Purpose: To demonstrate an objective approach to determining if a negative report from the Radiological Physics Center (RPC) of greater than 10% error is valid or has clinical significance. Methods: The discrepancy involved the clinical activity (mgRaEq) of Cs‐137 sources, some manufactured by 3M and some by Amersham. Measurements were made in the proprietary RPC Well Counter calibrated by the MD Anderson ADCL and our Well Counter (CNMC, Model 44D) calibrated by the same laboratory as well as the University of Wisconsin ADCL. In addition, we possess an Amersham Cs‐137 Check Source that had been calibrated by the UW‐ADCL in 2002. All clinical sources were checked in both Well Counters on the first visit. One clinical source and the Check Source were measured in a second visit that occurred 51 days later. Results: On the initial RPC visit, 9 of 25 sources had a minimum of an 8% discrepancy between the RPC and the Institution, with a maximum of 11%. Contributing errors included using the incorrect straw position by us, an unexplained 2.3% error in the RPC data identified 73 days post‐visit, a 2% variation in Chamber Factors for our Well Counter from the two ADCL's. When we use the 2004 value of Air Kerma Strength for the Check Source to determine a Calibration Factor of the Well Counter, all sources were within 0.5% of their decayed value established in 2002. Conclusions: This work emphasizes the value of having simple Constancy Check systems in a Quality Assurance program as ‘Accuracy’ has error bars. The disagreement in calibration data between the ADCL Laboratories, which was at the 2% maximum quoted in their Calibration Reports, is a reminder that there is uncertainty in measurements. Constancy Checks allow one to sort out discrepancies and to answer challenges to the validity of your program.

Helical tomotherapy is a relatively new modality with integrated treatment planning and delivery hardware for radiation therapy treatments. In view of the uniqueness of the hardware design of the helical tomotherapy unit and its implications in routine clinical practice, the Therapy Physics Committee (TPC) of the American Association of Physicists in Medicine (AAPM) commissioned Task Group 148 (TG‐148) to review this modality and make recommendations for quality assurance related methodologies. This report summarizes the findings of the Task Group and aims to provide the practicing clinical medical physicist with the insight into the technology that is necessary to establish an independent and comprehensive quality assurance program for a helical tomotherapy unit. In this task group report an overview of the TomoTherapy system and its unique aspects is provided. Delivery, imaging, and treatment planning quality assurance are discussed in three separate chapters of this report. Lastly quality assurance aspects are summarized according to their recommended frequency.

History: Helical tomotherapy is a relatively new modality with integrated imaging, planning and delivery hardware for radiation therapy treatments. In view of the unique hardware design and its implications for routine quality assurance, the Therapy Physics Committee (TPC) of the AAPM commissioned Task Group 148 to review this modality and to make quality assurance recommendations. General Outline: Initial chapters provided a brief overview of the technology and describe unique aspects of the technology. These chapters are followed by three chapters that are dedicated to the delivery, imaging, and planning aspects. A final chapter summarizes the QA recommendations and details daily, monthly, quarterly, and annual procedures. Major Highlights: This report is designed to provide guidance to the physicist that is charged with establishing a routine QA program for helical tomotherapy. Since the imaging and treatment planning aspects are intimately connected to the physical machine hardware, each of these aspects is covered in this report such that TG-148 provides comprehensive guidelines. Implementation Plan: The summary chapter list daily, monthly, quarterly, and annual tests. This chapter is designed to facilitate the implementation of the recommended QA procedures. Timeline for the Report Release: This task group was submitted in February 2010 to the Medical Physics Journal for review. Conflict of Interest: Gustavo Olivera is an employee of TomoTherapy, Inc.; John Balog owns TomoTherapy stock; Katja Langen hold a research agreement with TomoTherapy, Inc. Learning Objectives: 1. Understand the unique aspects of helical tomotherapy 2. Understand QA aspects of the delivery, imaging, and planning components of helical tomotherapy 3. Implement a routine QA program for helical tomotherapy

