Investigation of the change in marker geometry during respiration motion: a preliminary study for dynamic-multi-leaf real-time tumor tracking.

BACKGROUND: The use of stereotactic body radiotherapy (SBRT) is rapidly increasing. Presently, the most accurate method uses fiducial markers implanted near the tumor. A shortcoming of this method is that the beams turn off during the majority of the respiratory cycle, resulting in a prolonged treatment time. Recent advances in collimation technology have enabled continuous irradiation to a moving tumor. However, the lung is a dynamic organ characterized by inhalation exhalation cycles, during which marker/tumor geometry may change (i.e., misalignment), resulting in under-dosing to the tumor. FINDINGS: Eight patients with lung cancer who were candidates for stereotactic radiotherapy were examined with 4D high-resolution CT. As a marker surrogate, virtual bronchoscopy using the pulmonary artery (VBPA) was conducted. To detect possible marker/tumor misalignment during the respiration cycle, the distance between the peripheral bronchus, where a marker could be implanted, and the center of gravity of a tumor were calculated for each respiratory phase. When the respiration cycle was divided into 10 phases, the median value was significantly larger for the 30%-70% respiratory phases compared to that for the 10% respiratory phase (P<0.05, Mann-Whitney U-test). CONCLUSIONS: These results demonstrate that physiological aspect must be considered when continuous tumor tracking is applied to a moving tumor. To minimize an "additional" internal target volume (ITV) margin, a marker should be placed approximately 2.5 cm from the tumor.

Adaptive external gating based on the updating method of internal/external correlation and gating window before each beam delivery.

The purpose of this study is to evaluate the performance of an adaptive gating method, which is designed to accommodate the beam-to-beam and day-to-day variation of the internal/external correlation, as well as the real tumor position during respiratory-gated fractionated radiotherapy. We define a two-step procedure: (1) before each treatment, target positions are detected and synchronized with an external surrogate for establishing the internal/external correlation model and determining the position of the gating window, and then (2) during the delivery of the treatment beam, the gating is triggered by an external signal based on the updated internal/external correlation and window position. This correlation is described by a linear-quadratic model including a time shift between the internal and external signals. To simulate the proposed method, data of tumor motion in the superior-inferior direction synchronized with an external surrogate during hypo-fractionated radiotherapy from five lung patients are analyzed retrospectively. Duty cycle (DC), target coverage (TC) and the average distance (AD) between the internal target position and the edge of the gating window for all false positives are calculated as evaluative criteria. Under a 5 mm gating window, the average TC is 88.9%, with a DC around 45% and a mean AD of 0.7 mm. A daily update is also simulated for comparison, and it is found that beam-to-beam updating is superior. In conclusion, the combined updating of internal/external correlation and the gating window for each beam can improve the accuracy and reliability of respiratory-gated radiotherapy.

Clinical characteristics and computed tomography findings in children with 2009 pandemic influenza A (H1N1) viral pneumonia.

In this article we review the clinical characteristics and computed tomography (CT) findings in children with 2009 pandemic H1N1 influenza viral pneumonia. The medical charts of 88 children with pandemic H1N1 influenza virus infection, admitted to our hospital in Japan from 10 August to 28 December 2009, were reviewed; we compared the clinical features of these children with those of 61 children admitted with seasonal influenza A during the previous 3 seasons. Of 88 patients, 53 (60%) had radiographic findings consistent with pneumonia and 34 patients underwent a chest computed tomography (CT) scan. Pneumonia was a more frequent complication in children with pandemic H1N1 influenza compared with those with seasonal influenza (60% vs 11%; p < 0.001). The predominant CT findings were unilateral or bilateral multifocal consolidation (15/34; 44%) associated with ground-glass opacities in the peribronchovascular region. The second most common CT finding was unilateral diffuse consolidation or atelectasis in 1 or more lung zones (12/34; 35%). The chest CT findings of unilateral or bilateral multifocal consolidation often associated with ground-glass opacities were commonly seen in children with pandemic H1N1 influenza viral pneumonia. Atelectasis was seen in patients who required oxygen administration.

