Abstract
BackgroundPatient-specific dose verification for treatment planning in helical tomotherapy is routinely performed using a homogeneous virtual water cylindrical phantom of 30 cm diameter and 18 cm length (Cheese phantom). Because of this small length, treatment with total marrow irradiation (TMI) requires multiple deliveries of the dose verification procedures to cover a wide range of the target volumes, which significantly prolongs the dose verification process. We propose a fast, simple, and informative patient-specific dose verification method which reduce dose verification time for TMI with helical tomotherapy.MethodsWe constructed a two-step solid water slab phantom (length 110 cm, height 8 cm, and two-step width of 30 cm and 15 cm), termed the Whole Body Phantom (WB phantom). Three ionization chambers and three EDR-2 films can be inserted to cover extended field TMI treatment delivery. Three TMI treatment plans were conducted with a TomoTherapy HiArt Planning Station and verified using the WB phantom with ion chambers and films. Three regions simulating the head and neck, thorax, and pelvis were covered in a single treatment delivery. The results were compared to those with the cheese phantom supplied by Accuray, Inc. following three treatment deliveries to cover the body from head to pelvis.ResultsUse of the WB phantom provided point doses or dose distributions from head and neck to femur in a single treatment delivery of TMI. Patient-specific dose verification with the WB phantom was 62% faster than with the cheese phantom. The average pass rate in gamma analysis with the criteria of a 3-mm distance-to-agreement and 3% dose differences was 94% ± 2% for the three TMI treatment plans. The differences in pass rates between the WB and cheese phantoms at the upper thorax to abdomen regions were within 2%. The calculated dose agreed with the measured dose within 3% for all points in all five cases in both the WB and cheese phantoms.ConclusionsOur dose verification method with the WB phantom provides simple and rapid quality assurance without limiting dose verification information in total marrow irradiation with helical tomotherapy.
Highlights
Patient-specific dose verification for treatment planning in helical tomotherapy is routinely performed using a homogeneous virtual water cylindrical phantom of 30 cm diameter and 18 cm length (Cheese phantom)
Helical tomotherapy offers a high intensity modulated beam with multileaf collimator while translating the couch into the gantry [1,2]. This allows the delivery of an intensity modulated beam for the treatment of very long targets, such as in total body irradiation (TBI) and total marrow irradiation (TMI) [3,4,5,6,7,8,9,10,11]
The cheese phantom made of Virtual waterTM is a cylindrical phantom of 15 cm radius and 18 cm length which is cut into two semi cylindrical halves where a sheet of film can lie along the central axis of the phantom (Figure 1 (a))
Summary
The doses were recalculated in the phantom by using the sinogram from the original TMI planning in human body This recalculation was based on the image value-to-density calibration (IVDC) table consisting of 13 different density plugs which was used for the patient dose calculation. These three DQA treatment procedures were delivered to the cheese phantom as a conventional method. The DQA procedure was delivered to the WB phantom and point doses and planer dose distributions were measured by the ionization chambers and EDR-2 films, respectively. Mann–Whitney U test using Dr SPSS II software (IBM, New York, NY)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
