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Dosimetric comparison between IMRT delivery modes: Step-and-shoot, sliding window, and volumetric modulated arc therapy - for whole pelvis radiation therapy of intermediate-to-high risk prostate adenocarcinoma.

Herman Tde L, Schnell E, Young J, Hildebrand K, Algan O, Syzek E, Herman T, Ahmad S - J Med Phys (2013)

Bottom Line: Doses to all critical structures were higher on average with SW method compared to SS, but insignificant.Normal tissue volumes receiving doses in the 20-30 Gy range were reduced for VMAT compared to SS.In conclusion, similar target coverage and normal tissue doses were found by the three compared modes and the dosimetric differences were small.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA.

ABSTRACT
THIS STUDY WAS PERFORMED TO EVALUATE DOSIMETRIC DIFFERENCES BETWEEN CURRENT INTENSITY MODULATED RADIATION THERAPY (IMRT) DELIVERY MODES: Step-and-shoot (SS), sliding window (SW), and volumetric modulated arc therapy (VMAT). Plans for 15 prostate cancer patients with 10 MV photon beams using each IMRT mode were generated. Patients had three planning target volumes (PTVs) including prostate, prostate plus seminal vesicles, and pelvic lymphatics. Dose volume histograms (DVHs) of PTVs and organs at risk (OARs), tumor control probability (TCP) and normal tissue complication probabilities (NTCPs), conformation number, and monitor units (MUs) used were compared. Statistical analysis was performed using the analysis of variance (ANOVA) technique. The TCPs were < 99% with insignificant differences among modalities (P > 0.99). Doses to all critical structures were higher on average with SW method compared to SS, but insignificant. NTCP values were lowest for VMAT in all structures excepting bladder. Normal tissue volumes receiving doses in the 20-30 Gy range were reduced for VMAT compared to SS. Percentage of MUs required for VMAT to deliver a comparable plan to SS and SW was at least 40% less. In conclusion, similar target coverage and normal tissue doses were found by the three compared modes and the dosimetric differences were small.

No MeSH data available.


Related in: MedlinePlus

Conformation number (CN): (a) The ring represents the reference isodose line (RI) that includes the planning target volume (PTV) and organs at risk (OARs), (b) The first term of the CN formula (TVRI/TV) is less than one if TV is not covered entirely by the volume of RI, and the second term (TVMRI/VRI) is less than one if OAR is within the volume of RI
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Figure 1: Conformation number (CN): (a) The ring represents the reference isodose line (RI) that includes the planning target volume (PTV) and organs at risk (OARs), (b) The first term of the CN formula (TVRI/TV) is less than one if TV is not covered entirely by the volume of RI, and the second term (TVMRI/VRI) is less than one if OAR is within the volume of RI

Mentions: Where VRI is the volume of the prescription isodose (RI), TV is the target volume, and TVRI is the target volume covered by the prescription. The first term in the equation is less than one if any target volume is not covered by the volume of the prescription isodose line, and the second term is less than one if any normal tissue is within the volume of the prescription isodose line, as is shown in Figure 1.


Dosimetric comparison between IMRT delivery modes: Step-and-shoot, sliding window, and volumetric modulated arc therapy - for whole pelvis radiation therapy of intermediate-to-high risk prostate adenocarcinoma.

Herman Tde L, Schnell E, Young J, Hildebrand K, Algan O, Syzek E, Herman T, Ahmad S - J Med Phys (2013)

Conformation number (CN): (a) The ring represents the reference isodose line (RI) that includes the planning target volume (PTV) and organs at risk (OARs), (b) The first term of the CN formula (TVRI/TV) is less than one if TV is not covered entirely by the volume of RI, and the second term (TVMRI/VRI) is less than one if OAR is within the volume of RI
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3958995&req=5

Figure 1: Conformation number (CN): (a) The ring represents the reference isodose line (RI) that includes the planning target volume (PTV) and organs at risk (OARs), (b) The first term of the CN formula (TVRI/TV) is less than one if TV is not covered entirely by the volume of RI, and the second term (TVMRI/VRI) is less than one if OAR is within the volume of RI
Mentions: Where VRI is the volume of the prescription isodose (RI), TV is the target volume, and TVRI is the target volume covered by the prescription. The first term in the equation is less than one if any target volume is not covered by the volume of the prescription isodose line, and the second term is less than one if any normal tissue is within the volume of the prescription isodose line, as is shown in Figure 1.

Bottom Line: Doses to all critical structures were higher on average with SW method compared to SS, but insignificant.Normal tissue volumes receiving doses in the 20-30 Gy range were reduced for VMAT compared to SS.In conclusion, similar target coverage and normal tissue doses were found by the three compared modes and the dosimetric differences were small.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA.

ABSTRACT
THIS STUDY WAS PERFORMED TO EVALUATE DOSIMETRIC DIFFERENCES BETWEEN CURRENT INTENSITY MODULATED RADIATION THERAPY (IMRT) DELIVERY MODES: Step-and-shoot (SS), sliding window (SW), and volumetric modulated arc therapy (VMAT). Plans for 15 prostate cancer patients with 10 MV photon beams using each IMRT mode were generated. Patients had three planning target volumes (PTVs) including prostate, prostate plus seminal vesicles, and pelvic lymphatics. Dose volume histograms (DVHs) of PTVs and organs at risk (OARs), tumor control probability (TCP) and normal tissue complication probabilities (NTCPs), conformation number, and monitor units (MUs) used were compared. Statistical analysis was performed using the analysis of variance (ANOVA) technique. The TCPs were < 99% with insignificant differences among modalities (P > 0.99). Doses to all critical structures were higher on average with SW method compared to SS, but insignificant. NTCP values were lowest for VMAT in all structures excepting bladder. Normal tissue volumes receiving doses in the 20-30 Gy range were reduced for VMAT compared to SS. Percentage of MUs required for VMAT to deliver a comparable plan to SS and SW was at least 40% less. In conclusion, similar target coverage and normal tissue doses were found by the three compared modes and the dosimetric differences were small.

No MeSH data available.


Related in: MedlinePlus