Evaluation of the need for simultaneous orthogonal gated setup imaging.

Image-guided patient setup for respiratory-gated radiotherapy often relies on a pair of respiratory-gated orthogonal radiographs, acquired one after the other. This study quantifies the error due to changes in the internal/external correlation which may affect asynchronous (non-simultaneous) imaging. The dataset from eight patients includes internal and external coordinates acquired at 30Hz during multi-fraction SBRT treatments using the Mitsubishi RTRT system coupled with an external surrogate gating device. We performed a computational simulation of the position of an implanted fiducial marker in an asynchronous orthogonal image set. A comparison is made to the reference position, the actual 3D fiducial location at the initial time point, as would be obtainable by simultaneous orthogonal setup imaging at that time point. The time interval between the two simulated radiographic acquisitions was set to a minimum of 30, 60 or 90 seconds, based on our clinical experience. The setup position is derived from a combination of both the initial (AP) and the final (LR) simulated 2D images in the following way: LRsetup = LRinitial , SIsetup = SIinitial + (SIfinal - SIinitial)/2, APsetup = APfinal. The 3D error is then the magnitude of the vector from the initial (reference) position to the setup position. The calculation was done for every exhale phase in the data for which there was another one at least 30, 60 or 90 seconds later, at an amplitude within 0.5 mm from the first. A correlation between the time interval and the 3D error was also sought. The mean 3D error is found to be roughly equivalent for time intervals (tinterval) of 30, 60 and 90 seconds between the orthogonal simulated images (0.8 mm, 0.8 mm, 0.6 mm, respectively). The 3D error is less than 1, 2 and 3 mm for 77%, 89% and 98% of the data points, respectively. The actual time between simulated images turned out to be very close to tinterval, with 90% of the second simulated image acquisitions being completed within 38, 68 and 95 seconds of the first simulated image for tinterval of 30, 60 and 90 seconds, respectively. No correlation was found between the length of the time interval and the 3D error. When acquiring respiratory-gated radiographs for patient setup, only small errors should be expected if those images are not taken simultaneously.

Image-guided adaptive gating of lung cancer radiotherapy: a computer simulation study.

The purpose of this study is to investigate the effect that image-guided adaptation of the gating window during treatment could have on the residual tumor motion, by simulating different gated radiotherapy techniques. There are three separate components of this simulation: (1) the 'Hokkaido Data', which are previously measured 3D data of lung tumor motion tracks and the corresponding 1D respiratory signals obtained during the entire ungated radiotherapy treatments of eight patients, (2) the respiratory gating protocol at our institution and the imaging performed under that protocol and (3) the actual simulation in which the Hokkaido Data are used to select tumor position information that could have been collected based on the imaging performed under our gating protocol. We simulated treatments with a fixed gating window and a gating window that is updated during treatment. The patient data were divided into different fractions, each with continuous acquisitions longer than 2 min. In accordance to the imaging performed under our gating protocol, we assume that we have tumor position information for the first 15 s of treatment, obtained from kV fluoroscopy, and for the rest of the fractions the tumor position is only available during the beam-on time from MV imaging. The gating window was set according to the information obtained from the first 15 s such that the residual motion was less than 3 mm. For the fixed gating window technique the gate remained the same for the entire treatment, while for the adaptive technique the range of the tumor motion during beam-on time was measured and used to adapt the gating window to keep the residual motion below 3 mm. The algorithm used to adapt the gating window is described. The residual tumor motion inside the gating window was reduced on average by 24% for the patients with regular breathing patterns and the difference was statistically significant (p-value = 0.01). The magnitude of the residual tumor motion depended on the regularity of the breathing pattern suggesting that image-guided adaptive gating should be combined with breath coaching. The adaptive gating window technique was able to track the exhale position of the breathing cycle quite successfully. Out of a total of 53 fractions the duty cycle was greater than 20% for 42 fractions for the fixed gating window technique and for 39 fractions for the adaptive gating window technique. The results of this study suggest that real-time updating of the gating window can result in reliably low residual tumor motion and therefore can facilitate safe margin reduction.

