Biomedical subjects

J Jacky

Publications and source records attributed to J Jacky.

10 recordsLinked to original sources

PubMed1997

Automated planning target volume generation: an evaluation pitting a computer-based tool against human experts.

PURPOSE: Software tools are seeing increased use in three-dimensional treatment planning. However, the development of these tools frequently omits careful evaluation before placing them in clinical use. This study demonstrates the application of a rigorous evaluation methodology using blinded peer review to an automated software tool that produces ICRU-50 planning target volumes (PTVs). METHODS AND MATERIALS: Seven physicians from three different institutions involved in three-dimensional treatment planning participated in the evaluation. Four physicians drew partial PTVs on nine test cases, consisting of four nasopharynx and five lung primaries. Using the same information provided to the human experts, the computer tool generated PTVs for comparison. The remaining three physicians, designated evaluators, individually reviewed the PTVs for acceptability. To exclude bias, the evaluators were blinded to the source (human or computer) of the PTVs they reviewed. Their scorings of the PTVs were statistically examined to determine if the computer tool performed as well as the human experts. RESULTS: The computer tool was as successful as the human experts in generating PTVs. Failures were primarily attributable to insufficient margins around the clinical target volume and to encroachment upon critical structures. In a qualitative analysis, the human and computer experts displayed similar types and distributions of errors. CONCLUSIONS: Rigorous evaluation of computer-based radiotherapy tools requires comparison to current practice and can reveal areas for improvement before the tool enters clinical practice.

Expert Systems↗

PubMed1997

Consistency of three-dimensional planning target volumes across physicians and institutions.

PURPOSE: Three-dimensional treatment planning depends upon exact and consistent delineation of target volumes. This study tested whether different physicians from different institutions vary significantly in their creation of planning target volumes (PTVs). METHODS AND MATERIALS: Eight physicians from three different institutions created partial planning target volumes for nine clinical test cases. Their target volumes were evaluated qualitatively and quantitatively. Quantitative results were tested for significant differences. RESULTS: Qualitative analysis showed the physicians to vary in (a) the margin placed around the clinical target volume, (b) the margin used near critical structures, and (c) handling of concavities in the clinical target volume. Quantitative analysis showed these variations to result in statistically significant differences in the measured volume of the physicians' planning target volumes. CONCLUSIONS: Individual physicians and institutions differ significantly in their creation of planning target volumes, suggesting individual and institutional differences in the working definition for the PTV. Implications of this fact are discussed, along with areas where standardization can be improved.

Analysis of Variance↗

PubMed1995

Three dimensional planning target volumes: a model and a software tool.

PURPOSE: Three dimensional (3D) target volumes are an essential component of conformal therapy because the goal is to shape the treatment volume to the target volume. The planning target volume (PTV) is defined by ICRU 50 as the clinical target volume (CTV) plus a margin to ensure that the CTV receives the prescribed dose. The margin must include all interfractional and intrafractional treatment variations. This paper describes a software tool that automatically generates 3D PTVs from CTVs for lung cancers and immobile head and neck cancers. METHODS AND MATERIALS: Values for the interfractional and intrafractional treatment variations were determined by a literature review and by targeted interviews with physicians. The software tool is written in Common LISP and conforms to the specifications for shareable software of the Radiotherapy Treatment Planning Tools Collaborative Working Group. RESULTS: The tool is a rule-based expert system in which the inputs are the CTV contours, critical structure contours, and qualitative information about the specific patient. The output is PTV contours, which are a cylindrical expansion of the CTV. A model for creating PTVs from CTVs is embedded in the tool. The interfractional variation of setup uncertainty and the intrafractional variations of movement of the CTV (e.g., respiration) and patient motion are included in the model. Measured data for the component variations is consistent with modeling the components as independent samples from 3D Gaussian distributions. The components are combined using multivariate normal statistics to yield the cylindrical expansion factors. Rules are used to represent the values of the components for certain patient conditions (e.g., setup uncertainty for a head and neck patient immobilized in a mask). The tool uses a rule interpreter to combine qualitative information about a specific patient with rules representing the value of the components and to enter the appropriate component values for that patient into the cylindrical expansion formula. CONCLUSION: The portable software tool allows the rapid, consistent, and automatic generation of 3D PTVs from CTVs.

