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Conventional ultrasound (US) devices use the time of flight (TOF) of reflected US pulses to calculate distances inside the scanned tissues and thus create images. The speed of sound (SOS) is assumed to be constant in all human soft tissues at a generally accepted average value of 1540 m s−1. This assumption is a source of systematic errors up to several millimeters and of image distortion in quantitative US imaging. In this work, an extension of a method recently published by Fontanarosa et al (2011 Med. Phys. 38 2665–73) is presented: the aim is to correct SOS aberrations in three-dimensional (3D) US images in those cases where a spatially co-registered computerized tomography (CT) scan is also available; the algorithm is then applicable to a more general case where the lines of view (LOV) of the US device are not necessarily parallel and coplanar, thus allowing correction also for US transducers other than linear. The algorithm was applied on a multi-modality pelvic US phantom, scanned through three different liquid layers on top of the phantom with different SOS values; the results show that the correction restores a better match between the CT and the US images, reducing the differences to sub-millimeter agreement. Fifteen clinical cases of prostate cancer patients were also investigated: the SOS corrections of prostate centroids were on average +3.1 mm (max + 4.9 mm–min + 1.3 mm). This is in excellent agreement with reports in the literature on differences between measured prostate positions by US and other techniques, where often the discrepancy was attributed to other causes.

Purpose Accurate tumor positioning in stereotactic body radiation therapy (SBRT) of liver lesions is often hampered by motion and setup errors. We combined 3-dimensional ultrasound imaging (3DUS) and active breathing control (ABC) as an image guidance tool. Methods and Materials We tested 3DUS image guidance in the SBRT treatment of liver lesions for 11 patients with 88 treatment fractions. In 5 patients, 3DUS imaging was combined with ABC. The uncertainties of US scanning and US image segmentation in liver lesions were determined with and without ABC. Results In free breathing, the intraobserver variations were 1.4 mm in left-right (L-R), 1.6 mm in superior-inferior (S-I), and 1.3 mm anterior-posterior (A-P). and the interobserver variations were 1.6 mm (L-R), 2.8 mm (S-I), and 1.2 mm (A-P). The combined uncertainty of US scanning and matching (inter- and intraobserver) was 4 mm (1 SD). The combined uncertainty when ABC was used reduced by 1.7 mm in the S-I direction. For the L-R and A-P directions, no significant difference was observed. Conclusion 3DUS imaging for IGRT of liver lesions is feasible, although using anatomic surrogates in the close vicinity of the lesion may be needed. ABC-based breath-hold in midventilation during 3DUS imaging can reduce the uncertainty of US-based 3D table shift correction.

It has been suggested that modern dose calculation algorithms should be able to report absorbed dose both as dose to the local medium, D-m,D-m, and as dose to a water cavity embedded in the medium, D-w,D-m, using conversion factors from cavity theory. Assuming that the cell nucleus with its DNA content is the most important target for biological response, the aim of this study is to investigate, by means of Monte Carlo (MC) simulations, the relationship of the dose to a cell nucleus in a medium, D-n,D-m, to D-m,D-m and D-w,D-m, for different combinations of cell nucleus compositions and tissue media for different photon energies used in brachytherapy. As D-n,D-m is very impractical to calculate directly for routine treatment planning, while D-m,D-m and D-w,D-m are much easier to obtain, the questions arise which one of these quantities is the best surrogate for D-n,D-m and which cavity theory assumptions should one use for its estimate. The Geant4.9.4 MC code was used to calculate D-m,D-m, D-w,D-m and D-n,D-m for photon energies from 20 (representing the lower energy end of brachytherapy for Pd-103 or I-125) to 300 keV (close to the mean energy of Ir-192) and for the tissue media adipose, breast, prostate and muscle. To simulate the cell and its nucleus, concentric spherical cavities were placed inside a cubic phantom (10 x 10 x 10 mm(3)). The diameter of the simulated nuclei was set to 14 mu m. For each tissue medium, three different setups were simulated; (a) D-n,D-m was calculated with nuclei embedded in tissues (MC-D-n,D-m). Four different published elemental compositions of cell nuclei were used. (b) D-w,D-m was calculated with MC (MC-D-w,D-m) and compared with large cavity theory calculated D-w,D-m (LCT-D-w,D-m), and small cavity theory calculated D-w,D-m (SCT-D-w,D-m). (c) D-m,D-m was calculated with MC (MC-D-m,D-m). MC-D-w,D-m is a good substitute for MC-D-n,D-m for all photon energies and for all simulated nucleus compositions and tissue types. SCT-D-w,D-m