Synchronous monitoring of external/internal respiratory motion: validity of respiration-gated radiotherapy for liver tumors.

PURPOSE: Four-dimensional (4D) radiotherapy, in particular respiration gating for the treatment of lung tumors, is gaining popularity. Its utility for other sites, however, has not been investigated fully. The purpose of this study was to see whether 4D therapy is feasible for liver tumors. MATERIAL AND METHODS: Six patients (five with hepatomas and one with metastatic liver tumor) had a fiducial, gold marker 1.5 mm in diameter implanted in the vicinity of their liver tumors. The inner and external (i.e., upper abdominal wall) respiratory movements were simultaneously recorded using a real-time tumor-tracking radiotherapy system and respiration monitor equipment applied to the mid to upper abdomen. RESULTS: The fluctuations from the baseline position of liver tumors were small; the mean absolute value was 3.92 +/- 1.94 mm. The mean right-left, anteroposterior, and craniocaudal total movements were 4.19 +/- 2.46, 7.23 +/- 2.96, and 15.98 +/- 6.02 mm, respectively. The phase shift was negligible. CONCLUSION: Liver tumors may be suitable for respiration-gated radiotherapy, and they may become curable with 4D radiotherapy.

Gating based on internal/external signals with dynamic correlation updates.

Precise localization of mobile tumor positions in real time is critical to the success of gated radiotherapy. Tumor positions are usually derived from either internal or external surrogates. Fluoroscopic gating based on internal surrogates, such as implanted fiducial markers, is accurate however requiring a large amount of imaging dose. Gating based on external surrogates, such as patient abdominal surface motion, is non-invasive however less accurate due to the uncertainty in the correlation between tumor location and external surrogates. To address these complications, we propose to investigate an approach based on hybrid gating with dynamic internal/external correlation updates. In this approach, the external signal is acquired at high frequency (such as 30 Hz) while the internal signal is sparsely acquired (such as 0.5 Hz or less). The internal signal is used to validate and update the internal/external correlation during treatment. Tumor positions are derived from the external signal based on the newly updated correlation. Two dynamic correlation updating algorithms are introduced. One is based on the motion amplitude and the other is based on the motion phase. Nine patients with synchronized internal/external motion signals are simulated retrospectively to evaluate the effectiveness of hybrid gating. The influences of different clinical conditions on hybrid gating, such as the size of gating windows, the optimal timing for internal signal acquisition and the acquisition frequency are investigated. The results demonstrate that dynamically updating the internal/external correlation in or around the gating window will reduce false positive with relatively diminished treatment efficiency. This improvement will benefit patients with mobile tumors, especially greater for early stage lung cancers, for which the tumors are less attached or freely floating in the lung.

A real-time dynamic-MLC control algorithm for delivering IMRT to targets undergoing 2D rigid motion in the beam's eye view.

An MLC control algorithm for delivering intensity modulated radiation therapy (IMRT) to targets that are undergoing two-dimensional (2D) rigid motion in the beam's eye view (BEV) is presented. The goal of this method is to deliver 3D-derived fluence maps over a moving patient anatomy. Target motion measured prior to delivery is first used to design a set of planned dynamic-MLC (DMLC) sliding-window leaf trajectories. During actual delivery, the algorithm relies on real-time feedback to compensate for target motion that does not agree with the motion measured during planning. The methodology is based on an existing one-dimensional (ID) algorithm that uses on-the-fly intensity calculations to appropriately adjust the DMLC leaf trajectories in real-time during exposure delivery [McMahon et al., Med. Phys. 34, 3211-3223 (2007)]. To extend the 1D algorithm's application to 2D target motion, a real-time leaf-pair shifting mechanism has been developed. Target motion that is orthogonal to leaf travel is tracked by appropriately shifting the positions of all MLC leaves. The performance of the tracking algorithm was tested for a single beam of a fractionated IMRT treatment, using a clinically derived intensity profile and a 2D target trajectory based on measured patient data. Comparisons were made between 2D tracking, 1D tracking, and no tracking. The impact of the tracking lag time and the frequency of real-time imaging were investigated. A study of the dependence of the algorithm's performance on the level of agreement between the motion measured during planning and delivery was also included. Results demonstrated that tracking both components of the 2D motion (i.e., parallel and orthogonal to leaf travel) results in delivered fluence profiles that are superior to those that track the component of motion that is parallel to leaf travel alone. Tracking lag time effects may lead to relatively large intensity delivery errors compared to the other sources of error investigated. However, the algorithm presented is robust in the sense that it does not rely on a high level of agreement between the target motion measured during treatment planning and delivery.

