Image reconstruction by Mumford-Shah regularization for low-dose CT with multi-GPU acceleration.
Abstract Mumford-Shah (MS) functional has emerged as a regularization technique in X-ray computed tomography (CT) recently. However, for high-resolution CT applications, the huge size of both projection data and image leads to an implementation difficulty. In this work, we propose an approach to implement and accelerate MS regularization on a multi-GPU platform to resolve the issue of data size and rich onboard memory and computing units. We have established a novel partition scheme of the 3D volume under reconstruction and corresponding multithread parallel acceleration strategy to fully utilize the computing res...
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Zhu Y, Wang Q, Li M, Jiang M, Zhang P Tags: Phys Med Biol Source Type: research

IPEM Topical Report: A 2018 IPEM survey of MRI use for external beam radiotherapy treatment planning in the UK.
Conclusion:
 The primary barriers reported to MRI implementation in EBRT planning included costs (e.g., lack of a national tariff for planning MRI), lack of MRI access and/or capacity within hospitals. Despite these challenges, significant interest remains in increasing MRI-assisted EBRT planning over the next five years.&#13. PMID: 31239419 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Speight R, Schmidt MA, Liney GP, Johnstone R, Eccles CL, Dubec M, George B, Henry A, McCallum HM Tags: Phys Med Biol Source Type: research

A preclinical PET detector constructed with a monolithic scintillator ring.
Abstract This paper presents an unique preclinical positron emission tomography (PET) detector constructed with a monolithic scintillator ring (MSR) and two rings of silicon photomultipliers (SiPM). The inner diameter, outer diameter and length of the MSR were 48.5 mm, 58.5 mm, and 25.1 mm, respectively. The two SiPM rings, constructed with 46 SiPMs, were air-coupled to the two ends of the MSR detector. The center of gravity (COG) and artificial neural network (ANN) methods were adapted to decode the positions of the gamma interactions in the circumferential (θ) and axial (Z) directions, respectively. Collim...
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Xu J, Xie S, Zhang X, Tao W, Yang J, Zhao Z, Weng F, Huang Q, Yi F, Peng Q Tags: Phys Med Biol Source Type: research

Development of a dosimetric model for < i > in vitro < /i > labelled cells with β+ emitters in PET tracking studies.
Development of a dosimetric model for in vitro labelled cells with β+ emitters in PET tracking studies. Phys Med Biol. 2019 Jun 26;: Authors: Jacquemin M, Broggio D, Franck D, Desbree A Abstract Positron emission tomography (PET) offers an effective method for tracking β+ emitters-labeled cells in vivo. However, in vitro high labelling activities used may cause cell damage or death. Our understanding of the impact of such procedure remains limited by the fact that the biological effects are usually linked to the activity per cell rather than the absorbed dose. To assess the dose delivered to...
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Jacquemin M, Broggio D, Franck D, Desbree A Tags: Phys Med Biol Source Type: research

Experimental verification of a non-invasive method to monitor the lateral pencil beam position in an anthropomorphic phantom for carbon-ion radiotherapy.
M, Martisikova M Abstract The dose conformation and the sparing of neighboring critical healthy structures are improved in carbon-ion beam radiotherapy in comparison to conventional photon radiotherapy. Inter and intrafractional plan adaptation strategies may preclude the quality assurance (QA) of the actually applied treatment plan before the treatment starts. Therefore, independent measurements of the positions of scanned pencil &amp;lt;sup&amp;gt;12&amp;lt;/sup&amp;gt;C ion beams are of interest in order to monitor the beam application during the treatment and the beam in the isocenter. In this...
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Félix-Bautista R, Gehrke T, Ghesquière-Diérickx L, Reimold M, Amato C, Turecek D, Jakubek J, Ellerbrock M, Martisikova M Tags: Phys Med Biol Source Type: research

On light sharing TOF-PET modules with depth of interaction and 157 ps FWHM coincidence time resolution.
Abstract The performance of a light sharing and recirculation mechanism that allows the extraction of depth of interaction (DOI) are investigated in this paper, with a particular focus on timing. In parallel, a method to optimize the coincidence time resolution (CTR) of PET detectors by use of the DOI information is proposed and tested. For these purposes, a dedicated 64-channels readout setup has been developed with intrinsic timing resolution of 16 ps FWHM. Several PET modules have been produced, based on LYSO:Ce scintillators and commercial silicon photomultiplier (SiPM) arrays, with 3x3 mm2 individual SiPM siz...
Source: Physics in Medicine and Biology - June 26, 2019 Category: Physics Authors: Pizzichemi M, Polesel A, Stringhini G, Gundacker S, Lecoq P, Tavernier S, Paganoni M, Auffray E Tags: Phys Med Biol Source Type: research

