Anatomy- vs. fluence-based planning for prostate cancer treatments using VMAT.

The purpose of this study was to compare the planning approaches used in two treatment planning systems (TPS) provided by Elekta for VMAT treatments. Ten prostate patients were studied retrospectively. Plan comparison was performed in terms of delivery efficiency and accuracy, as well as in terms of target coverage and critical organ protection by utilizing physical and radiobiological indices. These include: DVH (dose volume histogram) values, CI (conformity index), HI(%) (homogeneity index) and TCP (tumor control probability) for target coverage; mean doses, DVH values, dose to the normal non-target tissue, NTCP (normal tissue complication probability) and GI (gradient index) for critical organ sparing; MU/fraction and treatment time for delivery efficiency. The comparisons were performed using the two-sided Wilcoxon matched-pair signed rank test. Plans generated using the anatomy-based approach in ERGO++ and fluence-based approach in Monaco were found similar in terms of target coverage and TCP values, as well as in terms of rectum protection and corresponding NTCP values. The former exhibited increased delivery efficiency (comparable to that of 3D conformal radiotherapy) due to the relatively larger segments used. On the other hand advantages of the fluence-based approach in Monaco include increased conformity, better target dose homogeneity and higher dose gradient (lower dose to normal non-target-tissue) mainly due to the higher degree of modulation offered by the fluence-based approach, while the Monte Carlo algorithm used for dose calculation provides plans with increased accuracy despite the relatively small segments used.

Suggestion for a new grading scale for radiation induced pneumonitis based on radiological findings of computerized tomography: correlation with clinical and radiotherapeutic parameters in lung cancer patients.

BACKGROUND: The objective of this research is the computed axial tomography (CT) imaging grading of radiation induced pneumonitis (RP) and its correlation with clinical and radiotherapeutic parameters. MATERIALS AND METHODS: The chest CT films of 20 patients with non-small cell lung cancer who have undergone three- dimensional conformal radiation therapy were reviewed. The proposed CT grading of RP is supported on solely radiological diagnosis criteria and distinguishes five grades. The manifestation of RP was also correlated with any positive pre-existing chronic obstructive pulmonary disease (COPD) history, smoking history, the FEV1 value, and the dosimetric variable V20. RESULTS: The CT grading of RP was as follows: 3 patients (15%) presented with ground glass opacity (grade 1), 9 patients (45%) were classified as grade 2, 7 patients (35%) presented with focal consolidation, with or without elements of fibrosis (grade 3), and only one patient (5%) presented with opacity with accompanying atelectasis and loss of pulmonary volume (grade 4). Both univariate and multivariate analysis revealed as prognostic factors for the radiological grading of RP the reduction of FEV1 and the V20 (P=0.026 and P=0.003, respectively). There was also a significant (P<0.001) correlation of radiological grading of RP with FEV1 and V20 (spearman rho 0.92 and 0.93, respectively). CONCLUSIONS: The high correlation of the proposed radiological grading with the FEV1 and the V20 is giving a satisfactory clinical validity. Although the proposed grading scale seems relevant to clinical practice, further studies are needed for the confirmation of its validity and reliability.

Radiation doses to patients from extracorporeal shock wave lithotripsy.

The aim of this study was to determine the radiation doses to patients during extracorporeal shock wave lithotripsy (ESWL) and compare them with the available bibliographical data. In this method localization of the renal stones is attained by the use of fluoroscopy, and thus ESWL is included among those medical practices associated with patient radiation exposure. The entrance surface dose was measured using 3-4 thermoluminescent dosimeters positioned on the patients' backs at the entrance surfaces of the two x-ray beams for 50 ESWL procedures. Fluoroscopy time and number of spot films were also recorded. The average entrance surface dose at the patient's side with the renal stone was estimated to be 76.5 mGy for the oblique x-ray beam and 44.5 mGy for the PA x-ray beam. The mean fluoroscopy time was 204 s while 4 spot films were acquired on average. The mean effective dose (E) was estimated as 1.63 mSv per patient. The mean entrance surface dose values recorded in this study are comparable to but smaller than the values reported in the literature for ESWL, while the mean fluoroscopy time is within the range of values reported by other authors. On the other hand, the estimated E value is relatively higher compared to the corresponding values given in the literature based on patient measurements. However, it is comparable to recent published data acquired using extended measurements in an anthropomorphic phantom.

