Purpose: To design and implement an Oncology Information System (OIS) around an existing IT infrastructure to optimize performance, meet clinical requirements, and minimize implementation costs. University of Pittsburgh Medical Center (UPMC) is a large health system with 50 medical and radiation oncology centers. To improve the quality, safety, and efficiency of patient centric care, an initiative was undertaken to integrate the patients' data and health information of all cancer centers on a centralized OIS with interfaces to the rest of the UPMC and affiliated hospitals. Methods: The OIS must incorporate the existing isolated oncology systems and devices and aggregate all of the patient's electronic medical records (EMR) including imaging, planning, and treatment creating a single point of patient information reference built upon the existing UPMC infrastructure. The distributed nature of UPMC CancerCenter and its multi‐vendor systems requires rigorous evaluation and testing for multiple levels of software, hardware, infrastructure, and environmental platforms and comparison and validation of their capabilities with the clinical workflow. Results: We successfully implemented the “integrated and centralized” OIS with ARIA at 16 of the 22 radiation and 5 of the 28 medical oncology sites at the rate of 1 site every 2 months. We completed all inbound and outbound interfaces transferring data to and from ARIA and other UPMC systems. We interfaced 1 of 9 affiliated Non‐UPMC health systems. Conclusion: To fit the OIS technical and clinical requirements with existing health system IT infrastructure and maximize the OIS performance at minimum cost, we customized OIS data locations providing the best data flow patterns across the network. This provided a comprehensive Electronic Health Record from multiple EMRs and platforms giving physicians a unique view into each patient's information. The OIS optimized the best options for medical oncology, radiation oncology, image based planning, and image guided radiotherapy and radiosurgery.

Purpose: he purpose of this study is to acquire baseline values for the standard deviations of MU and angle reported by a Varian 23ex linac following the delivery of a RapidArc field. Methods: During the delivery of RapidArc fields, the Varian linac records the gantry angle and cumulative MU every 50 ms. By comparing this data to the corresponding planned data, the system calculates the standard deviations of the MUs and the gantry angles for each field. These standard deviations are reported to the linac screen at the completion of each field and documented daily for each field along with the patient, plan, treatment site, and date. The data was then entered into Micorsoft Excel for analysis. This data was acquired for every RapidArc patient (88 total patients) over the course of the first year of RapidArc use. Results: The maximum MU standard deviation was 0.09 and the maximum gantry angle standard deviation was 0.30°. The averages are 0.05 MU and 0.19° respectively. No specific treatment site (prostate/prostate fossa, head and neck, brain, thorax, or other) differed significantly from these averages. Conclusion: If the MU standard deviation is greater than 0.1 or the gantry angle standard deviation is greater than 0.3°, the RapidArc QA tests of the linac and the plan should be promptly repeated to identify any possible problems. These baseline values may be specific to the linac in question but provide a point of reference for other linacs as well.

This study is aimed at providing a dosimetric evaluation of the irregular motion of lung tumors due to variations in patients' respiration. Twenty-three lung cancer patients are retrospectively enrolled in this study. The motion of the patient clinical target volume is simulated and two types of irregularities are defined: characteristic and uncharacteristic motions. Characteristic irregularities are representative of random fluctuations in the observed target motion. Uncharacteristic irregular motion is classified as systematic errors in determination of the target motion during the planning session. Respiratory traces from measurement of patient abdominal motion are also used for the target motion simulations. Characteristic irregular motion was observed to cause minimal changes in target dosimetry with the largest effect of 2.5% ± 0.9% (1σ) reduction in the minimum target dose (D(min)) observed for targets that move 2 cm on average and exhibiting 50% amplitude variations within a session. However, uncharacteristic irregular motion introduced more drastic changes in the clinical target volume (CTV) dose; 4.1% ± 1.7% reduction for 1 cm motion and 9.6% ± 1.7% drop for 2 cm. In simulations with patients' abdominal motion, corresponding changes in target dosimetry were observed to be negligible (<0.1%). Only uncharacteristic irregular motion was identified as a clinically significant source of dosimetric uncertainty.

