We propose a novel self-correcting tracking technique that can minimize the dynamic distortion during magnetic tracking. In our method, the magnetic field distortion is estimated through field expansion and then minimized in an iterative tracking procedure. Sparse sensor arrays are designed to measure the spatial gradient tensors of the magnetic field for our method. Numerical results demonstrate that the tracking error caused by field distortion could be reduced from several tens of millimeters to below 2 mm.

PURPOSE:TomoTherapy systems lack real-time, tumor tracking. A possible solution is to use electromagnetic markers; however, eddy-current magnetic fields generated in response to a magnetic source can be comparable to the signal, thus degrading the localization accuracy. Therefore, the tracking system must be designed to account for the eddy fields created along the inner bore conducting surfaces. The aim of this work is to investigate localization accuracy using magnetic field gradients to determine feasibility toward TomoTherapy applications. METHODS:Electromagnetic models are used to simulate magnetic fields created by a source and its simultaneous generation of eddy currents within a conducting cylinder. The source position is calculated using a least-squares fit of simulated sensor data using the dipole equation as the model equation. To account for field gradients across the sensor area (≈ 25 cm(2)), an iterative method is used to estimate the magnetic field at the sensor center. Spatial gradients are calculated with two arrays of uniaxial, paired sensors that form a gradiometer array, where the sensors are considered ideal. RESULTS:Experimental measurements of magnetic fields within the TomoTherapy bore are shown to be 1%-10% less than calculated with the electromagnetic model. Localization results using a 5 × 5 array of gradiometers are, in general, 2-4 times more accurate than a planar array of sensors, depending on the solenoid orientation and position. Simulation results show that the localization accuracy using a gradiometer array is within 1.3 mm over a distance of 20 cm from the array plane. In comparison, localization errors using single array are within 5 mm. CONCLUSIONS:The results indicate that the gradiometer method merits further studies and work due to the accuracy achieved with ideal sensors. Future studies should include realistic sensor models and extensive numerical studies to estimate the expected magnetic tracking accuracy within a TomoTherapy system before proceeding with prototype development.

Real-time, electromagnetic tumor tacking for Tomotherapy systems is an unsolved problem. The problem is due to eddy current magnetic fields. Eddy fields are generated in response to the magnetic source fields, where eddy currents are created within conducting surfaces along the ring-gantry. To solve this problem, we developed a method to separate the source from the background fields. We modeled the ring-gantry environment using electromagnetic simulation software. The gantry was modeled as a 5 mm thick x 1.2 m diameter stainless-steel cylinder, with 1.2 m length. The transponder solenoid was modeled as a 10 mm x 1 mm conducting cylinder, with azimuth directed current, which was assumed to have a frequency range of 300-500 kHz. The search coil configuration was assumed to be a 5 x 5 array of 5-7 cm square current loops with 6.7 cm separation. An algorithm based on free space calculations and measurements was developed to calculate the solenoid position and orientation within the cylinder, in the presences of relatively large eddy magnetic fields that were generated at the same frequency as the source. Using our method, we were able to calculate the transponder position to within 1 mm of the true position for a clinical range of interest. The orientation was calculated with errors less than 0.2°. Using only one noise measurement within the gantry, calculation errors were shown to be minimal over 10 mm displacements and 5° rotations, indicating algorithm robustness over significant deviations in magnetic field. This method can be implemented for real-time tumor tracking during Tomotherapy treatment. The method is based on a simple detection system and only 1 source, which should minimize cost, development time, and invasiveness. Our next task is to develop a prototype system for clinical testing.

PURPOSE:Real-time, electromagnetic tumor tacking during 4DCT is an unsolved problem. The underlying problem is due to eddy current magnetic fields generated within the conducting surfaces in response to the source's alternating magnetic fields.To solve this problem, we developed a method to separate the source from the background fields, which can be measured with simple search coil sensors, such as those used by the Calypso (Seattle, WA) tracking system.METHOD:We modeled the environment using ANSYS Maxwell electromagnetic simulation software. The gantry was modeled as a 5 mm thick × 1.2 m diameter stainless-steel cylinder, with variable length. The transponder solenoid was modeled as a 10 mm × 1 mm conducting cylinder, with azimuth directed current, which was assumed to have a frequency range of 300-500 kHz. The search coil configuration was assumed to be a 5 × 5 array of 5-7 cm square current loops with 6.7 cmseparation. An algorithm based on free space calculations and measurements was developed to calculate the solenoid position within the cylinder, in the presences of relatively large eddy magnetic fields that were generated at the same frequency as the source.RESULTS:Of the various methods and sensor configurations investigated, we found a method that localized the transponder solenoid within 1 mm over all solenoid locations and gantry lengths. We also found that gradient techniques did not significantly increase localization accuracy as expected. Complex solutions were found but not suitable for rapid clinical implementation.CONCLUSIONS:This method can be used to localize a Calypso® Beacon transponder during 4DCT to accurately track tumor positions. Furthermore, the method was based on inexpensive search coils with comparable dimensions to preserve the source-sensor distance. The next task is to create a system and investigate clinical implementation.