Exhale fluctuation in respiratory-gated radiotherapy of the lung: a pitfall of respiratory gating shown in a synchronized internal/external marker recording study.

PURPOSE: For optimal respiratory-gated radiotherapy, exhale fluctuation was assessed by monitoring internal fiducials in a synchronized internal/external marker detection system. METHODS: Synchronized internal/external position data were collected during the entire course of treatments for 12 lung patients with 24 fiducials. Baseline was determined in the exhale phase during pre-treatment observation time, and a gating level of external waves was set in each treatment session in a simulation of respiratory-gated radiotherapy. Patients were treated under a real-time tumor-tracking (RTRT) system with an external (abdominal) respiratory motion detector. In the simulation, external gating windows were defined as those below the 30% amplitude level (i.e., imaginary beams would be triggered when part of the respiratory wave falls into this window). Exhale fluctuation (EF) was defined as the phenomenon in which the lowest point of the external wave crossed downward past the pre-determined baseline. Gating efficiency (GE) was defined as the ratio between the amount of gate-ON time and the total treatment time. RESULTS: EF occurred in 18.4% of total measurements. EF varied depending on the patient, fiducial sites, and treatment session. The mean incidence of EF for each patient varied from 2.9% to 37.5% (18.4+/-9.9). The EF magnitude was 0.2-12.2 mm in the left-right direction, 0.7-12.7 mm in the cranio-caudal direction, and 0.4-9.7 mm in the anterior-posterior direction. Total fiducial movement was 0.5-28.7 mm. GE was 36.1-69.2% (55.4+/-11.0). EF magnitude correlated with total fiducial movement. CONCLUSION: This study showed that EF is not a rare phenomenon and needs to be taken into consideration for individualized precise 4D radiotherapy.

Adaptive prediction of respiratory motion for motion compensation radiotherapy.

One potential application of image-guided radiotherapy is to track the target motion in real time, then deliver adaptive treatment to a dynamic target by dMLC tracking or respiratory gating. However, the existence of a finite time delay (or a system latency) between the image acquisition and the response of the treatment system to a change in tumour position implies that some kind of predictive ability should be included in the real-time dynamic target treatment. If diagnostic x-ray imaging is used for the tracking, the dose given over a whole image-guided radiotherapy course can be significant. Therefore, the x-ray beam used for motion tracking should be triggered at a relatively slow pulse frequency, and an interpolation between predictions can be used to provide a fast tracking rate. This study evaluates the performance of an autoregressive-moving average (ARMA) model based prediction algorithm for reducing tumour localization error due to system latency and slow imaging rate. For this study, we use 3D motion data from ten lung tumour cases where the peak-to-peak motion is greater than 8 mm. Some strongly irregular traces with variation in amplitude and phase were included. To evaluate the prediction accuracy, the standard deviations between predicted and actual motion position are computed for three system latencies (0.1, 0.2 and 0.4 s) at several imaging rates (1.25-10 Hz), and compared against the situation of no prediction. The simulation results indicate that the implementation of the prediction algorithm in real-time target tracking can improve the localization precision for all latencies and imaging rates evaluated. From a common initial setting of model parameters, the predictor can quickly provide an accurate prediction of the position after collecting 20 initial data points. In this retrospective analysis, we calculate the standard deviation of the predicted position from the twentieth position data to the end of the session at 0.1 s interval. For both regular and irregular lung tumour motions, with prediction the range of average errors is 0.4-2.5 mm in the SI direction from shorter to longer latency, corresponding to a range of 0.8-4.3 mm without prediction; for the AP direction a range of 0.3-1.6 mm is obtained with prediction, corresponding to a range of 0.6-3.0 mm without prediction. For 0.2 s and 0.4 s system latency, with prediction the localization based on a relatively slow imaging rate (2.5 Hz) can achieve a better or similar precision compared with no prediction but on a fast imaging rate (10 Hz). This means that precise localization can be realized at a slow imaging rate. This is important for the application of kV x-ray imaging systems and EPID-based systems in image-guided radiotherapy. In conclusion, the adaptive predictor can successfully predict irregular respiratory motion, and the adaptive prediction of respiration motion can effectively improve the delivery precision of real-time motion compensation radiotherapy.

