Effects of multiple breath hold reproducibility on treatment localization and dosimetric accuracy in radiotherapy of left-sided breast cancer with voluntary deep inspiration breath hold technique.

The purpose of this study was to investigate the effects of breath hold reproducibility on positional and dosimetric errors in radiotherapy of patients with left-sided breast cancer (LSBC) treated with voluntary deep inspiration breath hold (vDIBH) technique. Clinical data from 2 groups of patients with LSBC were retrospectively investigated: (1) those irradiated for the whole breast only (WB group, n = 20) using typically from 3 to 5 breath holds per treatment session and (2) those irradiated simultaneously also for supraclavicular lymph nodes (WB + SLN group, n = 27) using from 7 to 9 breath holds per fraction. Setup and field images (n = 1365) from tangential breast fields, and anterior and posterior lymph node fields were analyzed to obtain total, inter-, and intrafractional residual positional errors of the chest wall and clavicle. The dosimetric effect of intrafractional positional errors was investigated at the abutment level of breast and lymph node fields. The total systematic setup error in the longitudinal (superior-inferior [SI]) direction was 1.4 and 1.9 mm (1 standard deviation, p = 0.049) for the WB and WB + SLN groups, respectively, whereas in the anterior/lateral direction, the error was 1.2 mm for both groups. In the SI direction, the systematic intrafractional error was also larger in the WB + SLN group (1.9 vs 1.1 mm, p = 0.003). The latter positional errors correlated moderately (ρ = 0.51) with the number of breath holds. Mean intrafractional errors of at least 2 mm were observed for 38% of the patients in the WB + SLN group. These errors resulted in a dosimetric error from 8.3% to 10.1% (1 cc). The total localization errors and needed setup margins were wider for the WB + SLN group, due to increased amount of breath holds in treatment session. Mean intrafraction movements ≥ 2 mm were shown to occur with this patient group in the SI direction, requiring intrafractional positional monitoring and corrective actions in daily practice.

Treatment accuracy without rotational setup corrections in intracranial SRT.

The aim of this study was to evaluate the impact of actual rotational setup errors on dose distributions in intracranial stereotactic radiotherapy (SRT) with different alternatives for treatment position selection. A total of 38 SRT fractions from 18patients were retrospectively evaluated with rotational setup errors obtained from actual treatments. The planning computed tomography (CT) images were rotated according to online cone-beam CT (CBCT) images and the dose distribution was recalculated to the rotated CT images using three different patient positionings derived from: 1) an automatic 6D match neglecting rotation correction (Auto6D); 2) an automatic 3D match (Auto3D); and 3) a manual 3D match from actual treatment (Treat3D). The mean conformity index (CI) was 0.92 for the original plans and 0.91 for the Auto6D plans. The mean CI decreased significantly (p < 0.01) to 0.78 and 0.80 for the Auto3D and the Treat3D plans, respectively. The mean minimum dose of the planning target volume (PTVmin) was 91.9% of the prescribed dose for the original plans and 92.1% for the Auto6D plans, while for the Auto3D and the Treat3D plans PTVmin decreased significantly (p < 0.01) to 78.9% and 80.2%, respectively. No significant differences were seen between the Auto6D and the original treatment plans in terms of the dose parameters. However, the Auto3D and the Treat3D plans were statistically significantly inferior (p < 0.01) to the Auto6D and the original plans. In addition, a significant negative correlation (p < 0.01, |r| > 0.38) was found in the Auto3D and the Treat3D cases between the rotation error and CI, PTVmin or minimum dose of gross tumour volume. In SRT, a treatment plan of comparable quality to 6D rotation correction can be achieved by using 6D registration without a rotational correction in the selection of patient positioning. This was demonstrated for typical rotation errors seen in clinical practice.

Full Monte Carlo and measurement-based overall performance assessment of improved clinical implementation of eMC algorithm with emphasis on lower energy range.