Magnetic tracking is sensitive to the eddy currents induced on the conducting gantry during radiotherapy tumor localization. We propose a unique magnetic tracking method that can resist the eddy current distortion. Our method uses a specific sensor array to estimate the secondary magnetic field generated from the eddy currents. An optimization procedure is adopted to reduce the distortion effects. A technique of providing the initial guess is also presented to accelerate the convergence of the algorithm. Numerical results demonstrate the effectiveness of our method for tumor localization inside radiotherapy gantry bores.

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.

Purpose: Real‐time tumor tracking for Tomotherapy systems is a problem in need of a solution. Currently, magnetic tracking systems, such as Calypso, are unable to localize a magnetic source due to the conducting bore. Eddy currents generated in response to the source create additional magnetic fields, at the source frequency, that are difficult to model and filter from the signal. Therefore, we are presenting an innovative method to solve this problem. Method: We have developed a localization algorithm based on a transponder source within a conducting cylinder, and a cost effective sensor configuration. The algorithm uses magnetic field gradients, as well as the magnetic fields, to effectively filter magnetic fields generated from surrounding eddy currents induced along the gantry. Solution accuracy depends on the sensor geometry and configuration; and therefore, the method is a combination of algorithm and sensor parameters to maximize accuracy, while minimizing cost to create a practical system. We modeled the gantry and transponder system to simulate the magnetic fields throughout the environment. The sensor fields were used as algorithm input to calculate the transponder location. The location of the transponder was compared with the calculation. Results: We investigated different algorithms, sensor geometry, and sensor configuration. We compared our method to traditional localization methods of Wilson, Nara, Chao, Hashi, and McGary. Those methods were unable to attain suitable clinical treatment accuracy due to the conducting bore. The method presented here was able to locate the transponder within 1–2 mm over a large extent of possible transponder positions and orientations. In certain regions, the localization error increased to about 3–4 mm due to the nearby eddy currents. Conclusions: The method, algorithm and sensor design, is capable of locating a transponder, for real‐time tumor tracking, in a modeled Tomotherapy gantry bore within 2–4 mm.Financial support from Tomotherapy, Inc. was provided, in part, to fund some of the research presented here. Other support came from the Golfers Against Cancer.

Purpose: Real‐time, tumor tracking for 4DCT does not exist, which is needed for accurate gated therapy. Magnetic tracking is a possible method, however, eddy currents induced from the magnetic source create magnetic noise that is difficult to filter from the signal; the noise shares the same frequency as the signal and other characteristics have to be addressed. We present a method, based on a specialized algorithm, sensor configuration, and magnetic shielding to accurately calculate the transponder position.Method: The CT and transponder were modeled to calculate the magnetic fields within the ideal CT environment, where the gantry was a conducting cylinder. The magnetic fields were simulated using the Ansoft Maxwell electromagnetic solver. The sensors were modeled as search coils of finite dimension, with different size, number, and geometry. An innovative algorithm was developed to use magnetic gradient information to filter eddy current noise. Magnetic material applied to the gantry was modeled to optimize the signal frequency, the magnetic permeability, and thickness. Results: We found that 4 detectors, with 7 sensors, were able to locate the transponder within 2 mm over the majority of points within the CT bore; however, there were regions where the errors were in excess of 4–5 mm. After modeling the magnetic layer on the gantry surface, we found that the localization accuracy was a function of permeability and magnetic thickness. Results showed a minimum in error as a function of magnetic thickness. The localization error in that region was less than 1 mm. Conclusions: We have developed an innovative method to localize a tumor in 4DCT to within 1 mm using a specifically developed algorithm, sensor configuration, and magnetic material along the CT surface. We believe this technique may solve the problem of real‐time 4DCT.

