SOME RECENT DEVELOPMENTS IN TREATMENTPLANNING SOFTWARE A N D METHODOLOGY FOR BNCT

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1 5 BE r SOME RECENT DEVELOPMENTS IN TREATMENTPLANNING SOFTWARE A N D METHODOLOGY FOR BNCT David W. Nigg, Floyd J. Wheeler, Daniel E. Wessol, Charles A. Wemple Idaho Nationa7 Engineering Laboratory, P.O. Box 1625, Idaho Fa77s, Idaho, USA Ray Babcock Montana State University, Bozeman, Montana, USA Jacek Capala Brookhaven Nationa7 Laboratory, Upton, NY 11973, USA Over t h e p a s t several y e a r s the Idaho National Engineering Laboratory ( I N E L ) has led the development [l-31 of a unique, internationally-recognized set o f software modules (BNCT r t p e ) f o r computional dosimetry and treatment pl anning f o r Boron Neutron Capture Therapy (BNCT). The computational c a p a b i l i t y represented by t h i s software i s e s s e n t i a l t o the proper a d m i n i s t r a t i o n of a l l forms of radiotherapy f o r cancer. Such software addresses t h e need t o perform pretreatment computation and optimization of t h e r a d i a t i o n dose d i s t r i b u t i o n i n the t a r g e t volume. T h i s permits the achievement of the optimal t h e r a p e u t i c r a t i o (tumor dose r e l a t i v e t o c r i t i c a l normal tissue dose) f o r each individual p a t i e n t v i a a systematic procedure f o r s p e c i f y i n g the appropriate i r r a d i a t i o n parameters t o be employed f o r a given t r e a t m e n t. These parameters include angle of therapy beam incidence, beam aperture and shape, and beam i n t e n s i t y as a function of p o s i t i o n a c r o s s the beam f r o n t. The INEL software i s used f o r treatment planning i n t h e c u r r e n t series of human glioma trials [ 4 ] a t Brookhaven National Laboratory (BNL) and h a s also been licensed f o r research and developmental purposes t o several o t h e r BNCT research centers i n t h e US and i n Ewope. Reconstruction of p a t i e n t geometry from medical images i n BNCT-rtpe i s based on the c a l c u l a t i o n of free-form non-uniform r a t i o n a l B-spline (NURB) s u r f a c e s f i t t e d t o t h e various t i s s u e compartments ( o r any desired subcompartments) of i n t e r e s t. W i t h t h i s method, one f i r s t o u t l i n e s the r e g i o n s of i n t e r e s t (e.g., s k i n, s k u l l, brain, t a r g e t volume, etc.) on each computer-displayed medical image plane. T h i s may be done either manually o r i n some cases automatically v i a edge d e t e c t i o n algorithms. Figure 1 shows an a x i a l Magnetic Resonance Image (MRI) scan of a glioma p a t i e n t. In t h i s case the normal anatomical regions a s w e l l - a s the tumor region and a 2-cm margin d e f i n i n g the t a r g e t volume a r e o u t l i n e d on t h e image planes. Several new f e a t u r e s a r e a v a i l a b l e f o r medical image i n p u t, manipulation, and d i s p l a y. Additional MR and Computed Tomography (CT) image format t r a n s l a t i o n capabi 1i t i es a r e incorporated a s needed in response t o cl i ent requi rements. New image colornap, c o n t r a s t, and brightness t o o l s have been developed along w i t h a v e r t i c a l l y and h o r i z o n t a l l y s c r o l l a b l e image container window.

2 Once the region outlines for all image slices are established, these representations are then mathematically combined to produce detailed equations describing the 3-D surfaces that enclose each volume of interest. The surface equations generated in the B-spline region reconstructions, in conjunction with appropriate region material descriptions, completely describe the problem and are subsequently used in a Monte Carlo radiation transport cal cul ation performed by a speci a1 i zed modul e incorporated into BNCT-rtpe. The ray-trace algorithm for the Monte Carlo calculation is based on searching nested hierarchies of bounding volumes enclosing the points of intersection of particles (neutrons or photons) with each reconstructed geometric NURBS surface describing a particular compartment o f the patient anatomy. The spline surfaces can be combined with geometric primitive surfaces to further specify the calculational geometry, if needed. Any type of tomographic medical image data can be input to BNCT rtpe. The radiation transport computational modul e within BNCT-rtpe wtl1 a1 so accept para1 1 el pi ped arrays constructed using the so-called "voxel reconstruction" technique [5], if des i red. ' --I Figure 2 illustrates some typical computed total physical dose contours registered on the original PlR image of Figure 1, which was used to construct the computational model. Thiese results are based on the assumption that the patient is treated using the Brookhaven Medical Research Reactor (BMRR) epithermal-neutron beam as it was configured at the initiation of human studies in September, In the display the boron concentration is assumed to be 15 parts per million (ppm), uniformly distributed throughout the brain. The contours are thus representative o f what would be seen by the normal tissue. The total dose includes the boron dose at 15 ppm as well as the contributions from the fast neutron component of the beam, the incident and capture photon components, the nitrogen component, as well as a fifth component that includes a felw other small contributions from various other neutron interactions. The 100% contour corresponds to approximately 9.1 cgy per minute per megawatt of EtMRR reactor power. Although BPA-f is typically present in the normal brain at about the same concentration as in the blood, -_-this agent tends to concentrate in the malignant tissue at a level that is roughly 3-4 times the blood concentration for most patients. lhus the tumor dose includes all of the background components as well as a significantly higher boron dose correspondling to the higher tumor boron concentration. The tumor dose contours can alsal be displayed since the actual treatment plan is based on tumor dose, constra,ined by normal tissue tolerance, just as in photon therapy. Dose-volume histograms for each defined volume of interest can also be constructed as needed. Efforts to include much1 faster, albeit approximate, dose computation methods in BNCT rtpe are undierway. An algorithm based on multidimensional parameter fi ttieg from precomputed kernel functions (closely-re1 ated to the so-called "pencil -beam" methlods) has be,en incorporated and has proven to be quite effective for use in dlose optimization studies prior to performing a Monte Carlo calculation for the final optimized plan for each patient. This capability should prove to be especially useful as clinical application of BNCT moves into the more coaiplicated realm of multi-port irradiations. In addition, an informal collaboration has been established with The Ohio State University to explore the utility of incorporating a computational option based on removal-diffusion theory [6]. Finally, it may be noted that the b a s i c physics modules have tieen significantly upgraded to allow incident

