Whole gamma imaging: a new concept of PET combined with Compton imaging.
Abstract We proposed a concept of whole gamma imaging (WGI) that utilizes all detectable gamma rays for imaging. An additional detector ring, which is used as the scatterer, is inserted in the field-of-view of a PET ring so that single gamma rays can be detected by the Compton imaging method. In particular, for the non-pure positron emitters which emit an additional gamma ray almost at the same time, triple gamma imaging will be enabled; localization on each line-of-response (LOR) is possible by using the Compton cone of the additional gamma ray. We developed a prototype to show a proof of the WGI concept. The dia...
Source: Physics in Medicine and Biology - April 29, 2020 Category: Physics Authors: Yoshida E, Tashima H, Nagatsu K, Tsuji A, Kamada K, Parodi K, Yamaya T Tags: Phys Med Biol Source Type: research

Multi-level feature aggregation network for instrument identification of endoscopic image.
This study proposes a novel multilevel feature-aggregated deep convolutional neural network (MLFA-Net) for identifying surgical instruments in endoscopic images. First, a global feature augmentation layer is created on the top layer of the backbone to improve the localization ability of object identification by boosting the high-level semantic information to the feature flow network. Second, a modified interaction path of cross-channel features is proposed to increase the nonlinear combination of features in the same level and improve the efficiency of information propagation. Third, a multiview fusion branch of features i...
Source: Physics in Medicine and Biology - April 28, 2020 Category: Physics Authors: Chu Y, Yang XM, Li H, Ai D, Ding Y, Fan J, Song H, Yang J Tags: Phys Med Biol Source Type: research

Image quality of list-mode proton imaging without front trackers.
c I, Seco J Abstract List mode proton imaging relies on accurate reconstruction of the proton most likely path (MLP) through the patient. This typically requires two sets of position sensitive detector systems, one upstream (front) and one downstream (rear) of the patient. However, for a clinical implementation it can be preferable to omit the front trackers (single-sided proton imaging). For such a system, the MLP can be computed from information available through the beam delivery system and the remaining rear tracker set. In this work, we use Monte Carlo simulations to compare a conventional double-sided (using...
Source: Physics in Medicine and Biology - April 28, 2020 Category: Physics Authors: Sølie JRR, Volz L, Pettersen HESES, Piersimoni P, Odland OH, Roehrich D, Helstrup H, Peitzmann T, Ullaland K, Varga-Kofarago M, Mehendale S, Grøttvik OS, Eikeland VN, Meric I, Seco J Tags: Phys Med Biol Source Type: research

Body-size-dependent phantom library constructed from ICRP mesh-type reference computational phantoms.
Abstract Recently, ICRP Task Group 103 developed new mesh-type reference computational phantoms (MRCPs) for the adult male and female by converting the current voxel-type reference computational phantoms (VRCPs) of ICRPPublication 110into a high-quality/fidelity mesh format. Utilizing the great deformability/flexibility of the MRCPs compared with the VRCPs, in the present study, we established a body-size-dependent phantom library by modifying the MRCPs. The established library includes 108 adult male and 104 adult female phantoms in different standing heights and body weights, covering most body sizes representat...
Source: Physics in Medicine and Biology - April 28, 2020 Category: Physics Authors: Choi C, Yeom YS, Lee H, Han H, Shin B, Nguyen TT, Kim CH Tags: Phys Med Biol Source Type: research

Time-resolved dosimetry for validation of 4D dose calculation in PBS proton therapy.
In this study a novel approach of time-resolved dosimetry using five pinpoint ionization chambers (IC) embedded in an anthropomorphic dynamic phantom was employed and validated against beam delivery details. Beam intensity variations as well as beam delivery time-structure were well reflected with an accuracy comparable to the temporal resolution of the IC measurements. The 4D dosimetry approach was further applied for benchmarking 4D-DC implemented in the RayStation 6.99 treatment planning system. The agreement between computed values and measurements was investigated for: (i) partial doses based on individual breathing p...
Source: Physics in Medicine and Biology - April 27, 2020 Category: Physics Authors: Kostiukhina N, Palmans H, Stock M, Knopf AC, Georg D, Knaeusl B Tags: Phys Med Biol Source Type: research

Quantitative imaging of coronary flows using 3D ultrafast doppler coronary angiography.
In this study, we introduce 3-D Ultrafast Doppler Coronary Angiography (3-D UDCA), an ultrasound-based method to assess coronary blood flows in three-dimensions at high volume-rate and in one single heartbeat. We demonstrate that 3-D UDCA can visualize the coronary vasculature with high temporal and spatial resolution and quantify the absolute flow. The feasibility of the technique was demonstrated in an open-chest swine model. The flow rate of the left-anterior descending artery (LAD) assessed by 3-D UDCA was reconstructed successfully at the early diastolic and late diastolic phases and was in good agreement with an inva...
Source: Physics in Medicine and Biology - April 27, 2020 Category: Physics Authors: Correia M, Maresca D, Goudot G, Villemain O, Bize A, Sambin L, Tanter M, Ghaleh B, Pernot M Tags: Phys Med Biol Source Type: research