Quantitative characterization of breast tissues with dedicated CT imaging.
Abstract A quantitative characterization of the soft tissues composing the human breast is achieved by means of a monochromatic CT phase-contrast imaging system, through accurate measurements of their attenuation coefficients within the energy range of interest for breast CT clinical examinations. Quantitative measurements of linear attenuation coefficients are performed on tomographic reconstructions of surgical samples, using monochromatic X-ray beams from a synchrotron source and a free space propagation setup. An online calibration is performed on the obtained reconstructions, in order to reassess the validity...
Source: Physics in Medicine and Biology - June 24, 2019 Category: Physics Authors: Piai A, Contillo A, Arfelli F, Bonazza D, Brombal L, Cova MA, Delogu P, Di Trapani V, Donato S, Golosio B, Mettivier G, Oliva P, Rigon L, Taibi A, Tonutti M, Tromba G, Zanconati F, Longo R Tags: Phys Med Biol Source Type: research

Assessing lesion malignancy by scanning small-angle X-ray scattering of breast tissue with microcalcifications.
We report a characteristic Bragg peak found around q=1.725~nm&amp;lt;sup&amp;gt;-1&amp;lt;/sup&amp;gt; that occurs primarily for malignant lesions. Such a clear SAXS fingerprint is potentially linked to structural changes of the breast tissue and correspond to dimensions of about 3.7~nm. Such a material property could be used as an early indicator of malignancy development, as it is readily assessed by SAXS. If this fingerprint is combined with other known SAXS features, which also indicate the level of malignancy, such as lipid spacing and collagen periodicity, it could complement traditional pathology-bas...
Source: Physics in Medicine and Biology - June 24, 2019 Category: Physics Authors: Arboleda C, Lütz-Bueno V, Wang Z, Villanueva-Perez P, Guizar-Sicairos M, Liebi M, Varga Z, Stampanoni MFM Tags: Phys Med Biol Source Type: research

Development of a globally optimised model of the cerebral arteries.
Abstract The cerebral arteries are difficult to reproduce from first principles, featuring interwoven territories, and intricate layers of grey and white matter with differing metabolic demand. The aim of this study was to identify the ideal configuration of arteries required to sustain an entire brain hemisphere based on minimisation of the energy required to supply the tissue. The 3D distribution of grey and white matter within a healthy human brain was first segmented from magnetic resonance images. A novel simulated annealing algorithm was then applied to determine the optimal configuration of arteries require...
Source: Physics in Medicine and Biology - June 21, 2019 Category: Physics Authors: Keelan J, Chung EML, Hague JP Tags: Phys Med Biol Source Type: research

Real-time intrafraction motion monitoring in external beam radiotherapy.
Abstract Radiotherapy (RT) aims to deliver a spatially conformal dose of radiation to tumours while maximizing the dose sparing to healthy tissues. However, the internal patient anatomy is constantly moving due to respiratory, cardiac, gastrointestinal and urinary activity. The long term goal of the RT community to "see what we treat, as we treat" and to act on this information instantaneously has resulted in rapid technological innovation. Specialized treatment machines, such as robotic or gimbal-steered linear accelerators (linac) with in-room imaging suites, have been developed specifically for real-t...
Source: Physics in Medicine and Biology - June 21, 2019 Category: Physics Authors: Bertholet J, Knopf AC, Eiben B, McClelland JR, Grimwood A, Harris E, Menten MJ, Poulsen PR, Nguyen DT, Keall PJ, Oelfke U Tags: Phys Med Biol Source Type: research

Experimental comparison of proton CT and dual energy X-ray CT for relative stopping power estimation in proton therapy.
This study aimed at directly comparing the RSP accuracy of both modalities using phantoms scanned at an advanced prototype pCT scanner and a state-of-the-art DECT scanner.&amp;#13; &amp;#13; Two phantoms containing 13 tissue-mimicking inserts of known RSP were scanned at the pCT phase II prototype and a latest generation dual-source DECT scanner (Siemens SOMATOM Definition FORCE). RSP accuracy was compared by mean absolute percent error (MAPE) over all inserts. A highly realistic Monte Carlo (MC) simulation was used to gain insight on pCT image artifacts which degraded MAPE.&amp;#13; &amp;#13; MAPE was 0.55...
Source: Physics in Medicine and Biology - June 20, 2019 Category: Physics Authors: Dedes G, Dickmann J, Niepel KB, Wesp P, Johnson RP, Pankuch M, Bashkirov VA, Rit S, Volz L, Schulte RW, Landry G, Parodi K Tags: Phys Med Biol Source Type: research

A compact solution for estimation of physiological parameters from ultrafast prostate dynamic contrast enhanced MRI.
In this study, we present a compact solution allowing estimation of physiological parameters K&amp;lt;sup&amp;gt;trans&amp;lt;/sup&amp;gt; and v&amp;lt;sub&amp;gt;e&amp;lt;/sub&amp;gt; from ultrafast DCE acquisitions, without fitting DCE-MRI data to the standard Tofts pharmacokinetic model. Since the standard Tofts model can be simplified to the Patlak model at early times when contrast efflux from the extravascular extracellular space back to plasma is negligible, K&amp;lt;sup&amp;gt;trans&amp;lt;/sup&amp;gt; can be solved explicitly for a specific time. Further, v&amp;l...
Source: Physics in Medicine and Biology - June 20, 2019 Category: Physics Authors: He D, Fan X, Chatterjee A, Wang S, Medved M, Pineda F, Yousuf A, Antic T, Oto A, Karczmar GS Tags: Phys Med Biol Source Type: research

