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Dosimetric comparison between two techniques of volumetric-modulated arc therapy for prostate cancer
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Abstracts of the SFPM Annual Meeting 2013 / Physica Medica 29 (2013) e1–e46
118 DOSIMETRIC COMPARISON BETWEEN TWO TECHNIQUES OF VOLUMETRIC-MODULATED ARC THERAPY FOR PROSTATE CANCER A. Eva, J. Ribouton, G. Michel-Amadry, C. Udrescu, O. Chapet, P. Jalade. Service de Physique Médicale et Radioprotection, Centre Hospitalier Lyon Sud, Pierre Benite, France Introduction: The aim of this work was to evaluate two delivery techniques for prostate irradiation: RapidArc (Varian) and HybridArc (Brainlab). Materials and methods: HybridArc (HA) is a recent treatment technique which may combine optimized dynamic conformal arc (DCA) therapy with fixed port IMRT. RapidArc (RA) generates IMRT-quality dose distributions in one or two optimized arcs around the patient, being capable to deliver continuously modulated dose to the entire tumor volume while sparing healthy tissue. Seven patients were treated with RA with a total prescribed dose of 76 Gy. The dose to the PTV1 (prostate + seminal vesicles) was of 46 Gy and the dose to the PTV2 (prostate) was of 30 Gy. Two arcs were created for RA (130–230° and inversely) and one aperture-arc was optimized for HA with a gantry start-stop from 240–120° combined with 5-IMRT beams equally distributed over the arc. The weighting of the HA arcs were adjusted to 60%-DCA and 40%-IMRT. The PTV had to be covered by the 95% isodoseline in both plans. The two plans were compared using the conformal index (CI) for healthy tissue and the dose-volume histogram parameters. For the rectum, the volume that receives 60 Gy (V60), 74 Gy (V74) and the maximum dose (Dmax) were noted. Similarly, the values for the bladder (V60 and Dmax) and the femoral heads (Dmax) were reported. Results: The average [range] V95% for PTV1 was 99.6%[97.5–100%] and 99.7%[98.2–100%] and for PTV2 was 98.2%[95–99.9%] and 99.7[99.3–100%], for RA and HA, respectively. The CI average and range values for PTV1 were 0.9[0.8–1] and 0.8[0.8–.0.9] and for PTV2 were 0.9[0.9–1] and 0.8[0.8–0.9] for RA and HA, respectively. For the rectum, the average V74Gy were 3.5%[1.6–7.5%] and 6.9%[1.5– 13.7%] for RA and HA, respectively. For the bladder, the average V60Gy were 21.2%[9–38%] and 24.2%[10.9–38.9%] for the same plans. Conclusions: In our experience, RapidArc and HybridArc produced similar plans for PTV coverage. There was a significant difference between the two plans for rectum V74Gy (p = 0.02) and bladder V60Gy (p = 0.001) in favour of RA. Additionally, 5 hypophysis cases will be presented at the time of the meeting.
