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Initial dosimetric experience with mega voltage computed tomography detectors and estimation of pre and post-repair dosimetric parameters of a first Helical Hi-Art II tomotherapy machine in India.

Kinhikar RA, Master Z, Dhote DS, Deshpande DD - J Med Phys (2009)

Bottom Line: The results of lateral beam profiles showed an excellent agreement between the two normalized plots.The output from the rotational procedure revealed 99.7% while the energy was consistent over a period of twelve months.The Hi-Art II system has maintained its calibration to within +/- 2% and energy to within +/- 1.5% over the initial twelve-month period.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Physics, Tata Memorial Centre, Parel, Mumbai 400012, India.

ABSTRACT
A Helical Tomotherapy (HT) Hi-Art II (TomoTherapy, Inc., Madison, WI, USA) has been one of the important innovations to help deliver IMRT with image guidance. On-board, mega voltage computed tomography (MVCT) detectors are used for imaging and dosimetric purpose. The two objectives of this study are: (i) To estimate the dosimetric and general capability (TomoImage registration, reconstruction, contrast and spatial resolution, artifacts-free image and dose in TomoImage) of on-board MVCT detectors. (ii) To measure the dosimetric parameters (output and energy) following major repair. The MVCT detectors also estimated the rotational output constancy well. During this study, dosimetric tests were repeated after replacing MVCT detectors and the target. fixed-gantry/fixed-couch measurements were measured daily to investigate; the system stability. Thermoluminescense dosimeter (TLD) was used during both the measurements subsequently. The MVCT image quality with old and new detectors was comparable and hence acceptable clinically. The spatial resolution was optimal and the dose during TomoImage was 2 cGy (well within the manufacturer tolerance of 4 cGy). The results of lateral beam profiles showed an excellent agreement between the two normalized plots. The output from the rotational procedure revealed 99.7% while the energy was consistent over a period of twelve months. The Hi-Art II system has maintained its calibration to within +/- 2% and energy to within +/- 1.5% over the initial twelve-month period. Based on the periodic measurements for rotational output and consistency in the lateral beam profile shape, the on-board detector proved to be a viable dosimetric quality assurance tool for IMRT with Tomotherapy. Tomotherapy was stable from the dosimetric point of view during the twelve-month period.

No MeSH data available.


A customized water tank for profile measurement with ion chamber.
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Related In: Results  -  Collection

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Figure 0002: A customized water tank for profile measurement with ion chamber.

Mentions: A customized water tank (Dimensions: 45 cm width, 75 cm length and 30 cm height) supplied by the manufacturer is shown in Figure 2. It was positioned on the patient table about 50 cm from the front end. This water tank has only two-dimensional movements (longer direction and the vertical). The A1SL ion chamber was placed into the water tank. The A17 (1.9 CC) ion chamber (Standard Imaging, Middleton, WI) in its buildup cap was used as stationary reference chamber and placed just outside the tank. A static procedure was selected with the field width 5 cm × 40 cm (all leaves open) and the high energy and low-energy beam lateral profiles were first measured in water at a depth of 1.5 cm. The source to surface distance (SSD) was 85 cm. An eight-channel electrometer (TomoElectrometer, Application Bind V 2.2) capable of measuring collected charge every 100 ms was used for measurements. The same high-energy and low-energy beams were measured using on-board MVCT detectors. The couch was positioned so that nothing attenuated the beam except the gantry covers. The water-tank-measured high-energy beam profile was divided by the water tank measured, low-energy beam profile and normalized to unity at the isocenter. Likewise, the onboard detector measured high-energy profile was divided by the low-energy profile, and normalized to unity at the isocenter.


Initial dosimetric experience with mega voltage computed tomography detectors and estimation of pre and post-repair dosimetric parameters of a first Helical Hi-Art II tomotherapy machine in India.

Kinhikar RA, Master Z, Dhote DS, Deshpande DD - J Med Phys (2009)

A customized water tank for profile measurement with ion chamber.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2805893&req=5

Figure 0002: A customized water tank for profile measurement with ion chamber.
Mentions: A customized water tank (Dimensions: 45 cm width, 75 cm length and 30 cm height) supplied by the manufacturer is shown in Figure 2. It was positioned on the patient table about 50 cm from the front end. This water tank has only two-dimensional movements (longer direction and the vertical). The A1SL ion chamber was placed into the water tank. The A17 (1.9 CC) ion chamber (Standard Imaging, Middleton, WI) in its buildup cap was used as stationary reference chamber and placed just outside the tank. A static procedure was selected with the field width 5 cm × 40 cm (all leaves open) and the high energy and low-energy beam lateral profiles were first measured in water at a depth of 1.5 cm. The source to surface distance (SSD) was 85 cm. An eight-channel electrometer (TomoElectrometer, Application Bind V 2.2) capable of measuring collected charge every 100 ms was used for measurements. The same high-energy and low-energy beams were measured using on-board MVCT detectors. The couch was positioned so that nothing attenuated the beam except the gantry covers. The water-tank-measured high-energy beam profile was divided by the water tank measured, low-energy beam profile and normalized to unity at the isocenter. Likewise, the onboard detector measured high-energy profile was divided by the low-energy profile, and normalized to unity at the isocenter.

Bottom Line: The results of lateral beam profiles showed an excellent agreement between the two normalized plots.The output from the rotational procedure revealed 99.7% while the energy was consistent over a period of twelve months.The Hi-Art II system has maintained its calibration to within +/- 2% and energy to within +/- 1.5% over the initial twelve-month period.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Physics, Tata Memorial Centre, Parel, Mumbai 400012, India.

ABSTRACT
A Helical Tomotherapy (HT) Hi-Art II (TomoTherapy, Inc., Madison, WI, USA) has been one of the important innovations to help deliver IMRT with image guidance. On-board, mega voltage computed tomography (MVCT) detectors are used for imaging and dosimetric purpose. The two objectives of this study are: (i) To estimate the dosimetric and general capability (TomoImage registration, reconstruction, contrast and spatial resolution, artifacts-free image and dose in TomoImage) of on-board MVCT detectors. (ii) To measure the dosimetric parameters (output and energy) following major repair. The MVCT detectors also estimated the rotational output constancy well. During this study, dosimetric tests were repeated after replacing MVCT detectors and the target. fixed-gantry/fixed-couch measurements were measured daily to investigate; the system stability. Thermoluminescense dosimeter (TLD) was used during both the measurements subsequently. The MVCT image quality with old and new detectors was comparable and hence acceptable clinically. The spatial resolution was optimal and the dose during TomoImage was 2 cGy (well within the manufacturer tolerance of 4 cGy). The results of lateral beam profiles showed an excellent agreement between the two normalized plots. The output from the rotational procedure revealed 99.7% while the energy was consistent over a period of twelve months. The Hi-Art II system has maintained its calibration to within +/- 2% and energy to within +/- 1.5% over the initial twelve-month period. Based on the periodic measurements for rotational output and consistency in the lateral beam profile shape, the on-board detector proved to be a viable dosimetric quality assurance tool for IMRT with Tomotherapy. Tomotherapy was stable from the dosimetric point of view during the twelve-month period.

No MeSH data available.