ABSTRACT Purpose: Dose‐volume histogram (DVH) constraints are frequently used in IMRT planning. F... more ABSTRACT Purpose: Dose‐volume histogram (DVH) constraints are frequently used in IMRT planning. For example, a DVH constraint may state that 5% (but no more) of the voxels in the planning target volume may receive a dose below the prescription level. We want to find out if the percentage of violating voxels can be reduced. We are also interested in the “price” of this reduction of violating voxels, in terms of dose to other voxels and other structures. Methods and Materials: We introduce DVH objectives into IMRT planning. Here the objective is to minimize the number of voxels that violate a given dose constraint. We then integrate DVH objectives into a multi‐criteria optimization (MCO) framework, to analyze the trade offs between DVH objectives and other planning objectives. Relaxation of mixed integer programs (MIPs) used to produce the trade off curve yields a good approximation. This is contrary to relaxation of an MIP with DVH constraints in the conventional framework. A heuristic then fine tunes the relaxation results. Results: Our methods are applied to two clinical cases with both a dose‐volume objective on the tumor and a maximum dose objective on OAR. The trade off curve between those two objectives is calculated in around 20 minutes with the relaxed MIPs compared to 40 hours with the nominal MIPs. The two techniques differ on average by only .77% tumor volume coverage and the heuristic reduces this difference to .35%. Conclusion: The use of DVH objectives (instead of DVH constraints) has the potential to lead to better trade offs in IMRT treatment planning. Surprisingly, DVH objectives simplify the numerical handling of the problem and reduce calculation times.
ABSTRACT Purpose: To demonstrate a method for what-you-see-is-what-you-get multi-criteria Pareto ... more ABSTRACT Purpose: To demonstrate a method for what-you-see-is-what-you-get multi-criteria Pareto surface navigation for step and shoot IMRT treatment planning.
We examined the potential risk of tuberculosis transmission if we modified our policy for release... more We examined the potential risk of tuberculosis transmission if we modified our policy for release of patients from the "airborne precautions" category from three negative acid-fast bacillus (AFB) smears to two, or even one. Over a 4-year period, respiratory cultures from 42 patients grew Mycobacterium tuberculosis. Of these, 36 patients (81%) had a positive AFB smear result on the first submitted specimen. One additional patient (2%) had a first smear-positive finding on the second submitted specimen, and no patients had a first smear-positive result on the third submitted specimen. Respiratory cultures from five patients (12%) grew M. tuberculosis without ever having a positive AFB smear result. These data indicate that in our institution, reducing the number of negative smears required before removal of patients from the airborne precautions category would pose little, if any, increase in the risk of spreading tuberculosis.
Volumetric modulated arc therapy (VMAT) has found widespread clinical application in recent years... more Volumetric modulated arc therapy (VMAT) has found widespread clinical application in recent years. A large number of treatment planning studies have evaluated the potential for VMAT for different disease sites based on the currently available commercial implementations of VMAT planning. In contrast, literature on the underlying mathematical optimization methods used in treatment planning is scarce. VMAT planning represents a challenging large scale optimization problem. In contrast to fluence map optimization in intensity-modulated radiotherapy planning for static beams, VMAT planning represents a nonconvex optimization problem. In this paper, the authors review the state-of-the-art in VMAT planning from an algorithmic perspective. Different approaches to VMAT optimization, including arc sequencing methods, extensions of direct aperture optimization, and direct optimization of leaf trajectories are reviewed. Their advantages and limitations are outlined and recommendations for impro...
We provide common datasets (which we call the CORT dataset: common optimization for radiation the... more We provide common datasets (which we call the CORT dataset: common optimization for radiation therapy) that researchers can use when developing and contrasting radiation treatment planning optimization algorithms. The datasets allow researchers to make one-to-one comparisons of algorithms in order to solve various instances of the radiation therapy treatment planning problem in intensity modulated radiation therapy (IMRT), including beam angle optimization, volumetric modulated arc therapy and direct aperture optimization. We provide datasets for a prostate case, a liver case, a head and neck case, and a standard IMRT phantom. We provide the dose-influence matrix from a variety of beam/couch angle pairs for each dataset. The dose-influence matrix is the main entity needed to perform optimizations: it contains the dose to each patient voxel from each pencil beam. In addition, the original Digital Imaging and Communications in Medicine (DICOM) computed tomography (CT) scan, as well as...
