Preliminary evaluation of biomechanical modeling of lung deflation during minimally invasive surgery using pneumothorax computed tomography scans.
Abstract During minimally invasive surgery (MIS) for lung tumor resection, the localization of tumors or nodules relies on visual inspection of the deflated lung on intra-procedural video. For patients with tumors or nodules located deeper in the lung, this localization is not possible without prior invasive marking techniques. In efforts to avoid the increase of complication rates associated with these invasive techniques, this study investigates the use of biomechanical modeling of the lung deflation to predict the tumor localization during MIS, solely based on a pre-operative CT scan. The feasibility of the pro...
Source: Physics in Medicine and Biology - September 8, 2020 Category: Physics Authors: Lesage AJ, Rajaram R, Tam AL, Rigaud BS, Brock KK, Rice DC, Cazoulat G Tags: Phys Med Biol Source Type: research

Pancreas segmentation based on an adversarial model under two-tier constraints.
Abstract Pancreas segmentation is vital for the effective diagnosis and treatment of diabetic or pancreatic diseases. However, the irregular shape and strong variability of the pancreas in medical images pose significant challenges to accurate segmentation. In this paper, we propose a novel segmentation algorithm that imposes two-tier constrains on a conventional network through adversarial learning, namely UDCGAN. Specifically, we incorporate a dual adversarial training scheme in a conventional segmentation network, which further facilitates the probability maps from the segmentor to converge on the ground truth ...
Source: Physics in Medicine and Biology - September 8, 2020 Category: Physics Authors: Li M, Lian F, Guo S Tags: Phys Med Biol Source Type: research

A new dose quantity for evaluation and optimisation of MV photon dose distributions when using advanced algorithms: proof of concept and potential applications.
This study introduces a new dose quantity, the dose-to-reference-like medium, to overcome the aforementioned shortcomings. It is linked to a reference medium, water in this study (Dw,m*), and defined as the absorbed dose in a voxel of this reference medium surrounded by a reference-like medium with the same radiation transport characteristics as the original one. We propose to derive Dw,m* distributions by post-processing Dw,m or Dm,m applying a correction factor (CF) to each voxel which depends on its composition. We present and justify a simple and straightforward method to obtain CFs that only involves two phantoms with...
Source: Physics in Medicine and Biology - September 8, 2020 Category: Physics Authors: Jurado-Bruggeman D, Munoz-Montplet C, Vilanova JC Tags: Phys Med Biol Source Type: research

Impact of scanner harmonization on PET-based treatment response assessment in metastatic melanoma.
ConclusionsPET scanner harmonization has a major impact on individual lesion treatment response classification in metastatic melanoma patients. Harmonization using the NEMA phantom yielded similar results to harmonization using anthropomorphic phantom, while the only acceptable post-reconstruction technique was post-reconstruction filtering. Phantom-based harmonization is therefore strongly recommended when comparing lesion uptake across time-points when the images have been acquired on different PET scanners. PMID: 32906111 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - September 8, 2020 Category: Physics Authors: Weisman AJ, Bradshaw TJ, Namías M, Jeraj R Tags: Phys Med Biol Source Type: research

Tumor Control Probability Modeling and Systematic Review of the Literature of Stereotactic Body Radiation Therapy for Prostate Cancer.
CONCLUSIONS: We found significant variation in the published literature on target delineation, margins used, dose/fractionation, and treatment schedule. Despite this variation, TCP was excellent. Most prescription doses range from 35 to 40 Gy, delivered in 4 to 5 fractions. The literature did not provide detailed dose-volume data, and our dosimetric analysis was constrained to prescription doses. There are many areas in need of continued research as SBRT continues to evolve as a treatment modality for prostate cancer, including the durability of local control with longer follow-up across risk groups, the efficacy and safet...
Source: Physics in Medicine and Biology - September 4, 2020 Category: Physics Authors: Royce TJ, Mavroidis P, Wang K, Falchook AD, Sheets NC, Fuller DB, Collins SP, El Naqa I, Song DY, Ding GX, Nahum AE, Jackson A, Grimm J, Yorke E, Chen RC Tags: Int J Radiat Oncol Biol Phys Source Type: research

Impact of charge collection efficiency and electronic noise on the performance of solid-state 3D microdetectors.
This article addresses these issues to provide a framework on the physical constraints for the design and operation of solid-state microdosimeters. PMID: 32885791 [PubMed - in process] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - September 3, 2020 Category: Physics Authors: Prieto-Pena J, Gómez F, Guardiola C, Jiménez-Ramos MC, García López J, Baratto-Roldán A, Baselga M, Pardo-Montero J, Fleta C Tags: Phys Med Biol Source Type: research

Future of Radiation and Immunotherapy.
PMID: 32819614 [PubMed - in process] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 23, 2020 Category: Physics Authors: Formenti SC, Demaria S Tags: Int J Radiat Oncol Biol Phys Source Type: research

