Case Report: Treatment Planning Study to Demonstrate Feasibility of Transthoracic Ultrasound Guidance to Facilitate Ventricular Tachycardia Ablation With Protons.

Background: Cardiac arrhythmias, such as ventricular tachycardia, are disruptions in the normal cardiac function that originate from problems in the electrical conduction of signals inside the heart. Recently, a non-invasive treatment option based on external photon or proton beam irradiation has been used to ablate the arrhythmogenic structures. Especially in proton therapy, based on its steep dose gradient, it is crucial to monitor the motion of the heart in order to ensure that the radiation dose is delivered to the correct location. Transthoracic ultrasound imaging has the potential to provide guidance during this treatment delivery. However, it has to be noted that the presence of an ultrasound probe on the chest of the patient introduces constraints on usable beam angles for both protons and photon treatments. This case report investigates the possibility to generate a clinically acceptable proton treatment plan while the ultrasound probe is present on the chest of the patient. Case: A treatment plan study was performed based on a 4D cardiac-gated computed tomography scan of a 55 year-old male patient suffering from refractory ventricular tachycardia who underwent cardiac radioablation. A proton therapy treatment plan was generated for the actual treatment target in presence of an ultrasound probe on the chest of this patient. The clinical acceptability of the generated plan was confirmed by evaluating standard target dose-volume metrics, dose to organs-at-risk and target dose conformity and homogeneity. Conclusion: The generation of a clinically acceptable proton therapy treatment plan for cardiac radioablation of ventricular tachycardia could be performed in the presence of an ultrasound probe on the chest of the patient. These results establish a basis and justification for continued research and product development for ultrasound-guided cardiac radioablation.

Atlas Sampling for Prone Breast Automatic Segmentation of Organs at Risk: The Importance of Patients' Body Mass Index and Breast Cup Size for an Optimized Contouring of the Heart and the Coronary Vessels.

OBJECTIVE: Delineation of organs at risk is a time-consuming task. This study evaluates the benefits of using single-subject atlas-based automatic segmentation of organs at risk in patients with breast cancer treated in prone position, with 2 different criteria for choosing the atlas subject. Together with laterality (left/right), the criteria used were either (1) breast volume or (2) body mass index and breast cup size. METHODS: An atlas supporting different selection criteria for automatic segmentation was generated from contours drawn by a senior radiation oncologist (RO_A). Atlas organs at risk included heart, left anterior descending artery, and right coronary artery. Manual contours drawn by RO_A and automatic segmentation contours of organs at risk and breast clinical target volume were created for 27 nonatlas patients. A second radiation oncologist (RO_B) manually contoured (M_B) the breast clinical target volume and the heart. Contouring times were recorded and the reliability of the automatic segmentation was assessed in the context of 3-D planning. RESULTS: Accounting for body mass index and breast cup size improved automatic segmentation results compared to breast volume-based sampling, especially for the heart (mean similarity indexes >0.9 for automatic segmentation organs at risk and clinical target volume after RO_A editing). Mean similarity indexes for the left anterior descending artery and the right coronary artery edited by RO_A expanded by 1 cm were ≥0.8. Using automatic segmentation reduced contouring time by 40%. For each parameter analyzed (eg, D2%), the difference in dose, averaged over all patients, between automatic segmentation structures edited by RO_A and the same structure manually drawn by RO_A was <1.5% of the prescribed dose. The mean heart dose was reliable for the unedited heart segmentation, and for right-sided treatments, automatic segmentation was adequate for treatment planning with 3-D conformal tangential fields. CONCLUSIONS: Automatic segmentation for prone breast radiotherapy stratified by body mass index and breast cup size improved segmentation accuracy for the heart and coronary vessels compared to breast volume sampling. A significant reduction in contouring time can be achieved by using automatic segmentation.

Sparse proportional re-scanning with hadron beams.