The main approach to smooth Pareto surface navigation for radiation therapy multi-criteria treatm... more The main approach to smooth Pareto surface navigation for radiation therapy multi-criteria treatment planning involves taking real-time averages of pre-computed treatment plans. In fluence-based treatment planning, fluence maps themselves can be averaged, which leads to the dose distributions being averaged due to the linear relationship between fluence and dose. This works for fluence-based photon plans and proton spot scanning plans. In this technical note, we show that two or more sliding window volumetric modulated arc therapy (VMAT) plans can be combined by averaging leaf positions in a certain way, and we demonstrate that the resulting dose distribution for the averaged plan is approximately the average of the dose distributions of the original plans. This leads to the ability to do Pareto surface navigation, i.e. interactive multi-criteria exploration of VMAT plan dosimetric tradeoffs.
ABSTRACT Purpose: To efficiently find quality-guaranteed treatment plans with the minimum number ... more ABSTRACT Purpose: To efficiently find quality-guaranteed treatment plans with the minimum number of beams for stereotactic body radiation therapy using RayStation.
ABSTRACT Purpose: To evaluate automated multicriteria optimization (MCO)-- designed for intensity... more ABSTRACT Purpose: To evaluate automated multicriteria optimization (MCO)-- designed for intensity modulated radiation therapy (IMRT), but invoked with limited segmentation -- to efficiently produce high quality 3D conformal treatment (3D-CRT) plans. Methods: Ten patients previously planned with 3D-CRT were replanned with a low-segment inverse multicriteria optimized technique. The MCO-3D plans used the same number of beams, beam geometry and machine parameters of the corresponding 3D plans, but were limited to an energy of 6 MV. The MCO-3D plans were optimized using a fluence-based MCO IMRT algorithm and then, after MCO navigation, segmented with a low number of segments. The 3D and MCO-3D plans were compared by evaluating mean doses to individual organs at risk (OARs), mean doses to combined OARs, homogeneity indexes (HI), monitor units (MUs), physician preference, and qualitative assessments of planning time and plan customizability. Results: The MCO-3D plans significantly reduced the OAR mean doses and monitor units while maintaining good coverage and homogeneity of target volumes. MCO allows for more streamlined plan customization. All MCO-3D plans were preferred by physicians over their corresponding 3D plans. Conclusion: High quality 3D plans can be produced using IMRT optimization technology, resulting in automated field-in-field type plans with good monitor unit efficiency. Adopting this technology in a clinic could streamline treatment plan production.
ABSTRACT Purpose: In split-course radiotherapy, a patient is treated in several stages separated ... more ABSTRACT Purpose: In split-course radiotherapy, a patient is treated in several stages separated by weeks or months. This regimen has been motivated by radiobiological considerations. However, using modern image-guidance, it also provides an approach to reduce normal tissue dose by exploiting tumor shrinkage. In this work, we consider the optimal design of split-course treatments, motivated by the clinical management of large liver tumors for which normal liver dose constraints prohibit the administration of an ablative radiation dose in a single treatment.
The purpose of this study was to evaluate automated multicriteria optimization (MCO), which is de... more The purpose of this study was to evaluate automated multicriteria optimization (MCO), which is designed for intensity modulated radiation therapy (IMRT) but invoked with limited segmentation, to efficiently produce high-quality 3-dimensional (3D) conformal radiation therapy (3D-CRT) plans. Treatment for 10 patients previously planned with 3D-CRT to various disease sites (brain, breast, lung, abdomen, pelvis) was replanned with a low-segment inverse MCO technique. The MCO-3D plans used the same beam geometry of the original 3D plans but were limited to an energy of 6 MV. The MCO-3D plans were optimized with fluence-based MCO IMRT and then, after MCO navigation, segmented with a low number of segments. The 3D and MCO-3D plans were compared by evaluating mean dose for all structures, D95 (dose that 95% of the structure receives) and homogeneity indexes for targets, D1 and clinically appropriate dose-volume objectives for individual organs at risk (OARs), monitor units, and physician preference. The MCO-3D plans reduced the mean doses to OARs (41 of a total of 45 OARs had a mean dose reduction; P < .01) and monitor units (7 of 10 plans had reduced monitor units; the average reduction was 17% [P = .08]) while maintaining clinical standards for coverage and homogeneity of target volumes. All MCO-3D plans were preferred by physicians over their corresponding 3D plans. High-quality 3D plans can be produced by use of MCO-IMRT optimization, resulting in automated field-in-field-type plans with good monitor unit efficiency. Adoption of this technology in a clinic could improve plan quality and streamline treatment plan production by using a single system applicable to both IMRT and 3D planning.