Purpose: To evaluate a Web‐based Quality Assurance tool for maintaining the clinical integrity of the Tomotherapy machine. Method and Materials: This tool takes advantage of the output of the two distinct ion chamber systems on the Tomotherapy machine. One is the standard sealed ion chamber that resides in the head of a machine near the primary collimators and is used to calculate Monitor Units. The other is a set of pressurized Xenon detectors that are used for imaging. Both systems monitor ionizations independently and are rigidly attached so that their geometry is constant regardless of the orientation of the beam on the gantry which makes possible testing for both static and rotational modes. The collected data can be reviewed via a Web page and a downloadable Report in PDF format is available within seconds after collection of the data. Results: As an example, one performs a 200 second rotational delivery with the couch removed from the beam. The data are analyzed in both an integrated and pulse‐by pulse methodology to determine consistency between the two chamber systems, changes in output and changes in energy. The collected information is evaluated relative to a standard delivery created during machine commissioning. Comparison to standard ion chamber measurements in phantom under static conditions indicate that the analyses are consistent for calibration and more sensitive to energy changes than percentage depth dose measurements made in phantom. Additional information about the machine's performance is identified easily. Conclusion: New technology offers an opportunity to perform standard Quality Assurance tests in a new manner. The simple test described here is more sensitive and performed more quickly than traditional methodology. Other tests are possible. Conflict of Interest: Three authors are employees of Tomotherapy, Inc.

To assess long-term biochemical control and toxicity rates in patients with localized prostate cancer treated with a moderately hypofractionated IMRT approach. The study includes a total of 596 patients treated with full course IMRT (NOMOS system), utilizing a moderately hypofractionated schedule, i.e. mean dose of 7680 cGy at 2.19 cGy per fraction over 35 fractions. IMRT was not used as a boost approach. All patients were treated in the prone position, immobilized using a Vac-Lok bag and carrier-box system. Rectal balloon inflated with 100 cc of air was used for prostate gland immobilization during daily treatment. High-risk patients also received two years and four months of androgen deprivative therapy. Median follow-up was 48 months (3.7 months to 110 months). Biochemical failures were study endpoints, using both the first ASTRO consensus (1996)1 “three consecutive rise after a nadir” definition (F-bRFS) and the second ASTRO consensus (2005)2 “nadir + 2 ng/ml” definition (S-bRFS). RTOG scoring system was used to assess toxicity. The 5-year F-bRFS and S-bRFS rates were 92.3% and 92.8% for all cases respectively. For low, intermediate and high risk categories, the 5-year F-bRFS were 95.9%, 94.1% and 79.9%. The corresponding 5-year S-bRFS were 97.4%, 92.9% and 81.9%, respectively. Pre-treatment PSA, Gleason combined score and clinical stage predict both F-bRFS and S-bRFS. ≥ grade 2 and ≥ grade 3 GI toxicities at 5 years were 8.5% and 1.2% respectively. ≥ grade 2 and ≥ grade 3 GU toxicities at 5 years were 9.4% and 1.1%. With a median follow-up of 48 months, the long-term results after moderate dose hypofractionation IMRT are excellent. Late GI and GU toxicities are acceptable. This may be an alternative dose escalation schedule in the treatment of localized prostate cancer.1.Int J Radiat Oncol Biol Phys. 1997;37 (5):1035–1041.2.Int J Radiat Oncol Biol Phys. 2006;65 (4):965–974.

