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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.


The resultant dose profiles (lateral) measured with the ion chamber. The high energy and low-energy beam lateral beam profiles were first measured in water at a depth of 1.5 cm using an A1SL ion chamber. The SSD was 85 cm. The resultant dose profiles (lateral) measured with the on board MVCT detector. The same high-energy and low-energy beams were measured. The couch was positioned such that nothing attenuated the beam except the gantry covers.
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Figure 0004: The resultant dose profiles (lateral) measured with the ion chamber. The high energy and low-energy beam lateral beam profiles were first measured in water at a depth of 1.5 cm using an A1SL ion chamber. The SSD was 85 cm. The resultant dose profiles (lateral) measured with the on board MVCT detector. The same high-energy and low-energy beams were measured. The couch was positioned such that nothing attenuated the beam except the gantry covers.

Mentions: The resultant dose profiles for high-energy and low-energy beams measured with ion chamber and MVCT detectors are shown in Figure 4. Both plots are shown in Figure 5. Vertical error bars of +/− 0.5% were added to the water tank measured normalized plot. There is excellent agreement between the two normalized plots except at negative 18 to 20 cm on one side of the plot, and there is a slight anomaly at the center of the detector-normalized plot.


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)

The resultant dose profiles (lateral) measured with the ion chamber. The high energy and low-energy beam lateral beam profiles were first measured in water at a depth of 1.5 cm using an A1SL ion chamber. The SSD was 85 cm. The resultant dose profiles (lateral) measured with the on board MVCT detector. The same high-energy and low-energy beams were measured. The couch was positioned such that nothing attenuated the beam except the gantry covers.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 0004: The resultant dose profiles (lateral) measured with the ion chamber. The high energy and low-energy beam lateral beam profiles were first measured in water at a depth of 1.5 cm using an A1SL ion chamber. The SSD was 85 cm. The resultant dose profiles (lateral) measured with the on board MVCT detector. The same high-energy and low-energy beams were measured. The couch was positioned such that nothing attenuated the beam except the gantry covers.
Mentions: The resultant dose profiles for high-energy and low-energy beams measured with ion chamber and MVCT detectors are shown in Figure 4. Both plots are shown in Figure 5. Vertical error bars of +/− 0.5% were added to the water tank measured normalized plot. There is excellent agreement between the two normalized plots except at negative 18 to 20 cm on one side of the plot, and there is a slight anomaly at the center of the detector-normalized plot.

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.