Impact of Gaussian uncertainty assumptions on probabilistic optimization in particle therapy.
Abstract Range and setup uncertainties in charged particle therapy may induce a discrepancy between planned and delivered dose. Countermeasures based on probabilistic optimization assume a Gaussian probability density to model the underlying range and setup error. While this assumption is generally taken for granted, this work explicitly investigates dosimetric consequences if the actual errors obey a different probability density function (PDF) over the course of treatment than the one used during probabilistic treatment plan optimization. Discrete random sampling was performed for conventionally and probabilisti...
Source: Physics in Medicine and Biology - April 27, 2020 Category: Physics Authors: Wieser HP, Karger CP, Wahl N, Bangert M Tags: Phys Med Biol Source Type: research

Practical joint reconstruction of activity and attenuation with autonomous scaling for time-of-flight PET.
Abstract Recent research showed that attenuation images can be determined from emission data, jointly with activity images, up to a scaling constant when utilizing the time-of-flight (TOF) information. We aim to develop practical CT-less joint reconstruction for clinical TOF PET scanners to obtain quantitatively accurate activity and attenuation images. In this work, we present a joint reconstruction of activity and attenuation based on MLAA (maximum likelihood reconstruction of attenuation and activity) with autonomous scaling determination and joint TOF scatter estimation from TOF PET data. Our idea for scaling ...
Source: Physics in Medicine and Biology - April 27, 2020 Category: Physics Authors: Li Y, Matej S, Karp JS Tags: Phys Med Biol Source Type: research

Characterization of four readout circuits for an MR compatible, preclinical PET detector.
Abstract We are building a high sensitivity preclinical PET/MRI insert using a highly multiplexed light sharing PET module. Each module incorporates four 19×19 arrays of 1×1×20 mm3 LYSO crystals with dual-ended DOI encoding readout, requiring thirty-two readout channels for positioning and eight channels for timing. These constraints necessitate compact, robust electronics for digitization. We have characterized four linearized time-over-threshold circuits based on these detector requirements. The four circuits allow for high channel density and can digitize signals from highly multiplexed light ...
Source: Physics in Medicine and Biology - April 27, 2020 Category: Physics Authors: Selfridge AR, Cherry SR, Badawi RD Tags: Phys Med Biol Source Type: research

Image reconstruction for a multi-layer Compton Telescope: an analytical model for three interaction events.
, Oliver JF Abstract Compton Cameras are electronically collimated photon imagers suitable for sub-MeV to few MeV gamma-ray detection. Such features are desirable to enable in vivo range verification in hadron therapy, through the detection of secondary Prompt Gammas. A major concern with this technique is the poor image quality obtained when the incoming gamma-ray energy is unknown. Compton Cameras with more than two detector planes (multi-layer Compton Cameras) have been proposed as a solution, given that these devices incorporate more signal sequences of interactions to the conventional two interaction events. ...
Source: Physics in Medicine and Biology - April 24, 2020 Category: Physics Authors: Roser J, Muñoz E, Barrientos L, Barrio J, Bernabéu Alberola J, Borja-Lloret M, Etxebeste A, Llosa G, Ros A, Viegas R, Oliver JF Tags: Phys Med Biol Source Type: research

A novel procedure for determining the optimal MLC configuration parameters in treatment planning systems based on measurements with a Farmer chamber.
In this study we present a method that separates the effect of each dosimetric characteristic of the MLC, offering comprehensive equations for the determination of the configuration parameters used in the TPS model. The main advantage of the method is that it only requires prior knowledge of the nominal leaf width and is based on doses measured with a Farmer chamber, which is a very well established and robust methodology. Another significant advantage is the required time, since measuring the tests takes only about 30 minutes per energy. Firstly, we provide a theoretical general formalism in terms of the primary fluence c...
Source: Physics in Medicine and Biology - April 24, 2020 Category: Physics Authors: Saez J, Hernandez V, Goossens J, De Kerf G, Verellen D Tags: Phys Med Biol Source Type: research

Automated MV markerless tumor tracking for VMAT.
Abstract Tumor tracking during radiotherapy treatment can improve dose accuracy, conformity and sparing of healthy tissue. Many methods have been introduced to tackle this challenge utilizing multiple imaging modalities, including a template matching based approach using the megavoltage (MV) on-board portal imager demonstrated on 3D conformal treatments. However, the complexity of treatments is evolving with the introduction of VMAT and IMRT, and successful motion management is becoming more important due to a trend towards hypofractionation. We have developed a markerless lung tumor tracking algorithm, utilizing ...
Source: Physics in Medicine and Biology - April 24, 2020 Category: Physics Authors: Ferguson D, Harris T, Shi M, Jacobson MW, Myronakis ME, Lehmann M, Huber P, Morf D, Fueglistaller R, Baturin P, Valencia Lozano I, Williams CL, Berbeco RI Tags: Phys Med Biol Source Type: research

