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Total body irradiation with step translation and dynamic field matching.

Chen HH, Wu J, Chuang KS, Lin JF, Lee JC, Lin JC - Biomed Res Int (2013)

Bottom Line: The dose distribution in the overlapped region ranged from 98.5% to 102.8%.Lateral dose profiles at abdomen and head revealed 109.8% and 111.7% high doses, respectively, at the body edges.The results confirmed that the technique is capable of delivering a uniform dose distribution to the midline of the body in a small treatment room while keeping the lung dose within the tolerance level.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Taichung Veterans General Hospital, 1650 Taiwan Boulevard Sect. 4, Taichung 40705, Taiwan.

ABSTRACT
The purpose of this study is to develop a total body irradiation technique that does not require additional devices or sophisticated processes to overcome the space limitation of a small treatment room. The technique aims to deliver a uniform dose to the entire body while keeping the lung dose within the tolerance level. The technique treats the patient lying on the floor anteriorly and posteriorly. For each AP/PA treatment, two complementary fields with dynamic field edges are matched over an overlapped region defined by the marks on the body surface. A compensator, a spoiler, and lung shielding blocks were used during the treatment. Moreover, electron beams were used to further boost the chest wall around the lungs. The technique was validated in a RANDO phantom using GAFCHROMIC films. Dose ratios at different body sites along the midline ranged from 0.945 to 1.076. The dose variation in the AP direction ranged from 96.0% to 104.6%. The dose distribution in the overlapped region ranged from 98.5% to 102.8%. Lateral dose profiles at abdomen and head revealed 109.8% and 111.7% high doses, respectively, at the body edges. The results confirmed that the technique is capable of delivering a uniform dose distribution to the midline of the body in a small treatment room while keeping the lung dose within the tolerance level.

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Dynamic MLC fields consist of inclined radiation field. (a) The field geometry is shown. (b) The radiation fluence delivered by a dynamic field. When the beam is on, the leaves move continuously from the 20 cm position to the 17 cm position. (c) The fluence map of the inferior field when the A-leaves move in. (d) The fluence map of the superior field when the B-leaves move in.
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fig3: Dynamic MLC fields consist of inclined radiation field. (a) The field geometry is shown. (b) The radiation fluence delivered by a dynamic field. When the beam is on, the leaves move continuously from the 20 cm position to the 17 cm position. (c) The fluence map of the inferior field when the A-leaves move in. (d) The fluence map of the superior field when the B-leaves move in.

Mentions: The method of editing dynamic MLC leaf sequence files has been published previously [29]. For this study, the dynamic MLC fields were edited using the Shape Editor (Version 6.1, Varian Medical Systems, Palo Alto, CA, USA) to form a tapered field edge with the fluence decreasing gradually from the value in field to zero at the field edge. The superior dynamic field irradiated the upper part of the body with the B-leaves in motion. It consisted of two segments. The leaves of the first segment were set at the start position with dose fraction 0, and the leaves of the second segment were set at the stop position with dose fraction 1. The A-leaves were fixed at 20 cm. Similarly, the inferior dynamic field irradiating the lower part of the body was created with the A-leaves in motion. Crucially, these two dynamic fields must have the same leaf motion length. With this condition, the two adjacent inclined fields were matched complementarily to produce a uniform dose distribution in the overlapped region. Figure 3 shows the fluence distribution of the dynamic fields with the leaves moving from location 20 cm to location 17 cm.


Total body irradiation with step translation and dynamic field matching.

Chen HH, Wu J, Chuang KS, Lin JF, Lee JC, Lin JC - Biomed Res Int (2013)

Dynamic MLC fields consist of inclined radiation field. (a) The field geometry is shown. (b) The radiation fluence delivered by a dynamic field. When the beam is on, the leaves move continuously from the 20 cm position to the 17 cm position. (c) The fluence map of the inferior field when the A-leaves move in. (d) The fluence map of the superior field when the B-leaves move in.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3713376&req=5

fig3: Dynamic MLC fields consist of inclined radiation field. (a) The field geometry is shown. (b) The radiation fluence delivered by a dynamic field. When the beam is on, the leaves move continuously from the 20 cm position to the 17 cm position. (c) The fluence map of the inferior field when the A-leaves move in. (d) The fluence map of the superior field when the B-leaves move in.
Mentions: The method of editing dynamic MLC leaf sequence files has been published previously [29]. For this study, the dynamic MLC fields were edited using the Shape Editor (Version 6.1, Varian Medical Systems, Palo Alto, CA, USA) to form a tapered field edge with the fluence decreasing gradually from the value in field to zero at the field edge. The superior dynamic field irradiated the upper part of the body with the B-leaves in motion. It consisted of two segments. The leaves of the first segment were set at the start position with dose fraction 0, and the leaves of the second segment were set at the stop position with dose fraction 1. The A-leaves were fixed at 20 cm. Similarly, the inferior dynamic field irradiating the lower part of the body was created with the A-leaves in motion. Crucially, these two dynamic fields must have the same leaf motion length. With this condition, the two adjacent inclined fields were matched complementarily to produce a uniform dose distribution in the overlapped region. Figure 3 shows the fluence distribution of the dynamic fields with the leaves moving from location 20 cm to location 17 cm.

Bottom Line: The dose distribution in the overlapped region ranged from 98.5% to 102.8%.Lateral dose profiles at abdomen and head revealed 109.8% and 111.7% high doses, respectively, at the body edges.The results confirmed that the technique is capable of delivering a uniform dose distribution to the midline of the body in a small treatment room while keeping the lung dose within the tolerance level.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Taichung Veterans General Hospital, 1650 Taiwan Boulevard Sect. 4, Taichung 40705, Taiwan.

ABSTRACT
The purpose of this study is to develop a total body irradiation technique that does not require additional devices or sophisticated processes to overcome the space limitation of a small treatment room. The technique aims to deliver a uniform dose to the entire body while keeping the lung dose within the tolerance level. The technique treats the patient lying on the floor anteriorly and posteriorly. For each AP/PA treatment, two complementary fields with dynamic field edges are matched over an overlapped region defined by the marks on the body surface. A compensator, a spoiler, and lung shielding blocks were used during the treatment. Moreover, electron beams were used to further boost the chest wall around the lungs. The technique was validated in a RANDO phantom using GAFCHROMIC films. Dose ratios at different body sites along the midline ranged from 0.945 to 1.076. The dose variation in the AP direction ranged from 96.0% to 104.6%. The dose distribution in the overlapped region ranged from 98.5% to 102.8%. Lateral dose profiles at abdomen and head revealed 109.8% and 111.7% high doses, respectively, at the body edges. The results confirmed that the technique is capable of delivering a uniform dose distribution to the midline of the body in a small treatment room while keeping the lung dose within the tolerance level.

Show MeSH