The Dose Distribution Research In Leukemia Alternate Half Body Irradiation

[Objective]Alternate Half Body Irradiation (AHBI) is a new effective treatment method forleukemia and malignant lymphoma. Hematopoietic reconstruction could beperformed without marrow transplantation with AHBI. To prepare for clinical AHBI,we measured the dose distribution in vivo with standard phantom.According to the data, we want to further define the dose distribution of eachorgan with AHBI, choose the suitable dividing line of the upper and lower beam field,seek a feasible and reliable measurement technique for clinical application of AHBIin order to provide better service for clinical application.[Method]Under clinical AHBI conditions, the half body irradiation field is constructedwith water phantom, anthropomorphic phantom, plexiglass phantom, linearaccelerator. The dose distribution of anthropomorphic phantom is measured with TLDand the dose distribution of plexiglass phantom is measured with ionization chamber.We analyzed the correlation of TLD and chamber statistically so as to seek a feasibleand reliable measurement technique for clinical application. We consider theumbilicus as the dividing plane of upper and lower beam field and design fourdividing methods for juncture of upper and lower beam field. We measure the dosedistribution of phantom in vivo and body surface. Then four methods are comparedand the best one is defined according to the dose distribution of juncture with eachmethod. Several patients are treated according to the experiment results in order toconfirm the practical curative effect.[Results]1. In half body irradiation, the homogeneity of dose distribution in phantom waswithin±5%. 2. The dose of important organs such as cerebrum, cerebellum and lung and so on areobtained and each organ dose satisfies clinical requirement.3. The dose distribution in body surface measured by four dividing methods aredifferent statistically (p＜0.05), the dose distributes in vivo measured by the connectedmethod has better homogeneity and can avoid overdosage or less dosage of theoverlap, so it is a better dividing methods for juncture of upper and lower beam field.4. The dose distribution of central axis measured by TLD and chamber has noobvious difference; organ position value measured by TLD and chamber has adeviation less than 5% except head, so chamber is feasible in clinical application.5. Eight patients with acute leukemia were treated with AHBI, side effects includednausea, emesis, fever that was observed in some patients but hematopoieticreconstruction was observed in all of the patients. Long-term curative effect need tosurvey.