The noise navigator for MRI-guided radiotherapy: an independent method to detect physiological motion.
In this study we demonstrate the detection of various types of motion for three anatomical use cases of MRI-guided radiotherapy, i.e. torso (bulk movement and variable breathing), head-and-neck (swallowing) and cardiac. Furthermore, it is shown that the noise navigator can detect bulk movement, variable breathing and swallowing on a hybrid 1.5T MRI-linac system. Cardiac activity detection through the noise navigator seems feasible in an MRI-guided radiotherapy setting, but needs further optimization. The noise navigator is a versatile and fast (millisecond temporal resolution) motion detection method independent of MR sign...
Source: Physics in Medicine and Biology - April 24, 2020 Category: Physics Authors: Navest RJM, Mandija S, Zijlema SE, Stemkens B, Andreychenko A, Lagendijk JJW, Van den Berg CAT Tags: Phys Med Biol Source Type: research

Label-driven MRI-US registration using weakly-supervised learning for MRI-guided prostate radiotherapy.
CONCLUSION: This work presents a deep learning-based, weakly supervised network for accurate MRI-TURS image registration. Our proposed method has achieved promising registration performance in terms of Dice, TRE, MSD and HD. PMID: 32330922 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 24, 2020 Category: Physics Authors: Zeng Q, Fu Y, Tian Z, Lei Y, Zhang Y, Wang T, Mao H, Liu T, Curran WJ, Jani AB, Patel P, Yang X Tags: Phys Med Biol Source Type: research

Abdominal synthetic CT generation from MR Dixon images using a U-Net trained with & quot;semi-synthetic & quot; CT data.
This study investigates a deep learning-based method that generates synthetic CT volumes from T1-weighted MR Dixon images in support of MRI-based intrahepatic radiotherapy treatment planning. Training deep neutral networks for this purpose has been challenged by mismatches between CT and MR images due to motion and different organ filling status. This work proposes to resolve such challenge by generating "semi-synthetic" CT images from rigidly aligned CT and MR image pairs. Contrasts within skeletal elements of the "semi-synthetic" CT images were determined from CT images, while contrasts of soft tissue...
Source: Physics in Medicine and Biology - April 24, 2020 Category: Physics Authors: Liu L, Johansson A, Cao Y, Dow J, Lawrence TS, Balter JM Tags: Phys Med Biol Source Type: research

Precise analysis of the timing performance of Cherenkov-radiator-integrated MCP-PMTs: analytical deconvolution of MCP direct interactions.
Abstract In order to achieve the ultimate goal of reducing coincidence time resolution (CTR) to 10 ps, thus enabling reconstruction-less positron emission tomography, a Cherenkov-radiator-integrated microchannel plate photomultiplier tube (CRI) reaching CTR of sub-50 ps full width at half maximum (FWHM) has been developed. However, a histogram of time differences between a pair of the CRIs shows undesirable side peaks, which are caused by gamma rays directly interacting with the micro channel plates (MCPs). Such direct interaction events are detrimental to the timing performance of the CRI. In this paper, we demon...
Source: Physics in Medicine and Biology - April 23, 2020 Category: Physics Authors: Ota R, Nakajima K, Ogawa I, Tamagawa Y, Shimoi H, Suyama M, Hasegawa T Tags: Phys Med Biol Source Type: research

Penalized maximum-likelihood reconstruction for improving limited-angle artifacts in a dedicated head and neck PET system.
Abstract Positron emission tomography (PET) suffers from limited spatial resolution in current head and neck cancer management. We are building a dual-panel high-resolution PET system to aid the detection of tumor involvement in small lymph nodes (
Source: Physics in Medicine and Biology - April 23, 2020 Category: Physics Authors: Zhang H, Wang Y, Qi J, Abbaszadeh S Tags: Phys Med Biol Source Type: research

245 ps-TOF brain-dedicated PET prototype with a hemispherical detector arrangement.
Abstract Brain PET, which has led research in molecular imaging and diagnosis of brain cancer, epilepsy and neurodegenerative disorders, is being spotlighted again to promote earlier diagnosis of dementia with the advent of amyloid and tau tracers. To meet this demand, in this paper, we developed a brain-dedicated PET imaging device with a hemispherical detector arrangement, which provides comparable sensitivity with fewer detectors than conventional cylindrical geometries. The introduction of the time-of-flight (TOF) measurement capability was a key point for the development to get a gain in the image signal-to-n...
Source: Physics in Medicine and Biology - April 23, 2020 Category: Physics Authors: Yoshida E, Tashima H, Akamatsu G, Iwao Y, Takahashi M, Yamashita T, Yamaya T Tags: Phys Med Biol Source Type: research