Internal-external correlation investigations of respiratory induced motion of lung tumors.

In gated radiation therapy procedures, the lung tumor position is used directly (by implanted radiopaque markers) or indirectly (by external surrogate methods) to decrease the volume of irradiated healthy tissue. Due to a risk of pneumothorax, many clinics do not implant fiducials, and the gated treatment is primarily based on a respiratory induced external signal. The external surrogate method relies upon the assumption that the internal tumor motion is well correlated with the external respiratory induced motion, and that this correlation is constant in time. Using a set of data that contains synchronous internal and external motion traces, we have developed a dynamic data analysis technique to study the internal-external correlation, and to quantitatively estimate its underlying time behavior. The work presented here quantifies the time dependent behavior of the correlation between external respiratory signals and lung implanted fiducial motion. The corresponding amplitude mismatch is also reported for the lung patients studied. The information obtained can be used to improve the accuracy of tumor tracking. For the ten patients in this study, the SI internal-external motion is well correlated, with small time shifts and corresponding amplitude mismatches. Although the AP internal-external motion reveals larger time shifts than along the SI direction, the corresponding amplitude mismatches are below 5 mm.

Accuracy of tumor motion compensation algorithm from a robotic respiratory tracking system: a simulation study.

The Synchrony Respiratory Tracking System (RTS) is a treatment option of the CyberKnife robotic treatment device to irradiate extra-cranial tumors that move due to respiration. Advantages of RTS are that patients can breath normally and that there is no loss of linac duty cycle such as with gated therapy. Tracking is based on a measured correspondence model (linear or polynomial) between internal tumor motion and external (chest/abdominal) marker motion. The radiation beam follows the tumor movement via the continuously measured external marker motion. To establish the correspondence model at the start of treatment, the 3D internal tumor position is determined at 15 discrete time points by automatic detection of implanted gold fiducials in two orthogonal x-ray images; simultaneously, the positions of the external markers are measured. During the treatment, the relationship between internal and external marker positions is continuously accounted for and is regularly checked and updated. Here we use computer simulations based on continuously and simultaneously recorded internal and external marker positions to investigate the effectiveness of tumor tracking by the RTS. The Cyberknife does not allow continuous acquisition of x-ray images to follow the moving internal markers (typical imaging frequency is once per minute). Therefore, for the simulations, we have used data for eight lung cancer patients treated with respiratory gating. All of these patients had simultaneous and continuous recordings of both internal tumor motion and external abdominal motion. The available continuous relationship between internal and external markers for these patients allowed investigation of the consequences of the lower acquisition frequency of the RTS. With the use of the RTS, simulated treatment errors due to breathing motion were reduced largely and consistently over treatment time for all studied patients. A considerable part of the maximum reduction in treatment error could already be reached with a simple linear model. In case of hysteresis, a polynomial model added some extra reduction. More frequent updating of the correspondence model resulted in slightly smaller errors only for the few recordings with a time trend that was fast, relative to the current x-ray update frequency. In general, the simulations suggest that the applied combined use of internal and external markers allow the robot to accurately follow tumor motion even in the case of irregularities in breathing patterns.

