Cerebral blood flow and the thermal properties of the brain: a preliminary analysis

1989 ◽  
Vol 70 (4) ◽  
pp. 592-598 ◽  
Author(s):  
Michael Salcman ◽  
Eiji Moriyama ◽  
Henry J. Elsner ◽  
Herman Rossman ◽  
Robert A. Gettleman ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Thermal Properties ◽  
Specific Heat ◽  
Correlation Coefficient ◽  
Microwave Antenna ◽  
Microwave Antennas ◽  
Hydrogen Clearance Method ◽  
The Brain ◽  
Hydrogen Clearance

✓ Safe and effective use of hyperthermia for the treatment of brain tumors requires precise control of the distribution of temperatures (that is, the thermal field) within the tumor and within the adjacent brain. Major influences upon the distribution of temperatures include the passive thermal properties of the brain, such as its specific heat (Cb), and the contribution of cerebral blood flow (CBF). Recently, an electrical-mechanical analog model of heat flow within the brain has been developed from which an expression for CBF has been derived: CBF = Cb/(τρc) where τ is the thermal decay constant, ρ is the density of blood, and c is its specific heat. To test this model a series of experiments was carried out in adult dogs in which stereotaxically implanted microwave antennas operating at 2450 MHz, fluoro-optical thermometry probes, and platinum electrodes were used to simultaneously measure CBF by thermal washout and hydrogen clearance techniques. The correlation coefficient for estimates of CBF derived by the two methods in 52 paired observations was 0.89. Measurements of CBF were more reliable at increased distances from the microwave antenna, since CBF is sensitive to the degree of temperature elevation (ΔT). The ratio of post-heating CBF to pre-heating CBF varies linearly with ΔT and has a correlation coefficient of 0.86. When values of CBF determined by the hydrogen clearance method were employed in the above equation, it was possible to derive Cb as 0.70 ± 0.08 cal/gm-°C. Use of this value for Cb in this equation produces estimates of CBF by thermal clearance that are within 10% of the values for CBF as measured by the hydrogen clearance method. It is concluded that this model of thermal flow within the brain may have heuristic value for treatment planning and that microwave antennas and fluoro-optical probes may represent a new methodology for the clinical estimation of CBF. These methods have recently been employed in patients undergoing combined hyperthermia and chemotherapy.

scholarly journals The Effect of Local Infusion of Adenosine and Adenosine Analogues on Local Cerebral Blood Flow

1989 ◽  
Vol 9 (4) ◽  
pp. 556-562 ◽  
Author(s):  
David G. L. Van Wylen ◽  
T. S. Park ◽  
Rafael Rubio ◽  
Robert M. Berne
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Receptor Activation ◽  
Local Cerebral Blood Flow ◽  
Caudate Nuclei ◽  
Adenosine Concentration ◽  
The Brain ◽  
Adenosine Receptor Activation ◽  
Dialysis Technique ◽  
Hydrogen Clearance

The purpose of this study was to determine the effects of local infusion of adenosine (ADO) and non-metabolized ADO analogues on local cerebral blood flow (CBF) and interstitial fluid (ISF) ADO levels. The brain dialysis technique was used to (a) deliver drugs locally to brain tissue, (b) estimate cerebral ISF ADO levels, and (c) measure local CBF (hydrogen clearance). Dialysis probes were implanted bilaterally in the caudate nuclei of ketamine-anesthetized rats. The probe on one side was perfused with artificial CSF while the contralateral probe was perfused with artificial CSF containing ADO ( n = 5), or the ADO agonists 2-chloroadenosine (2-CADO; n = 4) or 5'-N-ethylcarboxamide adenosine (NECA; n = 4). When ADO was included in the artificial CSF at 10−5, 10−4, or 10−3 M, a 30% increase in local CBF was detected only with 10−3 M ADO. During perfusion with ADO, dialysate inosine and hypoxanthine levels increased, indicating that the cells adjacent to the probe metabolized the exogenous ADO. With 2-CADO included in the artificial CSF at 10−6, 10−5, or 10−4 M, local CBF increased 18, 131, and 201%, respectively. Perfusion with artificial CSF containing 10−7, 10−6, or 10−5 M NECA resulted in a 35, 112, and 187% increase in local CBF, respectively. In a separate group of rats ( n = 6), perfusion with artificial CSF containing 10−6 M NECA resulted in a sustained twofold increase in local CBF and 40% decrease in dialysate adenosine concentration, both of which could be reversed by including 8-( p-sulfophenyl)-theophylline, an ADO receptor antagonist, in the artificial CSF. These results are consistent with the known vascular actions of ADO and ADO analogues and suggest that there is a basal level of ISF ADO that can be reduced by increased CBF and/or adenosine receptor activation.