Design study of fully wearable high-performance brain PETs for neuroimaging in free movement.
Abstract A practical wearable brain PET scanner capable of dynamic neuroimaging during free bodily movement will enable potential breakthrough basic neuroscience studies and help develop imaging-based neurological diagnoses and treatments. Weight, brain coverage, and sensitivity are three fundamental technical obstacles in the development of Fully Wearable High-Performance (FWHP) brain PET scanners. The purpose of this study is to investigate the feasibility of building a FWHP brain PET using a limited volume of lutetium-yttrium oxyorthosilicate (LYSO) scintillator crystals. Six scanners, consisted of the same vol...
Source: Physics in Medicine and Biology - April 23, 2020 Category: Physics Authors: Tao W, Weng F, Chen G, Lv L, Zhao Z, Xie S, Zan Y, Xu J, Huang Q, Peng Q Tags: Phys Med Biol Source Type: research

Biomechanical modeling of radiation dose-induced volumetric changes of the parotid glands for deformable image registration.
Abstract Early animal studies suggest that parotid gland (PG) toxicity prediction could be improved by an accurate estimation of the radiation dose to sub-regions of the PG. Translation to clinical investigation requires voxel-level dose accumulation in this organ that responds volumetrically throughout treatment. To date, deformable image registration (DIR) has been evaluated for the PG using only surface alignment. We sought to develop and evaluate an advanced DIR technique capable of modeling these complex PG volume changes over the course of radiation therapy. Planning and mid-treatment magnetic resonance imag...
Source: Physics in Medicine and Biology - April 22, 2020 Category: Physics Authors: McCulloch M, Cazoulat G, Ford A, Elgohari BA, Bahig H, Kim AD, Elhalawani HM, He R, Wang J, Ding Y, Mohamed ASR, Polan DF, King J, Peterson CB, Ohrt AN, Fuller CD, Lai SY, Brock KK Tags: Phys Med Biol Source Type: research

A patient-independent CT intensity matching method using conditional generative adversarial networks (cGAN) for single x-ray projection based tumor localization.
CONCLUSION: A patient-independent CT intensity matching method was developed, based on which accurate tumor localization can be achieved. It does not require actual CBCT scan to be performed before treatment for each patient, therefore making it more efficient in the clinical workflow. PMID: 32320959 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 22, 2020 Category: Physics Authors: Wei R, Liu B, Zhou F, Bai X, Fu D, Liang B, Wu Q Tags: Phys Med Biol Source Type: research

Simultaneous determination of the dose and linear energy transfer (LET) of carbon-ion beams using radiochromic films.
Abstract Radiochromic films are useful as dosimeters in high-precision radiotherapy owing to their high spatial resolution. However, when a particle beam is measured using a radiochromic film, the dose cannot be estimated accurately because the film darkness varies with variations in linear energy transfer (LET). This paper proposes a novel method for estimating the LET and the dose based on the film darkness. In this method, after a high-LET particle beam, such as a carbon-ion beam, was incident on the film, the film was digitized and its net optical density was determined. Further, the non-linearity of the film ...
Source: Physics in Medicine and Biology - April 22, 2020 Category: Physics Authors: Kawashima M, Matsumura A, Souda H, Tashiro M Tags: Phys Med Biol Source Type: research

Computational model for detector timing effects in Compton-camera based prompt-gamma imaging for proton radiotherapy.
Abstract This paper describes a realistic simulation of a Compton-camera (CC) based prompt-gamma (PG) imaging system for proton range verification for a range of clinical dose rates, and its comparison to PG measured data with a pre-clinical CC. We used a Monte Carlo plus Detector Effects (MCDE) model to simulate the production of prompt gamma-rays (PG) and their energy depositions in the CC. With Monte Carlo, we simulated PG emission resulting from irradiation of a high density polyethylene phantom with a 150 MeV proton pencil beam at dose rates of 5.0×108, 2.6×109, and 4.6×109 p+/s. Realistic d...
Source: Physics in Medicine and Biology - April 22, 2020 Category: Physics Authors: Maggi P, Peterson SW, Panthi R, Mackin DS, Yang H, He Z, Beddar S, Polf J Tags: Phys Med Biol Source Type: research

Assessing the advantages of CFR-PEEK over titanium spinal stabilization implants in proton therapy - a phantom study.
Abstract High-density materials as titanium, used for spinal stabilization introduce several critical issues in proton therapy (PT). Artefacts affect both contouring and dose calculation. Subsequently, artefacts need to be corrected which is a time consuming process. Besides, titanium causes proton interactions that are unaccounted for in dose calculation. Result is a suboptimal treatment plan and indeed decreased local controls have been reported for these patients. Carbon fiber reinforced polyetheretherketone (CFR-PEEK) implant material, which is of low-density, potentially solves these issues. For this study, w...
Source: Physics in Medicine and Biology - April 21, 2020 Category: Physics Authors: Poel R, Belosi MF, Albertini F, Walser M, Gisep A, Lomax AJ, Weber DC Tags: Phys Med Biol Source Type: research

Physical characterization of a novel wireless DRX plus 3543C using both a carbon nano tube (CNT) mobile x-ray system and a traditional x-ray system.
In conclusion, we can show that the dynamic focal selection of the system equipped with CNT does not play a substantial role in image quality compared to a traditional system in terms of physical characterisation of the detector in our measurement conditions. PMID: 32311679 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 20, 2020 Category: Physics Authors: Nitrosi A, Bertolini M, Chendi A, Trojani V, Canovi L, Pattacini P, Iori M Tags: Phys Med Biol Source Type: research