Carcinoma of the floor of the mouth: a case treated with precisely controlled external beam radiotherapy.

A new external radiotherapy system has been developed for head and neck cancer and a case with T2 oral floor carcinoma treated with this system is presented in this report. The system consists of real-time tumor-tracking equipment and a gold-marker implanted mouthpiece. Accuracy of the order of 2 mm was achieved during the entire course of fractionated radiotherapy (a total of 52.5 Gy in 15 fractions). Planning target volume became smaller compared to the conventional parallel-opposed technique. Dose-volume histogram analysis demonstrated a significant reduction in the dose to the mandible bone compared to the conventional technique. A confluent fibrinous mucositis developed in the oral floor mucosa that corresponded to 90% dose area. Mucositis in the lower gum was minimal and analgesics were not required. The patient is currently free from both tumor and complication during a follow-up period of 48 months. External radiotherapy can be an option as a curative treatment for early stage carcinoma of the floor of the mouth provided that patient set-up is rigid and reproducible.

Residual motion of lung tumors in end-of-inhale respiratory gated radiotherapy based on external surrogates.

It has been noted that some lung tumors exhibit large periodic motion due to respiration. To limit the amount of dose to healthy lung tissues, many clinics have begun gating radiotherapy treatment using externally placed surrogates. It has been observed by several institutions that the end-of-exhale (EOE) tumor position is more reproducible than other phases of the breathing cycle, so the gating window is often set there. From a treatment planning perspective, end-of-inhale (EOI) phase might be preferred for gating because the expanded lungs will further decrease the healthy tissue within the treatment field. We simulate gated treatment at the EOI phase, using a set of recently measured internal/external anatomy patient data. This paper attempts to answer three questions: (1) How much is the tumor residual motion when we use an external surrogate gating window at EOI? (2) How could we reduce the residual motion in the EOI gating window? (3) Is there a preference for amplitude- versus phase-based gating at EOI? We found that under free breathing conditions the residual motion of the tumors is much larger for EOI phase than for EOE phase. The mean values of residual motion at EOI were found to be 2.2 and 2.7 mm for amplitude- and phase-based gating, respectively, and, at EOE, 1.0 and 1.2 mm for amplitude- and phase-based gating, respectively. However, we note that the residual motion in the EOI gating window is correlated well with the reproducibility of the external surface position in the EOI phase. Using the results of a published breath-coaching study, we deduce that the residual motion of a lung tumor at EOI would approach that at EOE, with the same duty cycle (30%), under breath-coaching conditions. Additionally, we found that under these same conditions, phase-based gating approaches the same residual motion as amplitude-based gating, going from a 28% difference to 11%, for the patient with the largest difference between the two gating modalities. We conclude that it is feasible to achieve the same reproducibility of tumor location at EOI as at EOE if breath coaching is implemented, enabling us to reap the benefits of the dosimetric advantage of EOI gating.

Residual motion of lung tumours in gated radiotherapy with external respiratory surrogates.

