BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:Beating the Diffraction Limit in Thermoacoustic Range Verification During Particle Therapy : theory and experimental reality - Sarah Patch ( Acoustic Range Estimates) DTSTART:20230517T103000Z DTEND:20230517T113000Z UID:TALK198112@talks.cam.ac.uk DESCRIPTION:Range verification limits clinical utility of particle therapy \, which concentrates dose in space compared to x-ray radiation therapy. T reatment plans can be computed with sub-millimeter precision\, but treatme nt is delivered without a feedback loop to verify dose accuracy in vivo. T herefore\, margins of several millimeters are added and robust planning se lects beam angles that are robust to range errors. Large margins and robus t planning tend to increase collateral damage\, reducing clinical benefit. \n \;\nAdding clinical benefit requires estimating range with millimet er accuracy. But thermoacoustic emissions are bandlimited below 100 kHz\, which implies a diffraction limit of 7.5 mm. Incorporating a priori inform ation from the patient images and treatment plan can be used to estimate r ange shifts with submillimeter accuracy.\n \;\nAs we retire technical risks\, the greatest impediments to transitioning thermoacoustic range ver ification into the clinic become clinical. Mathematicians may be happy wit h a table of range shifts reported in millimeters\, but clinicians may pre fer plots of dose volume histogram\, or image volumes of dose error.\n&nbs p\;\nTime permitting\, we will also discuss sampling requirements and cont rast with other range verification techniques. Because thermoacoustic emis sions are weak\, vertical resolution is a challenge. Thermoacoustic and nu clear (PET\, prompt gamma) emissions are generated during treatment. Range verification based upon these emissions are inverse source problems. Thes e techniques can be implemented passively\, without requiring additional r adiation or contrast agents. LOCATION:Seminar Room 1\, Newton Institute END:VEVENT END:VCALENDAR