Identifying < i > in vivo < /i > inflammation using magnetic nanoparticle spectra.
Identifying in vivo inflammation using magnetic nanoparticle spectra. Phys Med Biol. 2020 Apr 20;: Authors: Weaver J, Ness D, Fields J, Jyoti D, Gordon-Wylie S, Berwin BL, Mirza S, Fiering S Abstract We are developing magnetic nanoparticle (NP) methods to characterize inflammation and infection in vivo. Peritoneal infection in C57BL/6 mice was used as a biological model. An intraperitoneal NP injection was followed by measurement of magnetic nanoparticle spectroscopy of Brownian rotation (MSB) spectra taken over time. MSB measures the magnetization of NPs in a low frequency alternating magnetic field....
Source: Physics in Medicine and Biology - April 20, 2020 Category: Physics Authors: Weaver J, Ness D, Fields J, Jyoti D, Gordon-Wylie S, Berwin BL, Mirza S, Fiering S Tags: Phys Med Biol Source Type: research

Optimization and performance study of a proton CT system for pre-clinical small animal imaging.
arodi K Abstract Proton computed tomography (pCT) promises to reduce or even eliminate range uncertainties inherent in the conversion of Hounsfield units into relative stopping power (RSP) for proton therapy treatment planning. This is of particular interest for proton irradiation studies in animal models due to the high precision required and uncertainties in tissue properties. We propose a dedicated single-particle tracking pCT system consisting of low material budget floating strips Micromegas detectors for tracking and a segmented time-projection-chamber with vertical Mylar absorbers, functioning as a range te...
Source: Physics in Medicine and Biology - April 20, 2020 Category: Physics Authors: Meyer S, Bortfeldt J, Lämmer P, Englbrecht F, Pinto M, Schnürle K, Wuerl M, Parodi K Tags: Phys Med Biol Source Type: research

Characterization of spectral changes with measurement geometry and magnetic field strength in light guides used for scintillation dosimetry.
Abstract The purpose of this work was to characterize the stem-effect signal and the Cerenkov light ratio (CLR) in various light guides as functions of measurement geometry and magnetic field strength. Two PMMA-, two silica-, and one polystyrene-based light guides were considered in this work. Spectra measurements were performed as functions of depth, fiber-beam angle, and magnetic field strength using an optical spectrometer. All measurements were performed using a clinical linear accelerator at a nominal photon beam energy of 6MV. Depths ranging from 1cm to 10cm, fiber-beam angles ranging from 90degrees to 30deg...
Source: Physics in Medicine and Biology - April 20, 2020 Category: Physics Authors: Simiele EA, Kapsch RP, Ankerhold U, Culberson WS, DeWerd LA Tags: Phys Med Biol Source Type: research

Monte Carlo track-structure for the radionuclide Copper-64: characterization of S-values, nanodosimetry and quantification of direct damage to DNA.
In conclusion, the results of the S-values show that the absorbed dose strongly depends on the distribution of the radionuclide in the cell, the dose being higher when 64Cu is internalized in the cell nucleus, which is reinforced by the nanodosimetric study by the presence of DNA DSBs attributable to the Auger electrons emitted during the decay of 64Cu. PMID: 32303013 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 17, 2020 Category: Physics Authors: Carrasco-Hernandez J, Ramos-Mendez J, Faddegon BA, Jalilian AR, Moranchel M, Ávila-Rodríguez MÁ Tags: Phys Med Biol Source Type: research

A Monte Carlo based scatter removal method for non-isocentric cone-beam CT acquisitions using a deep convolutional autoencoder.
Abstract The primary cone-beam computed tomography (CBCT) imaging beam scatters inside the patient and produces a contaminating photon fluence that is registered by the detector. Scattered photons cause artifacts in the image reconstruction, and are partially responsible for the inferior image quality compared to diagnostic fan-beam CT. In this work, a deep convolutional autoencoder (DCAE) and projection-based scatter removal algorithm were constructed for the ImagingRingTM system on rails (IRr), which allows for non-isocentric acquisitions around virtual rotation centers with its independently rotatable source an...
Source: Physics in Medicine and Biology - April 15, 2020 Category: Physics Authors: van der Heyden B, Uray M, Fonseca GP, Huber P, Us D, Messner I, Law A, Parii A, Reisz N, Rinaldi I, Vilches-Freixas G, Deutschmann H, Verhaegen F, Steininger P Tags: Phys Med Biol Source Type: research

Multifaceted radiomics for distant metastasis prediction in head & neck cancer.
Multifaceted radiomics for distant metastasis prediction in head & neck cancer. Phys Med Biol. 2020 Apr 15;: Authors: Zhou Z, Wang K, Folkert MR, Liu H, Jiang SB, Sher D, Wang J Abstract Accurately predicting distant metastasis in head & neck cancer has the potential to improve patient survival by allowing early treatment intensification with systemic therapy for high-risk patients. By extracting large amounts of quantitative features and mining them, radiomics has achieved success in predicting treatment outcomes for various diseases. However, there are several challenges associated with conv...
Source: Physics in Medicine and Biology - April 15, 2020 Category: Physics Authors: Zhou Z, Wang K, Folkert MR, Liu H, Jiang SB, Sher D, Wang J Tags: Phys Med Biol Source Type: research