ABSTRACT Purpose: Dose‐volume histogram (DVH) constraints are frequently used in IMRT planning. F... more ABSTRACT Purpose: Dose‐volume histogram (DVH) constraints are frequently used in IMRT planning. For example, a DVH constraint may state that 5% (but no more) of the voxels in the planning target volume may receive a dose below the prescription level. We want to find out if the percentage of violating voxels can be reduced. We are also interested in the “price” of this reduction of violating voxels, in terms of dose to other voxels and other structures. Methods and Materials: We introduce DVH objectives into IMRT planning. Here the objective is to minimize the number of voxels that violate a given dose constraint. We then integrate DVH objectives into a multi‐criteria optimization (MCO) framework, to analyze the trade offs between DVH objectives and other planning objectives. Relaxation of mixed integer programs (MIPs) used to produce the trade off curve yields a good approximation. This is contrary to relaxation of an MIP with DVH constraints in the conventional framework. A heuristic then fine tunes the relaxation results. Results: Our methods are applied to two clinical cases with both a dose‐volume objective on the tumor and a maximum dose objective on OAR. The trade off curve between those two objectives is calculated in around 20 minutes with the relaxed MIPs compared to 40 hours with the nominal MIPs. The two techniques differ on average by only .77% tumor volume coverage and the heuristic reduces this difference to .35%. Conclusion: The use of DVH objectives (instead of DVH constraints) has the potential to lead to better trade offs in IMRT treatment planning. Surprisingly, DVH objectives simplify the numerical handling of the problem and reduce calculation times.
ABSTRACT Purpose: To demonstrate a method for what-you-see-is-what-you-get multi-criteria Pareto ... more ABSTRACT Purpose: To demonstrate a method for what-you-see-is-what-you-get multi-criteria Pareto surface navigation for step and shoot IMRT treatment planning.
We examined the potential risk of tuberculosis transmission if we modified our policy for release... more We examined the potential risk of tuberculosis transmission if we modified our policy for release of patients from the "airborne precautions" category from three negative acid-fast bacillus (AFB) smears to two, or even one. Over a 4-year period, respiratory cultures from 42 patients grew Mycobacterium tuberculosis. Of these, 36 patients (81%) had a positive AFB smear result on the first submitted specimen. One additional patient (2%) had a first smear-positive finding on the second submitted specimen, and no patients had a first smear-positive result on the third submitted specimen. Respiratory cultures from five patients (12%) grew M. tuberculosis without ever having a positive AFB smear result. These data indicate that in our institution, reducing the number of negative smears required before removal of patients from the airborne precautions category would pose little, if any, increase in the risk of spreading tuberculosis.
Volumetric modulated arc therapy (VMAT) has found widespread clinical application in recent years... more Volumetric modulated arc therapy (VMAT) has found widespread clinical application in recent years. A large number of treatment planning studies have evaluated the potential for VMAT for different disease sites based on the currently available commercial implementations of VMAT planning. In contrast, literature on the underlying mathematical optimization methods used in treatment planning is scarce. VMAT planning represents a challenging large scale optimization problem. In contrast to fluence map optimization in intensity-modulated radiotherapy planning for static beams, VMAT planning represents a nonconvex optimization problem. In this paper, the authors review the state-of-the-art in VMAT planning from an algorithmic perspective. Different approaches to VMAT optimization, including arc sequencing methods, extensions of direct aperture optimization, and direct optimization of leaf trajectories are reviewed. Their advantages and limitations are outlined and recommendations for impro...
We provide common datasets (which we call the CORT dataset: common optimization for radiation the... more We provide common datasets (which we call the CORT dataset: common optimization for radiation therapy) that researchers can use when developing and contrasting radiation treatment planning optimization algorithms. The datasets allow researchers to make one-to-one comparisons of algorithms in order to solve various instances of the radiation therapy treatment planning problem in intensity modulated radiation therapy (IMRT), including beam angle optimization, volumetric modulated arc therapy and direct aperture optimization. We provide datasets for a prostate case, a liver case, a head and neck case, and a standard IMRT phantom. We provide the dose-influence matrix from a variety of beam/couch angle pairs for each dataset. The dose-influence matrix is the main entity needed to perform optimizations: it contains the dose to each patient voxel from each pencil beam. In addition, the original Digital Imaging and Communications in Medicine (DICOM) computed tomography (CT) scan, as well as...