Head and Neck Neoplasms↗

PubMed1994

Impact of a multileaf collimator on treatment morbidity in localized carcinoma of the prostate.

PURPOSE: To evaluate the effectiveness of variable multileaf collimation, three-dimensional treatment planning, and computer-controlled conformal radiation therapy of prostate cancer. METHODS AND MATERIALS: Two hundred and forty-five patients with locally advanced prostate cancer have completed treatment over a 9-year time span using a multileaf collimator and conformal treatment techniques on the University of Washington cyclotron. All patients had three-dimensional treatment planning with computed tomography scans in the treatment position, and had treatment fields individually shaped to the target volume with a continuously variable multileaf collimator. Treatment was delivered under computer control with network transfer of the multileaf collimator settings from the treatment planning computer to the cyclotron control system. RESULTS: The multileaf collimator combined with three-dimensional treatment planning results in elegant dose distributions. These neuron dose distributions resulted in a reduced local/regional tumor failure rate with no increase in complications when compared to control treatment with photons in a randomized trial. Neutron treatment delivered at other institutions without conformal beam shaping resulted in the same improvement in local-regional tumor control rates, but was associated with a significantly higher normal tissue complication rate than seen with conformal neutron beam delivery techniques (grade 3 and 4 cumulative late normal tissue toxicity rates of 39% vs. 10%, p = 0.0007). CONCLUSIONS: Conformal treatment of prostate cancer using a multileaf collimated neutron beam results in increased local/regional tumor control rates with low normal tissue toxicities. This experience is directly applicable to the conformal treatment of prostate cancer with photons.

Humans↗

PubMed1994

Portable software tools for 3D radiation therapy planning.

PURPOSE: Produce a collection of software tools (computer programs) that support three-dimensional (3D) radiation therapy planning. The tools are not a complete 3D planning system. Instead, they work with any 3D planning system that meets certain minimal specifications. The tools assist in deriving anatomic data from images, generating target volume contours, evaluating treatment plans, and verifying accurate treatment delivery. The tools are portable: they can run without source code changes in any computing environment that provides a library of functions and data definitions called the Foundation. The Foundation couples the portable tools to the (usually nonportable) file system and dose calculation associated with a particular 3D planning system. METHODS AND MATERIALS: Tools were written at three different (geographically separated) institutions. Software developers from all three sites specified the Foundation. The programmers' interface to the Foundation is portable, but a Foundation implementation need not be portable. Each group implemented a Foundation adapted to the (different) 3D planning system used at their site. RESULTS: All tools run at all three sites without source code changes. Each Foundation was implemented in a few person-months of programming effort. The program text and documentation for the tools have been placed in the public domain. CONCLUSIONS: It is practical and economical to produce portable radiotherapy treatment planning tools. Providers of 3D planning programs should offer Foundations for their systems, so they can be used with tools. Researchers considering new computer programs should write them as tools, so they can work with any 3D planning system.

Costs and Cost Analysis↗

PubMed1994

Boron neutron capture therapy: a mechanism for achieving a concomitant tumor boost in fast neutron radiotherapy.

PURPOSE: For many years neutron radiation has been used to treat malignant disease both as fast neutron radiotherapy and as thermal neutron induced boron neutron capture therapy (BNCT). To date, these two approaches have been used independently of one another due to the large difference in neutron energies each employs. In this paper we discuss the potential application of BNCT to enhance the therapeutic effectiveness of a fast neutron radiotherapy beam. METHODS AND MATERIALS: Measurements are presented for the thermal neutron component that is spontaneously developed as the University of Washington fast neutron radiotherapy beam penetrates a water phantom. The biological effect of this thermalized component on cells "tagged" with boron-10 (10B) is modeled mathematically and the expected change in cell survival calculated. The model is then extended to estimate the effect this enhanced cell killing would have for increased tumor control. RESULTS: The basic predictions of the model on changes in cell survival are verified with in vitro measurements using the V-79 cell line. An additional factor of 10-100 in tumor cell killing appears achievable with currently available 10B carriers using our present neutron beam. A Poisson model is then used to estimate the change in tumor control this enhanced cell killing would produce in various clinical situations and the effect is sufficiently large so as to be clinically relevant. It is also demonstrated that the magnitude of the thermalized component can be increased by a factor of 2-3 with relatively simple changes in the beam generating conditions. CONCLUSION: BNCT may provide a means of enhancing the therapeutic effectiveness of fast neutron radiotherapy in a wide variety of clinical situations and is an area of research that should be aggressively pursued.