Responses to the 2018 and 2019 'One Big Discovery' Question: ASTRO membership's opinions on the most important research question facing radiation oncology …where are we headed?
Responses to the 2018 and 2019 'One Big Discovery' Question: ASTRO membership's opinions on the most important research question facing radiation oncology…where are we headed? Int J Radiat Oncol Biol Phys. 2020 Aug 13;: Authors: Dominello MM, Sanders T, Anscher M, Bayouth J, Brock KK, Carlson DJ, Hugo G, Joseph S, Knisely J, Mendonca MS, Mian OY, Moros EG, Singh AK, Yu JB PMID: 32798605 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 12, 2020 Category: Physics Authors: Dominello MM, Sanders T, Anscher M, Bayouth J, Brock KK, Carlson DJ, Hugo G, Joseph S, Knisely J, Mendonca MS, Mian OY, Moros EG, Singh AK, Yu JB Tags: Int J Radiat Oncol Biol Phys Source Type: research

The first visualization of chemotherapy-induced tumor apoptosis via magnetic particle imaging in a mouse model.
In this study, a simple and robust method was used to conjugate Alexa Fluor 647-AnnexinV (AF647-Anx), which can avidly bind to apoptotic cells, to superparamagnetic iron oxide (SPIO) nanoparticles, termed AF647-Anx-SPIO, which serves as an MPI-detectable tracer. Based on this apoptosis-specific tracer, MPI can accurately and unambiguously detect and quantify apoptotic tumor cells. AF647-Anx-SPIO showed relatively high affinity for apoptotic cells, and differences in binding between treated (apoptotic rate 67.21% ± 1.36%) and untreated (apoptotic rate 10.12 ± 0.11%) cells could be detected by MPI in vitro (P
Source: Physics in Medicine and Biology - August 6, 2020 Category: Physics Authors: Liang X, Wang K, Du J, Tian J, Zhang H Tags: Phys Med Biol Source Type: research

Anatomically-adaptive multi-modal image registration for image-guided external-beam radiotherapy.
Abstract Image-guided radiotherapy (IGRT) allows observation of the location and shape of the tumor and organs-at-risk (OAR) over the course of a radiation cancer treatment. Such information may in turn be used for reducing geometric uncertainties during therapeutic planning, dose delivery and response assessment. However, given the multiple imaging modalities and/or contrasts potentially included within the imaging protocol over the course of the treatment, the current manual approach to determining tissue displacement may become time-consuming and error prone. In this context, variational multi-modal deformable ...
Source: Physics in Medicine and Biology - August 6, 2020 Category: Physics Authors: Zachiu C, Denis de Senneville B, Willigenburg T, van der Voort van Zyp JRN, de Boer JCJ, Raaymakers BW, Ries MG Tags: Phys Med Biol Source Type: research

BrachyView: development of an algorithm for real-time automatic LDR brachytherapy seed detection.
Abstract BrachyView is a novel in-body imaging system developed to provide real-time 12 intraoperative dosimetry for low dose rate prostate brachytherapy treatments. Seed positions 13 can be reconstructed after in-vivo implantation using a high-resolution pinhole gamma camera 14 inserted into the patient rectum. The obtained data is a set of 2D projections of the seeds on the 15 image plane. The 3D reconstruction algorithm requires the identification of the seed's centre 16 of mass. This work presents the development and techniques adopted to build an algorithm that 17 provides the means for fully automatic seed c...
Source: Physics in Medicine and Biology - August 4, 2020 Category: Physics Authors: Brennen TJ, Galli L, Cutajar DL, Alnaghy S, Bucci JA, Bece A, Enari K, Favoino M, Carriero M, Tartaglia M, Archer J, Lerch MLF, Rosenfeld AB, Petasecca M Tags: Phys Med Biol Source Type: research

Prediction of the Ki-67 marker index in hepatocellular carcinoma based on CT radiomics features.
Abstract PURPOSE: To evaluate whether computed tomography (CT) radiomics feature analyses could aid in assessing the Ki-67 marker index in hepatocellular carcinoma (HCC). METHODS: The preoperative CT findings of 74 patients with HCC were analyzed retrospectively. The texture feature calculations were computed from MaZda 4.6 software, and the sequential forward selection algorithm was used as the selection method. The correlation between radiomics features and the Ki-67 marker index, as well as the difference between low Ki-67 (
Source: Physics in Medicine and Biology - August 4, 2020 Category: Physics Authors: Wu H, Han X, Wang Z, Mo L, Liu W, Guo Y, Wei X, Jiang X Tags: Phys Med Biol Source Type: research

The effect of simulation strategies on prediction of power deposition in the tissue around electronic implants during magnetic resonance imaging.
This study examines the effect of variations in anatomical details of the human body model and implant's geometry on predicted SAR values during MRI in a patient with a DBS implant. We used patient-derived models of a DBS implant as it covers a large cross section of the body from head to upper chest and performed numerical simulations to calculate the maximum SAR during MRI at 1.5T (64 MHz) and 3T (127 MHz). We then assessed the effect of uncertainties in dielectric properties of tissue, complexity of body model, truncation of body/DBS model, and DBS lead's geometry on SAR. Our results showed that 40% variation in the con...
Source: Physics in Medicine and Biology - August 4, 2020 Category: Physics Authors: Nguyen BT, Pilitsis J, Golestani Rad L Tags: Phys Med Biol Source Type: research