The main approach to smooth Pareto surface navigation for radiation therapy multi-criteria treatm... more The main approach to smooth Pareto surface navigation for radiation therapy multi-criteria treatment planning involves taking real-time averages of pre-computed treatment plans. In fluence-based treatment planning, fluence maps themselves can be averaged, which leads to the dose distributions being averaged due to the linear relationship between fluence and dose. This works for fluence-based photon plans and proton spot scanning plans. In this technical note, we show that two or more sliding window volumetric modulated arc therapy (VMAT) plans can be combined by averaging leaf positions in a certain way, and we demonstrate that the resulting dose distribution for the averaged plan is approximately the average of the dose distributions of the original plans. This leads to the ability to do Pareto surface navigation, i.e. interactive multi-criteria exploration of VMAT plan dosimetric tradeoffs.
ABSTRACT Purpose: To efficiently find quality-guaranteed treatment plans with the minimum number ... more ABSTRACT Purpose: To efficiently find quality-guaranteed treatment plans with the minimum number of beams for stereotactic body radiation therapy using RayStation.
ABSTRACT Purpose: To evaluate automated multicriteria optimization (MCO)-- designed for intensity... more ABSTRACT Purpose: To evaluate automated multicriteria optimization (MCO)-- designed for intensity modulated radiation therapy (IMRT), but invoked with limited segmentation -- to efficiently produce high quality 3D conformal treatment (3D-CRT) plans. Methods: Ten patients previously planned with 3D-CRT were replanned with a low-segment inverse multicriteria optimized technique. The MCO-3D plans used the same number of beams, beam geometry and machine parameters of the corresponding 3D plans, but were limited to an energy of 6 MV. The MCO-3D plans were optimized using a fluence-based MCO IMRT algorithm and then, after MCO navigation, segmented with a low number of segments. The 3D and MCO-3D plans were compared by evaluating mean doses to individual organs at risk (OARs), mean doses to combined OARs, homogeneity indexes (HI), monitor units (MUs), physician preference, and qualitative assessments of planning time and plan customizability. Results: The MCO-3D plans significantly reduced the OAR mean doses and monitor units while maintaining good coverage and homogeneity of target volumes. MCO allows for more streamlined plan customization. All MCO-3D plans were preferred by physicians over their corresponding 3D plans. Conclusion: High quality 3D plans can be produced using IMRT optimization technology, resulting in automated field-in-field type plans with good monitor unit efficiency. Adopting this technology in a clinic could streamline treatment plan production.
ABSTRACT Purpose: In split-course radiotherapy, a patient is treated in several stages separated ... more ABSTRACT Purpose: In split-course radiotherapy, a patient is treated in several stages separated by weeks or months. This regimen has been motivated by radiobiological considerations. However, using modern image-guidance, it also provides an approach to reduce normal tissue dose by exploiting tumor shrinkage. In this work, we consider the optimal design of split-course treatments, motivated by the clinical management of large liver tumors for which normal liver dose constraints prohibit the administration of an ablative radiation dose in a single treatment.
The purpose of this study was to evaluate automated multicriteria optimization (MCO), which is de... more The purpose of this study was to evaluate automated multicriteria optimization (MCO), which is designed for intensity modulated radiation therapy (IMRT) but invoked with limited segmentation, to efficiently produce high-quality 3-dimensional (3D) conformal radiation therapy (3D-CRT) plans. Treatment for 10 patients previously planned with 3D-CRT to various disease sites (brain, breast, lung, abdomen, pelvis) was replanned with a low-segment inverse MCO technique. The MCO-3D plans used the same beam geometry of the original 3D plans but were limited to an energy of 6 MV. The MCO-3D plans were optimized with fluence-based MCO IMRT and then, after MCO navigation, segmented with a low number of segments. The 3D and MCO-3D plans were compared by evaluating mean dose for all structures, D95 (dose that 95% of the structure receives) and homogeneity indexes for targets, D1 and clinically appropriate dose-volume objectives for individual organs at risk (OARs), monitor units, and physician preference. The MCO-3D plans reduced the mean doses to OARs (41 of a total of 45 OARs had a mean dose reduction; P < .01) and monitor units (7 of 10 plans had reduced monitor units; the average reduction was 17% [P = .08]) while maintaining clinical standards for coverage and homogeneity of target volumes. All MCO-3D plans were preferred by physicians over their corresponding 3D plans. High-quality 3D plans can be produced by use of MCO-IMRT optimization, resulting in automated field-in-field-type plans with good monitor unit efficiency. Adoption of this technology in a clinic could improve plan quality and streamline treatment plan production by using a single system applicable to both IMRT and 3D planning.
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Papers by David Craft