Purpose/Objective(s)This study is aimed to provide a dosimetric evaluation of the irregular motion of lung tumors due to variations in patients' respiration.Materials/MethodsTwenty-three lung cancer patients are retrospectively enrolled in this study in accordance with a University of Pittsburgh IRB protocol. Motions of the patient clinical target volumes (CTV) are simulated and two types of irregularities are defined: characteristic and uncharacteristic motions. Characteristic irregularities are representative of random fluctuations in the target motion. On the other hand, uncharacteristic irregular motion is classified as a source of systematic error during the radiotherapy planning stage where target motion amplitude is determined to be smaller than the mean respiratory motion. In addition to these motion types, actual respiratory trace of patients obtained from the motion of their abdomen is also used to model the variations in target motion as abdominal motion is relied in most clinics as a surrogate for the tumor motion. The dosimetric effects of different types of irregular motion are studied using metrics such as change in target minimum dose (Dmin) as well as changes in global metrics like Equivalent Uniform Dose (EUD) and Tumor Control Probability (TCP). Additional parameters of investigation were the effect of the plan geometry (varying target conformity), mean respiratory motion amplitude, and effect of respiratory coaching.ResultsCharacteristic irregular motion was observed to cause minimal changes in target dosimetry with largest effect of 2.5% ± 0.9% (1σ) reduction in Dmin observed for targets that move with 2 cm on average and exhibiting 50% amplitude variations within a session. However, uncharacteristic irregular motion introduced more drastic changes in CTV dose; 4.1% ± 1.7% reduction for 1 cm motion and 9.6% ± 1.7% drop for 2 cm. In studies using patients' abdominal motion, corresponding changes in target dosimetry was observed to be negligible (<0.1%), attributed mostly to the presence of respiratory coaching. Target conformity and plan complexity was observed to show no statistically significant changes in the results.ConclusionsIrregular respiratory motion was observed to have adverse effects on target dosimetry. Characteristic motion irregularities, which are mainly random fluctuations about modeled respiration motion, are not observed to have considerable clinical effect on target dosimetry. However, uncharacteristic irregularities resulting from inconsistencies between the determined respiration motion and what's representative of patient's overall respiration pattern are shown to have critical dosimetric consequences for the target coverage. Coaching techniques are suggested as potential ways to avoid such inconsistencies. Purpose/Objective(s)This study is aimed to provide a dosimetric evaluation of the irregular motion of lung tumors due to variations in patients' respiration. This study is aimed to provide a dosimetric evaluation of the irregular motion of lung tumors due to variations in patients' respiration. Materials/MethodsTwenty-three lung cancer patients are retrospectively enrolled in this study in accordance with a University of Pittsburgh IRB protocol. Motions of the patient clinical target volumes (CTV) are simulated and two types of irregularities are defined: characteristic and uncharacteristic motions. Characteristic irregularities are representative of random fluctuations in the target motion. On the other hand, uncharacteristic irregular motion is classified as a source of systematic error during the radiotherapy planning stage where target motion amplitude is determined to be smaller than the mean respiratory motion. In addition to these motion types, actual respiratory trace of patients obtained from the motion of their abdomen is also used to model the variations in target motion as abdominal motion is relied in most clinics as a surrogate for the tumor motion. The dosimetric effects of different types of irregular motion are studied using metrics such as change in target minimum dose (Dmin) as well as changes in global metrics like Equivalent Uniform Dose (EUD) and Tumor Control Probability (TCP). Additional parameters of investigation were the effect of the plan geometry (varying target conformity), mean respiratory motion amplitude, and effect of respiratory coaching. Twenty-three lung cancer patients are retrospectively enrolled in this study in accordance with a University of Pittsburgh IRB protocol. Motions of the patient clinical target volumes (CTV) are simulated and two types of irregularities are defined: characteristic and uncharacteristic motions. Characteristic irregularities are representative of random fluctuations in the target motion. On the other hand, uncharacteristic irregular motion is classified as a source of systematic error during the radiotherapy planning stage where target motion amplitude is determined to be smaller than the mean respiratory motion. In addition to these motion types, actual respiratory trace of patients obtained from the motion of their abdomen is also used to model the variations in target motion as abdominal motion is relied in most clinics as a surrogate for the tumor motion. The dosimetric effects of different types of irregular motion are studied using metrics such as change in target minimum dose (Dmin) as well as changes in global metrics like Equivalent Uniform Dose (EUD) and Tumor Control Probability (TCP). Additional parameters of investigation were the effect of the plan geometry (varying target conformity), mean respiratory motion amplitude, and effect of respiratory coaching. ResultsCharacteristic irregular motion was observed to cause minimal changes in target dosimetry with largest effect of 2.5% ± 0.9% (1σ) reduction in Dmin observed for targets that move with 2 cm on average and exhibiting 50% amplitude variations within a session. However, uncharacteristic irregular motion introduced more drastic changes in CTV dose; 4.1% ± 1.7% reduction for 1 cm motion and 9.6% ± 1.7% drop for 2 cm. In studies using patients' abdominal motion, corresponding changes in target dosimetry was observed to be negligible (<0.1%), attributed mostly to the presence of respiratory coaching. Target conformity and plan complexity was observed to show no statistically significant changes in the results. Characteristic irregular motion was observed to cause minimal changes in target dosimetry with largest effect of 2.5% ± 0.9% (1σ) reduction in Dmin observed for targets that move with 2 cm on average and exhibiting 50% amplitude variations within a session. However, uncharacteristic irregular motion introduced more drastic changes in CTV dose; 4.1% ± 1.7% reduction for 1 cm motion and 9.6% ± 1.7% drop for 2 cm. In studies using patients' abdominal motion, corresponding changes in target dosimetry was observed to be negligible (<0.1%), attributed mostly to the presence of respiratory coaching. Target conformity and plan complexity was observed to show no statistically significant changes in the results. ConclusionsIrregular respiratory motion was observed to have adverse effects on target dosimetry. Characteristic motion irregularities, which are mainly random fluctuations about modeled respiration motion, are not observed to have considerable clinical effect on target dosimetry. However, uncharacteristic irregularities resulting from inconsistencies between the determined respiration motion and what's representative of patient's overall respiration pattern are shown to have critical dosimetric consequences for the target coverage. Coaching techniques are suggested as potential ways to avoid such inconsistencies. Irregular respiratory motion was observed to have adverse effects on target dosimetry. Characteristic motion irregularities, which are mainly random fluctuations about modeled respiration motion, are not observed to have considerable clinical effect on target dosimetry. However, uncharacteristic irregularities resulting from inconsistencies between the determined respiration motion and what's representative of patient's overall respiration pattern are shown to have critical dosimetric consequences for the target coverage. Coaching techniques are suggested as potential ways to avoid such inconsistencies.

