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J C Heggie

Publications and source records attributed to J C Heggie.

22 records · Page 2Linked to original sources
PubMed1983

Internal radiotherapy for hepatic metastases I: The homogeneity of hepatic arterial blood flow.

Internal radiotherapy, in the form of arterially infused yttrium-90-labeled microspheres, theoretically appears encouraging as a method of treatment for hepatic metastases. Previous investigators have assumed a homogeneous distribution of these microspheres and given dosages of isotope based solely on an estimated liver mass. The purpose of this study has been to establish the homogeneity of isotope distribution in liver substance when 15 micrometers microspheres are arterially injected. This has been done in three mammalian species, with the results expressed as a mean percentage coefficient of variation of 28 +/- 5%. Also demonstrated is the fact that 15 micrometers particles, while not penetrating to the venous circulation, achieve a more homogeneous spread throughout the liver than larger particles. It has been demonstrated that to achieve this maximum homogeneity distribution, 4000 beads/g of liver tissue are required. This equates in the therapeutic situation to a maximum activity of 4 Ci/g of infused microspheres. These results are considered significant in that they indicate criteria necessary to achieve the maximum homogeneity of therapeutic agent within liver substance when it is administered by this method, and will allow confidence limits to be attached to direct in vivo measurement of hepatic irradiation.

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PubMed1983

Internal radiotherapy for hepatic metastases II: The blood supply to hepatic metastases.

Given that metastatic hepatic malignancy remains as a significant cause of death, with a median survival after diagnosis of only 7 months despite treatment, there exists a need for some effective treatment modality. Internal radiotherapy in the form of yttrium-90 microspheres infused into the hepatic artery appears to be a promising method of therapy. One criterion required for the success of this treatment is that of a differentially greater arterial supply to tumor as opposed to liver tissue. This arterial hypervascularity of tumor has been demonstrated before. However, some conflict has been reported as to the maintenance of this state as tumor size increases. Using 15 micrometers Cobalt-57 microspheres for studying salivary adenocarcinoma implants in DA rat livers, these experiments have demonstrated a constant blood flow in the tumor periphery of 3.9 times that within the normal hepatic parenchyma, regardless of tumor size. Also demonstrated is a progressive decrease in central tumor arterial blood flow after a tumor diameter of 6 mm has been exceeded. Arterial hypervascularity of liver tissue adjacent to the tumor has been demonstrated while an intermediate zone of liver tissue appeared hypovascular, suggesting the presence of shunting. In three humans with metastatic liver disease, hepatic artery infusion of particulate radiotracer has demonstrated the peripheral tumor hypervascularity and relative central tumor hypovascularity with good correlation obtained with the images of the metastases on conventional colloidal hepatic scintigraphy. This method allows assessment of the patient's suitability for internal radiotherapy by enabling assessment of the tumor vascularity and the degree of potentially dangerous extrahepatic irradiation.

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