Purpose: To develop a combined targeted, drug release and hyperthermia delivery system for simultaneous multimodality therapy with radiation therapy. Method and Materials: The system is based on nanoparticle‐assembled capsules (NACs) where a polymer, multivalent ion, and a nanoparticle are the only constituents required for self‐assembly formation. Poly(allylamine hydrochloride), disodium phosphate, and citrate bound magnetite nanoparticles were used to create the exterior NAC nanoshell, which encapsulates doxorubicin in the microcapsule core. An alternating magnetic field (AMF) of 20 A/m at 267 kHz was used to release the doxorubicin and heat the NAC solution. Three different nanoparticle sizes were used for these studies; 10, 30, and 50 nm to study heating rates and release profiles. Results: Magnetic nanoparticle NACs, with doxorubicin cores, were created with dimensions of ∼ 1 m capsule diameter and a ∼ 200 nm shell thickness. Heating rates of the NAC‐solution as a function of particle size were measured. Doxorubicin release profiles were measured as a function of time, nanoparticle size, and concentration. Heating rates were substantially larger for the 50 nm nanoparticles than the 10 nm particles, where temperatures in excess of 90° C over 15 minutes were measured as compared to 70° for the smaller particles. Release rate measurements show that rate is proportional to particle size. Radiation in excess of 100 Gy delivered to the NACs showed no behavioral or morphology change. Conclusion: We developed a magnetic, nanoparticle‐assembled capsule, which is a multifunctional device that can be used simultaneously for both controlled drug release and hyperthermia. The system is controlled externally through magnetic heat loss processes. These devices have many advantages; their surface can be functionalized for molecular targeting in conjunction with external magnetic field gradients and these capsules can easily be scaled up for pharmaceutical production.

We present a method for real-time tumor tracking in external beam radiotherapy using superconducting quantum interference device (SQUID) magnetometers. The objective is to develop a localization algorithm and determine a cost effective sensor configuration that is capable of long-range localization, ~1000 mm, with an accuracy of 1-2 mm. We developed several algorithms to calculate the location of a magnetic dipole for geometry relevant for four-dimensional computed tomography (4DCT) to investigate sensor configuration and accuracy. We determined that two cube detectors, located diametrically opposite, are a feasible design for the localization system.

Real-time internal markers are needed for 4DCT to acquire real-time tumor positioning for gated therapy. Currently, there is no real-time localization system due to CT environmental noise factors and geometric constraints. We have developed a scaled-up prototype transponder system that is capable of producing a detectable signal within a CT system for real-time tumor positioning to help solve this problem. This transponder is designed to work with our existing SQUID (superconducting quantum interference) detection system designed for 4DCT. The energizer component of the system is composed of an antenna, signal source (Tektronix 2024B), and resonant circuit capable of amplitude modulation at frequencies greater than 30 MHz. The transponder consists of a tank circuit in parallel with a low forward voltage diode where the circuit is scaled for an implant scale of less than 1 mm diameter by 7 mm length, where a novel thin film inductor (5 μH) is to be used for inductive coupling to the antenna magnetic field. Systems with operating frequencies of 20, 150, 300, and 550 kHz were designed and tested to determine the optimal configuration. Search coils and current probes were used to measure the transponder signal. Measurements were made at source to transponder distances from 1-30 cm along the center axis as well as off-axis points. Circuit models of the system were made using PSPICE and MATLAB/SIMULINK in combination with analytic solutions using Mathematica. The transponder creates a carrier frequency component and two side bands at twice the carrier frequency at 2/3 the amplitude of the carrier amplitude as predicted in the models. Experimental results compare well with the model calculations for frequencies less than 1 MHz; at higher frequencies, the agreement is within 25% due to power losses in the solenoid component. At distances greater than 20 cm, the side bands are not present due to low forward voltages resulting from coupling losses from the antenna. At higher frequencies, power losses reduce the signal-source distance, while at lower frequencies, ∼ 300-500 kHz, the distance is limited by maximum antenna field strengths defined by FCC. The advantage of this system is the ability to select an arbitrary frequency and remove the signal from the noise or reduce the frequency to within the bandwidth of the detection system, which is important for high gain detection systems. Furthermore, the amplitude modulation increases the signal to noise by a factor greater than 10, which improves localization accuracy. The disadvantage of this design is the forward voltage needed to operate the diode, which decreases the source-transponder distance. This will require an antenna design composing or multiple current loops with active selection due to couch motion.