Changes of blood flow in the adenohypophysis of normal and estrogen pretreated Fisher rats by tamoxifen

1989 ◽  
Vol 121 (6) ◽  
pp. 821-826 ◽  
Author(s):  
Andrzej Stawowy ◽  
Andras A. Kemeny ◽  
Jan Jakubowski
Keyword(s):  
Blood Flow ◽  
Cerebral Cortex ◽  
Cerebral Blood Flow ◽  
Arterial Pressure ◽  
Anterior Pituitary ◽  
Tamoxifen Treatment ◽  
Hydrogen Clearance Method ◽  
Pituitary Hyperplasia ◽  
F344 Rats ◽  
Hydrogen Clearance

Abstract. Blood flow was measured in the adenohypophysis and in the cerebral cortex of female F344 rats over a period of 90 min using the hydrogen clearance method. Tamoxifen, 1 mg/kg, administered iv reduced the blood flow in the adenohypophysis by 35%, whereas cerebral blood flow and arterial pressure remained unchanged. Seven days sc treatment with tamoxifen (1 mg/kg daily) had no demonstrable effect on blood flow. Anterior pituitary hyperplasia was induced in 15 rats with diethylstilbestrol containing implants. These rats responded to 7 days of sc tamoxifen treatment by 30% increase in adenohypophyseal blood flow. These results suggest that tamoxifen has a different effect on adenohypophysial circulation of the rat depending on whether it is administered in a low- or high-estrogen state.

Blood flow and oxygen consumption of the focally traumatized monkey brain

1977 ◽  
Vol 47 (3) ◽  
pp. 346-352 ◽  
Author(s):  
Albert N. Martins ◽  
Thomas F. Doyle
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Oxygen Consumption ◽  
Content Type ◽  
Superior Frontal Gyrus ◽  
Injured Brain ◽  
Post Traumatic ◽  
The Right ◽  
The Brain ◽  
Hydrogen Clearance

✓ The exposed left superior frontal gyrus of the anesthetized macaque brain was focally traumatized by a jet of compressed air. Focal blood flow in tissue around the lesion and total cerebral blood flow was determined before and during the 4 hours after trauma by the hydrogen clearance technique. Blood flow fell in tissue adjacent to the injured brain but the reduction was not statistically significant. Total cerebral blood flow, blood flow in the right superior-frontal gyrus, and oxygen consumption of the brain was unaffected by the trauma. The authors conclude that neither spreading ischemia within uninjured tissue surrounding focally traumatized brain nor post-traumatic diaschisis is readily provoked in the anesthetized brain of the monkey.

Vorläufige Ergebnisse von 99mTc-HMPAO-SPECT-Untersuchungen bei endogenen Psychosen

1989 ◽  
Vol 28 (03) ◽  
pp. 88-91
Author(s):  
J. Schröder ◽  
H. Henningsen ◽  
H. Sauer ◽  
P. Georgi ◽  
K.-R. Wilhelm
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Regional Cerebral Blood Flow ◽  
Regions Of Interest ◽  
Post Mortem ◽  
Regional Cerebral Blood ◽  
Hmpao Spect ◽  
Endogenous Psychoses ◽  
The Brain ◽  
99Mtc Hmpao

18 psychopharmacologically treated patients (7 schizophrenics, 5 schizoaffectives, 6 depressives) were studied using 99mTc-HMPAO-SPECT of the brain. The regional cerebral blood flow was measured in three transversal sections (infra-/supraventricular, ventricular) within 6 regions of interest (ROI) respectively (one frontal, one parietal and one occipital in each hemisphere). Corresponding ROIs of the same section in each hemisphere were compared. In the schizophrenics there was a significantly reduced perfusion in the left frontal region of the infraventricular and ventricular section (p < 0.02) compared with the data of the depressives. The schizoaffectives took an intermediate place. Since the patients were treated with psychopharmaca, the result must be interpreted cautiously. However, our findings seem to be in accordance with post-mortem-, CT- and PET-studies presented in the literature. Our results suggest that 99mTc-HMPAO-SPECT may be helpful in finding cerebral abnormalities in endogenous psychoses.