The use of an air-filled rectal balloon has been shown to decrease prostate motion during prostate radiotherapy. However, the perturbation of radiation dose near the air-tissue interfaces has raised clinical concerns of underdosing the prostate gland. The aim of this study was to investigate the dosimetric effects of an air-filled rectal balloon on the rectal wall/mucosa and prostate gland. Clinical rectal toxicity and dose-volume histogram (DVH) were also assessed to evaluate for any correlation. A film phantom was constructed to simulate the 4-cm diameter air cavity created by a rectal balloon. Kodak XV2 films were utilized to measure and compare dose distribution with and without air cavity. To study the effect in a typical clinical situation, the phantom was computed tomography (CT) scanned on a Siemens DR CT scanner for intensity-modulated radiation therapy (IMRT) treatment planning. A target object was drawn on the phantom CT images to simulate the treatment of prostate cancer. Because patients were treated in prone position, the air cavity was situated superiorly to the target. The treatment used a serial tomotherapy technique with the Multivane Intensity Modulating Collimator (MIMiC) in arc treatment mode. Rectal toxicity was assessed in 116 patients treated with IMRT to a mean dose of 76 Gy over 35 fractions (2.17-Gy fraction size). They were treated in the prone position, immobilized using a Vac-Loktrade mark bag and carrier-box system. Rectal balloon inflated with 100 cc of air was used for prostate gland immobilization during daily treatment. Rectal toxicity was assessed using modifications of the Radiation Therapy Oncology Group (RTOG) and late effects Normal Tissue Task Force (LENT) scales systems. DVH of the rectum was also evaluated. From film dosimetry, there was a dose reduction at the distal air-tissue interface as much as 60% compared with the same geometry without the air cavity for 15-MV photon beam and 2x2-cm field size. The dose beyond the interface recovered quickly and the dose reductions due to air cavity were 50%, 28%, 11%, and 1% at 2, 5, 10, and 15 mm, respectively, from the distal air-tissue interface. Evaluating the dose profiles of the more clinically relevant situation revealed the dose at air-tissue interface was approximately 15% lower in comparison to that without an air cavity. The dose built up rapidly so that at 1 and 2 mm, there was only an 8% and 5% differential, respectively. The dosimetric coverage at the depth of the posterior prostate wall was essentially equal with or without the air cavity. The median follow-up was 31.3 months. Rectal toxicity profile was very favorable: 81% (94/116) patients had no rectal complaint while 10.3% (12/116), 6.9% (8/116), and 1.7% (2/116) had grade 1, 2, and 3 toxicity, respectively. There was no grade 4 rectal toxicity. DVH analysis revealed that none of the patients had more than 25% of the rectum receiving 70 Gy or greater. Rectal balloon has rendered anterior rectal wall sparing by its dosimetric effects. In addition, it has reduced rectal volume, especially posterior and lateral rectal wall receiving high-dose radiation by rectal wall distension. Both factors may have contributed to decreased rectal toxicity achieved by IMRT despite dose escalation and higher than conventional fraction size. The findings have clinical significance for future very high-dose escalation trials whereby radiation proctitis is a major limiting factor.

Purpose: To identify the pertinent issues to be addressed in successfully implementing IMRT using sequential tomotherapy into clinical reality and presenting the maturation of quality assurance (QA) programs for both the delivery system and patient treatments that allow routine clinical use of the system.Methods and Materials: Initially, a cubic phantom containing silver halide film was exposed to the entire treatment before patient treatment. The processed films were digitized with a laser densitometer and the dose distributions were compared with that generated by the planning system. Later, software that calculates the dose delivered to any phantom employing the intensity patterns developed in the inverse planning system for an individual patient was implemented for point checks of dose. A measurement phantom for use with this software was developed and evaluated on a large number of patients. Invasive fixation was used for all cranial patients initially. To use sequential tomotherapy for other sites and larger targets, noninvasive immobilization systems using two types of thermoplastic masks for cranial targets and reusable, evacuated body cradles were evaluated for positional accuracy and suitability for use with port films for patient QA.Results: The program for equipment validation is divided into daily, weekly, and monthly programs that add only small amounts of time to routine QA programs. For the first 15 patients treated with this modality, the maximum dose measured on the film was within 5% of that predicted by the planning computer. The prescription isodose line was measured in the anteroposterior and lateral dimensions and the average discrepancy between measured and predicted was less than 2 mm. For an isodose line between 50% and 70% of the prescribed dose, the agreement was better than 3 mm. Success with the volume QA program was followed by a point check QA program that reduced the time required for individual patient QA from days to hours. Phantom measurements compared with computer predictions for 588 data points resulted in only 8% being outside a +/-5% criterion. These cases were identified and allow a further reduction in the frequency of tests. Thermoplastic mask materials have adequate restraint characteristics for use with the system and port films on 21 patients resulted in one standard deviation = 1.3 mm. Body cradles are less accurate and require more frequent port films. A QA system that reduces the frequency of port films was developed.Conclusion: The evolution of sequential tomotherapy in our department has been from a maximum of 3 cranial patients per day with invasive fixation to 60 patients per day for treatment of cranial, head-and-neck, and prostate tumors using different immobilization techniques. With proper preparation and refinement of tools used in commissioning and validation, sequential tomotherapy IMRT can become a routine clinical treatment modality. (C) 2003 Elsevier Inc.