Dark-field signal extraction in propagation-based phase-contrast imaging.
Abstract A method for extracting the dark-field signal in propagation-based phase-contrast imaging is proposed. In the case of objects consisting predominantly of a single material, or several different materials with similar ratios of the real decrement to the imaginary part of the complex refractive index, the proposed method requires a single image for extraction of the dark-field signal in two-dimensional projection imaging. In the case of three-dimensional tomographic imaging, the method needs only one image to be collected at each projection angle. Initial examples using simulated and experimental data indic...
Source: Physics in Medicine and Biology - August 4, 2020 Category: Physics Authors: Gureyev T, Paganin DM, Arhatari BD, Taba ST, Lewis S, Brennan PC, Quiney H Tags: Phys Med Biol Source Type: research

Convolutional neural network based proton stopping-power-ratio estimation with dual-energy CT: a feasibility study.
We present a convolutional neural network (CNN)-based framework to estimate proton SPR that accounts for patient geometry variation and addresses CT number variation. The proposed framework was tested on both prostate and head-and-neck (HN) patient datasets. Simulated CT images were used in order to have a well-defined ground-truth SPR for evaluation. Two training scenarios were evaluated: training with patient CT images (ideal scenario) and training with computational phantoms (realistic scenario). For the training in ideal scenario, computational phantoms were created based on 120 kVp patient CT images using a custom-def...
Source: Physics in Medicine and Biology - July 30, 2020 Category: Physics Authors: Lee HH, Park YK, Duan X, Jia X, Jiang SB, Yang M Tags: Phys Med Biol Source Type: research

A new detector for the beam energy measurement in proton therapy: a feasibility study.
aco V Abstract The proof of concept of a new device, capable of determining in a few seconds the energy of clinical proton beams by measuring the Time of Flight (ToF) of protons, is presented. The prototype consists of 2 thin Ultra Fast Silicon Detector (UFSD) pads, aligned along the beam direction in a telescope configuration and readout by a digitizer. The method developed for extracting the energy at the isocenter from the measured ToF, validated by Monte Carlo simulations, and the procedure used to calibrate the system are also presented and discussed in detail. The prototype was tested at the Centro Nazionale...
Source: Physics in Medicine and Biology - July 30, 2020 Category: Physics Authors: Vignati A, Giordanengo S, Mas Milian F, Ahmadi Ganjeh Z, Donetti M, Fausti F, Ferrero M, Hammad Ali O, Martì Villarreal OA, Mazza G, Shakarami Z, Sola V, Staiano A, Cirio R, Sacchi R, Monaco V Tags: Phys Med Biol Source Type: research

Direct determination ofkB ⃗,Q,Q0for cylindrical ionization chambers in a 6 MV 0.35 T MR-linac.
r S Abstract To ensure accurate reference dosimetry with ionization chambers in MR-linacs, the influence of the magnetic field on the response of the ionization chambers must be considered. The most direct method considering the influence of magnetic fields in dosimetry is to apply an appropriate absorbed-dose-to-water standard. At PTB, a new water calorimeter has been designed which is capable to determine Dw,Q in an MR-linac. The new device allows the direct calibration of ionization chambers in terms of absorbed dose to water for MR-linac irradiation conditions. Hence, the correction factors k_(B ⃗,Q,Q_0) can...
Source: Physics in Medicine and Biology - July 30, 2020 Category: Physics Authors: Krauss A, Spindeldreier CK, Klüter S Tags: Phys Med Biol Source Type: research

Thulium oxide nanoparticles as radioenhancers for the treatment of metastatic cutaneous squamous cell carcinoma.
Conclusions This is the first study to provide in vitro data demonstrating the independent radiosensitization effect of high-Z nanoparticles against metastatic cSCC with or without carboplatin. Further preclinical investigations with radiotherapy plus high-Z nanoparticles for the management of metastatic cSCC are warranted. PMID: 32726756 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 28, 2020 Category: Physics Authors: Perry JR, Minaei E, Engels E, Ashford B, McAlary L, Clark J, Gupta R, Tehei M, Corde S, Carolan M, Ranson M Tags: Phys Med Biol Source Type: research

Feasibility study of range verification based on proton-induced acoustic signals and recurrent neural network.
Abstract Range verification in proton therapy is a critical quality assurance task. We studied the feasibility of online range verification based on proton-induced acoustic signals, using a bidirectional long-short-term-memory recurrent neural network (Bi-LSTM RNN) and various signal processing techniques. Dose distribution of 1D pencil proton beams inside a CT image-based phantom was analytically calculated. The propagation of acoustic signal inside the phantom was modeled using the k-Wave toolbox. For signal processing, five methods were investigated: down-sampling (DS), DS+HT (Hilbert transform), Wavelet decomp...
Source: Physics in Medicine and Biology - July 28, 2020 Category: Physics Authors: Yao S, Hu Z, Zhang X, Lou E, Liang Z, Wang Y, Peng H Tags: Phys Med Biol Source Type: research

