PubMed Health⌕ Search

Biomedical subjects

D S Herron

Publications and source records attributed to D S Herron.

4 recordsLinked to original sources
PubMed1984

Lung corrections in photon beam treatment planning: are we ready?

This paper reviews reasons cited for and against the use of lung corrections. It is suggested that all the reasons cited for not making corrections are no longer viable. A phantom has been designed to simulate the thorax region of a patient at both CT and radiotherapy radiation energies. With this phantom, lung correction factors for the calculation of tumor dose have been measured for a typical lung cancer treatment regimen, and these results are shown to compare favorably with correction factors computed by all the commonly employed correction algorithms. Some algorithms are better than others, and one of the best is the readily hand-calculable generalized power-law TAR method. It is shown that failure to correct for lung transmission can severely limit the integrity of many interinstitutional studies, especially cooperative clinical trials. It is concluded that lung corrections for the calculation of tumor doses in the thorax region should be gradually introduced over the next several years.

Humans↗
PubMed1984

Estimation of ultrasonic attenuation and mean backscatterer size via digital signal processing.

The backscattered rf signals from the lungs of fetal sheep during their last trimester of development were digitized and processed in an attempt to correlate ultrasonic parameters with measured functional parameters related to lung maturation. The broadband, post- TGC , rf signal of a commercial B-mode ultrasonic scanner was digitized at a sampling rate of 25 MHz. Sorting excluded data from regions of rib shadowing and other nonlung structures from analysis. The sorted data were used to estimate the slope of the ultrasonic attenuation coefficient with respect to frequency via linear regression on the average difference of the logarithm of power spectra from separated data segments. The power spectra were also corrected for attenuation, averaged and used to compute the power cepstrum of the backscattered signal which can be related to mean backscatterer radius. Results are presented for eight fetal sheep.

Animals↗
PubMedDate not supplied

Sonographic identification of lung maturation in the fetal lamb.

Ultrasound evaluation of fetal lung development in utero could be a noninvasive method for frequent monitoring of the state of pulmonary maturity and predicting when parturition could occur with minimum or no risk of respiratory distress syndrome of the newborn. In cases of high-risk obstetric management in premature labor, this ability may be a particularly useful tool. To pursue this possibility, the lungs and livers of 13 living fetal lambs were successfully imaged with a modified clinical B-scanner under carefully controlled conditions; physiologic function tests on the excised lungs determined the state of pulmonary maturity. In eight cases, maturity or immaturity was correctly identified by sonographic criteria. The results wer ambiguous in four cases. One case of immature lung was incorrectly identified as mature. The trends established in these animal studies appear promising and with refinement may form the basis for sonographic assessment of fetal lung maturity in a clinical setting.

Animals↗