Purpose: The aim of this study is to investigate the dosimetric effects of the irregular respiratory motion of lung tumors treated using respiratory gating techniques. Several treatment parameters such as the gating window, average target motion, and the inclusion of respiratory coaching techniques are also investigated for their effect on target dosimetric coverage. Methods and Materials: Respiratory motion traces of 11 lung cancer patients are used to reflect the typical respiratory irregularities. From the entire respiratory motion data, an average respiratory cycle is calculated to represent the corresponding regular motion for the patient. Using the regular motion amplitude, target volume is expanded by the amount of residual motion observed within the gating window and a treatment plan is generated. The target is then subjected to both regular and irregular motions without affecting anatomical topology. Target dosimetry under regular and irregular motion conditions is compared for quantitative evaluations Results: The reduction in Dmin due to irregular motion was less than 1% (4%) for a mean target motion of 1.0 cm (2.0 cm) when no gating technologies utilized. The drop in target Dmin increased as the shorter gating window sizes are implemented. For gated treatments with 50% duty cycle, largest change in Dmin was 2% and 9% for 1.0 and 2.0 cm mean target motions respectively. More importantly, gated treatments were observed to undermine target dosimetry in cases where the synchronization between the target motion and the external respiratory signal doesn't stay constant as observed by other investigators. Within the parameter space investigated here, up to 35% reduction in target Dmin was observed. Conclusion: Being a more aggressive treatment strategy, respiratory gated treatments were observed to be more susceptible to dosimetric uncertainties as compared to traditional delivery techniques in presence of irregular respiratory motion.