Low-dose X-ray CT simulation from an available higher-dose scan.
Abstract In CT-imaging an optimal compromise between the radiation burden and the image quality for the imaging task is needed. Lower-dose CT is desirable, however, lowering the dose results in a lower signal-to-noise ratio and therefore in a reduced image quality. In this research, we aim to develop a tool to simulate lower-dose scans from an existing standard-dose scan. The main application of this tool is to determine the lowest possible radiation dose that still produces sufficient clinical information. The X-ray tube current reduction is modeled by estimating the noise equivalent number of photons in the high...
Source: Physics in Medicine and Biology - April 15, 2020 Category: Physics Authors: Elhamiasl M, Nuyts J Tags: Phys Med Biol Source Type: research

An end-to-end test for MR-guided online adaptive radiotherapy.
Abstract In the evolving field of adaptive MR guided radiotherapy, the need for dedicated procedures for acceptance and quality assurance is increasing. Research has been devoted to MR compatible dosimeters and phantoms, but to date no end-to-end test has been presented that covers an MRgRT workflow. Such an end-to-end test should comprise each step of the workflow and include all associated uncertainties. The purpose of this study was to investigate the usability of an anthropomorphic deformable and multimodal pelvis (ADAM-pelvis) phantom in combination with film dosimetry for end-to-end testing of an MRgRT adapt...
Source: Physics in Medicine and Biology - April 15, 2020 Category: Physics Authors: Hoffmans D, Niebuhr NI, Bohoudi O, Pfaffenberger A, Palacios MA Tags: Phys Med Biol Source Type: research

Pushing Cherenkov PET with BGO via coincidence time resolution classification and correction.
Abstract Bismuth germanate (BGO) shows good properties for PET applications, but was substituted by the development of faster crystals like Lutetium oxyorthosilicate (LSO) for time-of-flight PET (TOF-PET). Recent improvements in silicon photomultipliers (SiPM) and fast readout electronics make it possible to access the Cherenkov photon signal produced upon 511 keV interaction, which makes BGO a cost effective candidate for TOF-PET. Tails in the time delay distribution, however, remain a challenge. These are mainly caused by the high statistical fluctuation on the Cherenkov photons detected. To select fast events w...
Source: Physics in Medicine and Biology - April 8, 2020 Category: Physics Authors: Kratochwil N, Gundacker S, Lecoq P, Auffray E Tags: Phys Med Biol Source Type: research

Experimental comparison of clinically used ion beams for imaging applications using a range telescope.
Abstract In particle therapy, the X-ray based treatment planning converting photon attenuation values to relative stopping power ratio (RSP) introduces clinically relevant range uncertainties. Recently, novel imaging technologies using transmission ion beams have been investigated to directly assess the water equivalent thickness (WET) of tissue, showing improved accuracy in RSP reconstruction, while potentially reducing the imaging dose. Due to their greater availability, protons have been mostly used for ion imaging. To this end, in this work, the influence of three ion species (protons, helium and carbon ions) ...
Source: Physics in Medicine and Biology - April 8, 2020 Category: Physics Authors: Kopp B, Meyer S, Gianoli C, Magallanes L, Voss B, Brons S, Parodi K Tags: Phys Med Biol Source Type: research

Impact of charge collection efficency and electronic noise on the performance of solid state 3D-microdetectors.
eta C Abstract Microdosimetry has been traditionally performed through gaseous proportional counters, although in recent years different solid state microdosimeters have been proposed and constructed for this task. In this paper we analyze the response of solid state devices of micrometric size with no intrinsic gain developed by CNM-CSIC (Spain). There are two major aspects of the operation of these devices that affect the reconstruction of the probability distributions and momenta of stochastic quantities related to microdosimetry. On one side, for micrometric volumes, the drift and diffusion of the charge carri...
Source: Physics in Medicine and Biology - April 8, 2020 Category: Physics Authors: Prieto-Pena J, Gomez F, Guardiola C, Jimenez-Ramos MC, Garcia-Lopez J, Baratto-Roldán A, Baselga M, Pardo-Montero J, Fleta C Tags: Phys Med Biol Source Type: research

Comparison of X-ray speckle based imaging deflection retrieval algorithms for the optimization of radiation dose.
jon S Abstract X-ray phase contrast imaging can provide improved or complementary information to traditional attenuation-based X-ray imaging, making the field a vast and rapidly evolving research subject. X-ray Speckle Based Imaging (SBI) is one phase-contrast imaging approach that has shown high potential in providing both high sensitivity and high resolution while using a very simple experimental setup. With the aim of transferring such phase-contrast based imaging techniques from synchrotron to laboratory X-ray sources, the issue of the deposited radiation dose still remains to be addressed. In this work, we ex...
Source: Physics in Medicine and Biology - April 8, 2020 Category: Physics Authors: Rougé-Labriet H, Quenot L, Bohic S, Fayard B, Paganin DM, Brun E, Berujon S Tags: Phys Med Biol Source Type: research

