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P F Klemp

Publications and source records attributed to P F Klemp.

11 recordsLinked to original sources
PubMed1991

Dose distribution following selective internal radiation therapy.

Selective Internal Radiation Therapy is the intrahepatic arterial injection of microspheres labelled with 90Y. The microspheres lodge in the precapillary circulation of tumor resulting in internal radiation therapy. The activity of the 90Y injected is managed by successive administrations of labelled microspheres and after each injection probing the liver with a calibrated beta probe to assess the dose to the superficial layers of normal tissue. Predicted doses of 75 Gy have been delivered without subsequent evidence of radiation damage to normal cells. This contrasts with the complications resulting from doses in excess of 30 Gy delivered from external beam radiotherapy. Detailed analysis of microsphere distribution in a cubic centimeter of normal liver and the calculation of dose to a 3-dimensional fine grid has shown that the radiation distribution created by the finite size and distribution of the microspheres results in an highly heterogeneous dose pattern. It has been shown that a third of normal liver will receive less than 33.7% of the dose predicted by assuming an homogeneous distribution of 90Y.

Humans↗
PubMed1990

Selective internal radiation therapy: validation of intraoperative dosimetry.

In selective internal radiation (SIR) therapy of hepatic metastases, tumor vasculature is preferentially embolized with high-energy beta-emitting yttrium-90-labeled microspheres. To enable accurate estimation of the resultant absorbed radiation doses to tissues, an intraoperative beta detection probe is used to scan the liver surface. The validity of the response of this probe to Y-90 and its clinical application were assessed with a phantom containing varying activities and with biopsy samples obtained from patients being treated with SIR therapy. A linear relationship was found between the probe counts taken from the biopsy samples and the calculated tissue radiation doses from the specific activities of each sample. This relationship was repeated with probe counts determined against a water phantom containing various activities of Y-90. The probe was shown to respond minimally to bremsstrahlung. The use of the probe in measuring tissue radiation doses at laparotomy provides the opportunity to control dose administration during SIR therapy. In this way, subtherapeutic exposure of normal tissue can be assured while tumor tissue receives maximal radiation levels.

Brachytherapy↗
PubMed1989

Selective internal radiation therapy: distribution of radiation in the liver.

Selective internal radiation therapy for primary and secondary liver cancer involves the intra-hepatic arterial injection of microspheres containing yttrium-90. The microspheres become entrapped primarily in, and thus preferentially irradiate, tumour tissue. During a clinical trial with this therapy it has been possible to take tumour and normal liver tissue samples, after microsphere injection, and measure their specific activity. Absorbed tissue radiation doses were then calculated for tumour and normal tissue samples from a total of nine patients. The mean tumour to normal tissue ratio for radiation dose for the nine patients was approximately 6:1 with a range of 0.4:1-45:1. Injection of similar amounts of activity in different patients resulted in markedly differing tissue doses depending on liver size and tumour burden. Normal liver tissue doses of between 9 and 75 Gy were measured while corresponding tumour tissue doses ranged from 34 to 147 Gy. Selective internal radiation therapy, combined with the blood flow changes resulting from angiotensin II administration, can provide preferentially high radiation doses to tumour tissue within the liver whilst relatively sparing the surrounding normal liver tissue.

Adenocarcinoma↗
PubMed1988

Transpapillary iridium-192 wire in the treatment of malignant bile duct obstruction.

Twenty four patients with malignant bile duct obstruction were treated with intraluminal radiotherapy using iridium-192 wire inserted through an endoscopically placed nasobiliary catheter. Biliary drainage after treatment was maintained by an endoprosthesis. The median dose of intraluminal radiotherapy was 6000 cGy; two patients with cholangiocarcinoma were given a second course because of disease extension; four patients with pancreatic carcinoma received additional external irradiation (3000 cGy). There was one early death from a cerebrovascular accident (30 day mortality, 4.2%). Cholangitis (30%) was the major early complication and stent blockage (40%) the major late complication; there were no complications directly attributable to radiotherapy. The median survival for patients with pancreatic carcinoma was 250 days and for cholangiocarcinoma, 300 days. This method is technically feasible and may prove safer than the transhepatic technique. The ability of intraluminal irradiation to improve palliation or lengthen survival in patients with malignant bile duct obstruction remains uncertain. Assessment by a prospective, controlled trial is essential.

Adenoma, Bile Duct↗