Mechanical and dose delivery accuracy evaluation in radiosurgery using polymer gels.

The polymer gel-Magnetic Resonance Imaging (MRI) dosimetry technique was employed to evaluate the mechanical and dose delivery accuracy in Leksell gamma knife stereotactic radiosurgery for the treatment of multiple targets. Two different polymer gel dosimeter formulations that have been reported in the literature were prepared in-house. A plan for the treatment of four brain metastases (targets) was generated. The plan involved the delivery of four, 8 mm collimator shots using different prescription isodose lines and different prescription doses for each target, keeping the maximum dose constant for all the targets. A sample of each gel formulation was irradiated using a custom made phantom with an experimental procedure capable of testing the increased nominal mechanical accuracy of stereotactic radiosurgery. The irradiated dosimeters were evaluated using a clinical 1.5 T Philips ACS NT MR imager. Result manipulation in 3-D allowed for the determination of the mechanical accuracy in the delivery of each shot through the comparison of measured versus planned shot center coordinates. Dose delivery accuracy was also evaluated by comparison of maximum dose values measured at the center of each shot as well as dose distribution measurements, with corresponding treatment planning calculations. Polymer gel dosimetry was found capable of verifying the complete chain of radiosurgery treatment in gamma knife applications involving the irradiation of multiple targets.

Assessment of patient radiation doses during transcatheter closure of ventricular and atrial septal defects with Amplatzer devices.

The purpose of this study was to estimate the radiation dose to which children are exposed during cardiac catheterizations for the treatment of ventricular and atrial septal defects. Radiation doses were estimated for 46 children aged 1-18 years. These children were treated for secundum atrial septal defects (ASD group) for perimembranous ventricular septal defects (VSD group) or underwent a routine diagnostic catheterization (diagnostic group). Thermoluminescent dosimeters (TLDs) were attached in locations, representing the lateral entrance dose, the posterior entrance dose, the thyroid dose, and the gonad dose, respectively. A dose area product (DAP) meter was also attached externally on the posterior-anterior (PA) tube to give a direct value in cGy cm(2) for each procedure. The patient's entrance dose from the PA field ranged from 1.5 to 185.0 mGy for all patients, while the lateral entrance dose varied from 0.9 to 204 mGy. Radiation exposure to the thyroid and the gonads was found to vary from 0.4 to 8.3 and 0.1 to 2.1 mGy, respectively. The DAP meter recorded DAP values for the posterior tube, between 46 and 3,700 cGy cm(2). The mean effective dose was found to be 7.7, 16.2, and 33.3 mSv for the diagnostic, the ASD, and the VSD group, respectively. Very strong correlation was found between the DAP values and the entrance radiation dose measured with TLDs. The mean entrance dose received from therapeutic cardiac catheterizations using the Amplatzer devices was found approximately twice the dose received from a diagnostic one. Even for the most complex procedures, the maximum entrance dose was at least 10 times lower than the threshold, associated with skin erythema.

Quality assurance of Siemen's virtual wedge(TM)by using film dosimetry.

A film dosi netry method is proposed for measuring the non-uniform dose distribution generated by Virtual Wedges of a 6 MV Siemens Pr mus accelerator. This method was chosen due to the dose integration capabilities and the improved spatial resolution that films offer, giving the opportunity of measuring dose distribution in a single beam irradiation. Dose profiles were obtained and analyzed using a 16-bit Vidar film scanner and OmniPro-Accept software. Results were compared with corresponding ones measured with an array ionization chamber for both virtual and conventional wedges. A good agreement was found between the two methods for all the examined wedge angles. This study shows that film, dosimetry can be incorporated in a monthly quality asseurance program for virtual wedges in order to reduce the required effort.

Registration of electronic portal images for patient set-up verification.