Spot Scanning is a well-established technique to deliver the dose with hadron therapy systems. For many years re-scanning (called also re-painting) has been used to achieve uniform dose distribution in particular for moving organs, although it leads to an increase of the treatment time. Reducing this time is a major focus of present research. In this paper, after reviewing the current re-scanning techniques, sparse proportional re-scanning is defined and applied to 29 proton patient cases for a total of 54 fields. In this technique, only the highest weighted spot in the whole target is visited a number of times that is equal to the number N of re-scans. The number of visits of the beam spot to all remaining spots is scaled down proportionally to their weight. Sparse proportional re-scanning is advantageous especially in volumetric re-scanning. In order to quantify the potential advantages of this technique in terms of treatment time, a reduction factor of the number of scanned spots has been introduced, evaluated and analysed for 54 proton fields. The conclusion is that the reduction factor is a function of N (having values equal to 2.8 ±â€¯0.3 and 3.6 ±â€¯0.4 for N = 5 and N = 12 respectively) and does not depend either on the shape and volume of the target or on the distance between the scanned layers and the spot grid. The same values are approximately valid also for carbon ion treatments.

Effects of computing parameters and measurement locations on the estimation of 3D NPS in non-stationary MDCT images.

The goal of this study was to investigate the impact of computing parameters and the location of volumes of interest (VOI) on the calculation of 3D noise power spectrum (NPS) in order to determine an optimal set of computing parameters and propose a robust method for evaluating the noise properties of imaging systems. Noise stationarity in noise volumes acquired with a water phantom on a 128-MDCT and a 320-MDCT scanner were analyzed in the spatial domain in order to define locally stationary VOIs. The influence of the computing parameters in the 3D NPS measurement: the sampling distances bx,y,z and the VOI lengths Lx,y,z, the number of VOIs NVOI and the structured noise were investigated to minimize measurement errors. The effect of the VOI locations on the NPS was also investigated. Results showed that the noise (standard deviation) varies more in the r-direction (phantom radius) than z-direction plane. A 25 × 25 × 40 mm(3) VOI associated with DFOV = 200 mm (Lx,y,z = 64, bx,y = 0.391 mm with 512 × 512 matrix) and a first-order detrending method to reduce structured noise led to an accurate NPS estimation. NPS estimated from off centered small VOIs had a directional dependency contrary to NPS obtained from large VOIs located in the center of the volume or from small VOIs located on a concentric circle. This showed that the VOI size and location play a major role in the determination of NPS when images are not stationary. This study emphasizes the need for consistent measurement methods to assess and compare image quality in CT.

Feasibility and efficacy of accelerated weekly concomitant boost postoperative radiation therapy combined with concomitant chemotherapy in patients with locally advanced head and neck cancer.

BACKGROUND: The aim of this study was to assess feasibility and efficacy of weekly concomitant boost accelerated postoperative radiation therapy (PORT) with concomitant chemotherapy (CT) in patients with locally advanced head and neck cancer (LAHNC). METHODS AND MATERIALS: Conformal or intensity-modulated 66-Gy RT was performed in 5.5 weeks in 40 patients. Cisplatin was given at days 1, 22, and 43. Median follow-up was 36 months. RESULTS AND DISCUSSION: Grade 3 mucositis, dysphagia, and erythema was observed in ten (25%), nine (23%), and six (13%) patients, respectively. Grade 3 or more anemia was observed in two (6%) patients, and leukopenia in five (13%) patients. No grade 3 or 4 thrombocytopenia was observed. Grade 3 nephrotoxicity was observed in one patient (3%). No treatment-related mortality was observed. Grade 2 or more xerostomia and edema were observed in ten (25%) and one (3%) patient, respectively. Locoregional relapse occurred in eight patients, and seven patients developed distant metastases. Median time to locoregional relapse was 6 months. Three-year overall, disease-free survival, and locoregional control rates were 63%, 62%, and 81%, respectively. Multivariate analysis revealed that the only prognostic factor was nodal status. CONCLUSION: Reducing overall treatment time using accelerated PORT/CT by weekly concomitant boost (six fractions per week) combined with concomitant cisplatin CT is easily feasible with acceptable morbidity.

