TITLE:
A Clinical Dosimetry Analysis of Total Body Irradiation for Leukemia Patients
AUTHORS:
Lanchun Lu, Jonathan Filippi, Akshi Patel, Nilendu Gupta, Michael Weldon, Jeffery Woollard, Ahmet Ayan, Yi Rong, Douglas Martin, Christopher Pelloski, Meng Xu Welliver
KEYWORDS:
Total Body Irradiation (TBI); In Vivo Dosimetry; Lung Block; Compensators; Patient Setup; Treatment Planning
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.3 No.1,
January
29,
2014
ABSTRACT:
Background and
Purpose: To perform a retrospective in
vivo dosimetry study of 129 total body irradiation (TBI) on leukemia and
bone marrow transplant patients treated in our clinic from 2008 to 2011 and to
find out if there is any indication of the necessity of developing a new
efficient TBI approach. Materials and Methods: The in vivo dosimetry data of 129 patients treated with TBI between
2008 and 2011 were retrieved from the database and analyzed. These patients
were mostly treated with the regime of a single fraction or 6 fractions with
some exceptions of 8-fraction or 2-fraction treatments depending on the
protocols that were applied. For every fraction of treatment, 10 pairs of diode
dosimeters were used to monitor the doses to the midline of head, neck, arms, mediastinum,
left lung, right lung, umbilicus, thigh, knee, and ankle for both AP and PA
fields. The doses to the midline of the above body parts were considered to be
the average of the AP and PA readings of each diode pair. Dose deviation from
the prescribed value for each body part was studied by plotting the histogram
of the frequency versus deviation and comparing this with the dose delivered to
the midline of the umbilicus to where the dose was prescribed. The correlation
of dose deviation to body part thickness was also studied. By studying the dose
deviations, we can find the uniformity of general dose distributions for
conventional TBI treatments. Results: The retrospective dosimetry study of the
129 TBI patient treatments indicates that for most of the patients treated in
our clinic, the doses received
by different body parts monitored with in
vivo dosimetry were within the window of 10% difference from the prescribed
dose. The inhomogeneity of dose on different body parts could be manually
improved by using compensators, but the
method is cumbersome and time consuming. The dose deviation in many histograms
ranging from about ?10% to 10% indicates some incongruity of dose distribution.
This could be due to the method of using lead compensators for a manual dose
adjustment which could not ideally compensate for different body thicknesses
everywhere. Conclusions: The conventional TBI could give uniform dose to the major body parts
under the online in vivo dosimetry
monitoring at the level of 10%, but the treatment procedure is cumbersome and
time consuming. This implies the importance of developing a new and efficient
TBI method by adopting modern radiation therapy technique.