Images acquired from an electronic portal imaging device are aligned with digitally reconstructed radiographs (DRRs) or other portal images to verify patient positioning during radiation therapy. Most of the currently available computer aided registration methods are based on the manual placement of corresponding landmarks. The purpose of the paper is twofold: (a) the establishment of a methodology for patient set-up verification during radiotherapy based on the registration of electronic portal images, and (b) the evaluation of the proposed methodology in a clinical environment. The estimation of set-up errors, using the proposed methodology, can be accomplished by matching the portal image of the current fraction of the treatment with the portal image of the baseline treatment (reference portal image) using a nearly automated technique. The proposed registration method is tested on a number of phantom data as well as on data from four patients. The phantom data included portal images that corresponded to various positions of the phantom on the treatment couch. For each patient, a set of 30 portal images was used. For the phantom data (for both transverse and lateral portal images), the maximum absolute deviations of the translational shifts were within 1.5 mm, whereas the in-plane rotation angle error was less than 0.5 degrees. The two-way Anova revealed no statistical significant variability both within observer and between-observer measurements (P > 0.05). For the patient data, the mean values obtained with manual and the proposed registration methods were within 0.5 mm. In conclusion, the proposed registration method has been incorporated within a system, called ESTERR-PRO. Its image registration capability achieves high accuracy and both intra- and inter-user reproducibility. The system is fully operational within the Radiotherapy Department of 'HYGEIA' Hospital in Athens and it could be easily installed in any other clinical environment since it requires standardized hardware specifications and minimal human intervention.

Dose verification in clinical IMRT prostate incidents.

PURPOSE: In view of the need for dose-validation procedures on each individual intensity-modulated radiation therapy (IMRT) plan, dose-verification measurements by film, by ionization chamber, and by polymer gel-MRI dosimetry were performed for a prostate-treatment plan configuration. Treatment planning system (TPS) calculations were evaluated against dose measurements. METHODS AND MATERIALS: Intensity-modulated radiation therapy (IMRT) treatments were planned on a commercial TPS. Kodak EDR-2 films were used for the verification of two-dimensional (2D) dose distributions at 1 coronal and 5 axial planes in a water-equivalent phantom. Full three-dimensional (3D) dose distributions were measured by use of a novel polymer gel formulation and a 3D magnetic resonance imaging (MRI) readout technique. Calculations were compared against measurements by means of isocontour maps, gamma-index maps (3% dose difference, 3-mm distance to agreement) and dose-volume histograms. RESULTS: A good agreement was found between film measurements and TPS predictions for points within the 60% isocontour, for all the examined plans (gamma-index <1 for 96% of pixels). Three-dimensional dose distributions obtained with the polymer gel-MRI method were adequately matched with corresponding TPS calculations, for measurements in a gel phantom covering the planning-target volume (PTV). CONCLUSIONS: Measured 2D and 3D dose distributions suggest that, for the investigated prostate IMRT plan configuration, TPS calculations provide clinically acceptable accuracy.

Radiotherapy in conjunction with intravenous infusion of 180 mg of disodium pamidronate in management of osteolytic metastases from breast cancer: clinical evaluation, biochemical markers, quality of life, and monitoring of recalcification using assessments of gray-level histogram in plain radiographs.

PURPOSE: To evaluate the clinical improvement and radiographically monitor the effect of local radiotherapy in conjunction with disodium pamidronate (DP) on metastatic osteolytic disease. METHODS AND MATERIALS: Thirty-three patients with osteolytic metastasis from advanced breast cancer received radiotherapy with a 6-MV linear accelerator up to a dose of 30 Gy (3 Gy/fraction, 5 d/wk) combined with 24 monthly sessions of a 180-mg DP infusion. Conventional X-rays were obtained during the first six sessions of DP treatment, retaining the same settings for each exposure. The analysis of the image attributes was based on measuring the first-order statistics of the mean value and energy of gray-level histograms in the osteolytic region. RESULTS: The 6-month measurements compared with baseline showed statistically significant differences (p < 0.01, Wilcoxon test) in energy of gray-level histogram (-10.8%), mean value of gray-level histogram (+9.5%), pain score (-5.8 points), Eastern Cooperative Oncology Group status (-2.4 points), urine hydroxyproline/creatinine ratio (-41.7%), urine calcium/creatinine ratio (-58.8%), and bone alkaline phosphatase (-42.4%). Quality of life as determined by the European Organization for Research and Treatment of Cancer Core Quality of Life Questionnaire (version 3) also improved. During follow-up, 88% of patients had complete and 12% partial responses (International Union Against Cancer radiologic criteria). On multivariate analysis, greater changes in the mean value of the gray-level histogram and negative nodal status were predictors for a reduction in the number of skeletal complications after therapy. Flu-like syndrome occurred in 13 patients (39%) and was well managed with mild antipyretics. CONCLUSION: Image-processing in plain radiographs offers an objective way to assess recalcification. The image-processing indexes, along with the measurements of performance status, quality of life, and biochemical markers, improved significantly. Local radiotherapy combined with long-term high-dose DP up to 180 mg is tolerable and has a high therapeutic response.

