SD) of basal scans was 0.005 +/- 0.2 mL/min/mL, and during adenosine vasodilation was 0.05 +/- 0.32 mL/min/mL. Absolute perfusion (mean +/- 1 SD) at rest was 0.52 +/- 0.21 mL/min/mL. During adenosine infusion, perfusion increased to a mean of 0.84 +/- 0.42 mL/min/mL. Ultrafast CT and intravenous contrast can be used to assess relative myocardial perfusion in humans, at rest and during adenosine vasodilatation, although it may underestimate absolute perfusion, particularly at high flow.

Adenosine↗
PubMed1995

[Efficacy of simultaneous function and perfusion imaging on 99mTc-tetrofosmin myocardial scintigraphy].

The aim of this study was to determine whether the diagnosis for coronary artery disease (CAD) with 99mTc-tetrofosmin (Tf) myocardial scintigraphy was improved by the combination of function image and perfusion image as compared with perfusion alone. Tf myocardial scintigraphy was performed with one-day protocol (stress/rest) in 51 patients (CAD: 32, Non-CAD: 19) without previous myocardial infarction. Function image was obtained by first pass method, and perfusion image by SPECT. Number of diseased vessels was 14 in right coronary artery (RCA), 18 in left anterior descending (LAD), and 12 in left circumflex (LCX). Ischemia was diagnosed by 2 different parameters 1) perfusion image alone, 2) combination of perfusion image and regional ejection fraction (rEF). On perfusion image, accuracy was 53%, 94% and 86% in RCA, LAD, and LCX respectively. On perfusion + rEF, accuracy was 76%, 90% and 84% in RCA, LAD, and LCX respectively. Specificity in RCA was 45% on perfusion, 84% on perfusion + rEF. Sensitivity in RCA was 77% on perfusion, 54% on perfusion + rEF. LAD and LCX did not change by the addition of function image. By addition of function image, accuracy and specificity of diagnosis in area of RCA improved significantly (p < 0.01). Thus the addition of function image in Tf myocardial scintigraphy would be useful to improve the diagnosis, especially in region of RCA.

Aged↗
PubMed1997

[Quantitative evaluation of pulmonary perfusion volume using 99mTc-MAA SPECT: a comparison of COPD patients and healthy volunteers].

99mTc-MAA pulmonary perfusion single-photon emission computed tomography was performed on 18 patients with chronic obstructive pulmonary disease (COPD) and 41 healthy male volunteers. We quantified the extent of pulmonary perfusion with the Application Visualization System. We measured the pulmonary perfusion volume (PV) at 8 threshold levels encompassing 10 percentage points each from 21-100%. We also calculated the ratio of perfusion volume to total perfusion volume (TPV) at each threshold. Pulmonary perfusion volume in healthy volunteers remained relatively constant at levels of 31-70% and decreased gradually at levels of 71-100%. There was no significant difference in perfusion volume between smokers and non-smokers. Perfusion volume in COPD patients gradually decreased at levels of 31-60% and markedly decreased at levels greater than 60%. Perfusion volume differed significantly between COPD patients and healthy volunteers at levels of 41-100%. The mean PV/TPV value of COPD patients was significantly higher than that of healthy volunteers at levels of 21-40% and significantly lower than that of healthy volunteers at levels of more than 50%. This finding demonstrates that lung volume at high levels of pulmonary perfusion is decreased in COPD patients. The pulmonary perfusion volume at levels of more than 60% is an efficient means of distinguishing COPD patients from healthy subjects.

Adult↗
PubMed2005

The effect of inadequate in situ perfusion in the non heart-beating donor.

In situ aortic perfusion in the nonheart-beating donors (NHBD) is an important procedure to reduce primary warm ischaemic injury prior to formal donor organ retrieval. It allows an interim period to obtain donor family consent and theatre preparation. This study describes our experience of inadequate aortic perfusions resulting from difficult aortic cannulations and associated adverse outcome despite reasonable viability tests. Since 1998, all NHBD in our institution are perfused in situ using a double balloon triple lumen (DBTL) catheter inserted through a femoral artery cut-down procedure. The DBTL catheter is positioned with distal occlusive balloon at the aortic bifurcation using the "pull-back" technique, the proximal occlusive balloon lies above the renal arteries. This provides selective aortic perfusion in particular the kidneys. Venous decompression using a femoral vein catheter enables a "two-way infusion system". Pre-transplant viability status of retrieved kidneys is determined by measuring pressure/resistance characteristics to the flow and biochemical markers for ischaemic injury. There were 90 NHBD renal transplants performed from 72 donors. Three renal transplants were carried out from three donors of ineffective in situ perfusion secondary to cannulation difficulties. Femoral cannulation was difficult as a result of extensive atherosclerosis of donor vessels. The comparison of allograft outcome from effective and ineffective in situ perfusion of donors showed high rate of primary nonfunction (PNF) from ineffective perfusion (chi-squared, P < 0.0001). The cases demonstrated poor outcome from ineffective perfusion related to the cannulation difficulties. Therefore a strict policy should be taken in cases where aortic cannulation and perfusion is inadequate, despite pretransplant assessment. In these circumstances, the primary warm ischaemia time should be extended to include this period of ineffective perfusion.

Adult↗