Purpose/Objective: Endorectal balloons are being used for prostate immobilization during radiation. One concern is patient tolerance during the course of radiotherapy. This study’s aim is to assess patient tolerance and acute rectal toxicity of an endorectal balloon used for prostate immobilization during the delivery of IMRT for prostate cancer over 7 weeks. Materials/Methods: A review of 422 patients undergoing primary radiotherapy for the treatment of prostate cancer from October 1997 to November 2001 was performed. IMRT was routinely offered to all patients. The following factors were assessed: age, reason for four field technique, the presence of pretreatment ano-rectal disease, treatment break (reason and duration), development of acute rectal toxcities (severity, date and duration), Lidocaine jelly use, oral and topical prescriptions, the mean dose, number of arcs for IMRT and decrease in the balloon volume. The patients received a mean dose of 77Gy in 35 fractions over 7 weeks with no rectal block. The treatment technique has been described previously (Teh, et al., IJROBP,49(3):705–712). Results: Of the 422 patients, 396/422 (93.8%) underwent IMRT with a rectal balloon and 26/422 (6.2%) were treated with four-field technique without a balloon. Age between the two groups was not statistically different (p = 0.319). The mean age of the 422 patients was 71.8 years (50-88). Age was not related to the development of rectal toxicity (p=0.526). The most common reason for patients not undergoing IMRT with a balloon was personal preference 16/26 (61.5%) followed by obesity 4/26 (15.4%), arthritis 3/26 (11.5%), Parkinson’s disease 1/26 (3.8%), irritable bowel syndrome 1/26 (3.8%) and anal stenosis 1/26 (3.8%). The reasons for conventional treatment changed with time. Initially, patient preference dominated, but now practical issues predominate. The last patient to refuse was in July, 1999. 28 of 396 (7.1%) patients had pre-existing ano-rectal disease. 17 of 396 patients (4.3%) required Lidocaine jelly with insertion of the balloon. RTOG grade 1 rectal toxicity occurred in 54/396 (13.6%). RTOG grade 2 rectal toxicity occurred in 74/396 (18.7%). No RTOG grade 3 or 4 rectal toxicities occurred. When the grade 2 toxicities were separated by prescription, we found topical anal medications (e.g.,Anusol HC) constituted 47/74 (63.3%) and anti-diarrheal medications 27/74 (36.7%). The number of treatment arcs did not correlate with the development of rectal toxicity. Six of the 28 patients (21.4%) with pre-treatment ano-rectal disease used Lidocaine jelly, 2/28 (7.1%) had grade 1 and 12/28 (42.9%) the grade 2 toxicities. 50% of patients with pretreatment ano-rectal disease developed rectal toxicities over the course of 7 weeks of treatment. When these patients were excluded, 368 patients remained. 50 of these 368 (13.6%) had grade 1 and 61 (16.3%) had grade 2 toxicities. Three of 396 (0.8%) patients required a reduction in the volume of the balloon to 50cc. 393/396 (99.2%) tolerated 100cc. Rectal toxicity occurred most frequently in the third, fourth, fifth, or sixth week of treatment; 19.5%, 20.8%, 18.2%, 16.9% respectively. The duration of the toxicity measured lasted 1 week, 35.2%, 2 weeks, 31.0%, 3 weeks 15.5%, 4 weeks, 11.3%, 5 weeks, 4.2%, and 6 weeks 2.8%. The number of arcs did not correlate with rectal toxicity. No patient required a treatment break secondary to anal irritation. None of the treatment breaks were associated with ano-rectal toxicity. Conclusions: The vast majority of patients, 393/396 (99.2%), tolerated a 100cc endorectal immobilization balloon for IMRT. No patients stopped treatment because of ano-rectal toxicity. Currently, the most common reason for patients receiving conventional four-field therapy is because they are obese. The rate of acute ano-rectal toxicity was acceptable with no grade 3 or 4 toxicities. Most grade 2 ano-rectal toxicities, 63.4%, were related to anal irritation and 36.7% to diarrhea. Duration of the toxicities typically was 1 to 2 weeks. One caution was that 50% of patients with pre-treatment ano-rectal disease developed toxicity, 42.9% required medication.