Use of image processing techniques to assess effect of disodium pamidronate in conjunction with radiotherapy in patients with bone metastases.

The aim of this study was radiographically to monitor the effect of disodium pamidronate on metastatic bone disease, using image-processing techniques. Eighteen patients with osteolytic metastases from breast cancer received an intravenous infusion of 180 mg disodium pamidronate every 4 weeks for a period of 6 months. The first session of intravenous infusions was given concurrently with external beam radiotherapy with a 6 MV linear accelerator (total dose 30 Gy in 10 fractions). Radiographs of osteolytic lesions were obtained at every session of the treatment, retaining the same settings for each modality. The analysis of the attributes of the images was based on measuring the first-order statistics of the gray-level histogram in terms of mean value (MVGLH) and energy (EGLH). The measurements showed significant differences for MVGLH and EGLH values (p < 0.05, Wilcoxon test). Analytically, there was an 11.08% (95% CI = 10.21, 11.93) mean reduction of EGLH and an 11.63% (95% CI = 10.96, 12.29) mean increase of MVGLH of the x-ray images, before and after the combined treatment protocol. The changes in the image-processing indices were also highly correlated with the reduction of the patient's pain score. These findings indicate an important increase in bone mass and bone formation, which the radiologists found difficult to identify visually.

Liposomal doxorubicin in conjunction with reirradiation and local hyperthermia treatment in recurrent breast cancer: a phase I/II trial.

PURPOSE: This is the first study to evaluate the tolerability and activity of liposomal doxorubicin (Caelyx; Schering-Plough Pharmaceuticals) < or =60 mg/km(2) in patients with locally recurrent breast cancer, when administered in conjunction with reirradiation and local hyperthermia treatment. EXPERIMENTAL DESIGN: Fifteen female patients, who had undergone a radical mastectomy and conventional radiotherapy (60 Gy) in the front chest wall, were entered on a multimodal protocol consisting of initial treatment with radiotherapy and a monthly infusion of liposomal doxorubicin < or =60 mg/m(2) in conjunction with local hyperthermia treatment. All patients received reirradiation up to a total dose of 30.6 Gy (1.8 Gy/fraction, 5 days a week). To evaluate the drug's safety, the first 5 patients initially received a dose of 40 mg/m(2) liposomal doxorubicin, which was then escalated to 60 mg/m(2). The other 10 patients received 60 mg/m(2) for all six cycles of chemotherapy. Hyperthermia (HT) was produced in the region of interest (ROI) using waveguides at a frequency of 433 MHz. The RSS was obtained from the curves representing the change in the ROI's surface with time for each patient, as fitted by linear regression. Linear regression analysis was used to study the relationship between the time interval from liposomal doxorubicin infusion to HT and the RSS. RESULTS: At doses of < or =60 mg/m(2), liposomal doxorubicin was well tolerated, with only mild hematological and nonhematological toxicity. All patients showed an objective measurable response, with 3 patients (20%) demonstrating a clinically complete response. There was a significant correlation between the duration of response and Avg Min T(90) > 44 degrees C (r(s) = 0.917, P < 0.0001) and the Mean[Tmin] (r(s) = 0.909, P < 0.0001). The RSS was significantly correlated with the interval between liposomal doxorubicin infusion and HT, as the smaller the time interval, the greater the clinical benefit (r = 0.76, P = 0.001). CONCLUSIONS: The multimodal treatment was effective and well tolerated, producing an objective measurable response in all patients. Local HT had a significant effect on patients' response to the drug. The relationship between thermal dose and liposomal action requires further investigation.