Performance comparison of two commercial BGO-based PET/CT scanners using NEMA NU 2-2001.

Combined positron emission tomography and computed tomography (PET/CT) scanners play a major role in medicine for in vivo imaging in an increasing number of diseases in oncology, cardiology, neurology, and psychiatry. With the advent of short-lived radioisotopes other than 18F and newer scanners, there is a need to optimize radioisotope activity and acquisition protocols, as well as to compare scanner performances on an objective basis. The Discovery-LS (D-LS) was among the first clinical PET/CT scanners to be developed and has been extensively characterized with older National Electrical Manufacturer Association (NEMA) NU 2-1994 standards. At the time of publication of the latest version of the standards (NU 2-2001) that have been adapted for whole-body imaging under clinical conditions, more recent models from the same manufacturer, i.e., Discovery-ST (D-ST) and Discovery-STE (D-STE), were commercially available. We report on the full characterization both in the two- and three-dimensional acquisition mode of the D-LS according to latest NEMA NU 2-2001 standards (spatial resolution, sensitivity, count rate performance, accuracy of count losses, and random coincidence correction and image quality), as well as a detailed comparison with the newer D-ST widely used and whose characteristics are already published.

Treatment of penile carcinoma: to cut or not to cut?

PURPOSE: The aim of this study was to assess the outcome in patients with penile cancer. METHODS AND MATERIALS: A total of 60 patients with penile carcinoma were included. Of the patients, 45 (n = 27) underwent surgery, and 51 underwent definitive (n = 29) or postoperative (n = 22) radiotherapy (RT). Median follow-up was 62 months. RESULTS: Median time to locoregional relapse was 14 months. Local failure was observed in 3 of 23 patients (13%) treated with surgery with or without postoperative RT vs. in 19 of 33 patients (56%) given organ-sparing treatment (p = 0.0008). Of 22 local failures, 16 (73%) were salvaged with surgery. Of the 33 patients treated with definitive RT (n = 29) and the 4 patients refusing RT after excisional biopsy, local control was obtained with organ preservation in 13 (39%). In the remaining 20, 4 patients with local failure underwent salvage conservatively, resulting in an ultimate penis preservation rate of 17 of 33 (52%) patients treated with definitive RT. The 5-year and 10-year probability of surviving with an intact penis was 43% and 26%, respectively. There was no survival difference between the patients treated with definitive RT and primary surgery (56% vs. 53%; p = 0.16). In multivariate analysis, independent factors influencing survival were N-classification and pathologic grade. Surgery was the only independent predictor for better local control. CONCLUSION: Based on our study findings, in patients with penile cancer, local control is superior with surgery. However, there is no difference in survival between patients treated with surgery and those treated with definitive RT, with 52% organ preservation.

Monte Carlo calculation of the sensitivity of a commercial dose calibrator to gamma and beta radiation.

The detection process used in a commercial dose calibrator was modeled using the GEANT 3 Monte Carlo code. Dose calibrator efficiency for gamma and beta emitters, and the response to monoenergetic photons and electrons was calculated. The model shows that beta emitters below 2.5 MeV deposit energy indirectly in the detector through bremsstrahlung produced in the chamber wall or in the source itself. Higher energy beta emitters (E > 2.5 MeV) deposit energy directly in the chamber sensitive volume, and dose calibrator sensitivity increases abruptly for these radionuclides. The Monte Carlo calculations were compared with gamma and beta emitter measurements. The calculations show that the variation in dose calibrator efficiency with measuring conditions (source volume, container diameter, container wall thickness and material, position of the source within the calibrator) is relatively small and can be considered insignificant for routine measurement applications. However, dose calibrator efficiency depends strongly on the inner-wall thickness of the detector.