A prostate treatment immobilization system was evaluated with respect to setup errors and efficiency for a specific treatment setup. Prostate patients were treated in the prone position with a rectal catheter using the NOMOS intensity modulated radiotherapy system. Immobilization and setup consisted of a Vac-Loktrade mark bag (MED-TEC, Orange City, IO) fitted within a registration carrier box where patients were aligned to the bag using skin marks along the lower leg. Daily setup errors were analyzed using lateral portal films, registration plates mounted to the carrier box, and the pubic symphasis as a bony reference. Two studies were conducted to evaluate setup technique. In the first study, patient setup required 3-5 minutes for patient positioning and the corresponding superior/inferior errors were found to have a standard deviation of 3.5 mm. In the second study, the technique standards were reduced to allow for faster setup times and, consequently, larger errors; setup times were 1-2 minutes and the mean and standard deviation errors were approximately 2 and 5 mm, respectively.

We apply the concept of equivalent uniform dose (EUD) to our data set of model distributions and intensity modulated radiotherapy (IMRT) treatment plans as a method for analyzing large dose inhomogeneities within the tumor volume. For large dose nonuniformities, we find that the linear‐quadratic based EUD model is sensitive to the linear‐quadratic model parameters, α and β, making it necessary to consider EUD as a function of these parameters. This complicates the analysis for inhomogeneous dose distributions. EUD provides a biological estimate that requires interpretation and cannot be used as a single parameter for judging an inhomogeneous plan. We present heuristic examples to demonstrate the dose volume effect associated with EUD and the correlation to statistical parameters used for describing dose distributions. From these examples and patient plans, we discuss the risk of incorrectly applying EUD to IMRT patient plans.PACS number(s): 87.53.Tf

Intensity-modulated radiation therapy (IMRT) is a term applied to a new technology that uses nonuniform radiation beams to achieve conformal dose distributions. This article reviews the use of a commercial system, the Peacock system, which uses a special multileaf collimator (MIMiC) to deliver the dose distribution using arc therapy and segmented fields, similar to a moving strip. Although initially designed for stereotactic radiosurgery, this system has been employed to treat various body sites. More than 300 patients have been treated at our institution in the past 4 years, mainly for cranial, head-and-neck, and prostate tumors. Presently, we treat 40 to 45 patients per day with this technology using two linear accelerators operating with 10 MV and 15 MV x-rays, as Peacock has become a standard therapy procedure. Cases are presented that show the unique ability of IMRT to deliver conformal dose distributions. Why this type of technology can become a standard procedure and why it is cost-effective therapy for both the institution and the patient are discussed.

Intensity-modulated beam radiotherapy (IMRT) delivers a highly conformal, three-dimensional (3-D) distribution of radiation doses that is not possible with conventional methods. When administered to patients with head and neck tumors, IMRT allows for the treatment of multiple targets with different doses, while simultaneously minimizing radiation to uninvolved critical structures such as the parotid glands, optic chiasm, and mandible. With 3-D computerized dose optimization, IMRT is a vast improvement over the customary trial-and-error method of treatment planning. We retrospectively reviewed the charts of the first 28 head and neck patients at our institution who were treated with IMRT. All had head and neck neoplasms, including squamous cell carcinoma, adenoid cystic carcinoma, paraganglioma, and angiofibroma. Total radiation doses ranged from 1,400 to 7,100 cGy, and daily doses ranged from 150 to 400 cGy/day. A quality assurance system ensured that computer-generated dosimetry matched film dosimetry in all cases. For midline tumors, this system allowed us to decrease the dose to the parotid glands to less than 3,000 cGy. The incidence of acute toxicity was drastically lower than that seen with conventional radiotherapy delivery to similar sites. This is the first report of the application of IMRT strictly to head and neck neoplasms. We discuss the indications, technique, and initial results of this promising new technology. We also introduce the concept of the Simultaneous Modulated Accelerated Radiation Therapy boost technique, which has several advantages over other altered fractionation schemes.

