Inverse radiation treatment planning using the Dynamically Penalized Likelihood method

Llacer, J.

doi:10.1118/1.597961

Cited by 87 publications

(71 citation statements)

References 18 publications

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“…In other words, one can think of each beam as being divided into a large number of smaller beamlets of radiation. The weights of these beamlets can be optimized so as to produce the most favorable dose distribution [70,67,6,2,29,30,31,50,61,60,43,15,12,20]. Figure 3.1 shows three dose distributions produced using IMRT with seven equispaced beam angles.…”

Section: Imrt and Tomotherapymentioning

confidence: 99%

Optimizing the Delivery of Radiation Therapy to Cancer Patients

Shepard¹,

Ferris²,

Olivera³

et al. 1999

SIAM Rev.

219

163

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Abstract. In the field of radiation therapy, much of the research is aimed at developing new and innovative techniques for treating cancer patients with radiation. In recent years, new treatment machines have been developed that provide a much greater degree of computer control than was available with the machines of previous generations. One innovation has been the development of an approach called "tomotherapy." Tomotherapy can be defined as computer-controlled rotational radiotherapy delivered using an intensity-modulated fan beam of radiation. The successful implementation of the new delivery techniques requires the development of a suitable approach for optimizing each patient's treatment plan. One of the challenges is to quantify optimality in radiation therapy. We have tested a variety of objective functions and constraints in pursuit of a formulation that performs well for a wide variety of disease sites. An additional challenge stems from the sizable amount of data and the large number of variables that are involved in each optimization. This paper presents several approaches to optimizing treatment plans in radiation therapy, and the advantages and disadvantages of a number of formulations are explored.

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Section: Imrt and Tomotherapymentioning

confidence: 99%

Optimizing the Delivery of Radiation Therapy to Cancer Patients

Shepard¹,

Ferris²,

Olivera³

et al. 1999

SIAM Rev.

219

163

View full text Add to dashboard Cite

show abstract

“…The planner first chose the beam orientations by trying to spread the beams over a 2 steradian solid angle as evenly as possible without hitting any critical structures. The beams were then optimized using the maximum likelihood minimization, which dynamically changes the beam modulation to reduce a cost function based on the logarithm of dose ratios [14] . The dose-volume criterion for PTV was always 100% prescription dose (600 cGy) covering 100% volume; an organ at risk (OAR) was constrained to receive a maximum of 100% prescription dose when it involved the PTV.…”

Section: Treatment Planningmentioning

confidence: 99%

Hypofractionated Stereotactic Radiotherapy Using Intensity-Modulated Radiotherapy in Patients with One or Two Brain Metastases

Narayana

Chang

Yenice

et al. 2006

Stereotact Funct Neurosurg

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Purpose: A small fraction of patients with 1–2 brain metastases will not be suitable candidates to either surgical resection or stereotactic radiosurgery (SRS) due to either their location or their size. The objective of this study was to determine the local control, survival, patterns of relapse and the incidence of brain injury following a course of hypofractionated stereotactic radiotherapy while avoiding upfront whole brain radiation therapy (WBRT) in this subgroup of patients. Methods: A Gill-Thomas removable head frame system was used for immobilization. Brain LAB software with dynamic multileaf collimator hardware was used to design and deliver an intensity-modulated radiation therapy treatment plan. A dose of 600 cGy was prescribed to the 100% isodose line that would encompass the lesion with a 3-mm margin. A total dose of 3,000 cGy was delivered in 5 fractions using 2 fractions per week. The patients were followed with neurological examination and serial MRI images done every 3 months following the procedure. Results: Twenty patients have been treated using this fractionation schedule since April 2004. The 1-year local control at the site of original disease is 70%. The complete response, partial response and stable disease at the last follow-up were 15, 30 and 45%, respectively. Two patients had local recurrence at the site of original disease, while 5 had evidence of leptomeningeal disease. Two additional patients developed new brain metastases, resulting in a 1-year brain relapse-free survival of 36% following this approach. The median overall survival was 8.5 months. Three patients (15%) developed steroid dependency lasting 3 months or longer following the procedure. Four patients (20%) needed WBRT as salvage following this approach. Conclusions: The preliminary results of hypofractionated SRS are comparable to both surgery and SRS data for solitary brain metastases in terms of local control and overall survival with acceptable morbidity in this cohort of unfavorable patients.

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“…The algorithm itself is based on a maximum likelihood estimator (MLE) method of statistical parameter estimation used initially in image reconstruction. The relationship between the MLE and DPL is described in detail by Llacer 24 . The target function used in the algorithm is adapted from a PET image reconstruction algorithm developed by Shepp and Vardi 25 , 26 .…”

Section: Methodsmentioning

confidence: 99%

Patient specific quality assurance for the delivery of intensity modulated radiotherapy

Agazaryan

Solberg

DeMarco

2003

J Applied Clin Med Phys

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A patient specific quality assurance program has been developed to facilitate the clinical implementation of intensity modulated radiotherapy (IMRT) delivered using a micro‐multileaf collimator. The methodology includes several dosimetric tasks that are performed prior to the treatment of each patient. Film dosimetry is performed for each individual field and for the multifield composite plan. Individual field measurements are performed at a depth of 5 cm in a water equivalent slab phantom; export of dose calculations from the treatment planning system is similarly specified. For the composite distribution, parameters from the patient plan are applied to an IMRT phantom, and film is exposed in an axial orientation. Distributions are compared with the aid of software developed for the specific tasks. The measured and calculated dose distributions can be superimposed and positioned graphically using move, rotate, and mirror tools, as well as by specifying isocenter coordinates and using fiducial marks. Horizontal and vertical profiles are available for analysis. Dose difference, distance‐to‐agreement, and γ index, the minimum scaled multidimensional distance between a measurement and a calculation point determined in combined dose and physical distance space, are calculated along a specified isodose line and displayed. γ provides an excellent measure of disagreement between measurement and calculation for complex intensity distributions. We specify 3% dose difference and 3 mm distance as our scaling acceptability criteria. Absolute dosimetry for each composite plan is performed using an ionization chamber. To date, excellent agreement between measurements and calculations has been observed. © 2003 American College of Medical Physics.PACS number(s): 87.53.–j, 87.66.–a

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Inverse radiation treatment planning using the Dynamically Penalized Likelihood method

Cited by 87 publications

References 18 publications

Optimizing the Delivery of Radiation Therapy to Cancer Patients

Optimizing the Delivery of Radiation Therapy to Cancer Patients

Hypofractionated Stereotactic Radiotherapy Using Intensity-Modulated Radiotherapy in Patients with One or Two Brain Metastases

Patient specific quality assurance for the delivery of intensity modulated radiotherapy

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