Multi-step material decomposition for spectral computed tomography.
Abstract Spectral images from photon counting spectral detectors are being&amp;#13; explored for material decomposition applications such as for obtaining quantitative&amp;#13; maps of tissue types and contrast agents. While these detectors allow acquisition&amp;#13; of multi-energy data in a single exposure, separating the total photon counts into&amp;#13; multiple energy bins can lead to issues of count starvation and increased quantum&amp;#13; noise in resultant maps. Furthermore, the complex decomposition problem is often&amp;#13; solved in a single inversion step making it dicult to se...
Source: Physics in Medicine and Biology - June 19, 2019 Category: Physics Authors: Fredette NR, Kavuri A, Das M Tags: Phys Med Biol Source Type: research

Stereotactical fields applied in proton spot scanning mode with range shifter and collimating aperture.
f J Abstract Some clinical indications require small fields with sharp lateral dose gradients, which is technically challenging in proton beam therapy. This holds especially true for low-range fields applied with the spot scanning technique, where large beam profiles entering from the beam-line or the insertion of range shifting blocks lead to large lateral gradients. We regard the latter case and solve it by shifting the range shifting block far upstream in conjunction with a collimating aperture close to the patient. The experiments of the current work are based on a commercial proton therapy treatment head desi...
Source: Physics in Medicine and Biology - June 19, 2019 Category: Physics Authors: Bäumer C, Fuentes C, Janson M, Matic A, Timmermann B, Wulff J Tags: Phys Med Biol Source Type: research

A novel and rapid approach to estimate patient-specific distortions based on mDIXON MRI.
In conclusion, mDIXON imaging closely approximated conventional B&amp;lt;sub&amp;gt;0&amp;lt;/sub&amp;gt; mapping for patient-specific distortion assessment. Estimates in the brain were in good agreement, and slight differences were observed near air/tissue interfaces in the head and neck. Overall, mDIXON imaging-based B&amp;lt;sub&amp;gt;0&amp;lt;/sub&amp;gt; field maps may be advantageous for rapid patient-specific distortion correction without additional imaging.&amp;#13. PMID: 31216529 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - June 19, 2019 Category: Physics Authors: Weiss S, Nejad-Davarani SP, Eggers H, Orasanu E, Renisch S, Glide-Hurst CK Tags: Phys Med Biol Source Type: research

Comparison of two-compartment exchange and continuum models of dMRI in skeletal muscle.
Abstract Clinical diffusion MRI (dMRI) is sensitive to micrometer spin displacements, but the image resolution is $\sim$mm, so the biophysical interpretation of the signal relies on establishing appropriate subvoxel tissue models. A class of two-compartment exchange models originally proposed by K\"arger have been used successfully in neural tissue dMRI. Their use to interpret the signal in skeletal muscle dMRI is challenging because myocyte diameters are comparable to the root-mean-square of spin displacement and their membrane permeability is high. A continuum tissue model consisting of the Bloch-Torrey equ...
Source: Physics in Medicine and Biology - June 18, 2019 Category: Physics Authors: Naughton NM, Georgiadis JG Tags: Phys Med Biol Source Type: research

Performance evaluation of quantitative SPECT/CT using NEMA NU 2 PET methodology.
In this study, the quantitative performance of the Symbia Intevo SPECT/CT was evaluated for two common isotopes (99mTc, 177Lu) and benchmarked against the performance of a PET/CT. A further aim was to demonstrate the utility of adapting NEMA NU2 PET measurements to SPECT. In addition, dead-time and resolution recovery were evaluated to provide more complete system evaluations. Spatial resolution of the SPECT system at 1 cm from the center in the transverse direction was 13.1 mm and 22.4 mm for 99mTc and 177Lu respectively, compared with 4.3 mm (18F) and 5.8 mm (68Ga) for PET. Sensitivity at the center of the FoV was 119 cp...
Source: Physics in Medicine and Biology - June 17, 2019 Category: Physics Authors: Ryu H, Meikle SR, Willowson K, Eslick EM, Bailey DL Tags: Phys Med Biol Source Type: research

Modeling ultrasound attenuation in porous structures with mono-disperse random pore distributions using the independent scattering approximation: A 2D simulation study.
Abstract The validity of the Independent Scattering Approximation (ISA) to predict the frequency dependent attenuation in 2D models of simplified cortical bone is studied. Attenuation of plane waves at central frequencies ranging from 1 to 8 MHz propagating in geometries with mono-disperse random pore distributions having pore diameter and pore density in the range of those of cortical bone are evaluated by Finite Difference Time Domain numerical simulations. An approach to assess the multiple scattering of waves in random media is discussed to determine the pore diameter ranges at which the ISA is applicable. A m...
Source: Physics in Medicine and Biology - June 17, 2019 Category: Physics Authors: Yousefian O, Karbalaeisadegh Y, Muller M Tags: Phys Med Biol Source Type: research