Introduction: This multicentric in silico trial compares photon and proton radiotherapy for non-small cell lung cancer patients. The hypothesis is that proton radiotherapy decreases the dose and the volume of irradiated normal tissues even when escalating to the maximum tolerable dose of one or more of the organs at risk (OAR). Methods: Twenty-five patients, stage IA-IIIB, were prospectively included. On 4D F-18-labeled fluorodeoxyglucose-positron emission tomography-computed tomography scans, the gross tumor, clinical and planning target volumes, and OAR were delineated. Three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT) photon and passive scattered conformal proton therapy (PSPT) plans were created to give 70 Gy to the tumor in 35 fractions. Dose (de-)escalation was performed by rescaling to the maximum tolerable dose. Results: Protons resulted in the lowest dose to the OAR, while keeping the dose to the target at 70 Gy. The integral dose (ID) was higher for 3DCRT (59%) and IMRT (43%) than for PSPT. The mean lung dose reduced from 18.9 Gy for 3DCRT and 16.4 Gy for IMRT to 13.5 Gy for PSPT. For 10 patients, escalation to 87 Gy was possible for all 3 modalities. The mean lung dose and ID were 40 and 65% higher for photons than for protons, respectively. Conclusions: The treatment planning results of the Radiation Oncology Collaborative Comparison trial show a reduction of ID and the dose to the OAR when treating with protons instead of photons, even with dose escalation. This shows that PSPT is able to give a high tumor dose, while keeping the OAR dose lower than with the photon modalities.

To allow for high precision radiotherapy, imaging prior to a radiation session is performed in Image Guided Radiotherapy (IGRT). Electronic portal imaging (EPI) can visualise bony anatomy and fiducial markers (FM). However, for prostate cancer, visualising the organ itself is more desirable. Ultrasound (US) is a well known widely used diagnostic technique for qualitative imaging of soft tissues such as the prostate. Nowadays a quantitative intramodality 3D US system for radiotherapy image guidance is available (Clarity system, Elekta, Stockholm, Sweden). In this work a comparison was performed between 3D US image guidance and the currently used prostate localization procedure.

Positron emission tomography (PET) is a promising tool for monitoring the three-dimensional dose distribution in charged particle radiotherapy. PET imaging during or shortly after proton treatment is based on the detection of annihilation photons following the +-decay of radionuclides resulting from nuclear reactions in the irradiated tissue. Therapy monitoring is achieved by comparing the measured spatial distribution of irradiation-induced +-activity with the predicted distribution based on the treatment plan. The accuracy of the calculated distribution depends on the correctness of the computational models, implemented in the employed Monte Carlo (MC) codes that describe the interactions of the charged particle beam with matter and the production of radionuclides and secondary particles. However, no well-established theoretical models exist for predicting the nuclear interactions and so phenomenological models are typically used based on parameters derived from experimental data. Unfortunately, the experimental data presently available are insufficient to validate such phenomenological hadronic interaction models. Hence, a comparison among the models used by the different MC packages is desirable. In this work, starting from a common geometry, we compare the performances of MCNPX, GATE and PHITS MC codes in predicting the amount and spatial distribution of proton-induced activity, at therapeutic energies, to the already experimentally validated PET modelling based on the FLUKA MC code. In particular, we show how the amount of +-emitters produced in tissue-like media depends on the physics model and cross-sectional data used to describe the proton nuclear interactions, thus calling for future experimental campaigns aiming at supporting improvements of MC modelling for clinical application of PET monitoring. © 2012 Institute of Physics and Engineering in Medicine., SCOPUS: ar.j, info:eu-repo/semantics/published

To investigate the clinical impact of a recently introduced speed of sound (SOS) aberration correction algorithm in ultrasound (US) imaging systems for image guided radiotherapy (IGRT). The SOS algorithm was applied to four prostate cancer patients and two liver cancer patients to assess in a real clinical application the extent and spatial distribution of the corrections

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Background. The societal burden of lung cancer is high because of its high incidence and high lethality. From a theoretical point of view, radiotherapy with beams of protons and heavier charged particles, for example, carbon ions (C-ions), should lead to superior results, compared with photon beams. In this review, we searched for clinical evidence to justify implementation of particle therapy as standard treatment in lung cancer. Methods. A systematic literature review based on an earlier published comprehensive review was performed and updated through November 2009. Results. Eleven fully published studies, all dealing with non-small cell lung cancer (NSCLC), mainly stage I, were identified. No phase III trials were found. For proton therapy, 2- to 5-year local tumor control rates varied in the range of 57%-87%. The 2- and 5-year overall survival (OS) and 2- and 5-year cause-specific survival (CSS) rates were 31%-74% and 23% and 58%-86% and 46%, respectively. Radiation-induced pneumonitis was observed in about 10% of patients. For C-ion therapy, the overall local tumor control rate was 77%, but it was 95% when using a hypofractionated radiation schedule. The 5-year OS and CSS rates were 42% and 60%, respectively. Slightly better results were reported when using hypofractionation, 50% and 76%, respectively. Conclusion. The present results with protons and heavier charged particles are promising. However, the current lack of evidence on the clinical (cost-)effectiveness of particle therapy emphasizes the need to investigate the efficiency of particle therapy in an adequate manner. Until these results are available for lung cancer, charged particle therapy should be considered experimental. The Oncologist 2010; 15: 93-103

To correct speed of sound (SOS) aberrations in ultrasound (US) imaging systems for quantitative image guided radiotherapy (IGRT) applications. US waves travel at different speeds in different human tissues. Conventional qualitative US-based imaging systems assume instead that the SOS is constant in all tissues; 1540 m/s, which is an accepted average value for soft tissues. This assumption is a systematic source of errors and image distortion in quantitative US imaging, whereas in qualitative diagnostic imaging it is usually unimportant.