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Comparative Study
. 2015 Jan 8;16(1):5069.
doi: 10.1120/jacmp.v16i1.5069.

Comparing the monoisocentric and dual isocentric techniques in chest wall radiotherapy of mastectomy patients

Amin Banaei  1 , Bijan Hashemi, Mohsen Bakhshandeh
Affiliations
Comparative Study

Comparing the monoisocentric and dual isocentric techniques in chest wall radiotherapy of mastectomy patients

Amin Banaei et al. J Appl Clin Med Phys. .

Abstract

The monoisocentric (MIT) and dual isocentric (DIT) techniques are compared for the mastectomy patients undergoing chest wall radiotherapy, and a new practical method is suggested for determining the dose calculation reference point to be used in the MIT. Data of 18 mastectomy patients having chest wall radiotherapy were used. To find the appropriate dose calculation reference point for the MIT, the target tissue was divided into nine regions with 17 points as the appropriate candidates. After finding the best reference point for the MIT, dose calculations were made for each patient based on the MIT and DIT to determine the dose distributions of the target volume and organs at risk. The lateral component of the dose calculation reference point was found to be located at one-third of the distance between the geometrical center and the lateral border of the chest wall in the lateral direction toward the outer border. The longitudinal component of this point was found to be located at the geometrical center of the chest wall with a depth located around 2-3 cm under the patients' skin. There was no significant difference between the two radiotherapy planning techniques (MIT and DIT) regarding the dose distributions in the organs at risk and the 95% of the prescribed dose coverage of the target tissue. However, a significant difference for the 105% of the prescribed dose coverage, maximum dose delivered to the target tissue, and the level 2 lymph nodes dose was found, with the DIT showing higher values. Because of the good matching and no superposition observed between the treatment fields in the MIT, it was expected and confirmed that the hot and cold regions (with higher and lower doses than the prescribed dose) with the MIT are significantly fewer than that of the DIT. Therefore, to perform a better conformal radiotherapy for the patients having mastectomy, it could be recommended to use the MIT instead of the DIT and other conventional techniques.

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Figures

Figure 1
Figure 1
The MIT (a) and DIT (b) treatment fields showing the occurrence of hot and cold areas in the DIT
Figure 2
Figure 2
An example of the treatment planning configuration used for the MIT.
Figure 3
Figure 3
An example of the dose distributions obtained by the TPS for the DIT in the region where the tangential and supraclavicular fields overlap (in the transverse plane).
Figure 4
Figure 4
An example of the dose distributions obtained by the TPS for the MIT in the region where the tangential and supraclavicular fields collapse with each other (in the transverse plane).
Figure 5
Figure 5
A schematic figure showing the locations of the borders defined for a left breast on the chest wall at the coronal plane (a) and the regions showing the calculation reference point candidates (b). The edges of the three irradiation beams have been the same as shown in Fig. 2.
Figure 6
Figure 6
An example of the DVH of the target tissue and organs at risk calculated for one of the patients with the MIT (a) and DIT (b).
See this image and copyright information in PMC

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