A Bayesian network model of lymphatic tumor progression for personalized elective CTV definition in head and neck cancer.
Abstract Many tumors including head and neck squamous cell carcinoma (HNSCC) spread along the lymphatic network. Current imaging modalities can only detect sufficiently large metastases. Therefore, adjacent lymph node levels (LNL) are irradiated electively since they may harbor microscopic tumor. We apply Bayesian Networks (BN) to model lymphatic tumor progression. The model can subsequently be used to personalize the risk estimation of microscopic lymph node metastases in newly diagnosed patients based on their distribution of macroscopic metastases. A BN is a graphical representation of a joint probability distr...
Source: Physics in Medicine and Biology - June 17, 2019 Category: Physics Authors: Pouymayou B, Balermpas P, Riesterer O, Guckenberger M, Unkelbach J Tags: Phys Med Biol Source Type: research

Distribution of locoregional breast cancer recurrence in relation to postoperative radiation fields and biological subtypes.
ner S Abstract BACKGROUND: and purpose: To investigate incidence and location of locoregional recurrence (LRR) in patients who have received postoperative locoregional radiotherapy (LRRT) for primary breast cancer. LRR-position in relation to applied radiotherapy and the primary tumours biological subtype were analysed with the aim to evaluate current target guidelines and RT techniques in relation to tumour biology. MATERIALS AND METHODS: Medical records were reviewed for all patients who received postoperative LRRT for primary BC in southwestern Sweden from 2004-2008 (N=923). Patients with LRR as a first ev...
Source: Physics in Medicine and Biology - June 15, 2019 Category: Physics Authors: Adra J, Lundstedt D, Killander F, Holmberg E, Haghanegi M, Kjellén E, Karlsson P, Alkner S Tags: Int J Radiat Oncol Biol Phys Source Type: research

An in vitro study for the dosimetric and radiobiological validation of respiratory gating in conventional and hypofractionated radiotherapy of the lung: effect of dose, dose rate, and breathing pattern.
In this study, we perform our in vitro evaluation of the dosimetric and radiobiological effect of gated lung SBRT with simultaneous integrated boost (SIB) using both flattened and FFF beams. A moving thorax-shaped phantom with inserts and applicators were used for simulation, planning, gated treatment delivery measurements and in-vitro tests. The effect of gating window, dose rate, and breathing pattern is evaluated. Planned doses represented a typical conventional fractionation, 200cGy per fraction with SIB to 240cGy, flattened beam only, and SBRT, 800 cGy with SIB to 900 cGy, flattened and FFF beams. Ideal, as well as re...
Source: Physics in Medicine and Biology - June 12, 2019 Category: Physics Authors: Cervino L, Soultan D, Advani SJ, Cornell M, Yock A, Pettersson N, Song WY, Aguilera J, Murphy JD, Hoh CK, James C, Paravati A, Coope R, Gill B, Moiseenko VV Tags: Phys Med Biol Source Type: research

Imaging of fragment particles in water by nuclear spallation during carbon-ion irradiation.
Abstract Recently we found that the luminescence imaging of water during carbon-ion irradiation was possible using a cooled charge-coupled device (CCD) camera and the method could be used for range estimation of the beam. In the luminescence image, we found a luminescence from the fragment particles produced by the nuclear spallation reaction of carbon-ions. The luminescence may be used for the estimation of the distribution of the fragment particles by the nuclear spallation. For this purpose, we irradiated carbon-ion of 241.5 MeV/u to a water phantom and measured the luminescence image of water using CCD camera....
Source: Physics in Medicine and Biology - June 12, 2019 Category: Physics Authors: Yabe T, Komori M, Akagi T, Yamashita T, Yamamoto S Tags: Phys Med Biol Source Type: research

The effect of 220 kHz insonation scheme on rt-PA thrombolytic efficacy < i > in vitro < /i > .
The effect of 220 kHz insonation scheme on rt-PA thrombolytic efficacy in vitro. Phys Med Biol. 2019 Jun 12;: Authors: Kleven RT, Karani KB, Salido NG, Shekhar H, Haworth KJ, Mast TD, Tadesse DG, Holland CK Abstract Ultrasound-enhanced recombinant tissue plasminogen activator (rt-PA) thrombolysis is under development as an adjuvant to ischemic stroke therapy. The goal of this study was to design a pulsed ultrasound (US) exposure scheme that reduced intracranial constructive interference and tissue heating, and maintained thrombolytic efficacy relative to continuous wave (CW) insonation. Three 220-kHz ...
Source: Physics in Medicine and Biology - June 12, 2019 Category: Physics Authors: Kleven RT, Karani KB, Salido NG, Shekhar H, Haworth KJ, Mast TD, Tadesse DG, Holland CK Tags: Phys Med Biol Source Type: research

Deep learning-enabled accurate normalization of reconstruction kernel effects on emphysema quantification in low-dose CT.
This study presents a two-step deep learning architecture that enables accurate normalization of reconstruction kernel effects on emphysema quantification in low-dose CT. Deep learning is used to convert a CT image of a sharp kernel to that of a standard kernel with restoration of truncation artifacts and smoothing-free pixel size normalization. We selected 353 scans reconstructed by both standard and sharp kernels from four different CT scanners from the United States National Lung Screening Trial program database. A truncation artifact correction model was constructed with a combination of histogram extrapolation and a d...
Source: Physics in Medicine and Biology - June 11, 2019 Category: Physics Authors: Jin H, Heo C, Kim JH Tags: Phys Med Biol Source Type: research

