PubMed Health⌕ Search

Biomedical subjects

R T Groothedde

Publications and source records attributed to R T Groothedde.

6 recordsLinked to original sources
PubMed1990

The differential ratio. A method for describing blood flow in renal transplants.

The blood flow in renal transplants can be represented by (1) a K/A ratio, the ratio of the slopes of the ascending part of the renal perfusion curve and the arterial curve, (2) a perfusion index, the ratio of a part of the area under the first-pass arterial curve and renal curve, and (3) a height ratio, the ratio of the height of the renal curve and the arterial curve at the point of time upon which the arterial curve shows its very first maximum. Because it is sometimes rather difficult to find suitable parameters for these three methods, a differential ratio is proposed, the ratio of the maxima of the 1st derivative of the first-pass renal and arterial curve. Good correlation is found between the K/A ratio and the differential ratio as well as between the perfusion index and the height ratio. This implies that the differential ratio could be used instead of the K/A ratio and that the height ratio is a very good alternative for the perfusion index.

Humans↗
PubMed1985

The individual kidney function. A comparison between frame summation and deconvolution.

A variety of methods have been developed to estimate the individual kidney function. Many methods use a scintillation camera the data from which are processed in a computer system. To compare two of these methods, the principles of which are completely different, such as the 'Oberhausen' method of frame summation and background subtraction and a method that uses deconvolution, the scintillation camera data of 121 patients have been collected. A computer program was written to calculate the individual kidney function by which both methods were used. It is often asserted that specific techniques of frame summation and background subtraction are not suitable to define the individual kidney function. To see if this assertion is true, two different methods have been compared using the contribution of the left kidney to the individual kidney function. An excellent correlation between the two methods was found (R = 0.9808, n = 121) which proves the ability of both the 'Oberhausen' method and the method that uses deconvolution. However, it is also seen that the 'Oberhausen' method may give false results, caused by an increasing background count outside the kidneys in patients with a large difference in function between the two kidneys.

Humans↗
PubMed1975

CaSO4 (Dy) thermoluminescent dosimeters for the determination of gonadal doses.

For the measurement of gonadal doses sensitive dosimeters are necessary. Since CaSO4 (Dy) thermoluminescent dosimeters are very sensitive the energy dependence has been measured as compared to LiF in the tube potential region between 50 and 150 kV. Moreover the output of the LiF dosimeters was compared with the results of ionization chamber measurements. Although the energy dependence of CaSO4 (Dy) is well-known the actual dependence on the potential appears to be within +/- 10% for moderately filtered beams in the region from 50 to 150 kV.

Calcium↗