New version 13.6.23 of the electron Monte Carlo (eMC) algorithm in Varian Eclipse™ treatment planning system has a model for 4MeV electron beam and some general improvements for dose calculation. This study provides the first overall accuracy assessment of this algorithm against full Monte Carlo (MC) simulations for electron beams from 4MeV to 16MeV with most emphasis on the lower energy range. Beams in a homogeneous water phantom and clinical treatment plans were investigated including measurements in the water phantom. Two different material sets were used with full MC: (1) the one applied in the eMC algorithm and (2) the one included in the Eclipse™ for other algorithms. The results of clinical treatment plans were also compared to those of the older eMC version 11.0.31. In the water phantom the dose differences against the full MC were mostly less than 3% with distance-to-agreement (DTA) values within 2mm. Larger discrepancies were obtained in build-up regions, at depths near the maximum electron ranges and with small apertures. For the clinical treatment plans the overall dose differences were mostly within 3% or 2mm with the first material set. Larger differences were observed for a large 4MeV beam entering curved patient surface with extended SSD and also in regions of large dose gradients. Still the DTA values were within 3mm. The discrepancies between the eMC and the full MC were generally larger for the second material set. The version 11.0.31 performed always inferiorly, when compared to the 13.6.23.

Improving the reproducibility of voluntary deep inspiration breath hold technique during adjuvant left-sided breast cancer radiotherapy.

BACKGROUND: Adjuvant radiotherapy (RT) of left-sided breast cancer (LSBC) with voluntary deep inspiration breath hold (vDIBH) technique reduces the cardiac dose. In this study, the effect of marker block position and the efficacy of breath hold level (BHL) correction based on lateral kV setup images are evaluated to improve the daily reproducibility. MATERIAL AND METHODS: A total of 148 consecutive LSBC patients treated with vDIBH RT were included in this study. The real-time position management (RPM) marker block was placed on the abdominal wall in 63 patients (group A) and on the sternum in 85 patients (group S). Acquired 900 (group A) + 1040 (group S) orthogonal image pairs were retrospectively analyzed. The actual BHL was determined from the lateral kV images. The height of the BHL gating window in RPM was corrected if errors of the actual BHL exceeded 4 mm. Setup margins were calculated for the chest wall and for bony surrogates of the lymph node regions. RESULTS: The sternal marker block reduced the random residual errors in the actual BHL (p < 0.05). The BHL correction was required for 26/63 patients in group A and for 26/85 patients in group S. Correction of the BHL window significantly reduced both the systematic and the random residual error in both groups. In patients with lymph node irradiation, the effect of both marker placement and BHL window correction was significant in the superior-inferior direction. Correction of the BHL reduced the mean cardiac dose by 0.5 Gy (p < 0.01) in group A and 0.6 Gy (p < 0.05) in group S. CONCLUSIONS: Reproducibility of the BHL can be improved by placing the marker block on the sternum and correcting the height of the BHL window based on lateral kV setup images. Acquisition of lateral kV images in the first 3 fractions and once a week during RT is recommended.

Residual position errors of lymph node surrogates in breast cancer adjuvant radiotherapy: Comparison of two arm fixation devices and the effect of arm position correction.

Residual position errors of the lymph node (LN) surrogates and humeral head (HH) were determined for 2 different arm fixation devices in radiotherapy (RT) of breast cancer: a standard wrist-hold (WH) and a house-made rod-hold (RH). The effect of arm position correction (APC) based on setup images was also investigated. A total of 113 consecutive patients with early-stage breast cancer with LN irradiation were retrospectively analyzed (53 and 60 using the WH and RH, respectively). Residual position errors of the LN surrogates (Th1-2 and clavicle) and the HH were investigated to compare the 2 fixation devices. The position errors and setup margins were determined before and after the APC to investigate the efficacy of the APC in the treatment situation. A threshold of 5mm was used for the residual errors of the clavicle and Th1-2 to perform the APC, and a threshold of 7mm was used for the HH. The setup margins were calculated with the van Herk formula. Irradiated volumes of the HH were determined from RT treatment plans. With the WH and the RH, setup margins up to 8.1 and 6.7mm should be used for the LN surrogates, and margins up to 4.6 and 3.6mm should be used to spare the HH, respectively, without the APC. After the APC, the margins of the LN surrogates were equal to or less than 7.5/6.0mm with the WH/RH, but margins up to 4.2/2.9mm were required for the HH. The APC was needed at least once with both the devices for approximately 60% of the patients. With the RH, irradiated volume of the HH was approximately 2 times more than with the WH, without any dose constraints. Use of the RH together with the APC resulted in minimal residual position errors and setup margins for all the investigated bony landmarks. Based on the obtained results, we prefer the house-made RH. However, more attention should be given to minimize the irradiation of the HH with the RH than with the WH.