Combined modality treatment (neoadjuvant chemoradiotherapy followed by surgery) for locally advanced rectal cancer requires special attention to various organs at risk (OAR). As a result, the use of conformal dose delivery methods has become more common in this disease setting. Helical tomotherapy is an image-guided intensity modulated delivery system that delivers dose in a fan-beam manner at 7 degree intervals around the patient and can potentially limit normal tissue from high dose radiation while adequately treating targets. In this study we dosimetrically compare helical tomotherapy to 3D-CRT for stage T3 rectal cancer. The helical tomotherapy plans were optimized in the TomoPlan system to achieve an equivalent uniform dose of 45 Gy for 10 patients with T3N0M0 disease that was at least 5cm from the anal verge. The GTV included the rectal thickening and mass evident on colonoscopy and CT scan as well as with the help of a colorectal surgeon. The CTV included the internal iliac, obturator, and pre-sacral lymphatic chains. The OAR that were outlined included the small bowel, pelvic bone marrow, femoral heads, and bladder. Anatom-e system was used to assist in delineating GTV, CTV and OAR. These 10 plans were then duplicated and optimized into 3-field 3D-CRT plans within the Pinnacle planning system. The V[45], V[40], V[30], V[20], V[10], and mean dose to the OAR were compared between the helical tomotherapy and 3D-CRT plans. Statistically significant differences were achieved in the doses to all OAR, including all volumes and means except for V[10] for the small bowel and the femoral heads. Adequate dosimetric coverage of targets were achieved with both helical tomotherapy and 3D-CRT. Helical tomotherapy reduces the volume of normal tissue receiving high-dose RT when compared to 3D-CRT treatment. Both modalities adequately dose the tumor. Clinical studies addressing the dosimetric benefits are on-going.

