MENU

Click here to

×

Are you sure ?

Yes, do it No, cancel

Retrospective Phantom Study for Evaluating the Dosimetric Effects of High Frequency Percussive Ventilation Motion for Photon Radiotherapy

I Sala1*, D Solis2 , H Ramirez3 , N Myziuk4 , M Pankuch5 , T Guerrero6 , (1) Beaumont Hospital, Royal Oak, MI, (2) Mary Bird Perkins Cancer Center, Baton Rouge , LA, (3) Northwestern Medicine Chicago Proton Center, Warrenville, IL, (4) Beaumont Hospital, Royal Oak, MI(5) Northwestern Medicine Chicago Proton Center, Warrenville, IL, (6) Beaumont Hospital, Royal Oak, MI

Presentations

(Monday, 7/15/2019) 9:30 AM - 10:00 AM

Room: Exhibit Hall | Forum 6

Purpose: We have previously demonstrated that high frequency percussive ventilation (HFPV) can significantly reduce thoracic motion; the aim of this follow up retrospective study is to investigate the potential dosimetric benefits due to gradient effects for HFPV during photon radiotherapy.

Methods: Five normal and HFPV chest wall breathing curves of volunteers that previously underwent HFPV were utilized to drive a thoracic motion phantom that held high resolution GafChromic EBT3 film. Simultaneously, a predetermined static MLC (multi leaf collimator) defined photon (6MV) field was chosen to irradiate each film with a dose of 300 cGy. All films were placed on the motion platform at 100 cm SSD with 2 cm buildup. The mean peak-to-peak amplitude of the normal and HFPV breathing curves were 19.20 mm (SD: 3.33) and 2.33 mm (SD: 0.82), respectively. We evaluated the dosimetric effects of normal and HFPV relative to static by measuring the Gamma Index, as defined by Low et al, with 3%/2mm and 10% threshold criteria. Furthermore, hot and cold spots, relative to static, for a set ROI (region of interest), were evaluated for each film.

Results: When compared to the static films, the mean Gamma Index passing rates for normal and HFPV breathing curves was 79.29% (SD: 4.65) and 99.72% (SD: 0.37), respectively. We observed hot spots that ranged between 17.14-20.00% for films irradiated with normal breathing curves and 5.71-8.57% for HFPV.

Conclusion: In this retrospective phantom study, our results suggest that high frequency percussive ventilation can significantly improve the gradient effects when utilized as a thoracic immobilization technique for photon radiotherapy.

Keywords

Not Applicable / None Entered.

Taxonomy

TH- External beam- photons: Motion management (intrafraction)

Contact Email