Effects of remedies made in patient setup process on residual setup errors and margins in head and neck cancer radiotherapy based on 2D image guidance.

AIM: Patient setup errors were aimed to be reduced in radiotherapy (RT) of head-and-neck (H&N) cancer. Some remedies in patient setup procedure were proposed for this purpose. BACKGROUND: RT of H&N cancer has challenges due to patient rotation and flexible anatomy. Residual position errors occurring in treatment situation and required setup margins were estimated for relevant bony landmarks after the remedies made in setup process and compared with previous results. MATERIALS AND METHODS: The formation process for thermoplastic masks was improved. Also image matching was harmonized to the vertebrae in the middle of the target and a 5 mm threshold was introduced for immediate correction of systematic errors of the landmarks. After the remedies, residual position errors of bony landmarks were retrospectively determined from 748 orthogonal X-ray images of 40 H&N cancer patients. The landmarks were the vertebrae C1-2, C5-7, the occiput bone and the mandible. The errors include contributions from patient rotation, flexible anatomy and inter-observer variation in image matching. Setup margins (3D) were calculated with the Van Herk formula. RESULTS: Systematic residual errors of the landmarks were reduced maximally by 49.8% (p ≤ 0.05) and the margins by 3.1 mm after the remedies. With daily image guidance the setup margins of the landmarks were within 4.4 mm, but larger margins of 6.4 mm were required for the mandible. CONCLUSIONS: Remarkable decrease in the residual errors of the bony landmarks and setup margins were achieved through the remedies made in the setup process. The importance of quality assurance of the setup process was demonstrated.

Determination of the optimal matching position for setup images and minimal setup margins in adjuvant radiotherapy of breast and lymph nodes treated in voluntary deep inhalation breath-hold.

BACKGROUND: Adjuvant radiotherapy (RT) of left-sided breast cancer is increasingly performed in voluntary deep inspiration breath-hold (vDIBH). The aim of this study was to estimate the reproducibility of breath-hold level (BHL) and to find optimal bony landmarks for matching of orthogonal setup images to minimise setup margins. METHODS: 1067 sets of images with an orthogonal setup and tangential field from 67 patients were retrospectively analysed. Residual position errors were determined in the tangential treatment field images for different matches of the setup images. Variation of patient posture and BHL were analysed for position errors of the vertebrae, clavicula, ribs and sternum in the setup and tangential field images. The BHL was controlled with a Varian RPM® system. Setup margins were calculated using the van Herk's formula. Patients who underwent lymph node irradiation were also investigated. RESULTS: For the breast alone, the midway compromise of the ribs and sternum was the best general choice for matching of the setup images. The required margins were 6.5 mm and 5.3 mm in superior-inferior (SI) and lateral/anterior-posterior (LAT/AP) directions, respectively. With the individually optimised image matching position also including the vertebrae, slightly smaller margins of 6.0 mm and 4.8 mm were achieved, respectively. With the individually optimised match, margins of 7.5 mm and 10.8 mm should be used in LAT and SI directions, respectively, for the lymph node regions. These margins were considered too large. The reproducibility of the BHL was within 5 mm in the AP direction for 75% of patients. CONCLUSIONS: The smallest setup margins were obtained when the matching position of the setup images was individually optimised for each patient. Optimal match for the breast alone is not optimal for the lymph node region, and, therefore, a threshold of 5 mm was introduced for residual position errors of the sternum, upper vertebrae, clavicula and chest wall to retain minimal setup margins of 5 mm. Because random interfraction variation in patient posture was large, we recommend daily online image guidance. The BHL should be verified with image guidance.

Estimation of optimal matching position for orthogonal kV setup images and minimal setup margins in radiotherapy of whole breast and lymph node areas.