Acute radiation esophagitis is a common complication in the treatment of lung malignancies which can lead to treatment interruption and undesirable morbidity. We report our experience treating locally-advanced non-small cell lung cancers using chemoradiotherapy via IMRT and the associated acute treatment-related toxicities, and we determined potential dosimetric parameters predictive for acute esophagitis. This retrospective, multi-site study assessed 37 Stage IA-IV lung cancer patients who received IMRT. All patients were scanned during free breathing using coached retrospective 4D-CT and 21 had phase-based gated treatment delivery. A median dose of 70.0 Gy (range: 50 - 81.9 Gy) over 35 fractions (range 25 - 39 fractions) was delivered to the tumor using inhomogeneity correction. The esophagus was contoured and the mean dose and the volume of esophagus receiving 30, 50, 60 and 70 Gy (V30, V50, V60, V70, respectively) was calculated for each patient. Patients were graded for acute and chronic toxicities using the CTCAE 3.0 and logistic regression was performed to test associations between dosimetric parameters and esophageal toxicity. All simulated patients completed their course of chemoradiotherapy treatment. Twenty-eight patients (76%) received radiation treatment with concurrent chemotherapy. The most common acute toxicities were nausea, esophagitis, and fatigue observed in 11, 26, and 18 patients respectively. Only 3 patients (8%) developed Grade 3 radiation pneumonitis confirmed clinical and radiographically and required treatment with oral steroids. Acute Grade 1, 2 and 3 nausea was observed in 5, 4 and 2 patients; acute Grade 1, 2 and 3 esophagitis was observed in 8, 17 and 1 patients and acute Grade 1, 2 and 3 fatigue was observed in 9, 7 and 2 patients, respectively. Patients who experienced any esophagitis had a mean dose in excess of 28.7 Gy to the esophagus (Odds ratio: 1.09, 95% confidence interval: 1.02 - 1.18, p = 0.01). Univariate logistic regression correlated acute Grade ≥2 esophagitis with V60 (p = 0.045) and mean esophageal dose (p = 0.049). We did not identify significant differences in acute esophagitis between patients receiving concurrent chemotherapy and radiation versus those receiving radiation alone (p = 0.058). We were not able to correlate any parameters with late/chronic esophagitis. The mean dose to the esophagus and the volume of esophagus receiving higher doses of irradiation, but not chemotherapy, are associated with the development of esophagitis. Maintaining a mean doses to the esophagus below 28.7 Gy and restricting the volume of esophagus receiving 60 Gy or more can help to minimize treatment associated esophagitis.