Due to respiration, many tumours in the thorax and abdomen may move as much as 3 cm peak-to-peak during radiation treatment. To mitigate motion-induced irradiation of normal lung tissue, clinics have employed external markers to gate the treatment beam. This technique assumes that the correlation between the external surface and the internal tumour position remains constant inter-fractionally and intra-fractionally. In this work, a study has been performed to assess the validity of this correlation assumption for external surface based gated radiotherapy, by measuring the residual tumour motion within a gating window. Eight lung patients with implanted fiducial markers were studied at the NTT Hospital in Sapporo, Japan. Synchronized internal marker positions and external abdominal surface positions were measured during the entire course of treatment. Stereoscopic imaging was used to find the internal markers in four dimensions. The data were used retrospectively to assess conventional external surrogate respiratory-gated treatment. Both amplitude- and phase-based gating methods were investigated. For each method, three gating windows were investigated, each giving 40%, 30% and 20% duty cycle, respectively. The residual motion of the internal marker within these six gating windows was calculated. The beam-to-beam variation and day-to-day variation in the residual motion were calculated for both gating modalities. We found that the residual motion (95th percentile) was between 0.7 and 5.8 mm, 0.8 and 6.0 mm, and 0.9 and 6.2 mm for 20%, 30% and 40% duty cycle windows, respectively. Five of the eight patients showed less residual motion with amplitude-based gating than with phase-based gating. Large fluctuations (>300%) were seen in the residual motion between some beams. Overall, the mean beam-to-beam variation was 37% and 42% from the previous treatment beam for amplitude- and phase-based gating, respectively. The day-to-day variation was 29% and 34% from the previous day for amplitude- and phase-based gating, respectively. Although gating reduced the total tumour motion, the residual motion behaved unpredictably. Residual motion during treatment could exceed that which might have been considered in the treatment plan. Treatment margins that account for motion should be individualized and daily imaging should be performed to ensure that the residual motion is not exceeding the planned motion on a given day.

High dose three-dimensional conformal boost (3DCB) using an orthogonal diagnostic X-ray set-up for patients with gynecological malignancy: a new application of real-time tumor-tracking system.

The feasibility and accuracy of high dose three-dimensional conformal boost (3DCB) using three internal fiducial markers and a two-orthogonal X-ray set-up of the real-time tumor-tracking system on patients with gynecological malignacy were investigated in 10 patients. The standard deviation of the distribution of systematic deviations (Sigma) was reduced from 3.8, 4.6, and 4.9 mm in the manual set-up to 2.3, 2.3 and 2.7 mm in the set-up using the internal markers. The average standard deviation of the distribution of random deviations (sigma) was reduced from 3.7, 5.0, and 4.5 mm in the manual set-up to 3.3, 3.0, and 4.2 mm in the marker set-up. The appropriate PTV margin was estimated to be 10.2, 12.8, and 12.9 mm in the manual set-up and 6.9, 6.7, and 8.3 mm in the gold marker set-up, respectively, using the formula 2Sigma + 0.7sigma. Set-up of the patients with three markers and two fluoroscopy is useful to reduce PTV margin and perform 3DCB.

Reflux in the left ovarian vein: analysis of MDCT findings in asymptomatic women.

OBJECTIVE: The aim of this study was to clarify the CT features of ovarian vein reflux in asymptomatic women and to determine the possible cause of the reflux. MATERIALS AND METHODS: One hundred ten multiparous or uniparous and 41 nulliparous asymptomatic women were examined on MDCT. Degree, pathway, and associated findings of ovarian vein reflux were evaluated. We measured the diameters of the left renal vein (LRV), the ovarian veins, and the parauterine veins. Ratios of LRV diameters (lateral-aortomesenteric) were obtained. These data were then compared between the women with reflux and those without reflux. RESULTS: Reflux was found in 44% (48/110) of parous and 5% (2/41) of nulliparous women. Reflux flowed into the right ovarian vein through the parauterine and uterine veins in 25 women. Twenty-four of these 25 women were multiparous. In these cases, the parauterine veins showed varicose dilation (5.9 +/- 1.6 mm [mean +/- SD]). There was a statistically significant difference in left ovarian vein diameter (8.3 +/- 2.1 mm vs 4.9 +/- 1.3 mm, p < 0.0001) between parous women with reflux and those without reflux, respectively. The LRV diameter ratio (lateral-aortomesenteric) was also statistically significant (3.6 +/- 1.3 vs 1.7 +/- 0.7, p < 0.0001) between the same two groups. CONCLUSION: Reflux into the left ovarian vein is seen up into the contralateral ovarian plexus by passing through the dilated parauterine and uterine veins. This CT finding is common in asymptomatic multiparous women. Narrowing of the LRV at its aortomesenteric portion can be one of the causes of such reflux.