A dose voxel kernel method for rapid reconstruction of out-of-field neutron dose of patients in pencil beam scanning (PBS) proton therapy.
Abstract Monte Carlo (MC) radiation transport methods are used for dose calculation as 'gold standard.' However, the method is computationally time-consuming and thus impractical for normal tissue dose reconstructions for the large number of proton therapy patients required for epidemiologic investigations of late health effects. In the present study, we developed a new dose calculation method for the rapid reconstruction of out-of-field neutron dose to patients undergoing pencil beam scanning (PBS) proton therapy. The new dose calculation method is based on neutron dose voxel kernels (DVKs) generated by MC simula...
Source: Physics in Medicine and Biology - July 28, 2020 Category: Physics Authors: Yeom YS, Griffin KT, Mille M, Jung JW, Lee C, Lee C Tags: Phys Med Biol Source Type: research

Liver-ultrasound based motion modelling to estimate 4D dose distributions for lung tumours in scanned proton therapy.
This study demonstrated the feasibility of the proposed ultrasound-based motion modelling approach for its application in scanned proton therapy of lung tumours. PMID: 32721930 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 27, 2020 Category: Physics Authors: Giger AT, Krieger M, Jud C, Duetschler A, Salomir R, Bieri O, Bauman G, Nguyen D, Weber DC, Lomax AJ, Zhang Y, Cattin PC Tags: Phys Med Biol Source Type: research

Increased local tumor control through nanoparticle-mediated, radiation-triggered release of nitrite, an important precursor for reactive nitrogen species.
r E Abstract The efficacy of dose-enhancing gold nanoparticles (AuNPs) is negatively impacted by low tumor uptake, low cell membrane penetration, limited diffusion distance, and short lifetime of radiation-induced secondary particles. To overcome these limitations, we have developed a novel AuNP system capable of radiation-triggered release of nitrite, a precursor of reactive nitrogen species (RNS), and report here on the in vivo characterization of this system. AuNPs were functionalized through PEGylation, cell-penetrating peptides (CPP; AuNP@CPP), and nitroimidazole (nIm; AuNP@nIm-CPP). Mice with subcutaneous 4T...
Source: Physics in Medicine and Biology - July 27, 2020 Category: Physics Authors: Kim AS, Melemenidis S, Gustavsson AK, Abid D, Wu Y, Liu F, Hristov D, Schüler E Tags: Phys Med Biol Source Type: research

Physics and biology of ultrahigh dose-rate (FLASH) radiotherapy: a topical review.
Abstract Ultrahigh dose-rate (>40 Gy/s) radiotherapy, or "FLASH" therapy, has gained significant momentum since the publication by Favaudon et al. in 2014, in which reduced normal tissue toxicity and similar tumor control for ultrahigh dose-rate radiotherapy compared to conventional radiotherapy was demonstrated in vivo. A number of subsequent studies from this and other groups investigating FLASH normal tissue protection followed shortly and the literature has been since been inundated with FLASH publications. Today, FLASH therapy has been considered by some as being capable of "revolutionizing ...
Source: Physics in Medicine and Biology - July 27, 2020 Category: Physics Authors: Esplen NM, Mendonca MS, Bazalova-Carter M Tags: Phys Med Biol Source Type: research

An efficient and accurate parallel hybrid acoustic signal correction method for transcranial ultrasound.
Abstract Phased-control focused ultrasound transducers provide a new and noninvasive treatment method for brain disease. However, improving the accuracy of phase correction and reducing the calculation time during treatment have always been contradictory constraints. In this paper, a hybrid acoustic signal correction (HASC) method combined with k-Wave stage and holography stage was introduced for phase correction and simulation of transcranial focused ultrasound. The k-Wave stage is mainly used to calculate the sound field in a heterogeneous medium (skull), which divides the sound field calculation process into pa...
Source: Physics in Medicine and Biology - July 27, 2020 Category: Physics Authors: Wu N, Shen G, Qu X, Wu H, Qiao S, Wang E, Chen Y, Wang H Tags: Phys Med Biol Source Type: research

Half2Half: deep neural network based CT image denoising without independent reference data.
Abstract Reducing radiation dose of x-ray computed tomography (CT) and thereby decreasing the potential risk to patients are desirable in CT imaging. Deep neural network (DNN) has been proposed to reduce noise in low-dose CT images and showed promising results. However, most existing DNN-based methods require training a neural network using high-quality CT images as a reference. Lack of high-quality reference data has therefore been the bottleneck in the current DNN-based methods. Recently, a noise-to-noise (Noise2Noise) training method was proposed to train a denoising neural network with only noisy images. It ha...
Source: Physics in Medicine and Biology - July 23, 2020 Category: Physics Authors: Yuan N, Zhou J, Qi J Tags: Phys Med Biol Source Type: research

Simulation studies to understand sensitivity and timing characteristics of an optical property modulation-based radiation detection concept for PET.
Abstract The concept of using the modulation mechanisms of a material's optical properties for annihilation photon detection has been proposed as a potential method to significantly improve the coincidence time resolution (CTR) of positron emission tomography (PET) detectors. However, the possibility of detecting individual 511 keV photons with largely improved CTR using the proposed detection method has not yet been demonstrated, either experimentally or theoretically. In addition, the underlying physical picture of the optical modulation effects induced by annihilation photons has not been fully understood. In t...
Source: Physics in Medicine and Biology - July 23, 2020 Category: Physics Authors: Tao L, Jeong D, Wang J, Adams Z, Bryan P, Levin CS Tags: Phys Med Biol Source Type: research