Purpose: To evaluate if acquiring an ultrasound image at the time of CT simulation for comparison with daily ultrasound images improves daily localization of prostates. Method and Materials: Resonant Medical's® ultrasound localization system was installed and implemented in our clinic. The technique relies on acquiring a 3D ultrasound image at the time of CT simulation for daily comparison whereas other ultrasound localization techniques compare daily ultrasound images to the original CT image. Treatment planning is done on the CT. DRRs are also constructed from the CT, and fiducials implanted in the prostate are outlined on the DRRs. Each day a 3D ultrasound image was acquired and compared to the ultrasound that was acquired at the time of CT simulation. Daily, if the ultrasound image was approved by the physician, the couch was shifted to align the current prostate location with its location at the time of simulation. After the ultrasound, ports were taken as often as prescribed by the physician. The fiducial locations as seen in the ports were compared to their locations on the DRRs. Any necessary shifts were made to align the fiducials. Following the treatments, an analysis was made of the ultrasound localization as compared to the fiducial localization. 22 patients had 7 or more days in which both ultrasound and ports of fiducials were acquired and are included in this analysis. Results: The measured average difference between the ultrasound localization and the localization based on ports of fiducials is 7.2 mm. This is comparable to what is reported in literature for other ultrasound localization techniques. Conclusion: Using a 3D ultrasound image acquired at the time of CT simulation does not improve ultrasound localization accuracy as compared to techniques that compare daily ultrasound images to the simulation CT for localization.

This study assesses the feasibility and implementation of respiratory-gated whole-abdominal intensity-modulated radiation therapy (RG-WAIMRT). Three patients were treated with RG-WAIMRT. The planning target volume (PTV1) included the entire peritoneal cavity and a pelvic boost field was created (PTV2). The dose prescribed was 30 Gy to PTV1 and 14.4 Gy to PTV2. For comparison, a conventional three-dimensional (3D) plan was generated for each patient. In the WAIMRT plan, an average of 90% of PTV1 received 30 Gy compared to 70% for the conventional 3D plan. The percent volume receiving 30 Gy (V(30)) for liver averaged 54% (WAIMRT) vs 43% (3D). The percent volume receiving 20 Gy (V(20)) for kidneys averaged 19% vs 0%, and the mean V(20) for bone marrow was 74% vs 83%, respectively. Major acute toxicities were anemia (grade 2: 1/3), leukopenia (grade 3: 2/3 patients), and thrombocytopenia (grade 2: 1/3 patients, grade 3: 1/3 patients). One patient could not complete the whole-abdomen field after 19.5 Gy because of persistent nausea. No major subacute toxicity has been reported. WAIMRT demonstrated superior target coverage and reduced dose to bone marrow, with a slightly increased dose to liver and kidneys. WAIMRT is a novel and feasible technique for ovarian cancer treatment.

Purpose: This pilot study evaluated prostate localization by comparing ultrasound images to orthogonal MV portal images of fiducial markers implanted into the prostate. Method and Materials: Each prostate patient had gold fiducial markers implanted into his prostate prior to simulation. The Restitu™ ultrasound system (Resonant Medical, Inc.) was used to acquire the ultrasound images. The first ultrasound image was acquired immediately prior to acquiring the CT simulation image. These images were fused using the CT isocenter, and the prostate reference volume was contoured for each patient. This contour included a portion of the inferior bladder wall near the trigone to assist with daily localization. Each day, therapists acquired an ultrasound image and overlaid the prostate reference volume contour onto the current image. Orthogonal MV portal images were then acquired. Displacements of imaged fiducials from their expected locations as observed on the DRRs were removed by shifting the couch if the displacements exceeded 5 mm. Following treatment, the location of each fiducial in all 3 directions was measured on the final portal images for each day and averaged to measure the final prostate location. Differences in where the ultrasound image and where the portal images of fiducials would locate the prostate were compared. Results: For 11 patients, the differences are less than 6.1 mm within the 95% confidence interval. For 1 patient, ultrasound imaging did not consistently reproduce the prostate location to within 10 mm as compared to fiducials via our technique. Sources of deviation include slight discrepancies in calibrating the ultrasound systems, slice spacing, different users, fusion discrepancies, image quality, and random uncertainties. Conclusion: For most patients, ultrasound and ports of fiducials provide comparable localization information for prostates. However, sources of disagreement still exist. Anatomical landmarks can be useful in most cases but can also be misleading if improperly used.