Purpose/Objective(s)The visual evaluation of tumors and their relationship to normal structures is fundamental to the field of radiation oncology. Historically, significant improvements in dose deposition and avoidance were achieved as radiation oncologists progressed from 2D (two dimensional) to 3D (three dimensional) evaluation of tumors and their relationship to normal structures. The purpose of this study is to evaluate stereoscopic views of tumors and their relationship to normal structures, and to evaluate if it makes a difference in the decision making process of the radiation oncologist.Materials/MethodsAn Apple (Apple, Inc.) 8 core 2.8 GHZ processors with 16 GB of RAM and a NVIDIA (NVIDIA Corp.) Quadro FX 5600 1.5GB stereo 3D dual link DVI (Digital Visual Interface) graphics card utilizing Osiris software and a Planar (Planar Systems, Inc.) 24 inch stereoscopic monitor was utilized to create the stereoscopic visualization of tumors and normal structures. Osiris software allows the following manipulation of DICOM (Digital Imaging and Communications in Medicine) radiation therapy data sets. The Anatom-e (Anatom-e XRT Information Systems) anatomical reference system was used as a guide in defining anatomical structures. Ten patients with head and neck carcinoma were chosen. Isodose plans generated by the Pinnacle (Koninklijke Philips Electronics) treatment planning system, and the Helical TomoTherapy (TomoTherapy, Inc.) treatment planning system were evaluated in 2D, 3D, and stereoscopic visualization. Three staff radiation oncologists evaluated the treatment plans. The radiation oncologists were asked if their decision making process was changed as the visualization process progressed from 2D, 3D, and stereoscopically.ResultsStereoscopic visualization, which allows a left eye image to project to the left eye and a right eye image to project to the right eye and allows the visual system to merge the two images resulting in the perception of depth, provides clinically relevant information to the radiation oncologist. It was felt that the added information provided by allowing the visualization of the relationship of the target to the normal structures with visualization of isodose curves with depth perception, added significant clinical information in all 10 cases. This added information did not result in the radiation oncologist changing his dose constraints in all plans but did provide added assurance that his plans were safe and acceptable.ConclusionsStereoscopic visualization provided additional clinical information in all 10 cases that were evaluated. Our department is now evaluating head and neck cancer cases routinely with stereoscopic visualization. These preliminary results show that stereoscopic visualization may add further insight into improved deposition and avoidance of radiation. Purpose/Objective(s)The visual evaluation of tumors and their relationship to normal structures is fundamental to the field of radiation oncology. Historically, significant improvements in dose deposition and avoidance were achieved as radiation oncologists progressed from 2D (two dimensional) to 3D (three dimensional) evaluation of tumors and their relationship to normal structures. The purpose of this study is to evaluate stereoscopic views of tumors and their relationship to normal structures, and to evaluate if it makes a difference in the decision making process of the radiation oncologist. The visual evaluation of tumors and their relationship to normal structures is fundamental to the field of radiation oncology. Historically, significant improvements in dose deposition and avoidance were achieved as radiation oncologists progressed from 2D (two dimensional) to 3D (three dimensional) evaluation of tumors and their relationship to normal structures. The purpose of this study is to evaluate stereoscopic views of tumors and their relationship to normal structures, and to evaluate if it makes a difference in the decision making process of the radiation oncologist. Materials/MethodsAn Apple (Apple, Inc.) 8 core 2.8 GHZ processors with 16 GB of RAM and a NVIDIA (NVIDIA Corp.) Quadro FX 5600 1.5GB stereo 3D dual link DVI (Digital Visual Interface) graphics card utilizing Osiris software and a Planar (Planar Systems, Inc.) 24 inch stereoscopic monitor was utilized to create the stereoscopic visualization of tumors and normal structures. Osiris software allows the following manipulation of DICOM (Digital Imaging and Communications in Medicine) radiation therapy data sets. The Anatom-e (Anatom-e XRT Information Systems) anatomical reference system was used as a guide in defining anatomical structures. Ten patients with head and neck carcinoma were chosen. Isodose plans generated by the Pinnacle (Koninklijke Philips Electronics) treatment planning system, and the Helical TomoTherapy (TomoTherapy, Inc.) treatment planning system were evaluated in 2D, 3D, and stereoscopic visualization. Three staff radiation oncologists evaluated the treatment plans. The radiation oncologists were asked if their decision making process was changed as the visualization process progressed from 2D, 3D, and stereoscopically. An Apple (Apple, Inc.) 8 core 2.8 GHZ processors with 16 GB of RAM and a NVIDIA (NVIDIA Corp.) Quadro FX 5600 1.5GB stereo 3D dual link DVI (Digital Visual Interface) graphics card utilizing Osiris software and a Planar (Planar Systems, Inc.) 24 inch stereoscopic monitor was utilized to create the stereoscopic visualization of tumors and normal structures. Osiris software allows the following manipulation of DICOM (Digital Imaging and Communications in Medicine) radiation therapy data sets. The Anatom-e (Anatom-e XRT Information Systems) anatomical reference system was used as a guide in defining anatomical structures. Ten patients with head and neck carcinoma were chosen. Isodose plans generated by the Pinnacle (Koninklijke Philips Electronics) treatment planning system, and the Helical TomoTherapy (TomoTherapy, Inc.) treatment planning system were evaluated in 2D, 3D, and stereoscopic visualization. Three staff radiation oncologists evaluated the treatment plans. The radiation oncologists were asked if their decision making process was changed as the visualization process progressed from 2D, 3D, and stereoscopically. ResultsStereoscopic visualization, which allows a left eye image to project to the left eye and a right eye image to project to the right eye and allows the visual system to merge the two images resulting in the perception of depth, provides clinically relevant information to the radiation oncologist. It was felt that the added information provided by allowing the visualization of the relationship of the target to the normal structures with visualization of isodose curves with depth perception, added significant clinical information in all 10 cases. This added information did not result in the radiation oncologist changing his dose constraints in all plans but did provide added assurance that his plans were safe and acceptable. Stereoscopic visualization, which allows a left eye image to project to the left eye and a right eye image to project to the right eye and allows the visual system to merge the two images resulting in the perception of depth, provides clinically relevant information to the radiation oncologist. It was felt that the added information provided by allowing the visualization of the relationship of the target to the normal structures with visualization of isodose curves with depth perception, added significant clinical information in all 10 cases. This added information did not result in the radiation oncologist changing his dose constraints in all plans but did provide added assurance that his plans were safe and acceptable. ConclusionsStereoscopic visualization provided additional clinical information in all 10 cases that were evaluated. Our department is now evaluating head and neck cancer cases routinely with stereoscopic visualization. These preliminary results show that stereoscopic visualization may add further insight into improved deposition and avoidance of radiation. Stereoscopic visualization provided additional clinical information in all 10 cases that were evaluated. Our department is now evaluating head and neck cancer cases routinely with stereoscopic visualization. These preliminary results show that stereoscopic visualization may add further insight into improved deposition and avoidance of radiation.