http://dx.doi.org/10.1016/j.ejmp.2013.08.124
119 ‘‘FIELD IN FIELD” FOR THE TREATMENT OF BREAST CANCER WITH LYMPH NODES: A COMPARATIVE STUDY WITH CONVENTIONAL RADIOTHERAPY USING WEDGE FILTERS N. Defour, T. Brun, M. Massabeau, C. Lanaspeze, F. Carillo, T. Lacaze, S. Ochoa, B. Delafontan, F. Izar, R. Ferrand. Institut Claudius Regaud, Toulouse, France Introduction: Treatment of breast cancer with lymph nodes (internal mammary and clavicular nodes) is achieved in most of the centers using a conventional radiotherapy based on electron-photon beams with junctions and wedge filters. Wedge filters correct for surface obliquities but do not provide optimal dose homogeneity within the breast volume. This study aims at comparing treatment plans using the ‘‘field in field” technique, equivalent to a ‘‘simplified” intensity modulation with treatment plans using wedge filters. Material and methods: This study focused on eight patients (for half of the patients, the internal mammary nodes were included in
the breast fields) treated for breast cancer with lymph nodes using wedge filters. For these patients a ‘‘field in field” plan was prepared retrospectively. Patients were positioned supine with ipsilateral arm above the head and head turned to the opposite treatment side. The prescribed dose was 50 Gy to the PTV breast and 46–50 Gy for the lymph nodes. For both technics, after treatment plan optimization, doses delivered to targets, heart and ipsilateral lung are reported. Results: For the 8 patients and for the same coverage of breast and lymph nodes PTV, the volume of 105% (52.5 Gy) of the dose remaining in the breast volume was 2.65–24.29 cc (mean 13.9 cc) with the ‘‘field in field” technic and 9.49–231.63 cc (mean 98.5 cc) with wedge filters technic. For ipsilateral lung, the mean dose, V20 and V30 were respectively 15.1–16.6 Gy (average 15.8 Gy), 25.4– 27.1 Gy (average 26.1 Gy), and 17.3–19 Gy (mean 17.9 Gy) for both technics. Conclusion: For 8 patients, ‘‘field in field” treatment plans showed that remaining volume of 105% of the dose was up to 10 times smaller than using wedge filters treatment plans. This technics allowed reducing significantly overdosage areas and therefore having a better dose homogeneity in the breast.
http://dx.doi.org/10.1016/j.ejmp.2013.08.125
120 A COMPARISON OF 4 ROTATIONAL TECHNIQUES FOR CRANIAL STEREOTACTIC RADIOSURGERY ACCORDING TO THE POSITION AND THE TARGET NUMBER J. Molinier, C. Kerr, N. Ailleres, S. Simeon, M. Charissoux, D. Azria, P. Fenoglietto. Institut Régional du Cancer Val-d’Aurelle, Montpellier, France Introduction: In order to select the best one according to the number and the position of the lesions we compare in this study dynamic conformal arc (DCA), coplanar VMAT (RAC), noncoplanar VMAT (RANC) and entire arc VMAT with table rotations of 10° and 350° (RAT). Material and methods: 5 single lesions (case 1), 5 multiple lesions (case 2) and 5 single lesions close to organs at risk (case 3) were analyzed. Each technique was evaluated in regard to conformity and homogeneity indexes for PTV (CI = s(PTV covered by prescription isodose)t ˆ 2/(V_PTV*V_(prescription isodose)) and HI=(D_maxD_min)/D_mean ), the healthy brain tissue dose (V10Gy), Dmax (OAR) and the number of monitor units (MU). Results: For case 1, HI and CI are better for RANC (HI: 0.17 RANC – 0.22 RAT – 0.23 RAC 0.27 DCA and CI: 0.86 RAT – 0.85 RANC 0.83 RAC – 0.76 DCA) but DCA reduces brain tissue V10Gy (11.97 cc DCA – 14.51 cc RANC – 15.9 cc RAT – 18.34 cc RAC) and MU (3092 DCA – 4573 RAC – 4639 RANC – 5250 RAT). In case 2, HI is similar for VMAT (0.17 RANC and RAT – 0.18 RAC – 0.22 DCA) and CI is top with RAT (0.72 RAT – 0.68 RAC – 0.67 RANC – 0.65 DCA). The healthy brain is as well protected with DCA as with RANC (10.5 DCA and RANC – 15.08 RAT – 18.12 RAC) but MU decrease with RANC (4250 RANC – 4802 RAT – 4841 RAC – 7908 DCA). For case 3, RAT improves HI and CI (HI: 0.27 RAT – 0.3 RANC – 0.31 RAC – 0.57DCA and CI: 0.74 RAT – 0.65 RAC – 0.59 RANC 0.5 DCA) and spares brain tissue and OAR (V10Gy: 1.31 RAT – 1.56 RAC – 2 RANC – 2.31 DCA and Dmax (OAR): 12.17 RAT – 12.59 RAC – 12.77 RANC – 14.15 Gy DCA). The MU numbers decrease with DCA (2184 DCA – 3533 RANC – 3714 RAT – 3840 RAC). Conclusion: For simple case 1, DCA provide better plan considering low doses to healthy brain. For case 2, RANC is the best compromise
Abstracts of the SFPM Annual Meeting 2013 / Physica Medica 29 (2013) e1–e46
118 DOSIMETRIC COMPARISON BETWEEN TWO TECHNIQUES OF VOLUMETRIC-MODULATED ARC THERAPY FOR PROSTATE CANCER A. Eva, J. Ribouton, G. Michel-Amadry, C. Udrescu, O. Chapet, P. Jalade. Service de Physique Médicale et Radioprotection, Centre Hospitalier Lyon Sud, Pierre Benite, France Introduction: The aim of this work was to evaluate two delivery techniques for prostate irradiation: RapidArc (Varian) and HybridArc (Brainlab). Materials and methods: HybridArc (HA) is a recent treatment technique which may combine optimized dynamic conformal arc (DCA) therapy with fixed port IMRT. RapidArc (RA) generates IMRT-quality dose distributions in one or two optimized arcs around the patient, being capable to deliver continuously modulated dose to the entire tumor volume while sparing healthy tissue. Seven patients were treated with RA with a total prescribed dose of 76 Gy. The dose to the PTV1 (prostate + seminal vesicles) was of 46 Gy and the dose to the PTV2 (prostate) was of 30 Gy. Two arcs were created for RA (130–230° and inversely) and one aperture-arc was optimized for HA with a gantry start-stop from 240–120° combined with 5-IMRT beams equally distributed over the arc. The weighting of the HA arcs were adjusted to 60%-DCA and 40%-IMRT. The PTV had to be covered by the 95% isodoseline in both plans. The two plans were compared using the conformal index (CI) for healthy tissue and the dose-volume histogram parameters. For the rectum, the volume that receives 60 Gy (V60), 74 Gy (V74) and the maximum dose (Dmax) were noted. Similarly, the values for the bladder (V60 and Dmax) and the femoral heads (Dmax) were reported. Results: The average [range] V95% for PTV1 was 99.6%[97.5–100%] and 99.7%[98.2–100%] and for PTV2 was 98.2%[95–99.9%] and 99.7[99.3–100%], for RA and HA, respectively. The CI average and range values for PTV1 were 0.9[0.8–1] and 0.8[0.8–.0.9] and for PTV2 were 0.9[0.9–1] and 0.8[0.8–0.9] for RA and HA, respectively. For the rectum, the average V74Gy were 3.5%[1.6–7.5%] and 6.9%[1.5– 13.7%] for RA and HA, respectively. For the bladder, the average V60Gy were 21.2%[9–38%] and 24.2%[10.9–38.9%] for the same plans. Conclusions: In our experience, RapidArc and HybridArc produced similar plans for PTV coverage. There was a significant difference between the two plans for rectum V74Gy (p = 0.02) and bladder V60Gy (p = 0.001) in favour of RA. Additionally, 5 hypophysis cases will be presented at the time of the meeting.