Design, evaluation and comparison of endorectal coils for hybrid MR-PET imaging of the prostate.
Abstract Prostate cancer is one of the most common cancers among men and its early detection is critical for its successful treatment. The use of multimodal imaging, such as MR-PET, is most advantageous as it is able to provide detailed information about the prostate. However, as the human prostate is flexible and can move into different positions under external conditions, it is important to localise the focused region-of-interest using both MRI and PET under identical circumstances. In this work, we designed five commonly used linear and quadrature radiofrequency surface coils suitable for hybrid MR-PET use in e...
Source: Physics in Medicine and Biology - April 8, 2020 Category: Physics Authors: Choi CH, Felder T, Felder J, Tellmann L, Hong SM, Wegener HP, Shah NJ, Ziemons K Tags: Phys Med Biol Source Type: research

Restarted primal-dual Newton conjugate gradient method for enhanced spatial resolution of reconstructed cone-beam X-ray luminescence computed tomography images.
Abstract Cone-beam X-ray luminescence computed tomography (CB-XLCT) has been proposed as a promising imaging tool, which enables three-dimensional imaging of the distribution of nanophosphors (NPs) in small animals. However, the reconstruction performance is usually unsatisfactory in terms of spatial resolution due to the ill-posedness of CB-XLCT inverse problem. To alleviate this problem and to achieve high spatial resolution, a reconstruction method consisting of inner and outer iterations based on a restarted strategy is proposed. In this method, the primal-dual Newton Conjugate Gradient method (pdNCG) is adopt...
Source: Physics in Medicine and Biology - April 8, 2020 Category: Physics Authors: Gao P, Cheng K, Schueler E, Jia M, Zhao W, Xing L Tags: Phys Med Biol Source Type: research

Melanoma detection using adversarial training and deep transfer learning.
Abstract Skin lesion datasets consist predominantly of normal samples with only a small percentage of abnormal ones, giving rise to the class imbalance problem. Also, skin lesion images are largely similar in overall appearance owing to the low inter-class variability. In this paper, we propose a two-stage framework for automatic classification of skin lesion images using adversarial training and transfer learning toward melanoma detection. In the first stage, we leverage the inter-class variation of the data distribution for the task of conditional image synthesis by learning the inter-class mapping and synthesiz...
Source: Physics in Medicine and Biology - April 6, 2020 Category: Physics Authors: Zunair H, Ben Hamza A Tags: Phys Med Biol Source Type: research

Statistical approach to the selection of the tolerances for distance to agreement improves the quality control of the dose delivery in radiotherapy.
Abstract In the study a local approach to setting reference tolerance values for distance to agreement (DTA) component of gamma index is proposed. The reference tolerance values are calculated in simulations, following a dose delivery model presented in a previous work. An analytical model for determining the quantiles of DTA distribution is also proposed and verified. It is shown that the distributions of DTA values normalized with either quantiles or standard deviation of DTA distributions are universal over analyzed plans and points within a single plan. This enables statistically sound inference about quality ...
Source: Physics in Medicine and Biology - April 6, 2020 Category: Physics Authors: Baran M, Kabat D, Tulik M, Rzecki K, Sośnicki T, Tabor Z Tags: Phys Med Biol Source Type: research

A generalized system of tissue-mimicking materials for computed tomography (CT) and magnetic resonance imaging (MRI).
In conclusion, we have created a system of materials capable of producing tissue-like contrast for 3.0T MRI and CT imaging modalities. PMID: 32252048 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 6, 2020 Category: Physics Authors: Singhrao K, Fu J, Gao Y, Wu HH, Yang Y, Hu P, Lewis JH Tags: Phys Med Biol Source Type: research

Dose profiles and x-ray energy optimization for microbeam radiation therapy by high-dose, high resolution dosimetry using Sm-doped fluoroaluminate glass plates and Monte Carlo transport simulation.
Abstract Microbeam radiation therapy (MRT) utilizes highly collimated synchrotron generated x-rays to create narrow planes of high dose radiation for the treatment of tumors. Individual microbeams have a typical width of 30-50 µm and are separated by a distance of 200-500 µm. The dose delivered at the center of the beam is lethal to cells in the microbeam path, on the order of hundreds of Grays (Gy). The tissue between each microbeam is spared and helps aid in the repair of adjacent damaged tissue. Radiation interactions within the peak of the microbeam, such as the photoelectric effect and incoherent ...
Source: Physics in Medicine and Biology - April 3, 2020 Category: Physics Authors: Chicilo F, Hanson AL, Geisler FH, Belev G, Edgar A, Ramaswami KO, Chapman D, Kasap SO Tags: Phys Med Biol Source Type: research