Respiratory-gated treatment techniques have been introduced into the radiation oncology practice to manage target or organ motions. This paper will review the implementation of this type of gated treatment technique where the respiratory cycle is determined using an external marker. The external marker device is placed on the abdominal region between the xyphoid process and the umbilicus of the patient. An infrared camera tracks the motion of the marker to generate a surrogate for the respiratory cycle. The relationship, if any, between the respiratory cycle and the movement of the target can be complex. The four-dimensional computed tomography (4DCT) scanner is used to identify this motion for those patients that meet three requirements for the successful implementation of respiratory-gated treatment technique for radiation therapy. These requirements are (a) the respiratory cycle must be periodic and maintained during treatment, (b) the movement of the target must be related to the respiratory cycle, and (c) the gating window can be set sufficiently large to minimise the overall treatment time or increase the duty cycle and yet small enough to be within the gate. If the respiratory-gated treatment technique is employed, the end-expiration image set is typically used for treatment planning purposes because this image set represents the phase of the respiratory cycle where the anatomical movement is often the least for the longest time. Contouring should account for tumour residual motion, setup uncertainty, and also allow for deviation from the expected respiratory cycle during treatment. Respiratory-gated intensity-modulated radiation therapy (IMRT) treatment plans must also be validated prior to treatment. Quality assurance should be performed to check for positional changes and the output in association with the motion-gated technique. To avoid potential treatment errors, radiation therapist (radiographer) should be regularly in-serviced and made aware of the need to invoke the gating feature when prescribed for selected patients.

Purpose: To investigate the reproducibility of lung tumors motions and their characteristics during the course of the treatment. Materials and Methods: Two 4DCT scans were obtained at an interval of about three weeks with a GE‐scanner and Varian's RPM System under free breathing for 13 patients. Each respiration cycle had 10 phases. 14 GTVs and 10 lungs in all phases were contoured. Geometrical characteristics of these structures were obtained with Eclipse TPS for the motion reproducibility analysis. Results: The GTVs of the initial scans ranged from 2.0cc to 280.5cc with a median of 50.3cc. Their median relative change in the second scan was a 28% decrease. The 3D extent of the respiration‐induced motion of the GTVs' centroids in the first scan ranged from 0.34cm to 1.78cm with a median of 0.90cm. For the second scan it was 0.13cm, 1.99cm, and 0.89cm, respectively. The largest motion was in a projection on a sagittal plane. The overall displacements of the GTVs' edges exhibited same trend. These motion tracks from two scans overlapped along DICOM directions. The median change of phase 50 lung volumes in both scans relative to the tidal volume at the first scan was −12% for ipsilateral and −11% for contralateral lungs. The median tidal volume change between scans relative to the first scan volume was 8% for ipsilateral and 4% for contralateral lungs. Conclusion: Most of the patients results show reproducible patterns of motion. The hysteresis of the motion varies between scans. This might be due to GTV changes during the treatment. A large and anisotropic shape change perturbs the initial motion trajectory, however general patterns appear repetitive. The respiratory changes of lung volumes were similar. They are not indicative of the GTVs motion reproducibility.

Respiration-induced target and organ motion impacts the radiotherapy strategies of some cancers. Various methods and techniques have been used to investigate motion-related radiotherapy issues, including retrospective 4-dimensional (4D) computed tomography (CT), prospective gated CT, and breath-hold CT scans. This paper reviews these methods and, particularly, the method using retrospective 4D CT scans, which has been developed at our institution. Some motion studies based on retrospective 4D CT images of patients are also examined. These studies have led to reduced planning target volume (PTV) margins for a number of patients, because the respiratory motion was observed to be minimal or gated radiotherapy was used. Respiratory motion managed CTs and, particularly, retrospective 4D CTs are proving to be useful for measuring soft tissue motion, identifying patients who could benefit from gated radiotherapy, and evaluating the effects of respiratory motion during radiotherapy.

