SVIBOR - Project code: 3-01-255

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Project code: 3-01-255


A METHOD OF IN-VIVO DOSIMETRY IN TOTAL BODY RADIOTHERAPY


Main researcher: VRTAR, MLADEN (53442)


Assistants
Type of research: applied
Duration from: 01/01/91. to 12/31/93.
Papers on project (total): 20
Papers on project quoted in Current Contents: 4
Institution name: KBC, Znanstvena jedinica za patobiokemijska i klinička istraživanja, Zagreb (167)
Department/Institute: Institute of Oncology and Radiotherapy UHC Rebro Radiotherapy Center Department of Radiophysics
Address: Kišpatićeva 12
City: 10000 - Zagreb, Croatia
Communication
Phone: 385 (0)1 2333 233 /584
Summary: A new method of in vivo dosimetry in 60-Co gamma Total Body Irradiation (TBI) for anterior-posterior position was setup. It made possible to determine the absorbed dose in mid plane of a patient,s body by means of entrance dose reading, mid plane dose factor (MDF) and lung correction factor (CF). Experiments on: 1. cuboidal phantom consisting of 20 water filled basins in different dimensions (representing a man lying on his side), 2. real anatomic phantom (produced by a sculptor) and on 3. polystyrene phantom based on real patient,s CTs (including lung inhomogeneity), were verified in a theoretical model. In order to cover a whole practical range of irradiation procedures, theoretical model of the anatomic phantom, based on a number of cylindrical ellipsoides, had a possibility to change all dimensions and positions of its constituent parts, in length, width and weight. Agreement between the experiment and theory was verified on reference phantom within 2.1% for absorbed dose in all locations of interest in TBI. Now a generalisation of the theory to proportional phantom sozes was made. The model has been used in practice in TBI prior to Bone Marrow Transplantation in more than 250 cases. Also, a question of lung,s shielding (Y or N), in low dose rate TBI regime, was found to be without influence to the results of therapy. The model took into account the real scattering conditions in defining MDF and CF, due to the finite patient width. The established software enabled in vivo dose control during TBI.

Keywords: Total Body Irradiation, In vivo dosimetry, Dose correction factor, Local tissue air ratio, Anatomic phantom

Research goals: The principal aim of this scientific investigation will be to show that the dimensions, constitution and shape of the phantom,used in TBI radiotherapy, are very important and influence the values of the empiric dosimetric functions. Namely, the human body has specific dimensions and mass distribution in the near ofany absorbed dose point. Therefore, an effective field, which represents a single anatomic region (head, neck, abdomen...),would be defined by phantom,s contour and range of scattered irradiation for a number of theoreticaly defined models of cubic and anatomic TBI phantoms.We shall introduce the local dosimetric functions and in vivo dosimetry, which will be based on entrance and output dose readings and mid plane dose correction factors. A special attention should be paid to dose in lung and to influence of lung shielding in TBI prior to bone marrow transplantation.The theoretical model will be verified through measurements on cubic and real anatomic TBI phantoms. The mid plane absorbed dose will be measured by use of the entrance and output dose readings(semiconductor detectors) of a certain body,s region. and the correction factor, calculated in advance by use of a special software made for this purpose. We expect that the investigation will be a contribution to basic dosimetriy and a useful method inclinical practice.

COOPERATION - INSTITUTIONS


  1. Name of institution: Allgemeines Krankenhaus der Stadt Wien, Universitatsklinik fur Strahlentherapie und Strahlenbiologie (Dr Sc Werner Schmidt, Physiker)
    Type of institution: International organization
    City: 1090 - Wien, Austria

OTHER ACHIEVEMENTS


  1. Name: Razni softveri izrađeni u vezi s projektom 1.Program za absorbiranu dozu u TBI fantomu (Fortran)2.Program za čimbenike ispravka doze u TBI (Fortran) 3.Program za dozu u 60-Co TBI in vivo dozimetriji
    Type of achievement: Other
    Authors: M. Vrtar
Other information about the project.
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