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Dosimetric comparison of Acuros™ BV with AAPM TG43 dose calculation formalism in breast interstitial high-dose-rate brachytherapy with the use of metal catheters.

Sinnatamby M, Nagarajan V, Reddy K S, Karunanidhi G, Singhavajala V - J Contemp Brachytherapy (2015)

Bottom Line: This does not take into account tissue heterogeneity, attenuation and scatter in the metal applicator, and effects of patient boundary.Acuros™ BV is a Grid Based Boltzmann Solver code (GBBS), which takes into consideration all the above, was used to compute dosimetry and the two systems were compared.TG-43 algorithm seems to significantly overestimate the dose to various volumes of interest; GBBS based dose calculation algorithm has impact on CTV, heart, ipsilateral lung, heart, contralateral breast, skin, and ribs of the ipsilateral breast side; the prescription changes occurred due to effect of metal catheters, inhomogeneities, and scatter conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiotherapy, Regional Cancer Centre, JIPMER, Puducherry.

ABSTRACT

Purpose: Radiotherapy for breast cancer includes different techniques and methods. The purpose of this study is to compare dosimetric calculations using TG-43 dose formalism and Varian Acuros™ BV (GBBS) dose calculation algorithm for interstitial implant of breast using metal catheters in high-dose-rate (HDR) brachytherapy, using (192)Ir.

Material and methods: Twenty patients who were considered for breast conservative surgery (BCS), underwent lumpectomy and axillary dissection. These patients received perioperative interstitial HDR brachytherapy as upfront boost using rigid metal implants. Whole breast irradiation was delivered TG-43 after a gap of two weeks. Standard brachytherapy dose calculation was done by dosimetry. This does not take into account tissue heterogeneity, attenuation and scatter in the metal applicator, and effects of patient boundary. Acuros™ BV is a Grid Based Boltzmann Solver code (GBBS), which takes into consideration all the above, was used to compute dosimetry and the two systems were compared.

Results: Comparison of GBBS and TG-43 formalism on interstitial metal catheters shows difference in dose prescribed to CTV and other OARs. While the estimated dose to CTV was only marginally different with the two systems, there is a significant difference in estimated doses of starting from 4 to 53% in the mean value of all parameters analyzed.

Conclusions: TG-43 algorithm seems to significantly overestimate the dose to various volumes of interest; GBBS based dose calculation algorithm has impact on CTV, heart, ipsilateral lung, heart, contralateral breast, skin, and ribs of the ipsilateral breast side; the prescription changes occurred due to effect of metal catheters, inhomogeneities, and scatter conditions.

No MeSH data available.


Related in: MedlinePlus

Isodose distribution on Left Breast using 192Ir Gammamed HDR plus source with Acuros™ BV and isodose distribution on the same CT slice using 192Ir Gammamed HDR plus source with TG-43 formalism
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Figure 0001: Isodose distribution on Left Breast using 192Ir Gammamed HDR plus source with Acuros™ BV and isodose distribution on the same CT slice using 192Ir Gammamed HDR plus source with TG-43 formalism

Mentions: The Cumulative Dose Volume Histogram (DVH), different dose-volume indices were derived as shown in Table 2. Differences in the relative response as high as 11.5% were found from the homogeneous setup when the heterogeneous materials were inserted into the experimental phantom. The results derived from the phantom measurements show good agreement with the simulations and TPS calculations, using Acuros™ algorithm [15]. In this study, Acuros™ BV estimated mean CTVref was 4% less and reference dose enclosing CTV was 5% less (p < 0.001) compared to TG-43 dose calculations. Similarly, Acuros™ BV estimated V150% and V200% was 19% and 52% less than that of TG-43 estimates. In spite of higher percentage differences, in terms of absolute value, it is trivial. CI of 0.91 has been achieved for breast implant [3] but in this study using TG-43 formalism 0.93 was achieved. When using Acuros™ BV, 3% decrease was noted, which was due to heterogeneity correction. Mean DHI 0.70 ± 0.10 was 9% greater than TG-43 dose calculation indicates that homogeneity was better. OI and EI estimates were 53% and 19% less than the TG-43 based calculation. In Acuros™ BV calculations, mean COIN was 2% less, and a p-value of 0.03 was observed. Figure 1 shows the isodose distribution for comparison between Acuros™ BV and TG-43 formalism on the same CT slice using 192Ir Gammamed plus source. The DVH shown in Figure 2 depicts the noteworthy difference in DVH at a higher dose. The comparison of indices along with mean values are shown in Figure 3.