AIM: The aim was to find an optimal setup image matching position and minimal setup margins to maximally spare the organs at risk in breast radiotherapy. BACKGROUND: Radiotherapy of breast cancer is a routine task but has many challenges. We investigated residual position errors in whole breast radiotherapy when orthogonal setup images were matched to different bony landmarks. MATERIALS AND METHODS: A total of 1111 orthogonal setup image pairs and tangential field images were analyzed retrospectively for 50 consecutive patients. Residual errors in the treatment field images were determined by matching the orthogonal setup images to the vertebrae, sternum, ribs and their compromises. The most important region was the chest wall as it is crucial for the dose delivered to the heart and the ipsilateral lung. Inter-observer variation in online image matching was investigated. RESULTS: The best general image matching position was the compromise of the vertebrae, ribs and sternum, while the worst position was the vertebrae alone (p ≤ 0.03). The setup margins required for the chest wall varied from 4.3 mm to 5.5 mm in the lung direction while in the superior-inferior (SI) direction the margins varied from 5.1 mm to 7.6 mm. The inter-observer variation increased the minimal margins by approximately 1 mm. The margin of the lymph node areas should be at least 4.8 mm. CONCLUSIONS: Setup margins can be reduced by proper selection of a matching position for the orthogonal setup images. To retain the minimal margins sufficient, systematic error of the chest wall should not exceed 4 mm in the tangential field image.

The accuracy of Acuros XB algorithm for radiation beams traversing a metallic hip implant - comparison with measurements and Monte Carlo calculations.

In this study, the clinical benefit of the improved accuracy of the Acuros XB (AXB) algorithm, implemented in a commercial radiotherapy treatment planning system (TPS), Varian Eclipse, was demonstrated with beams traversing a high-Z material. This is also the first study assessing the accuracy of the AXB algorithm applying volumetric modulated arc therapy (VMAT) technique compared to full Monte Carlo (MC) simulations. In the first phase the AXB algorithm was benchmarked against point dosimetry, film dosimetry, and full MC calculation in a water-filled anthropometric phantom with a unilateral hip implant. Also the validity of the full MC calculation used as reference method was demonstrated. The dose calculations were performed both in original computed tomography (CT) dataset, which included artifacts, and in corrected CT dataset, where constant Hounsfield unit (HU) value assignment for all the materials was made. In the second phase, a clinical treatment plan was prepared for a prostate cancer patient with a unilateral hip implant. The plan applied a hybrid VMAT technique that included partial arcs that avoided passing through the implant and static beams traversing the implant. Ultimately, the AXB-calculated dose distribution was compared to the recalculation by the full MC simulation to assess the accuracy of the AXB algorithm in clinical setting. A recalculation with the anisotropic analytical algorithm (AAA) was also performed to quantify the benefit of the improved dose calculation accuracy of type 'c' algorithm (AXB) over type 'b' algorithm (AAA). The agreement between the AXB algorithm and the full MC model was very good inside and in the vicinity of the implant and elsewhere, which verifies the accuracy of the AXB algorithm for patient plans with beams traversing through high-Z material, whereas the AAA produced larger discrepancies.

Performance of dose calculation algorithms from three generations in lung SBRT: comparison with full Monte Carlo-based dose distributions.

The accuracy of dose calculation is a key challenge in stereotactic body radiotherapy (SBRT) of the lung. We have benchmarked three photon beam dose calculation algorithms--pencil beam convolution (PBC), anisotropic analytical algorithm (AAA), and Acuros XB (AXB)--implemented in a commercial treatment planning system (TPS), Varian Eclipse. Dose distributions from full Monte Carlo (MC) simulations were regarded as a reference. In the first stage, for four patients with central lung tumors, treatment plans using 3D conformal radiotherapy (CRT) technique applying 6 MV photon beams were made using the AXB algorithm, with planning criteria according to the Nordic SBRT study group. The plans were recalculated (with same number of monitor units (MUs) and identical field settings) using BEAMnrc and DOSXYZnrc MC codes. The MC-calculated dose distributions were compared to corresponding AXB-calculated dose distributions to assess the accuracy of the AXB algorithm, to which then other TPS algorithms were compared. In the second stage, treatment plans were made for ten patients with 3D CRT technique using both the PBC algorithm and the AAA. The plans were recalculated (with same number of MUs and identical field settings) with the AXB algorithm, then compared to original plans. Throughout the study, the comparisons were made as a function of the size of the planning target volume (PTV), using various dose-volume histogram (DVH) and other parameters to quantitatively assess the plan quality. In the first stage also, 3D gamma analyses with threshold criteria 3%/3mm and 2%/2 mm were applied. The AXB-calculated dose distributions showed relatively high level of agreement in the light of 3D gamma analysis and DVH comparison against the full MC simulation, especially with large PTVs, but, with smaller PTVs, larger discrepancies were found. Gamma agreement index (GAI) values between 95.5% and 99.6% for all the plans with the threshold criteria 3%/3 mm were achieved, but 2%/2 mm threshold criteria showed larger discrepancies. The TPS algorithm comparison results showed large dose discrepancies in the PTV mean dose (D50%), nearly 60%, for the PBC algorithm, and differences of nearly 20% for the AAA, occurring also in the small PTV size range. This work suggests the application of independent plan verification, when the AAA or the AXB algorithm are utilized in lung SBRT having PTVs smaller than 20-25 cc. The calculated data from this study can be used in converting the SBRT protocols based on type 'a' and/or type 'b' algorithms for the most recent generation type 'c' algorithms, such as the AXB algorithm.