http://dx.doi.org/10.1016/j.ejmp.2013.08.124
119 ‘‘FIELD IN FIELD” FOR THE TREATMENT OF BREAST CANCER WITH LYMPH NODES: A COMPARATIVE STUDY WITH CONVENTIONAL RADIOTHERAPY USING WEDGE FILTERS N. Defour, T. Brun, M. Massabeau, C. Lanaspeze, F. Carillo, T. Lacaze, S. Ochoa, B. Delafontan, F. Izar, R. Ferrand. Institut Claudius Regaud, Toulouse, France Introduction: Treatment of breast cancer with lymph nodes (internal mammary and clavicular nodes) is achieved in most of the centers using a conventional radiotherapy based on electron-photon beams with junctions and wedge filters. Wedge filters correct for surface obliquities but do not provide optimal dose homogeneity within the breast volume. This study aims at comparing treatment plans using the ‘‘field in field” technique, equivalent to a ‘‘simplified” intensity modulation with treatment plans using wedge filters. Material and methods: This study focused on eight patients (for half of the patients, the internal mammary nodes were included in
the breast fields) treated for breast cancer with lymph nodes using wedge filters. For these patients a ‘‘field in field” plan was prepared retrospectively. Patients were positioned supine with ipsilateral arm above the head and head turned to the opposite treatment side. The prescribed dose was 50 Gy to the PTV breast and 46–50 Gy for the lymph nodes. For both technics, after treatment plan optimization, doses delivered to targets, heart and ipsilateral lung are reported. Results: For the 8 patients and for the same coverage of breast and lymph nodes PTV, the volume of 105% (52.5 Gy) of the dose remaining in the breast volume was 2.65–24.29 cc (mean 13.9 cc) with the ‘‘field in field” technic and 9.49–231.63 cc (mean 98.5 cc) with wedge filters technic. For ipsilateral lung, the mean dose, V20 and V30 were respectively 15.1–16.6 Gy (average 15.8 Gy), 25.4– 27.1 Gy (average 26.1 Gy), and 17.3–19 Gy (mean 17.9 Gy) for both technics. Conclusion: For 8 patients, ‘‘field in field” treatment plans showed that remaining volume of 105% of the dose was up to 10 times smaller than using wedge filters treatment plans. This technics allowed reducing significantly overdosage areas and therefore having a better dose homogeneity in the breast.
http://dx.doi.org/10.1016/j.ejmp.2013.08.125
120 A COMPARISON OF 4 ROTATIONAL TECHNIQUES FOR CRANIAL STEREOTACTIC RADIOSURGERY ACCORDING TO THE POSITION AND THE TARGET NUMBER J. Molinier, C. Kerr, N. Ailleres, S. Simeon, M. Charissoux, D. Azria, P. Fenoglietto. Institut Régional du Cancer Val-d’Aurelle, Montpellier, France Introduction: In order to select the best one according to the number and the position of the lesions we compare in this study dynamic conformal arc (DCA), coplanar VMAT (RAC), noncoplanar VMAT (RANC) and entire arc VMAT with table rotations of 10° and 350° (RAT). Material and methods: 5 single lesions (case 1), 5 multiple lesions (case 2) and 5 single lesions close to organs at risk (case 3) were analyzed. Each technique was evaluated in regard to conformity and homogeneity indexes for PTV (CI = s(PTV covered by prescription isodose)t ˆ 2/(V_PTV*V_(prescription isodose)) and HI=(D_maxD_min)/D_mean ), the healthy brain tissue dose (V10Gy), Dmax (OAR) and the number of monitor units (MU). Results: For case 1, HI and CI are better for RANC (HI: 0.17 RANC – 0.22 RAT – 0.23 RAC 0.27 DCA and CI: 0.86 RAT – 0.85 RANC 0.83 RAC – 0.76 DCA) but DCA reduces brain tissue V10Gy (11.97 cc DCA – 14.51 cc RANC – 15.9 cc RAT – 18.34 cc RAC) and MU (3092 DCA – 4573 RAC – 4639 RANC – 5250 RAT). In case 2, HI is similar for VMAT (0.17 RANC and RAT – 0.18 RAC – 0.22 DCA) and CI is top with RAT (0.72 RAT – 0.68 RAC – 0.67 RANC – 0.65 DCA). The healthy brain is as well protected with DCA as with RANC (10.5 DCA and RANC – 15.08 RAT – 18.12 RAC) but MU decrease with RANC (4250 RANC – 4802 RAT – 4841 RAC – 7908 DCA). For case 3, RAT improves HI and CI (HI: 0.27 RAT – 0.3 RANC – 0.31 RAC – 0.57DCA and CI: 0.74 RAT – 0.65 RAC – 0.59 RANC 0.5 DCA) and spares brain tissue and OAR (V10Gy: 1.31 RAT – 1.56 RAC – 2 RANC – 2.31 DCA and Dmax (OAR): 12.17 RAT – 12.59 RAC – 12.77 RANC – 14.15 Gy DCA). The MU numbers decrease with DCA (2184 DCA – 3533 RANC – 3714 RAT – 3840 RAC). Conclusion: For simple case 1, DCA provide better plan considering low doses to healthy brain. For case 2, RANC is the best compromise