Boron Neutron Capture Therapy↗

PubMed1994

Enhancement of fast neutron beams with boron neutron capture therapy. A mechanism for achieving a selective, concomitant tumor boost.

Both fast neutron radiotherapy and boron neutron capture therapy (BNCT) have been utilized to treat malignant disease. Herein we discuss the potential of combining these treatments to enhance the effectiveness of fast neutron therapy through a concomitant BNCT boost. Using a fast neutron beam generated from a 50 MeV proton on beryllium reaction, we have determined that 0.1% of the beam per microgram of boron-10 per gram of tissue (microgram/g) can be deposited via BNCT. Our mathematical modeling predicts that BNCT enhancement of our beam will lead to an additional 1-2 logs of tumor cell kill for boron-10 concentrations of 30-50 micrograms/g. We have validated this via V-79 cell line in vitro measurements. A Poisson model estimation of how this additional cell kill will influence local tumor control, predicts that BNCT enhancement of fast neutron radiation will lead to a clinically significant improvement in outcome.

Animals↗

PubMed1990

Testing a 3-D radiation therapy planning program.

This report describes a systematic effort to test all functions of a large 3-D radiation therapy planning program, including graphics and user interaction. Previous studies in quality assurance for radiation therapy programs do not adequately address the problem of programming errors. They compare dose estimates calculated by planning programs to actual doses measured in phantoms, so they cannot distinguish programming errors from measurement errors or physical unsoundness of the beam model. Moreover, they fail to exercise graphics and user interaction functions. This report describes a different methodology: test cases are derived from the program specification, results are calculated by an independent technique, and compared to program output. Derivation of test cases is described in detail. Effectiveness of testing is assessed by reporting the number of errors revealed by testing and comparing to the number of errors discovered during routine use in five successive program versions. The size of the test set is related to the total program size, and the effort devoted to deriving and performing tests is compared to the total program development effort. We conclude that systematic testing can reveal errors that are not found by informal testing, routine program use, or comparison with measurements. However, additional errors remain that are only discovered during use. This study suggests that a typical large planning system may include more than 100 errors when it is released for clinical use. Methods for increasing testing effectiveness are recommended.

Radiotherapy, Computer-Assisted↗

PubMed1990

3-D radiation therapy treatment planning: overview and assessment.

A 3-D treatment planning system is one that can represent all radiation therapy treatment machine motions, and which can calculate the dose at any point in the patient treatment volume. As a corollary to these two requirements, a 3-D planning system must also be able to display 3-D plan geometry and doses in some useful way. This article reviews three visible aspects of 3-D planning systems: graphic displays, dose computation methods, and ease of use. It also discusses a less visible, but no less important, aspect: the underlying software engineering. Although 3-D planning systems first appeared in research institutions more than a decade ago, and potential benefits have been demonstrated, they are used only rarely in routine clinical practice. This review concludes that adequate displays and computation techniques are now available, but improved packaging, engineering, and ease of use are required before 3-D planning will be practiced widely.

Computer Graphics↗

PubMed1980

Programmable gas mixer for controlling concentration as a function of time.

A device for controlling gas concentration as a function of time according to a predetermined program is described. The apparatus is capable of producing any arbitrary time-varying gas concentration at frequencies up to about 4 Hz and can be set to ultra-low frequencies with excellent accuracy and repeatability. The apparatus consists of a single on/off solenoid valve for each gas in the mixture, all controlled by a microcomputer. The valve is rapidly pulsed open and closed, and the concentration of the corresponding gas in the mixture is proportional to the fraction of the cycle for which the valve remains open. Prior to an experiment, numerical values representing the amplitude of the desired concentration wave form at successive time intervals are entered into the computer memory. When the program is run, the microcomputer successively translates each of these values into a pulse-width modulated signal that opens and closes the valves via optically isolated relays. The processor can also translate an external control signal into the corresponding pulse train, permitting manual or automatic control of the mixture. The apparatus can be assembled in several hours from readily available components costing under $600, including the microcomputer.

Carbon Dioxide↗