Pilot study of modified version of CHOP plus radiotherapy for early-stage aggressive non-Hodgkin's lymphoma of the head and neck.

PURPOSE: To evaluate the safety and efficacy of a modified version of cyclophosphamide, doxorubicin, vincristine, prednisone (pirarubicin, cyclophosphamide, vincristine, and prednisone [THP-COP]) plus radiotherapy for early-stage aggressive non-Hodgkin's lymphoma of the head and neck. METHODS AND MATERIALS: Between December 1993 and December 1999, 41 patients with early-stage non-Hodgkin's lymphoma with intermediate-grade histologic features were enrolled in our study. The mean patient age was 51 years. Of the 41 patients, 27 had Stage I and 14 Stage II disease. The primary site was Waldeyer's ring, a neck node, or an extranodal site in 14, 11, and 16 patients, respectively. The immunophenotype was B cell in 29 and T cell in 12 patients. All patients were in the low-risk category according to the International Prognostic Index. Chemotherapy consisted of 40 mg/m(2) i.v. pirarubicin (THP-Adriamycin), 750 mg/m(2) i.v. cyclophosphamide, and 1.0 mg/m(2) i.v. vincristine, on Day 1 and 40 mg/m(2) p.o. prednisone on Days 1-5. The combination chemotherapy was given twice at a 14-day interval. Radiotherapy was given to involved areas at a fraction size of 2.0-2.5 Gy up to a total of 40 Gy within 4-5 weeks. The mean follow-up period was 63 months. RESULTS: The 5-year overall survival rate was 89%. The 5-year cause-specific survival and progression-free survival rate was 90% and 81%, respectively. The 5-year progression-free survival rate for patients with Waldeyer's ring primaries was 93%. Patients with tumor <5 cm in size had greater 5-year progression-free survival than those with tumor >5 cm in size (85% vs. 33%, p <0.05, log-rank test). Grade 4 neutropenia was seen in 12% of patients; however, 93% of patients (38 of 41) received chemotherapy as scheduled with the support of granulocyte colony-stimulating factor. CONCLUSION: Biweekly THP-COP plus radiotherapy is feasible and effective for Stage I-II low-risk non-Hodgkin's lymphoma.

Registration accuracy and possible migration of internal fiducial gold marker implanted in prostate and liver treated with real-time tumor-tracking radiation therapy (RTRT).

BACKGROUND AND PURPOSE: We have developed a linear accelerator synchronized with a fluoroscopic real-time tumor-tracking system to reduce errors due to setup and organ motion. In the real-time tumor-tracking radiation therapy (RTRT) system, the accuracy of tumor tracking depends on the registration of the marker's coordinates. The registration accuracy and possible migration of the internal fiducial gold marker implanted into prostate and liver was investigated. MATERIALS AND METHODS: Internal fiducial gold markers were implanted in 14 patients with prostate cancer and four patients with liver tumors. Computed tomography (CT) was carried out as a part of treatment planning in the 18 patients. A total of 72 follow-up CT scans were taken. We calculated the relative relationship between the coordinates of the center of mass (CM) of the organs and those of the marker. The discrepancy in the CM coordinates during a follow-up CT compared to those recorded during the planning CT was used to study possible marker migration. RESULTS: The standard deviation (SD) of interobserver variations in the CM coordinates was within 2.0 and 0.4 mm for the organ and the marker, respectively, in seven observers. Assuming that organs do not shrink, grow, or rotate, the maximum SD of migration error in each direction was estimated to be less than 2.5 and 2.0 mm for liver and prostate, respectively. There was no correlation between the marker position and the time after implantation. CONCLUSION: The degree of possible migration of the internal fiducial marker was within the limits of accuracy of the CT measurement. Most of the marker movement can be attributed to the measurement uncertainty, which also influences registration in actual treatment planning. Thus, even with the gold marker and RTRT system, a planning target volume margin should be used to account for registration uncertainty.