To evaluate the dose to the brachial plexus in patients treated with head and neck cancer by various treatment techniques, and to evaluate how placing a limitation of 60 Gy on the brachial plexus affects coverage of the target. The brachial plexus is not routinely delineated as an avoidance structure in the treatment of head and neck malignancies. The medial vertical extent of the roots was from the C4-5 interspace to T1-2 interspace. It continued inferiorly, above the subclavian artery, between the anterior and middle scalene muscles to traverse the interscalene triangle and then the costoclavicular space (between the inferior surface of the clavicle and the upper surface of the first rib). It then continues to reach the space between the pectoralis minor muscle and the anterosuperior chest wall where it finally surrounds the axillary artery, lateral to the pectoralis minor muscle. The anatomical location of the brachial plexus was defined utilizing the Anatom-e target delineation system. A patient with a T1N3 (7 cm right sided lymph node) undifferentiated carcinoma of the nasopharynx and a patient with T3N2b squamous cell carcinoma of the larynx status post total laryngectomy and left radical neck dissection were chosen as patient examples. The following dosimetric parameters for the brachial plexus were evaluated on treatment plans: mean dose, maximum dose, and minimum dose, along with the DVH for 60 Gy. There were no dose limitations placed on the brachial plexus on the initial plans. The neck in the postoperative patient was treated to 66 Gy, and the neck in the nasopharynx patient was treated to 70 Gy. A subsequent set of plan were performed placing a dose constraint on the brachial plexus of 60 Gy, and the target was evaluated for coverage. The following techniques were utlilized: Helical tomotherapy, serial tomotherapy, and fixed field IMRT with a 6 MV Varian linear accelerator. There was no separate supraclavicular field utilized in the treatment of the patient. Maximum doses did not vary significantly depending on technique when there were no dosimetric constraints placed on the brachial plexus, but maximum doses did exceed 72 Gy in the nasopharynx patient, and reach 68G in the post-op patient. Placing dosimetric constraints of 60 Gy on the brachial plexus significantly affected the DVH of the target. There was less impact on the DVH of the target when helical tomotherapy was utilized. Delineation of the brachial plexus as an avoidance structure can significantly effect the DVH of the target when 60 Gy is used as a dose constraint and the target dose is 66 or 70 Gy. When the brachial plexus is not defined as an avoidance structure, doses to the brachial plexus approximate the target dose. Hot spots can be seen in the brachial plexus that exceed 70 Gy. At this time in our clinic the brachial plexus is routinely delineated and evaluated for hot spots.

Computer visualization techniques (CVTs) are an emerging technology that can organize all cancer specialists. This article describes CVTs' ability to maximize the currently untapped advantages of intensity modulated radiotherapy (IMRT). The visual speed and dynamic strategies inherent in CVTs improves IMRT by distilling vast amounts of anatomic, multimodal imaging, textual/meaning, and surgical/outcome data into a large, rigorous, standardized evidence base of storable target delineation plans. This ability to standardize strategies will allow the collection of meaningful evidence based outcome data.

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.

Purpose: To report patient tolerance and acute anorectal toxicity of an endorectal balloon used for prostate immobilization during 35 daily fractions.Materials and Methods: The records of 396 patients treated for prostate cancer from October 1997 to November 2001 were reviewed. Patients were treated with intensity modulated radiation therapy (IMRT). Endorectal balloon catheter was inserted daily, inflated with 100 mL of air for immobilizing the prostate gland. Patient and treatment factors were analyzed. Patients received a mean dose of 77 Gy/35 fractions/7 weeks with no rectal block.Results: None of the 396 patients halted treatment because of associated ano-rectal toxicity. No patient stated that he would decline to be treated again with rectal balloon. Three of 396 (0.8%) patients required a reduction in the volume of the balloon to 50 mL. Seventeen of 396 (4.3%) patients required Lidocaine jelly with the insertion of balloon. Radiation Therapy Oncology Group (RTOG) grades 1 and 2 rectal toxicity occurred in 55/396 (13.9%) and 73/396 (18.4%), respectively. No RTOG grade 3 or 4 toxicities occurred. Topical anal medications were prescribed for 46 of 396 (11.6%) patients and antidiarrhea medication for 27 of 396 (6.8%) patients. Of patients with pretreatment anorectal disease, 50% developed rectal toxicities over the 7 weeks. Rectal toxicity occurred most frequently in the third, fourth, fifth, or sixth week; 19.5%, 20.8%, 18.2%, and 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%.Conclusion: Most of the patients, 393/396 (99.2%), tolerated a 100 mL endorectal immobilization balloon for IMRT. The rate of acute anorectal toxicity was acceptable with no grade 3 or 4 toxicities. Duration of the toxicities typically was 1 to 2 weeks. Patients with pre-existing anorectal disease are at higher risk of developing acute anorectal toxicity with the use of an endorectal balloon.