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Investigation on the effect of sharp phantom edges on point dose measurement during patient-specific dosimetry with Rapid Arc.

Kinhikar RA, Pandey VP, Jose RK, Mahantshetty U, Dhote DS, Deshpande DD, Shrivastava SK - J Med Phys (2013)

Bottom Line: The measured dose was compared with the planned dose for both the phantoms.Mean percentage deviation between measured and planned doses was found to be 4.19 (SD 0.82) and 3.63 (SD 0.89) for cylindrical and rectangular phantoms, respectively.No significant dosimetric variation was found due to the geometry (sharp edges) of the phantom.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Physics, Tata Memorial Hospital, Mumbai, India.

ABSTRACT
The objective of this work was to investigate and quantify the effect of sharp edges of the phantom on the point dose measurement during patient-specific dosimetry with Rapid Arc (RA). Ten patients with carcinoma of prostate were randomly selected for this dosimetric study. Rapid Arc plans were generated with 6 MV X-rays in the Eclipse (v 8.6.14) with single arc (clockwise). Dosimetry verification plans were generated for two phantoms (cylindrical and rectangular). The cylindrical phantom was solid water (diameter 34 cm) and the rectangular phantom was a water phantom (25 cm × 25 cm × 10 cm). These phantoms were pre-scanned in computed tomography (CT) machine with cylindrical ionization chamber (FC65) in place. The plans were delivered with Novalis Tx linear accelerator with 6 MV X-rays for both the phantoms separately. The measured dose was compared with the planned dose for both the phantoms. Mean percentage deviation between measured and planned doses was found to be 4.19 (SD 0.82) and 3.63 (SD 0.89) for cylindrical and rectangular phantoms, respectively. No significant dosimetric variation was found due to the geometry (sharp edges) of the phantom. The sharp edges of the phantom do not perturb the patient specific Rapid Arc dosimetry significantly.

No MeSH data available.


Related in: MedlinePlus

Percentage variation between measured and planned point doses with cylindrical and rectangular phantoms for Rapid Arc for 10 patients
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Figure 3: Percentage variation between measured and planned point doses with cylindrical and rectangular phantoms for Rapid Arc for 10 patients

Mentions: The linac output was within the acceptable range (±2%) for 6 MV X-rays for 10 cm × 10 cm field size prior to Rapid Arc measurements. Thus, the beam stability was satisfactory. For RA plans, the mean percentage variation between measured and planned doses was found to be 4.19 (SD 0.82) and 3.63 (SD 0.89) for cylindrical and rectangular phantoms, respectively [Figure 3]. The range of percentage variation was 3.07-5.8 for cylindrical phantom, while it was 2.4-4.6 with rectangular phantom. To statistically validate two datasets, Student's “t” test was performed and the value was found to be 0.019. Additionally, to substantiate this claim, the P value was estimated and found to be 0.00043 for measurements carried out with cylindrical phantom. For measurements carried out with rectangular phantom, the P value was 0.0001. There was no systematic trend observed in agreement of measured and calculated dose between the two phantoms. Instead, it was random trend observed in dosimetry with both the phantoms. Thus, no significant dosimetric variation was found due to the geometry (sharp edges) of the phantom. The studies with various commercial and customized phantoms reported the agreements within ±5%.[678910111213141516]


Investigation on the effect of sharp phantom edges on point dose measurement during patient-specific dosimetry with Rapid Arc.

Kinhikar RA, Pandey VP, Jose RK, Mahantshetty U, Dhote DS, Deshpande DD, Shrivastava SK - J Med Phys (2013)

Percentage variation between measured and planned point doses with cylindrical and rectangular phantoms for Rapid Arc for 10 patients
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3775038&req=5

Figure 3: Percentage variation between measured and planned point doses with cylindrical and rectangular phantoms for Rapid Arc for 10 patients
Mentions: The linac output was within the acceptable range (±2%) for 6 MV X-rays for 10 cm × 10 cm field size prior to Rapid Arc measurements. Thus, the beam stability was satisfactory. For RA plans, the mean percentage variation between measured and planned doses was found to be 4.19 (SD 0.82) and 3.63 (SD 0.89) for cylindrical and rectangular phantoms, respectively [Figure 3]. The range of percentage variation was 3.07-5.8 for cylindrical phantom, while it was 2.4-4.6 with rectangular phantom. To statistically validate two datasets, Student's “t” test was performed and the value was found to be 0.019. Additionally, to substantiate this claim, the P value was estimated and found to be 0.00043 for measurements carried out with cylindrical phantom. For measurements carried out with rectangular phantom, the P value was 0.0001. There was no systematic trend observed in agreement of measured and calculated dose between the two phantoms. Instead, it was random trend observed in dosimetry with both the phantoms. Thus, no significant dosimetric variation was found due to the geometry (sharp edges) of the phantom. The studies with various commercial and customized phantoms reported the agreements within ±5%.[678910111213141516]

Bottom Line: The measured dose was compared with the planned dose for both the phantoms.Mean percentage deviation between measured and planned doses was found to be 4.19 (SD 0.82) and 3.63 (SD 0.89) for cylindrical and rectangular phantoms, respectively.No significant dosimetric variation was found due to the geometry (sharp edges) of the phantom.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Physics, Tata Memorial Hospital, Mumbai, India.

ABSTRACT
The objective of this work was to investigate and quantify the effect of sharp edges of the phantom on the point dose measurement during patient-specific dosimetry with Rapid Arc (RA). Ten patients with carcinoma of prostate were randomly selected for this dosimetric study. Rapid Arc plans were generated with 6 MV X-rays in the Eclipse (v 8.6.14) with single arc (clockwise). Dosimetry verification plans were generated for two phantoms (cylindrical and rectangular). The cylindrical phantom was solid water (diameter 34 cm) and the rectangular phantom was a water phantom (25 cm × 25 cm × 10 cm). These phantoms were pre-scanned in computed tomography (CT) machine with cylindrical ionization chamber (FC65) in place. The plans were delivered with Novalis Tx linear accelerator with 6 MV X-rays for both the phantoms separately. The measured dose was compared with the planned dose for both the phantoms. Mean percentage deviation between measured and planned doses was found to be 4.19 (SD 0.82) and 3.63 (SD 0.89) for cylindrical and rectangular phantoms, respectively. No significant dosimetric variation was found due to the geometry (sharp edges) of the phantom. The sharp edges of the phantom do not perturb the patient specific Rapid Arc dosimetry significantly.

No MeSH data available.


Related in: MedlinePlus