Purpose: The objective of this study is to compare dosimetric characteristics of prostate treatments using HDR brachytherapy and IMRT technique. Method and Materials: Five HDR patients were selected for IMRT planning. Patients underwent ultrasound guided catheter placement for HDR. CT images were obtained and imported into the Nucletron PLATO Brachytherapy system. The prostate, urethra, bladder and rectum were contoured on axial slices. The dose was calculated and optimized by graphical optimization. The CT images of these structures were exported from the PLATO to Eclipse workstation for IMRT planning and comparison. For each patient, the DVH of HDR and IMRT plans were generated, drawn on the same scale and compared. Results: In IMRT plans the DVH curves for PTV dropped sharply and reached to zero volume of the prostate at about 6.4 Gy. In HDR plans the DVH curves for PTV showed a long tail up to a very high dose. About 10% of the PTV for prostate received greater than 12 Gy (200%) of the prescribed dose (6 Gy) in HDR plans. In contrast, the same volume in IMRT plans received less than 6 Gy (100%). Average prostate V90 and V100 dose was about 6.3 Gy and 4.12 Gy respectively for HDR, and 6.09 Gy and 5.74 Gy for IMRT plans, respectively. UrethraV90 dose for IMRT plans showed similar levels (93%), whereas in HDR the dose varied widely (60 to 100%). In all plans, the dose to the bladder and rectum was significantly lower in HDR than in IMRT plans. Conclusions: HDR brachytherapy may reduce normal tissue toxicities in prostate boost treatments, even though the dose homogeneity inside the PTV is far worse than in IMRT treatments. Another advantage of HDR over IMRT is that the organ motion is not a significant concern as in IMRT.

Purpose: A quality assurance device was developed for 4DCT (GE Medical System, Waukesha, Wisconsin) and the Real‐Time Position Management Respiratory Gating System (Varian Medical Systems, Palo Alto, CA). It verifies the temporal‐phase function of the 4DCT and the gated delivery function of the Linac.Method and Materials: The QA device is composed of a mobile phantom, static phantom, acrylic lobe, AC motor, power transformer and transmission mechanism. There are eight radio‐opaque lines embedded in the static phantom, which are used as reference indicators. A “Z” shape radio‐opaque marker is fixed on the top of the mobile. This phantom moves periodically with a maximum displacement of 3 cm in a horizontal direction. It was scanned under our 4DCT at a period of 5 seconds. The collected images were divided into 10 groups representing 10 phases of the moving cycle. The digitally reconstructed radiograph of each phase was generated for the verification of the temporal‐phase function of the 4DCT. To verify the gated delivery function of the Linac, a radiographic film was attached to the surface of the mobile phantom and a 0.5 cm by 10 cm X‐ray field was used to expose the film at certain phases. The expected position of 0% phase was marked by punching 2 small holes on the film. Results: The “Z” mark was correctly shown and aligned with the reference lines at each phase. The film exposed under the Linac has shown that the radiation had been delivered to the correct position. Conclusion: A reliable quality assurance device for 4DCT and respiratory gating system is necessary to ensure that the radiation dose is accurately delivered to the patient's target volume. This QA device is effective and convenient for checking temporal‐phase function on the 4DCT and RPM gating system.

Purpose: The purpose of this study is to quantify the phase lag of superior-inferior abdominal organ motion relative to an external marker block used to monitor respiratory motion. The diaphragm, liver, spleen, and kidneys were studied. Method and Materials: A 4DCT (GE Medical System, Waukesha, Wisconsin) scan correlated with respiratory motion using the Real-Time Position Management (RPM) Respiratory Gating System (Varian Medical Systems, Palo Alto, CA) was used to acquire scans of 10 patients. Up to 10 images at each slice location within one breathing cycle were acquired and sorted into respiratory phases evenly distributed in time. The superior and inferior edge of each organ was identified, and the average of these positions was used as the S-I position of the organ. The anterior edge of the external marker block was also recorded. These positions were identified for all respiratory phases. The data was then fit with a cosine squared function. The argument of the function was the observed respiratory phase plus a starting phase. The starting phase was then adjusted until the value generating the least square deviation among all measurements of the particular organ, diaphragm, or marker block for all phases was found. The difference of starting phase minus that of the marker block is then recorded as the phase lag relative to the marker block. Results: No phase lag is greater than 36° which is the minimum difference between successive phase for a respiratory cycle divided into 10 phases. Conclusion: The external marker block used to monitor respiration is observed to be in phase the motion of the abdominal organs and diaphragm within the measurement accuracy. Conflict of Interest: Software provided by GE Medical Systems.