A noise smoothing origin ensembles algorithm based on local filtering.
In this study, we propose a way to smooth out the noise in the OE algorithm. During the OE reconstruction, the algorithm stochastically modifies the current location to a random new voxel along the probable corresponding curve of each event depending on the relative event density of the new and old locations. In the original OE technique the event density is simply the number of events in the voxel. In the proposed method the event density is estimated from the filtering of a kernel window centered on the voxel. Incorporating the regional filtering is similar to perform OE algorithm on a smoothed image at each iteration an...
Source: Physics in Medicine and Biology - June 10, 2019 Category: Physics Authors: Chiang CC, Lin HH, Ni YC, Jan ML, Chuang KS Tags: Phys Med Biol Source Type: research

Investigation of the quinine sulfate dihydrate spectral properties and its effects on Cherenkov dosimetry.
ieu L Abstract Recent studies have proposed that adding quinine to water while performing Cherenkov volumetric dosimetry improves the skewed percent depth dose measurement. The aim of this study was to quantify the ability of quinine to convert directional Cherenkov emission to isotropic fluorescence and evaluate its contribution to the total emitted light. Aqueous solutions of quinine were prepared with distilled water at various concentrations (0.01 to 1.2 g/L). The solutions were irradiated with photon beams at 6 and 23 MV. The dependence of the light produced as a function of sample concentration was studied u...
Source: Physics in Medicine and Biology - June 10, 2019 Category: Physics Authors: Jean E, Delage MÈ, Beaulieu L Tags: Phys Med Biol Source Type: research

A finite element method for the determination of the relative response of ionization chambers in MR-linacs: simulation and experimental validation up to 1.5 T.
Abstract In magnetic resonance (MR) guided radiotherapy, the magnetic field-dependent change in the dose response of ionization chambers is typically included by means of a correction factor k_{\vec{B},M,Q}. This factor can be determined experimentally or calculated by means of Monte Carlo (MC) simulations. To date, a small number of experimental values for k_{\vec{B},M,Q} at magnetic flux densities above 1.2 T have been available to benchmark these simulations. Furthermore, MC simulations of the dose response of ionization chambers in magnetic fields (where such simulations are based on manufacturer blueprints) h...
Source: Physics in Medicine and Biology - June 10, 2019 Category: Physics Authors: Pojtinger S, Kapsch RP, Dohm OS, Thorwarth D Tags: Phys Med Biol Source Type: research

Attention-enabled 3D boosted convolutional neural networks for semantic CT segmentation using deep supervision.
This study demonstrated that attention-enabled boosted convolutional neural networks using deep supervision are capable of achieving superior prediction accuracy compared to current state-of-the-art automatic segmentation methods. PMID: 31181561 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - June 10, 2019 Category: Physics Authors: Kearney VP, Chan JW, Wang T, Perry A, Yom SS, Solberg TD Tags: Phys Med Biol Source Type: research

A 3D-printed patient-specific applicator guide for use in high-dose-rate interstitial brachytherapy for tongue cancer: a phantom study.
Abstract A patient-specific applicator guide system (PSAG) for tongue-cancer high-dose-rate (HDR) interstitial brachytherapy (ISBT) was developed by utilizing a 3D printing technique. An effectiveness of the 3D-printed PSAG (3D-PSAG) was evaluated for HDR ISBT. Six patients with tongue cancer were retrospectively selected for this study. For each patient, a total of three virtual clinical target volumes (CTV) requiring the insertion of four catheters (CTV4), six catheters (CTV6), and eight catheters (CTV8) were defined. For each CTV, treatment plans were generated to deliver 45 Gy in nine fractions. The 3D-PSAG wa...
Source: Physics in Medicine and Biology - June 6, 2019 Category: Physics Authors: Choi CH, Kim JI, Park JM Tags: Phys Med Biol Source Type: research

A preliminary study of using a deep convolution neural network to generate synthesized CT images based on CBCT for adaptive radiotherapy of nasopharyngeal carcinoma.
Conclusion: The DCNN model can generate high-quality synthesized CT images from CBCT images and be used for accurate dose calculations for NPC patients. This finding has great significance for the clinical application of adaptive radiotherapy for NPC.&amp;#13. PMID: 31170699 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - June 6, 2019 Category: Physics Authors: Li Y, Zhu J, Liu Z, Teng J, Xie Q, Zhang L, Liu X, Shi J, Chen L Tags: Phys Med Biol Source Type: research

An initial study of complete 2D shear wave dispersion images using a reverberant shear wave field.
We report preliminary studies on breast and liver tissues using the multi-frequency reverberant shear wave technique, employing frequencies up to 700 Hz in breast tissue, and robust reverberant patterns of shear waves across the entire liver and kidney in obese patients. Dispersion images are shown to have contrast between tissue types and with quantitative values that align with previous studies. PMID: 31170705 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - June 6, 2019 Category: Physics Authors: Ormachea J, Parker KJ, Barr RG Tags: Phys Med Biol Source Type: research