Evaluation of overall setup accuracy and adequate setup margins in pelvic image-guided radiotherapy: comparison of the male and female patients.

We evaluated adequate setup margins for the radiotherapy (RT) of pelvic tumors based on overall position errors of bony landmarks. We also estimated the difference in setup accuracy between the male and female patients. Finally, we compared the patient rotation for 2 immobilization devices. The study cohort included consecutive 64 male and 64 female patients. Altogether, 1794 orthogonal setup images were analyzed. Observer-related deviation in image matching and the effect of patient rotation were explicitly determined. Overall systematic and random errors were calculated in 3 orthogonal directions. Anisotropic setup margins were evaluated based on residual errors after weekly image guidance. The van Herk formula was used to calculate the margins. Overall, 100 patients were immobilized with a house-made device. The patient rotation was compared against 28 patients immobilized with CIVCO's Kneefix and Feetfix. We found that the usually applied isotropic setup margin of 8mm covered all the uncertainties related to patient setup for most RT treatments of the pelvis. However, margins of even 10.3mm were needed for the female patients with very large pelvic target volumes centered either in the symphysis or in the sacrum containing both of these structures. This was because the effect of rotation (p ≤ 0.02) and the observer variation in image matching (p ≤ 0.04) were significantly larger for the female patients than for the male patients. Even with daily image guidance, the required margins remained larger for the women. Patient rotations were largest about the lateral axes. The difference between the required margins was only 1mm for the 2 immobilization devices. The largest component of overall systematic position error came from patient rotation. This emphasizes the need for rotation correction. Overall, larger position errors and setup margins were observed for the female patients with pelvic cancer than for the male patients.

Estimation of adequate setup margins and threshold for position errors requiring immediate attention in head and neck cancer radiotherapy based on 2D image guidance.

BACKGROUND: We estimated sufficient setup margins for head-and-neck cancer (HNC) radiotherapy (RT) when 2D kV images are utilized for routine patient setup verification. As another goal we estimated a threshold for the displacements of the most important bony landmarks related to the target volumes requiring immediate attention. METHODS: We analyzed 1491 orthogonal x-ray images utilized in RT treatment guidance for 80 HNC patients. We estimated overall setup errors and errors for four subregions to account for patient rotation and deformation: the vertebrae C1-2, C5-7, the occiput bone and the mandible. Setup margins were estimated for two 2D image guidance protocols: i) imaging at first three fractions and weekly thereafter and ii) daily imaging. Two 2D image matching principles were investigated: i) to the vertebrae in the middle of planning target volume (PTV) (MID_PTV) and ii) minimizing maximal position error for the four subregions (MIN_MAX). The threshold for the position errors was calculated with two previously unpublished methods based on the van Herk's formula and clinical data by retaining a margin of 5 mm sufficient for each subregion. RESULTS: Sufficient setup margins to compensate the displacements of the subregions were approximately two times larger than were needed to compensate setup errors for rigid target. Adequate margins varied from 2.7 mm to 9.6 mm depending on the subregions related to the target, applied image guidance protocol and early correction of clinically important systematic 3D displacements of the subregions exceeding 4 mm. The MIN_MAX match resulted in smaller margins but caused an overall shift of 2.5 mm for the target center. Margins ≤ 5mm were sufficient with the MID_PTV match only through application of daily 2D imaging and the threshold of 4 mm to correct systematic displacement of a subregion. CONCLUSIONS: Adequate setup margins depend remarkably on the subregions related to the target volume. When the systematic 3D displacement of a subregion exceeds 4 mm, it is optimal to correct patient immobilization first. If this is not successful, adaptive replanning should be considered to retain sufficiently small margins.