SiPM signal readout for inter-crystal scatter event identification in PET detectors.
In this study, we propose a novel silicon photomultiplier (SiPM) readout method to identify ICS events in one-to-one coupled PET detectors with a reduced number of data acquisition channels. For concept verification, we assembled a PET detector that consists of a 16-channel SiPM array and 4×4 lutetium oxyorthosilicate (LSO) array with a 3.2-mm crystal pitch. The proposed SiPM readout scheme serializes the 16 SiPM anode signals into four pulse train outputs encoded with four increasing time-delays in steps of 250-ns intervals. A Sum signal of the 16 SiPM anodes provides the timing information for time-of-flight measur...
Source: Physics in Medicine and Biology - July 22, 2020 Category: Physics Authors: Park H, Lee JS Tags: Phys Med Biol Source Type: research

Impact of image reconstruction method on dose distributions derived from90Y PET images: phantom and liver radioembolization patient studies.
Conclusions: In this90Y radioembolization PET/CT study, the β parameter in regularized iterative (Q.Clear) reconstruction was investigated for image quality, accurate quantification and dose distributions based on phantom experiments and then applied to patient studies. Our results indicate that more accurate dose distribution can be achieved from smoother PET images, reconstructed with larger β values than those yielding the best activity quantification, but noisy images. Most importantly, these results suggest that, quantitative measures, which are commonly used in clinics, such as SUVmaxor SUVpeak(equivalent o...
Source: Physics in Medicine and Biology - July 22, 2020 Category: Physics Authors: Hou X, Ma H, Esquinas PL, Uribe CF, Tolhurst S, Bénard F, Liu D, Rahmim A, Celler A Tags: Phys Med Biol Source Type: research

Cost-function testing methodology for image-based registration of endoscopy to CT images in the head and neck.
Abstract One of the largest geometric uncertainties in designing radiotherapy treatment plans for squamous cell cancers of the head and neck is contouring the gross tumour volume. We have previously described a method of projecting mucosal disease contours, visible on endoscopy, to volumetrically reconstructed planning CT datasets, using electromagnetic (EM) tracking of a flexible endoscope, enabling rigid registration between endoscopic and CT images. However, to achieve better accuracy for radiotherapy planning, we propose refining this initial registration with image-based registration methods. In this paper, s...
Source: Physics in Medicine and Biology - July 22, 2020 Category: Physics Authors: Shi RB, Mirza S, Martinez D, Douglas C, Cho J, Irish JC, Jaffray DA, Weersink RA Tags: Phys Med Biol Source Type: research

Dual source hybrid spectral micro-CT using an energy-integrating and a photon-counting detector.
Abstract Preclinical micro-CT provides a hotbed in which to develop new imaging technologies, including spectral CT using photon counting detector (PCD) technology. Spectral imaging using PCDs promises to expand x-ray CT as a functional imaging modality, capable of molecular imaging, while maintaining CT's role as a powerful anatomical imaging modality. However, the utility of PCDs suffers due to distorted spectral measurements, affecting the accuracy of material decomposition. We attempt to improve material decomposition accuracy using our novel hybrid dual-source micro-CT system which combines a PCD and an energ...
Source: Physics in Medicine and Biology - July 22, 2020 Category: Physics Authors: Holbrook M, Clark DP, Badea CT Tags: Phys Med Biol Source Type: research

Improving the imaging performance of the 1.5 T MR-linac using a flexible, 32-channel, on-body receive array.
In conclusion, the proposed 32-channel array is compatible with MRIgRT and can significantly reduce scan times and/or improve the image quality of all on-line scans. PMID: 32698168 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 21, 2020 Category: Physics Authors: Zijlema SE, Tijssen RHN, van Dijk L, Hackett SL, Wolthaus JWH, Breimer W, Lagendijk JJW, Van den Berg CAT Tags: Phys Med Biol Source Type: research

Predicting voxel-level dose distributions for esophageal radiotherapy using densely connected network with dilated convolutions.
Abstract This work aims to develop a voxel-level dose prediction framework by integrating distance information between PTV and OARs as well as image information into a densely-connected network (DCNN). At first, a four-channel feature map consisting of PTV image, OARs image, CT image, and distance image is constructed. Then a densely connected neural network is built and trained for voxel-level dose prediction. Considering that the shape and size of OARs are highly inconsistent, the dilated convolution is employed to capture features from multiple scales. Finally, the propose network is evaluated with five-fold cr...
Source: Physics in Medicine and Biology - July 21, 2020 Category: Physics Authors: Zhang J, Liu S, Yan H, Li T, Mao R, Liu J Tags: Phys Med Biol Source Type: research