Improving GRAPPA reconstruction using joint nonlinear kernel mapped and phase conjugated virtual coils.
Conclusion: The proposed NL-VCC-extension to conventional GRAPPA brings visible improvements for imaging scenarios accelerated by the widely available uniform undersampling schemes in a practically efficient manner without iteration.&amp;#13. PMID: 31167169 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - June 5, 2019 Category: Physics Authors: Wang H, Jia S, Chang Y, Zhu Y, Zou C, Li Y, Liu X, Zheng H, Liang D Tags: Phys Med Biol Source Type: research

Computer-aided diagnosis of ground-glass opacity pulmonary nodules using radiomic features analysis.
Conclusions: This study demonstrates that: (1) the feasibility of using CT-based radiomic features analysis approach to distinguish between benign and malignant GGO nodules, (2) higher performance of CADx scheme in diagnosing GGO nodules comparing with radiologist, and (3) a consistently positive trend between classification performance and invasive grade of GGO nodules. Thus, to improve the CADx performance in diagnosing of GGO nodules, one should assemble an optimal training data set dominated with more nodules associated with non-invasive lung adenocarcinoma (i.e. AIS and MIA).&amp;#13. PMID: 31167172 [PubMed -...
Source: Physics in Medicine and Biology - June 5, 2019 Category: Physics Authors: Gong J, Liu JY, Hao W, Nie SD, Wang S, Peng W Tags: Phys Med Biol Source Type: research

Comparative study of alternative Geant4 hadronic ion inelastic physics models for prediction of positron-emitting radionuclide production in carbon and oxygen ion therapy.
Abstract The distribution of fragmentation products predicted by Monte Carlo simulations of heavy ion therapy depend on the hadronic physics model chosen in the simulation. This work aims to evaluate three alternative hadronic inelastic fragmentation physics options available in the Geant4 Monte Carlo radiation physics simulation framework to determine which model most accurately predicts the production of positron-emitting fragmentation products observable using in-beam PET imaging. Fragment distributions obtained with the BIC, QMD, and INCL++ physics models in Geant4 version 10.2.p03 are compared to experimental...
Source: Physics in Medicine and Biology - June 5, 2019 Category: Physics Authors: Chacon A, Guatelli S, Rutherford H, Bolst D, Mohammadi A, Ahmed AM, Nitta M, Nishikido F, Iwao Y, Tashima H, Yoshida E, Akamatsu G, Takyu S, Kitagawa A, Hofmann T, Pinto M, Franklin DR, Parodi K, Yamaya T, Rozenfeld AB, Safavi-Naeini M Tags: Phys Med Biol Source Type: research

Design optimization of a periodic microstructured array anode for hard X-ray grating interferometry.
Abstract Talbot-Lau grating interferometer (TLGI) has great advantages in X-ray imaging contrasts, especially for low-Z materials, over conventional absorption contrast. A microstructured array anode target (MAAT) source offers significantly higher imaging throughput than the combination of an extended X-ray source paired with an absorption grating (also known as source grating). The performance of the MAAT source can be optimized with respect to the areal density, dimensions, and choice of material for the microstructured metal inserts (MMI) and the substrate in which they are embedded. In this paper, we analyze ...
Source: Physics in Medicine and Biology - June 4, 2019 Category: Physics Authors: Zan G, Vine D, Spink RI, Yun W, Wang Q, Wang G Tags: Phys Med Biol Source Type: research

Improving single-event proton CT by removing nuclear interaction events within the energy/range detector.
This study demonstrates the dependence of the accuracy of the usual 3σ WEPL filter on uncertainties arising within the energy detector. By enabling to remove such uncertainties, the ΔE-E method proved tor yield some potential for improving the accuracy of pCT. PMID: 31158820 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - June 3, 2019 Category: Physics Authors: Volz L, Piersimoni P, Johnson RP, Bashkirov VA, Schulte RW, Seco J Tags: Phys Med Biol Source Type: research

A comparative study of NaI(Tl), CeBr < sub > 3 < /sub > , and CZT for use in a real-time simultaneous nuclear and fluoroscopic dual-layer detector.
Conclusion&amp;#13; The performance of regular NaI(Tl)-based gamma cameras deteriorates when exposed to high x-ray doses. CeBr3 and CZT are much better suited for introduction into a dual-layer detector but have high associated costs. Addition of a high-pass filter and shorting circuit into the PMT of a NaI(Tl)-based detector is a cost-effective solution that works well for low dose levels. PMID: 31158823 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - June 3, 2019 Category: Physics Authors: Koppert WJC, Dietze MMA, van der Velden S, Steenbergen LJH, de Jong HWAM Tags: Phys Med Biol Source Type: research

