Page 217 - 2014 Printable Abstract Book
P. 217
involving hypofractionated radiotherapy (HFRT) that suggested improved outcomes with reduced
treatment times and neurological complications. However, heterogeneity in GBM across and within
patients presents a significant challenge to evaluating response to therapy and confounds the
interpretation of clinical trial results. Patient-specific tumor evolution and response to therapy can be
described quantitatively with a biomathematical proliferation-invasion model. Simulations allow for
comparison of outcomes from different radiotherapy plans in silico on a per patient and per cohort basis.
Here we present a method for conducting virtual clinical trials for glioblastoma in the context of HFRT,
although the method is applicable to a variety of therapies. We generate virtual cohorts of GBM patients
by sampling patient-specific parameters from representative distributions established from a population
actual GBM patients. Tumor growth and the effects of chemo-radiation for four experimental protocols
and the standard-of-care were simulated. Overall survival and equivalent uniform dose to healthy brain
were compared for all protocols for each cohort while the standard-of-care is compared to the population
level control. We found that there is enough inter-patient variability to result in phase I and II trials that
return contradictory results and that this approach can be used to differentiate experimental treatments
in silico before initiating and human clinical trial. The ability to conduct repeated virtual clinical trials for
a variety of cohorts is valuable with the limited availability of patients with newly diagnosed GBM for new
trials. Moreover, insights into the diversity of the patient population can be leveraged to generate power
analyses for future clinical trials.
(PS3-49) Real time measurement of the lateral beam profile and peak dose rate of a micro-planar X-ray
1
1
beam using a nano-scintillator fiber-optic dosimeter. Matthew D. Belley ; Ian N. Stanton ; Brian W.
2
1
2
2
1
2
2
Langloss ; Mike Hadsell ; Rachel Ger ; Jianping Lu ; Otto Zhou ; Sha X. Chang ; Michael J. Therien ; and
1
1
Terry T. Yoshizumi , Duke University, Durham, NC and University of North Carolina, Chapel Hill, NC
2
Microbeam radiation therapy techniques have been shown to achieve high therapeutic ratios via
the use of multiple, parallel, planar X-ray beams with lateral widths of less than ~1mm. Micro-planar X-
ray beams are difficult to characterize due to the small lateral beam dimension and the associated steep
dose gradient. Here we present a technique that utilizes a nano-crystalline scintillator fiber-optic detector
(NS-FOD) for real-time measurement obtaining the absolute dose rate and beam profile of a micro-planar
X-ray beam generated from a carbon nanotube cathode X-ray irradiator, and compare the results to
Radiochromic film. The collimated X-ray beam was generated using a carbon-nanotube cathode operated
at 160kVp. The NS-FOD detector was comprised of a nano-crystalline scintillator material, fixed on the
end of a 600 µm diameter fiber-optic. The NS-FOD light output was converted to soft tissue dose readings
by cross calibrating to an ion chamber using free-in-air and un-collimated beam geometry. The NS-FOD
was placed in a hole drilled along the central axis of a 2cm diameter phantom made of tissue equivalent
plastic, used to simulate deep tissue dose to a mouse. A motorized translation stage was used to step the
phantom and fiber-detector assembly through the collimated beam at a speed of ~4 µm/s and data was
recorded in real time at 20Hz. The peak dose rate at the center of the microbeam measured with the
nano-FOD was 1.91 ± 0.06 cGy/s, representing a 4% difference compared to Radiochromic film
measurements which yielded a dose rate of 1.83 ± 0.17 cGy/s. These results indicate that the NS-FOD
detector has the potential to be developed into a novel tool that may provide advanced dosimetry and
real time characterization of sub-millimeter sized X-ray beams.
215 | P a g e
treatment times and neurological complications. However, heterogeneity in GBM across and within
patients presents a significant challenge to evaluating response to therapy and confounds the
interpretation of clinical trial results. Patient-specific tumor evolution and response to therapy can be
described quantitatively with a biomathematical proliferation-invasion model. Simulations allow for
comparison of outcomes from different radiotherapy plans in silico on a per patient and per cohort basis.
Here we present a method for conducting virtual clinical trials for glioblastoma in the context of HFRT,
although the method is applicable to a variety of therapies. We generate virtual cohorts of GBM patients
by sampling patient-specific parameters from representative distributions established from a population
actual GBM patients. Tumor growth and the effects of chemo-radiation for four experimental protocols
and the standard-of-care were simulated. Overall survival and equivalent uniform dose to healthy brain
were compared for all protocols for each cohort while the standard-of-care is compared to the population
level control. We found that there is enough inter-patient variability to result in phase I and II trials that
return contradictory results and that this approach can be used to differentiate experimental treatments
in silico before initiating and human clinical trial. The ability to conduct repeated virtual clinical trials for
a variety of cohorts is valuable with the limited availability of patients with newly diagnosed GBM for new
trials. Moreover, insights into the diversity of the patient population can be leveraged to generate power
analyses for future clinical trials.
(PS3-49) Real time measurement of the lateral beam profile and peak dose rate of a micro-planar X-ray
1
1
beam using a nano-scintillator fiber-optic dosimeter. Matthew D. Belley ; Ian N. Stanton ; Brian W.
2
1
2
2
1
2
2
Langloss ; Mike Hadsell ; Rachel Ger ; Jianping Lu ; Otto Zhou ; Sha X. Chang ; Michael J. Therien ; and
1
1
Terry T. Yoshizumi , Duke University, Durham, NC and University of North Carolina, Chapel Hill, NC
2
Microbeam radiation therapy techniques have been shown to achieve high therapeutic ratios via
the use of multiple, parallel, planar X-ray beams with lateral widths of less than ~1mm. Micro-planar X-
ray beams are difficult to characterize due to the small lateral beam dimension and the associated steep
dose gradient. Here we present a technique that utilizes a nano-crystalline scintillator fiber-optic detector
(NS-FOD) for real-time measurement obtaining the absolute dose rate and beam profile of a micro-planar
X-ray beam generated from a carbon nanotube cathode X-ray irradiator, and compare the results to
Radiochromic film. The collimated X-ray beam was generated using a carbon-nanotube cathode operated
at 160kVp. The NS-FOD detector was comprised of a nano-crystalline scintillator material, fixed on the
end of a 600 µm diameter fiber-optic. The NS-FOD light output was converted to soft tissue dose readings
by cross calibrating to an ion chamber using free-in-air and un-collimated beam geometry. The NS-FOD
was placed in a hole drilled along the central axis of a 2cm diameter phantom made of tissue equivalent
plastic, used to simulate deep tissue dose to a mouse. A motorized translation stage was used to step the
phantom and fiber-detector assembly through the collimated beam at a speed of ~4 µm/s and data was
recorded in real time at 20Hz. The peak dose rate at the center of the microbeam measured with the
nano-FOD was 1.91 ± 0.06 cGy/s, representing a 4% difference compared to Radiochromic film
measurements which yielded a dose rate of 1.83 ± 0.17 cGy/s. These results indicate that the NS-FOD
detector has the potential to be developed into a novel tool that may provide advanced dosimetry and
real time characterization of sub-millimeter sized X-ray beams.
215 | P a g e