Radiological pulmonary findings after breast cancer irradiation: A prospective study.

The aim of this study was to evaluate radiation-induced pulmonary abnormalities of breast cancer patients. Altogether 202 consecutive patients receiving postoperative radiotherapy entered the study. Plain chest radiographs taken at entry and 3, 6 and 12 months after radiotherapy were evaluated according to modified Arriagada classification. In addition, pulmonary symptoms were recorded. Supplementary high-resolution computed tomography (HRCT) was employed in a subgroup of patients (n?=?15). Plain radiographs were interpreted by a radiologist, and uncertain findings were re-evaluated by a radiologist together with a radiation oncologist. Grade 2 pneumonitis was the most common abnormality. The proportion of patients yielding a grade 2 finding was 22.5%, 28.1%, and 16.0% at three, six, and twelve months, respectively. There were 2 normal findings in HRCTscans, and 8 in plain radiographs of the same patients. Radiological lung abnormalities are common after radiotherapy, but they are usually reversible, and their significance for the patient's well-being is minor. No correlation between symptoms and lung or pleural reactions was seen.

Evaluation of dose-response models and parameters predicting radiation induced pneumonitis using clinical data from breast cancer radiotherapy.

The purpose of this work is to evaluate the predictive strength of the relative seriality, parallel and LKB normal tissue complication probability (NTCP) models regarding the incidence of radiation pneumonitis, in a large group of patients following breast cancer radiotherapy, and furthermore, to illustrate statistical methods for examining whether certain published radiobiological parameters are compatible with a clinical treatment methodology and patient group characteristics. The study is based on 150 consecutive patients who received radiation therapy for breast cancer. For each patient, the 3D dose distribution delivered to lung and the clinical treatment outcome were available. Clinical symptoms and radiological findings, along with a patient questionnaire, were used to assess the manifestation of radiation-induced complications. Using this material, different methods of estimating the likelihood of radiation effects were evaluated. This was attempted by analysing patient data based on their full dose distributions and associating the calculated complication rates with the clinical follow-up records. Additionally, the need for an update of the criteria that are being used in the current clinical practice was also examined. The patient material was selected without any conscious bias regarding the radiotherapy treatment technique used. The treatment data of each patient were applied to the relative seriality, LKB and parallel NTCP models, using published parameter sets. Of the 150 patients, 15 experienced radiation-induced pneumonitis (grade 2) according to the radiation pneumonitis scoring criteria used. Of the NTCP models examined, the relative seriality model was able to predict the incidence of radiation pneumonitis with acceptable accuracy, although radiation pneumonitis was developed by only a few patients. In the case of modern breast radiotherapy, radiobiological modelling appears to be very sensitive to model and parameter selection giving clinically acceptable results in certain cases selectively (relative seriality model with Seppenwoolde et al and Gagliardi et al parameter sets). The use of published parameters should be considered as safe only after their examination using local clinical data. The variation of inter-patient radiosensitivity seems to play a significant role in the prediction of such low incidence rate complications. Scoring grades were combined to give stronger evidence of radiation pneumonitis since their differences could not be strictly associated with dose. This obviously reveals a weakness of the scoring related to this endpoint, and implies that the probability of radiation pneumonitis induction may be too low to be statistically analysed with high accuracy, at least with the latest advances of dose delivery in breast radiotherapy.

Evaluation of a segmentation procedure to delineate organs for use in construction of a radiation therapy planning atlas.

OBJECTIVES: This paper evaluates a semi-automatic segmentation procedure to enhance utilizing atlas based treatment plans. For this application, it is crucial to provide a collection of 'reference' organs, restorable from the atlas so that they closely match those of the current patient. To enable assembling representative organs, we developed a semi-automatic procedure using an active contour method. METHOD: The 3D organ volume was identified by defining contours on individual slices. The initial organ contours were matched to patient volume data sets and then superimposed on them. These starting contours were then adjusted and refined to rapidly find the organ outline of the given patient. Performance was evaluated by contouring organs of different size, shape complexity, and proximity to surrounding structures. We used representative organs defined on CT volumes obtained from 12 patients and compared the resulting outlines to those drawn by a radiologist. RESULTS: A strong correlation was found between the area measures of the delineated liver (r = 0.992), lung (r = 0.996) and spinal cord (r = 0.81), obtained by both segmentation techniques. A paired Student's t-test showed no statistical difference between the two techniques regarding the liver and spinal cord (p > 0.05). CONCLUSION: This method could be used to form 'standard' organs, which would form part of a whole body atlas (WBA) database for radiation treatment plans as well as to match atlas organs to new patient data.