MD-NDNet: multi-dimension convolutional neural network for false positive reduction in pulmonary nodule detection.
Abstract Pulmonary nodule false positive reduction is of great significance for automated nodule detection in clinical diagnosis of low-dose computerized tomography (LDCT) lung cancer screening. Due to individual intra-nodule variations and visual similarities between true nodules and false positives as soft tissues in the LDCT images, the current clinical practices remain subject to shortcomings of potential high-risk and time-consumption issues. In this paper, we propose a multi-dimension nodule detection network (MD-NDNet) for automatic nodule false positive reduction using deep convolutional neural network (DC...
Source: Physics in Medicine and Biology - July 21, 2020 Category: Physics Authors: Wu Z, Ge R, Shi G, Zhang L, Chen Y, Luo L, Cao Y, Yu H Tags: Phys Med Biol Source Type: research

Flexible numerical simulation framework for dynamic PET-MR data.
Abstract This paper presents a simulation framework for dynamic PET-MR. The main focus of this framework is to provide motion-resolved MR and PET data and ground truth motion information. This can be used in the optimisation and quantitative evaluation of image registration and in assessing the error propagation due to inaccuracies in motion estimation in complex motion-compensated reconstruction algorithms. Contrast and tracer kinetics can also be simulated and are available as ground truth information. To closely emulate medical examination, input and output of the simulation are files in standardised open-sourc...
Source: Physics in Medicine and Biology - July 20, 2020 Category: Physics Authors: Mayer J, Brown R, Thielemans K, Ovtchinnikov E, Pasca E, Atkinson D, Gillman A, Marsden P, Ippoliti M, Makowski M, Schaeffter T, Kolbitsch C Tags: Phys Med Biol Source Type: research

Dictionary learning based image-domain material decomposition for spectral CT.
Abstract The potential huge advantage of spectral computed tomography (CT) is that it can provide accurate material identification and quantitative tissue information. It is of great significance for many clinical applications, such as brain angiography, early tumor recognition, etc. To achieve more accurate material components with better image quality, a dictionary learning based image-domain material decomposition (DLIMD) is proposed for spectral CT. The procedure of DLIMD can be divided into four steps. First, spectral CT images are reconstructed from projections and then material coefficient matrix is calcula...
Source: Physics in Medicine and Biology - July 20, 2020 Category: Physics Authors: Wu W, Yu H, Chen P, Luo F, Liu F, Wang Q, Zhu Y, Zhang Y, Feng J, Yu H Tags: Phys Med Biol Source Type: research

Experimental validation of a coincidence time resolution metric including depth-of-interaction bias for TOF-PET.
Abstract Depth-of-interaction (DOI) variability of annihilation photons is known to be a source of coincidence time resolution (CTR) degradation for fast TOF-PET detectors. An analytical model was recently proposed to explicitly include the DOI time bias separately from variance-related statistical factors, such as scintillation photon emission and photosensor jitter, in the CTR evaluation. In the present work, an experimental validation of this new model is provided. An unconventional signal readout configuration was used to magnify the DOI bias with 20 mm long LYSO:Ce crystals. In a head-to-head orientation of t...
Source: Physics in Medicine and Biology - July 20, 2020 Category: Physics Authors: Loignon-Houle F, Toussaint M, Lee MS, Cates JW, Lecomte R Tags: Phys Med Biol Source Type: research

Identification of patterns of tumour change measured on CBCT images in NSCLC patients during radiotherapy.
In this study, we propose a novel approach to investigate changes in the visible tumour and surrounding tissues with the aim of distinguishing modes of tumour change (elastic versus non-elastic) without segmentation on the follow-up images. On-treatment cone-beam computed tomography (CBCT) images of 240 non-small cell lung cancer (NSCLC) patients who received 55 Gy of radiotherapy were included. CBCTs were aligned onto planning computed tomography (planning CT) scan using a two-step rigid registration process. To explore density changes across the lung-tumour boundary, eight shells confined to the shape of the gross tumour...
Source: Physics in Medicine and Biology - July 20, 2020 Category: Physics Authors: Amugongo LM, Vasquez Osorio E, Green AF, Cobben D, van Herk M, McWilliam A Tags: Phys Med Biol Source Type: research

Comprehensive data set to include interference effects in Monte Carlo models of x-ray coherent scattering inside biological tissues.
ibi A Abstract Interference effects are included in the X-ray coherent scattering models used in Monte Carlo codes by modifying each material form factor through a proper interference function, which is obtained directly from the measured scattering pattern. This approach is effective for non-biological materials, but it is impractical for biological tissues, due the wide composition variability they can feature. Instead, a given biological sample can be considered as a proper mixture of four basis materials: fat, water, collagen and calcium hydroxyapatite. The sample form factor can then be obtained through a wei...
Source: Physics in Medicine and Biology - July 20, 2020 Category: Physics Authors: Paternò G, Cardarelli P, Gambaccini M, Taibi A Tags: Phys Med Biol Source Type: research

