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  • 1
    ISSN: 1619-7089
    Keywords: Partition model ; Yttrium-90 ; Radiation doses ; Hepatic tumours
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A uniform distribution of yttrium-90 (90Y) microspheres throughout the entire liver has always been assumed for dose calculation in treating hepatic tumours. A simple mathematical model was formulated which allows estimation of the activities of a therapeutic dose of90Y microspheres partitioned between the lungs, the tumour and the normal liver, and hence the radiation doses to them. The doses to the tumour and normal liver were verified by intra-operative direct beta-probing. The percentage of activity shunted to the lung and the tumour-to-normal tissue ratio (T/N) were obtained from gamma scintigraphy using technetium-99m-labelled macroaggregated albumin (MAA) which simulates the90Y microspheres used in subsequent treatment. The intrahepatic activity was partitioned between the tumour and the normal liver based on the T/N and their masses determined from computerized tomography slices. The corresponding radiation doses were computed using the MIRD formula. The estimated radiation doses were correlated with the doses directly measured using a calibrated beta-probe at laparotomy by linear regression. The radiation doses to the tumour and the normal liver, estimated using the partition model, were close to that measured directly with coefficients of correlation for linear regression: 0.862 for the tumours and 0.804 for the normal liver compartment (P〈0.001). The partition model permits a distinction between the radiation doses received by the tumour and the normal liver to be made and the doses thus estimated are close to the actual doses received. The optimal doses to the tumour and normal liver and hence the required quantity of90Y microspheres to be administered can be easily predetermined.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1619-7089
    Keywords: Partition model ; Clinical evaluation ; Yttrium-90 microspheres ; Hepatic cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Radiation doses to the tumour and non-tumorous liver compartments from yttrium-90 microspheres in the treatment of hepatic cancer, as estimated by a partition model, have been verified by correlation with the actual doses measured with a beta probe at open surgery. The validity of the doses to the lungs, the tumour and non-tumorous liver compartment as estimated by the partition model was further evaluated in clinical settings. On the basis of the observation that one of three patients who received more than 30 Gy from a single treatment and one of two patients who received more than 50 Gy from multiple treatments developed radiation pneumonitis, it was deduced that an estimated lung dose 〈30 Gy from a single treatment and a cumulative lung dose 〈50 Gy from multiple treatments were probably the tolerance limits of the lungs. Three of five patients who received lung doses 〉30 Gy as estimated by the partition model and were predicted to develop radiation pneumonitis, did so despite the use of partial hepatic embolization to reduce the degree of lung shunting. Furthermore, a higher radiological response rate and prolonged survival were found in the group of patients who received higher tumour doses, as estimated by the partition model, than in the group with lower estimated tumour doses. Thus the radiation doses estimated by the partition model can be used to predict (a) complication rate, (b) response rate and (c) duration of survival in the same manner as the actual radiation doses measured with a beta probe at open surgery. The partition model has made selective internal radiation therapy using90Y microspheres safe and repeatable without laparotomy.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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