Effects of positioning uncertainty and breathing on dose delivery and radiation pneumonitis prediction in breast cancer.

The quality of the radiation therapy delivered in the treatment of breast cancer is susceptible to setup errors and organ motion uncertainties. For 60 breast cancer patients (24 resected with negative node involvement, 13 resected with positive node involvement and 23 ablated) who were treated with three different irradiation techniques. these uncertainties are simulated. The delivered dose distributions in the lung were recalculated taking positioning uncertainty and breathing effects into account. In this way the real dose distributions delivered to the patients are more closely determined. The positioning uncertainties in the anteroposterior (AP) and the craniocaudal (CC) directions are approximated by Gaussian distributions based on the fact that setup errors are random. Breathing is assumed to have a linear behavior because of the chest wall movement during expiration and inspiration. The combined frequency distribution of the positioning and breathing distributions is obtained by convolution. By integrating the convolved distribution over a number of intervals, the positions and the weights of the fields that simulate the original 'effective fields' are calculated. Opposed tangential fields are simulated by a set of 5 pairs of fields in the AP direction and 3 such sets in the CC direction. Opposed AP + PA fields are simulated by a set of 3 pairs of fields in the AP direction and 3 such sets in the CC direction. Single frontal fields are simulated by a set of 5 fields. In radiotherapy for breast cancer, the lung is often partly within the irradiated volume even though it is a sensitive organ at risk. The influence of the deviation in the dose delivered by the original and the adjusted treatment plans on the clinical outcome is estimated by using the relative seriality model and the biologically effective uniform dose concept. Radiation pneumonitis is used as the clinical endpoint for lung complications. The adjusted treatment plans show larger lung complication probabilities than the original plans. This means that the true expected complications are often underestimated in clinical practice. The lung density variation during breathing is calculated from the maximal change in average density during tidal breathing. The change in density in the lung due to breathing is shown to have almost no influence on the dose distribution in the lung. The proposed treatment-plan adjustments taking positioning uncertainty and breathing effects into account indicate significant deviations in the dose delivery and the predicted lung complications.

Early skin and lung reactions in breast cancer patients after radiotherapy: prospective study.

PURPOSE: The association between early radiological lung reactions consequent upon radiotherapy and patients' symptoms is not well established. This prospective study examined the association between symptoms experienced by the patient, clinical findings observed by the physician and reactions visible in chest X-ray as interpreted by a radiologist, as well as the association between skin or breast symptoms and lung symptoms induced by radiotherapy after different methods of surgery. METHODS: Altogether 207 consecutive breast cancer patients entered the trial between 1st October 1997 and 31st December 1998. Chest X-rays were taken at entry and 3, 6 and 12 months after radiotherapy. The frequency and intensity of symptoms as well as clinical and chest X-ray findings were assessed over time. RESULTS: Skin and breast symptoms were common after radiotherapy but seldom severe (9%). Lung reactions were seen in chest X-ray in 47% of patients in re-evaluation by a radiologist at 3 months. The frequency of lung or skin symptoms did not correlate with chest X-ray findings, but there was a significant correlation between skin and lung symptoms. Radiotherapy after conservative surgery for node-positive breast cancer caused lung reactions seen in chest X-ray more often than after mastectomy when using other techniques. The reactions were most common at the 6 month evaluation (P=0.01). Concomitant adjuvant chemo- or endocrine therapy did not significantly increase the incidence of lung reactions. CONCLUSIONS: Skin, breast and lung symptoms were frequent after radiotherapy, but there was no real association between lung or skin symptoms and chest X-ray findings. The only correlation noted was between skin or breast symptoms and lung symptoms experienced by patients. Radiotherapy after conservative surgery was more frequently linked to chest X-ray findings than radiotherapy after mastectomy. We conclude that routine chest X-ray after radiotherapy gives no more clinically relevant information than the symptoms of the patient and we do not recommend routine chest X-rays for that reason.