Resolution modeling in projection space using a factorized multi-block detector response function for PET image reconstruction.
In conclusion, the RM method proposed in this study can yield better reconstructed images in terms of resolution and MSE value, compared to conventional reconstruction without RM. PMID: 31158824 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - June 3, 2019 Category: Physics Authors: Xu H, Lenz M, Caldeira L, Bo M, Pietrzyk U, Lerche CW, Shah NJ, Scheins JJ Tags: Phys Med Biol Source Type: research

Conversion of computational human phantoms into DICOM-RT for normal tissue dose assessment in radiotherapy patients.
Abstract Radiotherapy treatment planning systems are designed for the fast calculation of dose to the tumor bed and nearby organs at risk using x-ray computed tomography (CT) images. However, CT images for a patient are typically available for only a small portion of the body, and in some cases, such as for retrospective epidemiological studies, no images may be available at all. When dose to organs that lie out-of-scan must be estimated, a convenient alternative for the unknown patient anatomy is to use a matching whole-body computational phantom as a surrogate. The purpose of the current work is to connect such ...
Source: Physics in Medicine and Biology - June 3, 2019 Category: Physics Authors: Griffin KT, Mille M, Pelletier C, Gopalakrishnan M, Jung JW, Lee C, Kalapurakal J, Pyakuryal A, Lee C Tags: Phys Med Biol Source Type: research

MLC-tracking performance on the Elekta unity MRI-linac.
Abstract Recently, multileaf collimator (MLC)-tracking has been technically and clinically demonstrated showing promising improvements of radiotherapy of mobile sites. Furthermore, magnetic resonance imaging ( MRI )-guided treatments have shown to provide superior targetting performance due to on-line soft-tissue imaging. Hitherto, the combination of MLC -tracking and MRI has not been &amp;#13; investigated using clinically released hardware. In this note we aim to describe the technical feasibilty of such a combination on a clinically operating MRI -linac.&amp;#13; &amp;#13; The MLC -tracking system i...
Source: Physics in Medicine and Biology - June 3, 2019 Category: Physics Authors: Glitzner M, Woodhead PL, Borman PTS, Lagendijk JJW, Raaymakers BW Tags: Phys Med Biol Source Type: research

Potential applications of the quantitative susceptibility mapping (QSM) in MR-guided radiation therapy.
Conclusion: The proposed QSM-based technique relies on the standard MR pulse sequences and visualize the conventional MR-invisible metallic devices with CT-like positive contrast solely through post-processing. Upon in-vivo validation of the technique, QSM may have the potential to replace CT for an MR-only guided radiation therapy. &amp;#13. PMID: 31151120 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 31, 2019 Category: Physics Authors: Nosrati R, Paudel MR, Ravi A, Pejovic-Milic A, Morton G, Stanisz G Tags: Phys Med Biol Source Type: research

Quantification of the dependencies of the Bragg peak degradation due to lung tissue in proton therapy on a CT-based lung tumor phantom.
Abstract The fine, sub-millimeter sized structure of lung tissue causes a degradation of the Bragg peak curve in particle therapy. The Bragg peak is degraded because particles of the same energy traverse lung tissue of different compositions of high and low density materials. Hence, they experience different energy losses resulting in variable ranges and a broadened Bragg peak. &amp;#13; Since this fine structure of lung tissue is not resolved in standard treatment-planning CTs, current state-of-the-art dose calculation procedures used in the clinical routine are unable to account for this degradation. Neglect...
Source: Physics in Medicine and Biology - May 31, 2019 Category: Physics Authors: Flatten V, Baumann KS, Weber U, Engenhart-Cabillic R, Zink K Tags: Phys Med Biol Source Type: research

Use of statistical approaches to improve the quality control of the dose delivery in radiotherapy.
In this study a ROC analysis is used to demonstrate the limits of the performance of the global gamma index as a method for detecting dose delivery errors. The performance of a global gamma index is compared with two approaches based on statistical tests for outliers detection. Two statistical approaches are considered: according to the first the distribution of the delivered doses is estimated based on an appropriate calibration procedure. According to the second one the distribution of the delivered doses is estimated based on the detection of relatively homogeneous regions of a plan and analyzing the distributions of pl...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Tulik M, Kabat D, Baran M, Kycia RA, Tabor Z Tags: Phys Med Biol Source Type: research

Range verification of radioactive ion beams of < sup > 11 < /sup > C and < sup > 15 < /sup > O using in-beam PET imaging.
Range verification of radioactive ion beams of 11C and 15O using in-beam PET imaging. Phys Med Biol. 2019 May 30;: Authors: Mohammadi A, Tashima H, Iwao Y, Takyu S, Akamatsu G, Nishikido F, Yoshida E, Kitagawa A, Parodi K, Yamaya T Abstract In advanced ion therapy, the visualization of the range of incident ions in a patient's body is important for exploiting the advantages of this type of therapy. It is ideal to use radioactive ion beams for in-beam positron emission tomography (PET) imaging in particle therapy due to the high quality of PET images caused by the high signal-to-noise ratio. We have sh...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Mohammadi A, Tashima H, Iwao Y, Takyu S, Akamatsu G, Nishikido F, Yoshida E, Kitagawa A, Parodi K, Yamaya T Tags: Phys Med Biol Source Type: research