[Antiandrogen gynecomastia: an inescapable harm? Radiotherapy: a simple and efficient solution!]. / La gynécomastie sous anti-androgènes: un mal inéluctable? La radiothérapie: une solution simple et efficace!

Anti-androgen induced gynecomastia, resulting from a treatment induced imbalance between oestrogens and androgens, is a frequently encountered side effect in the hormonal treatment of patients with prostatic cancer. One might expect to face an increase in the overall incidence of this side effect in the next-coming years as randomized trials clearly point to the evidence of the therapeutic benefit of anti-androgenic treatment for this prostatic cancer. Gynecomastia is often accompanied by mastodynia and does hamper quality of life. Surgery should be considered for established irreversible gynecomastia characterized by hyalinization and extensive fibrosis. However, radiotherapy is the treatment of choice for gynecomastia at it's early stage, or could eventually be considered as a prophylactic treatment in high risk patients. It is a safe and extremely well tolerated treatment resulting in a high degree of therapeutic success with a demonstrated effect on quality of life as reported in randomized trials. To date no medical treatment is proven effective nor devoid from deleterious effects and licenced for this indication.

Determination of the efficiency of commercially available dose calibrators for beta-emitters.

OBJECTIVES: The goals of this investigation are to determine whether commercially available dose calibrators can be used to measure the activity of beta-emitting radionuclides used in pain palliation and to establish whether manufacturer-supplied calibration factors are appropriate for this purpose. METHODS: Six types of commercially available dose calibrators were studied. Dose calibrator response was controlled for 5 gamma-emitters used for calibration or typically encountered in routine use. For the 4 most commonly used beta-emitters ((32)P, (90)Sr, (90)Y, and (169)Er) dose calibrator efficiency was determined in the syringe geometry used for clinical applications. Efficiency of the calibrators was also measured for (153)Sm and (186)Re, 2 beta-emitters with significant gamma-contributions. Source activities were traceable to national standards. RESULTS: All calibrators measured gamma-emitters with a precision of +/-10%, in compliance with Swiss regulatory requirements. For beta-emitters, dose calibrator intrinsic efficiency depends strongly on the maximal energy of the beta-spectrum and is notably low for (169)Er. Manufacturer-supplied calibration factors give accurate results for beta-emitters with maximal beta-energy in the middle-energy range (1 MeV) but are not appropriate for use with low-energy ((169)Er) or high-energy ((90)Y) beta-emitters. beta-emitters with significant gamma-contributions behave like gamma-emitters. CONCLUSION: Commercially available dose calibrators have an intrinsic efficiency that is sufficient for the measurement of beta-emitters, including beta-emitters with a low maximum beta-energy. Manufacturer-supplied calibration factors are reliable for gamma-emitters and beta-emitters in the middle-energy range. For low- and high-energy beta-emitters, the use of manufacturer-supplied calibration factors introduces significant measurement inaccuracy.

Influence of scatter reduction method and monochromatic beams on image quality and dose in mammography.

In mammography, the image contrast and dose delivered to the patient are determined by the x-ray spectrum and the scatter to primary ratio S/P. Thus the quality of the mammographic procedure is highly dependent on the choice of anode and filter material and on the method used to reduce the amount of scattered radiation reaching the detector. Synchrotron radiation is a useful tool to study the effect of beam energy on the optimization of the mammographic process because it delivers a high flux of monochromatic photons. Moreover, because the beam is naturally flat collimated in one direction, a slot can be used instead of a grid for scatter reduction. We have measured the ratio S/P and the transmission factors for grids and slots for monoenergetic synchrotron radiation. In this way the effect of beam energy and scatter rejection method were separated, and their respective importance for image quality and dose analyzed. Our results show that conventional mammographic spectra are not far from optimum and that the use of a slot instead of a grid has an important effect on the optimization of the mammographic process. We propose a simple numerical model to quantify this effect.