Low-dose spectral CT reconstruction based on image-gradient L0-norm and adaptive spectral PICCS.
Abstract The photon-counting detector based spectral computed tomography (CT) is promising for lesion detection, tissue characterization, and material decomposition. However, the lower signal-noise-ratio (SNR) within multi-energy projection dataset can result in poor reconstructed image quality. Recently, a high-quality spectral mean image as prior information was introduced into the prior image constrained compressed sensing (PICCS) framework to suppress noise, leading to spectral PICCS (SPICCS). In the original SPICCS model, the image gradient L1-norm is employed, and it can cause blurred edge structures in the ...
Source: Physics in Medicine and Biology - July 20, 2020 Category: Physics Authors: Wang S, Wu W, Feng J, Liu F, Yu H Tags: Phys Med Biol Source Type: research

A dedicated phantom design for positron emission mammography performance evaluation.
uez-Villafuerte M Abstract A standard protocol for performance evaluation of Positron Emission Mammography (PEM) systems has not yet been established. In this work we propose a methodology based on the design of specific phantoms for this imaging modality with component dimensions in accordance with typical breast lesion sizes together with the adaptation of current international protocols designed for clinical and preclinical PET systems. This methodology was used to evaluate the performance of the Flex Solo II PEM scanner in terms of spatial resolution, uniformity and contrast lesion detectability, recovery coef...
Source: Physics in Medicine and Biology - July 20, 2020 Category: Physics Authors: Torres-Urzúa LF, Alva-Sanchez H, Martinez-Davalos A, García-Pérez FO, Peruyero-Rivas RM, Rodriguez-Villafuerte M Tags: Phys Med Biol Source Type: research

Harmonization strategies for multicenter radiomics investigations.
Abstract Carrying out large multicenter studies is one of the key goals to be achieved towards a faster transfer of the radiomics approach in the clinical setting. This requires large-scale radiomics data analysis, hence the need for integrating radiomic features extracted from images acquired in different centers. This is challenging as radiomic features exhibit variable sensitivity to differences in scanner model, acquisition protocols and reconstruction settings, which is similar to the so-called 'batch-effects' in genomics studies. In this review we discuss existing methods to perform data integration with the...
Source: Physics in Medicine and Biology - July 19, 2020 Category: Physics Authors: Da-Ano R, Visvikis D, Hatt M Tags: Phys Med Biol Source Type: research

A GPU-accelerated fully 3D OSEM image reconstruction for a high-resolution small animal PET scanner using dual-ended readout detectors.
Abstract In this work a GPU-accelerated fully 3D ordered-subset expectation maximization (OSEM) image reconstruction with point spread function (PSF) modeling was developed for a small animal PET scanner with long axial field of view (FOV). Dual-ended readout detectors that provided high depth of interaction (DOI) resolution were used for the small animal PET scanner to simultaneously achieve uniform high spatial resolution and high sensitivity. First we developed a novel sinogram generation method that the dimension of the sinogram was determined first and then an event was assigned to a few neighboring sinogram ...
Source: Physics in Medicine and Biology - July 16, 2020 Category: Physics Authors: Zeng T, Gao J, Gao D, Kuang Z, Sang Z, Wang X, Hu L, Chen Q, Chu X, Liang D, Liu X, Yang Y, Zheng H, Hu Z Tags: Phys Med Biol Source Type: research

Brain tumor segmentation using 3D mask R-CNN for dynamic susceptibility contrast enhanced perfusion imaging.
Abstract The segmentation of neoplasms is an important part of radiotherapy treatment planning, monitoring disease progression, and predicting patient outcome. In the brain, functional magnetic resonance imaging (MRI) like dynamic susceptibility contrast enhanced (DSCE) or T1-weighted dynamic contrast enhanced (DCE) perfusion MRI are important tools for diagnosis. They play a crucial role in providing pre-operative assessment of tumor histology, grading, and tumor biopsy guidance. However, the manual contouring of these neoplasms is tedious, expensive, time-consuming, and contains inter-observer variability. In th...
Source: Physics in Medicine and Biology - July 15, 2020 Category: Physics Authors: Jeong J, Lei Y, Kahn S, Liu T, Curran WJ, Shu HK, Mao H, Yang X Tags: Phys Med Biol Source Type: research

Small-cavity chamber dose response in megavoltage photon beams coupled to magnetic fields.
Abstract In MRgRT, dosimetry measurements are performed in the presence of magnetic fields. For high-resolution measurements, small-cavity ionization chambers are required. While Monte Carlo simulations are essential to determine dosimetry correction factors, models of small-chambers require careful validation with experimental measurements. The aim of this study is to characterize small-cavity chamber response coupled to magnetic fields. Small-cavity chambers (PTW31010, PTW31016, PTW31021 and PTW3022) are irradiated by a 6 MV photon beam for nine magnetic field strengths between -1.5T and +1.5T. The chamber axis ...
Source: Physics in Medicine and Biology - July 15, 2020 Category: Physics Authors: Cervantes Y, Billas I, Shipley DR, Duane S, Bouchard H Tags: Phys Med Biol Source Type: research