133Xe-DSPECT: Normalwerte von zerebraler Ruhedurchblutung und Reservekapazität

1987 ◽  
Vol 26 (05) ◽  
pp. 192-197 ◽  
Author(s):  
T. Kreisig ◽  
P. Schmiedek ◽  
G. Leinsinger ◽  
K. Einhäupl ◽  
E. Moser
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Cerebrovascular Disease ◽  
Correlation Coefficient ◽  
Regional Cerebral Blood Flow ◽  
Regression Line ◽  
Reserve Capacity ◽  
Regional Cerebral Blood ◽  
Quantitative Measurements ◽  
Before And After

Using the 133Xe-DSPECT technique, quantitative measurements of regional cerebral blood flow (rCBF) were performed before and after provocation with acetazolamide (Diamox) i. v. in 32 patients without evidence of brain disease (normals). In 6 cases, additional studies were carried out to establish the time of maximal rCBF increase which was found to be approximately 15 min p. i. 1 g of Diamox increases the rCBF from 58 ±8 at rest to 73±5 ml/100 g/min. A Diamox dose of 2 g (9 cases) causes no further rCBF increase. After plotting the rCBF before provocation (rCBFR) and the Diamox-induced rCBF increase (reserve capacity, Δ rCBF) the regression line was Δ rCBF = −0,6 x rCBFR +50 (correlation coefficient: r = −0,77). In normals with relatively low rCBF values at rest, Diamox increases the reserve capacity much more than in normals with high rCBF values before provocation. It can be expected that this concept of measuring rCBF at rest and the reserve capacity will increase the sensitivity of distinguishing patients with reversible cerebrovascular disease (even bilateral) from normals.

Neuroimaging in Drug Discovery and Development: Paradigms for Accelerating New Drug Availability

2001 ◽  
Vol 14 (5) ◽  
pp. 407-415
Author(s):  
John T. Metz ◽  
Malcolm D. Cooper ◽  
Terry F. Brown ◽  
Leann H. Kinnunen ◽  
Declan J. Cooper
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Glucose Metabolism ◽  
Phase Ii ◽  
New Drugs ◽  
Central Effects ◽  
Drug Discovery And Development ◽  
Psychological Tasks ◽  
The Brain ◽  
Phase Iv

The process of discovering and developing new drugs is complicated. Neuroimaging methods can facilitate this process. An analysis of the conceptual bases and practical limitations of different neuroimaging modalities reveals that each technique can best address different kinds of questions. Radioligand studies are well suited to preclinical and Phase II questions when a compound is known or suspected to affect well-understood mechanisms; they are also useful in Phase IV to characterize effective agents. Cerebral blood flow studies can be extremely useful in evaluating the effects of a drug on psychological tasks (mostly in Phase IV). Glucose metabolism studies can answer the simplest questions about whether a compound affects the brain, where, and how much. Such studies are most useful in confirming central effects (preclinical and early clinical phases), in determining effective dose ranges (Phase II), and in comparing different drugs (Phase IV).

Measurement of local blood flow of the intestine by hydrogen clearance method; Experimental study

1979 ◽  
Vol 9 (1) ◽  
pp. 63-70 ◽  
Author(s):  
Yoshio Mishima ◽  
Hiroshi Shigematsu ◽  
Yoshiaki Horie ◽  
Masanori Satoh
Keyword(s):  
Experimental Study ◽  
Blood Flow ◽  
Local Blood Flow ◽  
Hydrogen Clearance Method ◽  
Hydrogen Clearance
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