Medical PhysicsVolume 24, Issue 8 p. 1323-1324 Comment on “Reporting and analyzing dose distributions: A concept of equivalent uniform dose” [Med. Phys. 24, 103–109 (1997)] John E. McGary, John E. McGary Department of Radiology, Baylor College of Medicine, Houston, Texas 77030Search for more papers by this authorWalter Grant III, Walter Grant III Department of Radiology, Baylor College of Medicine, Houston, Texas 77030Search for more papers by this authorShaio Y. Woo, Shaio Y. Woo Department of Radiology, Baylor College of Medicine, Houston, Texas 77030Search for more papers by this authorE. Brian Butler, E. Brian Butler Department of Radiology, Baylor College of Medicine, Houston, Texas 77030Search for more papers by this author John E. McGary, John E. McGary Department of Radiology, Baylor College of Medicine, Houston, Texas 77030Search for more papers by this authorWalter Grant III, Walter Grant III Department of Radiology, Baylor College of Medicine, Houston, Texas 77030Search for more papers by this authorShaio Y. Woo, Shaio Y. Woo Department of Radiology, Baylor College of Medicine, Houston, Texas 77030Search for more papers by this authorE. Brian Butler, E. Brian Butler Department of Radiology, Baylor College of Medicine, Houston, Texas 77030Search for more papers by this author First published: 04 June 1998 https://doi.org/10.1118/1.598024Citations: 12 0094-2405, Medical Physics, 24, 103 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. REFERENCES 1A. Niemierko, “Reporting and analyzing dose distributions: A concept of equivalent uniform dose,” Med. Phys. 24, 103– 109 (1997). Citing Literature Volume24, Issue8August 1997Pages 1323-1324 ReferencesRelatedInformation

PURPOSE:The goal of modulated-beam conformal therapy is to reduce the dose to healthy tissue and sensitive structures around a uniformly irradiated target volume. Multiple intensity-modulated fields offer improved tissue-sparing dose distributions. New computer-based systems for planning and delivering such treatments may soon be available from different commercial sources that will make the formulation of an intensity-modulated treatment plan and its execution widely available at any treatment facility that has the resources to acquire the necessary equipment. This work reports on a study of the integration of two such systems. METHODS AND MATERIALS:Treatment planning was done using a commercially available inverse planning algorithm based on simulated annealing. The plans arbitrarily assumed nine coplanar x-ray beams at nonopposed gantry angles. Intensity modulation was computed for each beam. The modulated field at each gantry angle was broken down into a series of uniform (nonmodulated) subfields, which could be delivered as a sequence to produce the desired dose distribution. Because a large number of subfields was delivered, a multileaf collimator (MLC) was used for field shaping. This allowed rapid and accurate field shaping for treatments made up of several hundred subfields. Computer control of the MLC and linear accelerator allowed delivery of doses less than .01 Gy per subfield. Treatment was delivered on a prototype, computer-controlled accelerator and MLC system. Resulting dose distributions were analyzed using film and an anatomically specific, homogeneous phantom. RESULTS:The treatment plans were evaluated using dose-volume histogram analysis. The plans provided acceptably uniform irradiation of the target volume without exceeding dose tolerances for nearby critical structures. The plans were successfully delivered by a prototype dynamic MLC. The time needed to deliver a sequence of subfields at one gantry angle ranged from 0.7 to 2.0 min. Isodoses from film agreed reasonably well with planned isodose distributions. CONCLUSIONS:It is feasible to plan and deliver fixed gantry, modulated-beam conformal therapy for head and neck tumors with systems being developed commercially. The planned dose distributions exhibit significant potential for sparing closely spaced normal tissue structures in the head and neck.

PURPOSE:To develop a catheter system for fractionated high-dose rate (HDR) brachytherapy for intracranial gliomas.METHODS AND MATERIALS:The catheter system for stereotactic placement as well as delivery of the high-dose rate iridium-192 source wire is described. The force of the impulse wave from the source wire entering brain equivalent material was measured. Dose volume histograms for the first 5 patients treated are presented.RESULTS:The catheter system was found to be satisfactory. The maximum force of the impulse wave was less than 1 acceleration of gravity (which is safe). The patients tolerated the treatment well with no significant problems related to the catheters being left in situ for up to 14 days.CONCLUSION:Based on this pilot experience a phase I dose escalating and morbidity study has been initiated.