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4 neutron energies up t o about 100 MeV, with an e x p l i c i t treatment of r e c o i l proton t r a n s p o r t, expanding t h e u t i l i t y of this software i n t o the f i e l d of f a s t neutron radiotherapy, w i t h o r without BNCT augmentation. Acknowledgements This s t u d y was performed under the auspices of the U.S. Department o f Energy, Office of Energy Research, DOE Idaho Operations Off i ce, under Contract Number DE-AC07-94ID13223, and under Brookhaven National Laboratory Contract Number DE-ACOZ-76CH References 1. Nigg DW: Methods f o r radiation dose d i s t r i b u t i o n analysis and treatment planning i n boron neutron capture therapy. I n t. J. Rad Onc. Bio, Phys 28: , Wheeler FJ, Nigg DW: Three-dimensional radiation dose d i s t r i b u t i o n a n a l y s i s f o r boron neutron capture therapy. Nucl. Sci. Eng. 110:16-31, \. 3. Wessol DE, Wheeler FJ: Methods f o r creating and using free-form geometries i n Monte Carlo p a r t i c l e t r a n s p o r t. Nucl. Sci. Eng. 113: , Coderre J A, Bergland R, Capala J, Chadha M, Chanana AJ, Elowitz E, Joel DD, L i u HB, S l a t k i n D: Boron Neutron Capture Therapy for Glioblastoma Mu1 t i forme using p-boronophenylalanine and epithermal neutrons - T r i a l design and e a r l y c l i n i c a l results. In publication, Journal of Neuro-Oncology. 5. Zarnenhof R, Brenner 3, Yanch J, Wazer D, Madoc-Jones H. S a r i s S, Harling 0: Treatment planning f o r neutron capture therapy of glioblastoma multiforme using epithermal neutron beam from t h e MITR-I1 research r e a c t o r and Monte Carlo simu1ation.in: Allen BJ, Moore D E, Harrington B V ( e d s ), Progress In KeuiT%n Capture Therapy'for Cancer, Plenum Press, New York, NY, 1992, pp Niemkiewicz J, Blue TE: Removal-diffusion theory f o r c a l c u l a t i o n of neutron d i s t r i b u t i o n s i n BNCT. In: Barth R, Soloway A (eds), Advances i n Neutron Capture Therapy, Plenum Press, New York, NY, 1993, pp DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

5 Figure Legends 1. Axial magnetic image image o f a glioma patient showing the outlines constructed by BNCT-RTPE for the various regions o f interest, including the tumor and target regions. 2. Typical total physical absorbed dose contours in normal tissue that would be produced by the BMRR epithermal-neutron beam for a human glioma patient with a uniform brain-boron concentration o f 15 ppm. The 100% dose contour corresponds to approximately 9.1 cgy/min per MW o f BMRR power.,

6 Figure 1. Axial magnetic image of a glioma patient showing the outlines constructed by BNCT-rtpe for the various regions of interest, including the tumor and target regions. Figure 2. Typical total physical absorbed dose contours in normal tissue that would be produced by the BMRR epithermal-neutron beam for a human glioma patient with a uniform brain-boron concentration of 15 pprn. The 100% dose contour corresponds to approximately 9.1 cgy/min per MW of BMRR power.

7 Figure 1. Axial magnetic image of a glioma patient showing the outlines constructed by BNCT-rtpe for the various regions of interest, including the tumor and target regions.. - Figure 2. Typical total physical absorbed dose contours in normal tissue that would be produced by the BMFIR epithermal-neutron beam for a human glioma patient with a uniform brain-boron concentration of 15 ppm. The 100% dose contour corresponds tc approximately 9.1 sgy!rnin per MW of BMRR pcwer.