2D range modulator for high-precision water calorimetry in scanned carbon-ion beams.
Abstract Ionization chamber-based dosimetry for carbon-ion beams still shows a significantly higher standard uncertainty than high-energy photon dosimetry. This is mainly caused by the high standard uncertainty of the correction factor for beam quality k_Q,Q0 . Due to a lack of experimental data, the given values for k_Q,Q0 are based on theoretical calculations. To reduce this standard uncertainty, k_Q,Q0 factors for different irradiation conditions and ICs are determined experimentally by means of water calorimetry. In this article, we describe the process of creating a suitable irradiation technique and the char...
Source: Physics in Medicine and Biology - July 15, 2020 Category: Physics Authors: Holm KM, Weber U, Simeonov Y, Krauss A, Jaekel O, Greilich S Tags: Phys Med Biol Source Type: research

Feasibility and safety of non-invasive ultrasound therapy (NIUT) on porcine aortic valve.
not M Abstract Calcific aortic stenosis (CAS) is associated with advanced age and comorbidities, therefore a non-invasive therapy would be beneficial. We previously demonstrated that ultrasound therapy (UT) improved calcified bioprosthetic valves function, in open chest model. For translational application, we tested Non-Invasive Ultrasound Therapy (NIUT) transthoracically on swine's aortic valves and the need of antithrombotic treatment at follow-up. Primary objective: feasibility and safety of NIUT. Secondary objectives: occurrence, severity and evolution of side effects during therapy and one-month follow-up. T...
Source: Physics in Medicine and Biology - July 15, 2020 Category: Physics Authors: Messas E, Rémond MC, Goudot G, Zarka S, Penot R, Mateo P, Kwiecinski W, Suarez Escudero D, Bel A, Ialy-Radio N, Bertrand B, Bruneval P, Marijon E, Spaargaren R, Tanter M, Pernot M Tags: Phys Med Biol Source Type: research

Silent 3D MR sequence for quantitative and multicontrast T1 and proton density imaging.
This study aims to develop a silent, fast and 3D method for T1 and proton density (PD) mapping, while generating time series of T1-weighted (T1w) images with bias-filed correction. Undersampled T1w images at different effective inversion times (TIs) were acquired using the inversion recovery (IR) prepared RUFIS sequence with an interleaved K-space trajectory. Unaliased images were reconstructed by constraining the signal evolution to a temporal subspace which was learned from the signal model. Parameter maps were obtained by fitting the data to the signal model, and bias-field correction was conducted on T1w images. Accura...
Source: Physics in Medicine and Biology - July 13, 2020 Category: Physics Authors: Liu X, Gómez PA, Solana AB, Wiesinger F, Menzel MI, Menze B Tags: Phys Med Biol Source Type: research

Obtaining PET/CT images from non-attenuation corrected PET images in a single PET system using Wasserstein generative adversarial networks.
Abstract Positron emission tomography (PET) imaging plays an indispensable role in early disease detection and postoperative patient staging diagnosis. However, PET imaging not only requires additional computed tomography (CT) imaging to provide anatomical information but also requires attenuation correction (AC) maps computed from CT images for accurate PET quantification, which inevitably demands that patients undergo additional doses of ionizing radiation. To reduce the radiation dose and simultaneously obtain high-quality PET/CT images, in this work, we present a new approach based on deep learning that can es...
Source: Physics in Medicine and Biology - July 13, 2020 Category: Physics Authors: Hu Z, Li Y, Zou S, Xue H, Sang Z, Liu X, Yang Y, Zhu X, Liang D, Zheng H Tags: Phys Med Biol Source Type: research

Automatic IMRT planning via static field fluence prediction (AIP-SFFP): a deep learning algorithm for real-time prostate treatment planning.
Abstract PURPOSE: To develop a Deep Learning (DL) based algorithm, Automatic IMRT Planning via Static Field Fluence Prediction (AIP-SFFP), for automated prostate IMRT planning with real-time planning efficiency. METHODS: AIP-SFFP generates a prostate IMRT plan through predictions of fluence maps using the patient anatomy. No inverse planning is required. AIP-SFFP centralizes a custom-build deep learning neuro network for fluence map prediction. Predictions are imported to a commercial treatment planning system for dose calculation and plan generation. AIP-SFFP was demonstrated for prostate IMRT simultaneously...
Source: Physics in Medicine and Biology - July 13, 2020 Category: Physics Authors: Li X, Zhang J, Sheng Y, Chang Y, Yin FF, Ge Y, Wu QJ, Wang C Tags: Phys Med Biol Source Type: research

Three-dimensional shear wave elastography on conventional ultrasound scanners with external vibration.
Abstract Two-dimensional (2-D) ultrasound shear wave elastography (SWE) has been widely used for soft tissue properties assessment. Given that shear waves propagate in three dimensions (3-D), extending SWE from 2-D to 3-D is important for comprehensive and accurate stiffness measurement. However, implementation of 3-D SWE on a conventional ultrasound scanner is challenging due to the low volume rate (tens of Hertz) associated with limited parallel receive capability of the scanner's hardware beamformer. Therefore, we developed an external mechanical vibration-based 3-D SWE technique allowing robust 3-D shear wave ...
Source: Physics in Medicine and Biology - July 13, 2020 Category: Physics Authors: Huang C, Song P, Mellema DC, Gong P, Lok UW, Tang S, Ling W, Meixner DD, Urban MW, Manduca A, Greenleaf JF, Chen S Tags: Phys Med Biol Source Type: research