Dosimetric comparison of Acuros™ BV with AAPM TG43 dose calculation formalism in breast interstitial high-dose-rate brachytherapy with the use of metal catheters.

Sinnatamby M, Nagarajan V, Reddy K S, Karunanidhi G, Singhavajala V - J Contemp Brachytherapy (2015)

Isodose distribution on Left Breast using 192Ir Gammamed HDR plus source with Acuros™ BV and isodose distribution on the same CT slice using 192Ir Gammamed HDR plus source with TG-43 formalism
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643735&req=5

Figure 0001: Isodose distribution on Left Breast using 192Ir Gammamed HDR plus source with Acuros™ BV and isodose distribution on the same CT slice using 192Ir Gammamed HDR plus source with TG-43 formalism
Mentions: The Cumulative Dose Volume Histogram (DVH), different dose-volume indices were derived as shown in Table 2. Differences in the relative response as high as 11.5% were found from the homogeneous setup when the heterogeneous materials were inserted into the experimental phantom. The results derived from the phantom measurements show good agreement with the simulations and TPS calculations, using Acuros™ algorithm [15]. In this study, Acuros™ BV estimated mean CTVref was 4% less and reference dose enclosing CTV was 5% less (p < 0.001) compared to TG-43 dose calculations. Similarly, Acuros™ BV estimated V150% and V200% was 19% and 52% less than that of TG-43 estimates. In spite of higher percentage differences, in terms of absolute value, it is trivial. CI of 0.91 has been achieved for breast implant [3] but in this study using TG-43 formalism 0.93 was achieved. When using Acuros™ BV, 3% decrease was noted, which was due to heterogeneity correction. Mean DHI 0.70 ± 0.10 was 9% greater than TG-43 dose calculation indicates that homogeneity was better. OI and EI estimates were 53% and 19% less than the TG-43 based calculation. In Acuros™ BV calculations, mean COIN was 2% less, and a p-value of 0.03 was observed. Figure 1 shows the isodose distribution for comparison between Acuros™ BV and TG-43 formalism on the same CT slice using 192Ir Gammamed plus source. The DVH shown in Figure 2 depicts the noteworthy difference in DVH at a higher dose. The comparison of indices along with mean values are shown in Figure 3.

Bottom Line: This does not take into account tissue heterogeneity, attenuation and scatter in the metal applicator, and effects of patient boundary.Acuros™ BV is a Grid Based Boltzmann Solver code (GBBS), which takes into consideration all the above, was used to compute dosimetry and the two systems were compared.TG-43 algorithm seems to significantly overestimate the dose to various volumes of interest; GBBS based dose calculation algorithm has impact on CTV, heart, ipsilateral lung, heart, contralateral breast, skin, and ribs of the ipsilateral breast side; the prescription changes occurred due to effect of metal catheters, inhomogeneities, and scatter conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiotherapy, Regional Cancer Centre, JIPMER, Puducherry.

ABSTRACT

Purpose: Radiotherapy for breast cancer includes different techniques and methods. The purpose of this study is to compare dosimetric calculations using TG-43 dose formalism and Varian Acuros™ BV (GBBS) dose calculation algorithm for interstitial implant of breast using metal catheters in high-dose-rate (HDR) brachytherapy, using (192)Ir.

Material and methods: Twenty patients who were considered for breast conservative surgery (BCS), underwent lumpectomy and axillary dissection. These patients received perioperative interstitial HDR brachytherapy as upfront boost using rigid metal implants. Whole breast irradiation was delivered TG-43 after a gap of two weeks. Standard brachytherapy dose calculation was done by dosimetry. This does not take into account tissue heterogeneity, attenuation and scatter in the metal applicator, and effects of patient boundary. Acuros™ BV is a Grid Based Boltzmann Solver code (GBBS), which takes into consideration all the above, was used to compute dosimetry and the two systems were compared.

Results: Comparison of GBBS and TG-43 formalism on interstitial metal catheters shows difference in dose prescribed to CTV and other OARs. While the estimated dose to CTV was only marginally different with the two systems, there is a significant difference in estimated doses of starting from 4 to 53% in the mean value of all parameters analyzed.

Conclusions: TG-43 algorithm seems to significantly overestimate the dose to various volumes of interest; GBBS based dose calculation algorithm has impact on CTV, heart, ipsilateral lung, heart, contralateral breast, skin, and ribs of the ipsilateral breast side; the prescription changes occurred due to effect of metal catheters, inhomogeneities, and scatter conditions.

No MeSH data available.


Related in: MedlinePlus