Biomedical subjects

R R Brechner

Publications and source records attributed to R R Brechner.

3 recordsLinked to original sources

PubMed1994

Association of intratumoral pharmacokinetics of fluorouracil with clinical response.

In-vivo fluorine-19 nuclear magnetic resonance spectroscopy (NMRS) allows non-invasive, real-time, chemical identification of specific fluorinated compounds inside human tumours after administration of fluorouracil (5-fluorouracil). Kinetic measures of the administered drug and metabolites allow estimation of the tumoral half-life of fluorouracil. We studied 57 patients by 19F NMRS immediately after they had received 600 mg/m2 fluorouracil intravenously. Serial spectra were acquired with the surface coil positioned on the skin above the tumour. We defined an intratumoral half-life of fluorouracil of 20 min or more as indicating trapping of the drug, based on the blood half-life of 8-12 min. 19 patients had intratumoral half-lives indicating trapping of fluorouracil, 27 had half-lives less than 20 min, and 11 had no detectable fluorouracil in their tumours. 8 of 9 evaluable patients whose tumours showed trapping had partial responses to chemotherapy that included fluorouracil compared with only 2 of 25 patients whose tumours did not trap the drug (p = 0.000021). 19F NMRS can identify patients likely to respond to chemotherapy with fluorouracil and could be used clinically to tailor optimum treatment.

Fluorouracil↗

PubMed1990

Experimental test-object study of electronically collimated SPECT.

The imaging performance of a prototype electronically collimated single-photon emission computed tomography (SPECT) camera comprising a unique 4 x 4 germanium detector backed by an uncollimated scintillation camera has been evaluated. Three-dimensional images of cylindrical test-objects containing either 99mTc (140 keV) or 137Cs (662 keV) are reported. Electronically collimated counts were acquired from the objects rotated to 20 or 40 angular positions in front of the germanium detector to simulate a cylindrical scanning system. For comparison, mechanically collimated data were also acquired from the test-objects. The SPECT images show a slightly better resolution for mechanical over electronical collimation (1.3 +/- 0.25 cm mechanical, 1.5 +/- 0.25 cm electronical at 140 keV; 1.5 +/- 0.25 cm mechanical, 1.7 +/- 0.25 cm electronical at 662 keV). The equi-resolution sensitivity, however, was deduced to be approximately an order of magnitude higher with electronic collimation to image a head-sized object using 99mTc. In addition, the sensitivity gain increases with increasing energy, suggesting the unique potential of electronic collimation in high-energy SPECT.

Electronics↗

PubMed1986

Noninvasive estimation of bound and mobile platinum compounds in the kidney using a radiopharmacokinetic model.

Nephrotoxicity remains a major limitation in the use of cisplatin [cis-diamminedichloroplatinum(II)]. Although several strategies are in use to limit this serious side effect, none is fully satisfactory. Classical pharmacokinetic studies of cisplatin have been based on blood and urine samples. As nephrotoxicity plays a significant role in the design of the therapeutic strategy, the kidneys should be considered as a separate state in any model formulated for ultimate control purposes. Previous studies of organ pharmacokinetics have relied on population measurements. The authors have developed an organ compartmental model from individual animal data obtained noninvasively. The eight-compartment model used to represent the distribution of cisplatin considers free and bound platinum in plasma, platinum in the erythrocytes, mobile and bound platinum in the kidneys, mobile and bound platinum in the tissues, and platinum in the urine. Data were collected from experiments with anesthetized female rats, after intravenous administration of [195mPt]cisplatin. Both arterial and bladder samples, and multiple images obtained with an Anger camera interfaced to a microcomputer were used. The model was estimated from individual data obtained after injection of a bolus of cisplatin (six animals). The model was validated by using it to predict data obtained from forcing the system with a different input function, a 0.5-h intravenous infusion (three animals). The results of this work show that it is possible to noninvasively study drug kinetics in organs that are not readily accessible to direct measurements in an individual, rather than relying on invasive measurements performed on a population.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