Motion correction of respiratory-gated PET images using deep learning based image registration framework.
CONCLUSIONS: In this work, we proposed a motion correction method for respiratory-gated PET images using deep learning based image registration framework. It does not require the knowledge of the true deformation field for training the network, which makes it very convenient to implement. We validated the proposed method using simulation and clinical data and showed its ability to reduce motion artifacts while utilizing all gated PET data. PMID: 32244230 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 3, 2020 Category: Physics Authors: Li T, Zhang M, Qi W, Asma E, Qi J Tags: Phys Med Biol Source Type: research

Improved myocardial perfusion PET imaging using artificial neural networks.
Abstract Myocardial perfusion (MP) PET imaging plays a key role in risk assessment and stratification of patients with coronary artery disease. In this work, we proposed a patch-based artificial neural network (ANN) fusion approach that integrates information from the maximum-likelihood (ML) and the post-smoothed ML reconstruction to improve MP PET imaging. To enhance quantification and tasked-based MP defect detection, the proposed method fused features from patches of the ML and the post-smoothed ML reconstructed images with different noise levels and spatial resolution. Using the XCAT phantom, we simulated thre...
Source: Physics in Medicine and Biology - April 3, 2020 Category: Physics Authors: Wang X, Yang B, Moody JB, Tang J Tags: Phys Med Biol Source Type: research

A rapid, accurate image simulation strategy for mega-voltage cone-beam computed tomography.
In this study, a fast, accurate simulation strategy for MV-CBCT utilizing the FastEPID technique has been developed and validated. During FastEPID simulation, photon detection was determined by pre-calculated photon energy deposition efficiency (η) and particle transport within the EPID was replaced with a pre-calculated optical photon spread function. This method is capable of reducing the time required for EPID image simulation by a factor of 90-140, without compromising image quality. MV-CBCT images reconstructed from the FastEPID simulated projections have been validated against measurement in terms of mean Hounsfi...
Source: Physics in Medicine and Biology - April 3, 2020 Category: Physics Authors: Shi M, Myronakis ME, Jacobson MW, Lehmann M, Ferguson D, Baturin P, Huber P, Fueglistaller R, Harris T, Valencia Lozano I, Williams C, Morf D, Berbeco RI Tags: Phys Med Biol Source Type: research

Comparator-less PET data acquisition system using single-ended memory interface input receivers of FPGA.
In this study, we propose a linear field-programmable gate array (FPGA)-based charge measurement method by combining a charge-to-time converter (QTC) with a single-ended memory interface (SeMI) input receiver. The QTC automatically converts the input charge into a dual-slope pulse, which has a width proportional to the input charge. Dual-slope pulses are directly digitized by the FPGA input/output (I/O) buffers configured with SeMI input receivers. A proof-of-concept comparator-less QTC/SeMI data acquisition (DAQ) system, consisting of 132 energy and 33 timing channels, was developed and applied to a prototype brain-dedica...
Source: Physics in Medicine and Biology - April 3, 2020 Category: Physics Authors: Won JY, Ko GB, Kim KY, Park H, Lee S, Son JW, Lee JS Tags: Phys Med Biol Source Type: research

Consistent and invertible deformation vector fields for a breathing anthropomorphic phantom: a post-processing framework for the XCAT phantom.
Abstract Breathing motion is challenging for radiotherapy planning and delivery. This requires advanced four-dimensional (4D)-imaging and motion mitigation strategies and associated validation tools with known deformations. Numerical phantoms such as the XCAT provide reproducible and realistic data for simulation-based validation. However, the XCAT generates partially inconsistent and non-invertible deformations where tumours remain rigid and structures can move through each other. We address these limitations by post-processing the XCAT deformation vector fields (DVF) to generate a breathing phantom with realisti...
Source: Physics in Medicine and Biology - April 1, 2020 Category: Physics Authors: Eiben B, Bertholet J, Menten MJ, Nill S, Oelfke U, McClelland JR Tags: Phys Med Biol Source Type: research

An integrated quality assurance phantom for frameless single-isocenter multitarget stereotactic radiosurgery.
Conclusions:OneIso provides a streamlined, single-setup workflow for single-isocenter multitarget frameless linac-based SRS QA. Additionally, with the ability to quantify off-axis spatial-discrepancies, we can determine limitations on the maximum distance between targets to ensure a single-isocenter multitarget SRS program meets recommended guidelines. PMID: 32235050 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 1, 2020 Category: Physics Authors: Capaldi DPI, Skinner LB, Dubrowski P, Yu AS Tags: Phys Med Biol Source Type: research

Biological washout modelling for in-beam PET: rabbit brain irradiation by < sup > 11 < /sup > C and < sup > 15 < /sup > O ion beams.
This study provides basic data for modelling of the biological washout effect. PMID: 32235057 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 1, 2020 Category: Physics Authors: Toramatsu C, Mohammadi A, Wakizaka H, Seki C, Nishikido F, Sato S, Kanno I, Takahashi M, Karasawa K, Hirano Y, Yamaya T Tags: Phys Med Biol Source Type: research