Purpose: A quality assurance device was developed for 4DCT (GE Medical System, Waukesha, Wisconsin) and the Real‐Time Position Management Respiratory Gating System (Varian Medical Systems, Palo Alto, CA). It verifies the temporal‐phase function of the 4DCT and the gated delivery function of the Linac. Method and Materials: The QA device is composed of a mobile phantom, static phantom, acrylic lobe, AC motor, power transformer and transmission mechanism. There are eight radio‐opaque lines embedded in the static phantom, which are used as reference indicators. A “Z” shape radio‐opaque marker is fixed on the top of the mobile. This phantom moves periodically with a maximum displacement of 3 cm in a horizontal direction. It was scanned under our 4DCT at a period of 5 seconds. The collected images were divided into 10 groups representing 10 phases of the moving cycle. The digitally reconstructed radiograph of each phase was generated for the verification of the temporal‐phase function of the 4DCT. To verify the gated delivery function of the Linac, a radiographic film was attached to the surface of the mobile phantom and a 0.5 cm by 10 cm X‐ray field was used to expose the film at certain phases. The expected position of 0% phase was marked by punching 2 small holes on the film. Results: The “Z” mark was correctly shown and aligned with the reference lines at each phase. The film exposed under the Linac has shown that the radiation had been delivered to the correct position. Conclusion: A reliable quality assurance device for 4DCT and respiratory gating system is necessary to ensure that the radiation dose is accurately delivered to the patient's target volume. This QA device is effective and convenient for checking temporal‐phase function on the 4DCT and RPM gating system.

Purpose: MarkerMatch is an automated marker match software feature developed by Varian in on‐board imaging. It may calculate inter‐fractional prostate motion with internal fiducial markers identified on CT scans. Before each treatment, a pair of portal images was taken and fiducial markers are identified. Based on the portal image pair, MarkerMatch calculates the optimized couch displacement in 3D to maximally restore the marker positions to their reference positions. To evaluate MarkerMatch's clinical performance, we did a phantom test and a retrospective study on patients implanted with radio‐opaque fiducial markers. Method and Materials: We used a phantom implanted with 4 cylindrical‐shaped markers of 1mm in diameter and 3mm in length. MarkerMatch localizes the markers based on CT images. In order to test MarkerMatch's ability to handle CT images of different quality, we scanned the phantom with four CT spacing. The portal image pair taken before treatment is normally at AP/Lateral gantry angles, but sometimes it is difficult to identify markers from the lateral image. To test MarkerMatch's ability to handle non‐orthogonal portal image pair, we took portal images at 7 different gantry angles. As a preliminary test for the use of Markermatch in clinic, we retrospectively analyzed five patients implanted with 2–3 gold markers based on 43 pairs of weekly setup portal images. Results: In our phantom test, MarkerMatch is able to measure overall marker displacements within 1mm in each direction, regardless of the spacing used in the CT scans. Using different gantry separation angles, the measured overall marker displacements agree with each other within 1mm. Retrospective analysis of five patients is also presented. Conclusion: Initial studies indicate that MarkerMatch is robust in detecting and analyzing patient motion in 3D and can provide valuable information of inter‐fractional prostate motion in clinic. Conflict of Interest: Funded in part by Varian Research Grant.