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Biomedical subjects

P Shapiro

Publications and source records attributed to P Shapiro.

54 records · Page 3Linked to original sources
PubMed1977

Multiple hepatic tumors and peliosis hepatis in Fanconi's anemia treated with androgens.

We report the case of a 13-year-old boy who was known to have Fanconi's anemia for five years. For treatment of this condition he was given androgens and corticosteroids. Two months before his death, severe varicella developed complicated by pneumonia, jaundice, and prolonged fever; all of which resolved during a five-week hospitalization. Three weeks later he died of Clostridium septicum sepsis caused by necrotizing enterocolitis. At autopsy he was found to have multiple hepatocellular neoplasms. A striking feature of the neoplasms was cholestasis. The liver also showed peliosis hepatis. The association of the use of certain androgenic steroids with hepatic neoplasms histologically resembling hepatocarcinomas, but characterized by lack of metastases and apparent reversibility, suggests the desirability of a new nomenclature for these hepatocellular lesions.

Adolescent↗
PubMed1976

Stripping-theory analysis of thick-target neutron production for D + Be.

The Serber theory for deuteron stripping is employed to predict the shape of the neutron energy spectrum produced by 35 MeV deuterons (D+) on a thick beryllium target. In particular, the observation that the maximum of the neutron energy spectrum (at 0degrees relative to the deuteron beam direction) occurs at approximately 0-4Ed, where Ed is the incident deuteron energy, is explained reasonably well by the calculations. The explanation stems mainly from the fact that the stripping theory for thin targets predicts a narrow maximum at 0-5Ed, and thick target effects shift the maximum downward in energy to approximately 0-4Ed. A number of recent spectral measurements are in agreement with these predictions for a wide range of target materials and incident deuteron energies. The application of this theory also accounts for the previously observed Dd2-99 dependence of the absorbed dose in tissue,per unit charge of D+ ions on target, in the direction of the incident beam. This approximate Ed3 dependence is shown to be a characteristic property of deuteron stripping in a thick target and follows directly from the calculations that predict the neutron energy spectrum.

Beryllium↗
PubMedDate not supplied

Aortic anatomy in children with myelomeningocele and congenital lumbar kyphosis.

Preoperative aortograms were reviewed in six children with thoracic myelomeningocele and lumbar kyphosis at an average age of 25 months. In all children, the abdominal aorta bridged the lumbar kyphosis. In four children, the upper renal poles were close to the spine and were at potential risk during kyphectomy. All children had aortic shortening with an increased variability in origin of the major abdominal aortic branches. Abnormal lumbar arteries were noted in four children.

Aorta↗
PubMedDate not supplied

Displacement correction factor for fast-neutron dosimetry in a tissue-equivalent phantom.

The displacement correction factor to be used for analysis of fast-neutron dosimetric measurements using air-filled EG and G tissue-equivalent ion chambers in a tissue-equivalent phantom has been investigated using the MANTA neutron radiotherapy beam generated by 35-MeV deuterons on a thick Be target. The displacement correction factor inferred from these measurements is 0.970 for the EG and G IC-17 (1.0-cm3) ion chamber, and is 0.989 for the EG and G IC-18 (0.1-cm3 ion chamber. This multiplicative displacement correction factor has no significant dependence on depth in the phantom or on neutron beam size.

Fast Neutrons↗
PubMedDate not supplied

Scattered radiation from a neutron collimator.

Fast-neutron beams are being employed in radiotherapy trials and associated radiobiology studies at numerous centers in the U.S., Europe, and Japan. Since collimated beams of various sizes and shapes are employed, it is desirable to know the composition of the scattered radiation component contributed by the collimator. A simple method is shown for deducing the field composition in terms of a three-component model, from measurements made with three ionization chambers (tissue-equivalent, graphite, and magnesium). The dose contributed by the scattered radiation in the present example was found to be predominantly due to fast neutrons indistinguishable from those in the primary spectrum (from 35-MeV D+ on Be). This method may prove useful for measurements in phantoms as well.

Fast Neutrons↗
PubMedDate not supplied

Computer generation of dose distributions for a fast-neutron therapy beam.

A system has been developed for the computer generation of dose distributions for the MANTA-NRL fast-neutron radiotherapy beam. This program is based on scatter-air ratio (SAR) techniques. A method has been developed to unfold the effect of the neutron-beam profile in the derivation of SARs so that the SARs obtained are those which would be derived if the beam profile were flat. Tables of zero-area tissue-air ratios and SARs are presented. Comparisons of calculated and measured dose distributions are shown. An empirical correction to the usual SAR methods was required to obtain agreement between calculated and measured dose distributions at source-to-skin distances (SSD) which are different from the SSD at which the SAR are derived.

Computers↗
PubMedDate not supplied

Calorimetric and ionimetric dosimetry intercomparisons I: U.S. neutron radiotherapy centers.

In the U.S. neutron radiotherapy trial centers, absorbed dose is routinely measured using commercially available A-150 tissue equivalent (TE) plastic ionization chambers. The collecting volumes of these chambers are filled with either methane-based tissue equivalent gas or air. Absorbed dose in A-150 plastic, determined with these ionization chambers, was compared to that measured by an A-150 plastic calorimeter in an A-150 plastic phantom. These comparisons have yielded the following information: (1) Agreement of the total absorbed dose measured using the ionization chambers was within 2.5% of the calorimeter at all the centers visited to date. (2) For all the neutron fields measured, the product of the stopping power ratio (sw,g)N' between the A-150 plastic chamber wall and TE gas, and the average energy expended in the gas per ion pair formed, WN/e, was computed assuming Bragg-Gray theory and found to be 31.0 +/- 0.7 J/C. (3) The displacement correction factor employed to normalize measurements at a depth in a phantom using the type IC-17 ionization chamber was verified to be approximately 0.97 +/- 0.01.

Calorimetry↗