About the Marty model of blood-brain barrier closure after its disruption using focused ultrasound.
rat B Abstract Many studies have demonstrated that pulsed ultrasound combined with circulating microbubbles can permeate the Blood-Brain Barrier in a reversible manner. In 2012, our group demonstrated that the BBB remains permeable to small MRI contrast agents up to 24 hours after ultrasound application and also that this duration was dependent on nanoparticle size. We exhibited a simple theoretical model explaining these observations (Marty et al. J Cereb Blood Flow Metab. 2012). However, in this original paper the expression of the BBB closure time (t&amp;lt;sub&amp;gt;1/2&amp;lt;/sub&amp;gt;) as...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Conti A, Mériaux S, Larrat B Tags: Phys Med Biol Source Type: research

MRI-based treatment planning for proton radiotherapy: dosimetric validation of a deep learning-based liver synthetic CT generation method.
This study proposes to integrate dense block into a 3D cycle-consistent generative adversarial networks (cycle GAN) framework in an effort to effectively learn the nonlinear mapping between MRI and CT pairs. A cohort of 21 patients with co-registered CT and MR pairs were used to test the deep learning-based sCT generation method by leave-one-out cross validation. The CT image quality, dosimetric accuracy and the distal range fidelity were rigorously checked, using side-by-side comparison against the corresponding original CT images. The average mean absolute error (MAE) was 72.87±18.16 HU. The relative differences o...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Liu Y, Lei Y, Wang Y, Wang T, Ren L, Lin L, McDonald M, Curran WJ, Liu T, Zhou J, Yang X Tags: Phys Med Biol Source Type: research

Assessment of imaging Cherenkov and scintillation signals in head and neck radiotherapy.
Abstract The goal of this study was to test the utility of time-gated optical imaging of head and neck radiotherapy treatments to measure surface dosimetry in real-time and inform possible interfraction replanning decisions. The benefit of both Cherenkov and scintillator imaging in head and neck treatments is direct daily feedback on dose, with no change to the clinical workflow. Emission from treatment materials was characterized by measuring radioluminescence spectra during irradiation and comparing emission intensities relative to Cherenkov emission produced in phantoms and scintillation from small plastic targ...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Alexander DA, Tendler II, Bruza P, Cao X, Schaner PE, Marshall BS, Jarvis LA, Gladstone DJ, Pogue BW Tags: Phys Med Biol Source Type: research

Basic evaluation of a novel four-dimensional target and human body phantom.
In this study, we investigated the basic performance of a multi-cell 4D phantom. All the CT numbers of the phantom were very close to those of human data. The geometric maximum amplitudes were 4.57 mm in the lateral direction, 4.59 mm in the ventrodorsal direction, and 3.68 mm in the cranio-caudal direction. Geometric errors were 0.84, 0.58, and 0.40 mm, respectively. Movements of the abdominal surface were stable for 60 seconds. Repeated measurements show no actual differences in target movements between multiple measurements and indicated high reproducibility (r &amp;gt; 0.97). End-to-end tests using Gafchromic film ...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Matsumoto Y, Kabuki S, Sugawara A, Kitahara T, Akiba T, Fujita Y, Kawamata I, Yamada K, Amino K, Sasaki Y, Nishida M, Murakami K, Sugahara K, Saito N, Kunieda E Tags: Phys Med Biol Source Type: research

< i > In vitro < /i > assessment of stiffness-dependent histotripsy bubble cloud activity in gel phantoms and blood clots.
In this study, histotripsy pulses were generated in agarose phantoms of Young's moduli ranging from 12.3 to 142 kPa, and &amp;lt;i&amp;gt;in vitro&amp;lt;/i&amp;gt; clot models with mild and strong platelet-activated retraction. Bubble cloud emissions were tracked with passive cavitation imaging, and the threshold acoustic power associated with phantom liquefaction was extracted with receiver operator characteristic analysis. The power of histotripsy-generated emissions and the degree of liquefaction were tabulated for both clot models. For the agarose phantoms, the acoustic power associated with liquefacti...
Source: Physics in Medicine and Biology - May 30, 2019 Category: Physics Authors: Hendley S, Bollen V, Anthony GJ, Paul JD, Bader KB Tags: Phys Med Biol Source Type: research

Monte Carlo calculation of monoenergetic and polyenergetic DgN coefficients for mean glandular dose estimates in mammography using a homogeneous breast model.
Abstract We computed normalized glandular dose (DgN) coefficients for mean glandular dose estimates in contemporary 2D mammography units, taking into account a realistic homogeneous model for the breast. We developed a Monte Carlo code based on the simulation toolkit GEANT4 ver. 10.00. The breast was modelled as a cylinder with a semi-cylindrical section with a radius of 10 cm, enveloped in a 1.45-mm thick skin layer, as found out in recent reports from the University of California Davis team in the analysis of breast computed tomography clinical scans. The compressed breast thickness was between 3 cm and 8 cm. Th...
Source: Physics in Medicine and Biology - May 29, 2019 Category: Physics Authors: Sarno A, Tucciariello RM, Mettivier G, di Franco F, Russo P Tags: Phys Med Biol Source Type: research