Quantifying the ultrastructure of carotid arteries using high-resolution micro-diffusion tensor imaging-comparison of intact versus open cut tissue.
Abstract Diffusion magnetic resonance imaging (dMRI) can provide insights into the microstructure of intact arterial tissue. The current study employed high magnetic field MRI to obtain ultra-high resolution dMRI at an isotropic voxel resolution of 117 µm(3) in less than 2 h of scan time. A parameter selective single shell (128 directions) diffusion-encoding scheme based on Stejskel-Tanner sequence with echo-planar imaging (EPI) readout was used. EPI segmentation was used to reduce the echo time (TE) and to minimise the susceptibility-induced artefacts. The study utilised the dMRI analysis with diffus...
Source: Physics in Medicine and Biology - November 9, 2017 Category: Physics Authors: Shahid SS, Gaul RT, Kerskens C, Flamini V, Lally C Tags: Phys Med Biol Source Type: research

Fluorescence detection, enumeration and characterization of single circulating cells < i > in vivo < /i > : technology, applications and future prospects.
Fluorescence detection, enumeration and characterization of single circulating cells in vivo: technology, applications and future prospects. Phys Med Biol. 2017 Nov 08;: Authors: Hartmann C, Patil R, Lin CP, Niedre MJ Abstract There are many diseases and biological processes that involve circulating cells in the bloodstream, such as cancer metastasis, immune reaction/inflammation, reproductive medicine, and stem cell therapies. This has driven significant interest in new technologies for the study of circulating cells in small animal research models and clinically. Most currently used methods require ...
Source: Physics in Medicine and Biology - November 8, 2017 Category: Physics Authors: Hartmann C, Patil R, Lin CP, Niedre MJ Tags: Phys Med Biol Source Type: research

Multiple image x-radiography for functional lung imaging.
Abstract Detection and visualization of lung tissue structures is impaired by predominance of air. However, by using synchrotron x-rays, refraction of x-rays at the interface of tissue and air can be utilized to generate contrast which may in turn enable quantification of lung optical properties. We utilized multiple image radiography, a variant of diffraction enhanced imaging, at the Canadian Light Source to quantify changes in unique x-ray optical properties of lungs, namely attenuation, refraction and Ultra Small-Angle Scatter (USAXS or width) contrast ratios as a function of lung orientation in free-breathing ...
Source: Physics in Medicine and Biology - November 8, 2017 Category: Physics Authors: Aulakh GK, Mann A, Belev G, Wiebe S, Kuebler WM, Singh B, Chapman D Tags: Phys Med Biol Source Type: research

Non-rigid CT/CBCT to CBCT registration for online external beam radiotherapy guidance.
Abstract Image-guided external beam radiotherapy (EBRT) allows radiation dose deposition with a high degree of accuracy and precision. Guidance is usually achieved by estimating the displacements, via image registration, between cone beam computed tomography (CBCT) and computed tomography (CT) images acquired at different stages of the therapy. The resulting displacements are then used to reposition the patient such that the location of the tumor at the time of treatment matches its position during planning. Moreover, ongoing research aims to use CBCT-CT image registration for online plan adaptation. However,...
Source: Physics in Medicine and Biology - November 8, 2017 Category: Physics Authors: Zachiu C, de Senneville BD, Tijssen RHN, Kotte ANTJ, Houweling AC, Kerkmeijer LGW, Lagendijk JJW, Moonen CTW, Ries MG Tags: Phys Med Biol Source Type: research

Improvement of single detector proton radiography by incorporating intensity of time-resolved dose rate functions.
Abstract Proton radiography, which images patients with the same type of particles as what they are to be treated with, is a promising approach to image guidance and water equivalent path length (WEPL) verification in proton radiation therapy. We have shown recently that proton radiographs could be obtained by measuring time-resolved dose rate functions (DRF) using an x-ray amorphous silicon flat panel. The WEPL values were derived solely from the root-mean-square (RMS) of DRFs while the intensity information in the DRFs was filtered out. In this work, we explored the use of such intensity information for potentia...
Source: Physics in Medicine and Biology - November 8, 2017 Category: Physics Authors: Zhang R, Jee KW, Cascio EW, Sharp GC, Flanz JB, Lu HM Tags: Phys Med Biol Source Type: research

Numerical assessment of low-frequency dosimetry from sampled magnetic fields.
Abstract Low-frequency dosimetry is commonly assessed by evaluating the electric field in the human body using the scalar potential finite dif- ference method. This method is effective only when the sources of the magnetic field are completely known and the magnetic vector po- tential can be analytically computed. The aim of the paper is to present a rigorous method to characterize the source term when only the magnetic flux density is available at discrete points, e.g. in case of field measurements. The method is based on the solution of the discrete magnetic curl equation. The system is restricted to the in- dep...
Source: Physics in Medicine and Biology - November 8, 2017 Category: Physics Authors: Freschi F, Giaccone L, Cirimele V, Canova A Tags: Phys Med Biol Source Type: research

A line fiducial method for geometric calibration of cone-beam CT systems with diverse scan trajectories.
Abstract Modern cone-beam CT systems, especially C-arms, are capable of diverse source-detector orbits. However, geometric calibration of these systems using conventional configurations of spherical fiducials (BBs) may be challenged for novel source-detector orbits and system geometries. In part, this is because the BB configurations are designed with careful forethought regarding the intended orbit so that BB marker projections do not overlap in projection views. Examples include helical arrangements of BBs (Rougee et al Proc. SPIE 1897 161-9) such that markers do not overlap in projections acquired from a circul...
Source: Physics in Medicine and Biology - November 8, 2017 Category: Physics Authors: Jacobson MW, Ketcha MD, Capostagno S, Martin A, Uneri A, Goerres J, De Silva T, Reaungamornrat S, Han R, Manbachi A, Stayman JW, Vogt S, Kleinszig G, Siewerdsen JH Tags: Phys Med Biol Source Type: research

Topology-guided deformable registration with local importance preservation for biomedical images.
Abstract The demons registration (DR) model is well recognized for its deformation capability. However, it might lead to misregistration due to erroneous diffusion direction when there are no overlaps between corresponding regions. We propose a novel registration energy function, introducing topology energy, and incorporating a local energy function into the DR in a progressive registration scheme, to address these shortcomings. The topology energy that is derived from the topological information of the images serves as a direction inference to guide diffusion transformation to retain the merits of DR. The local e...
Source: Physics in Medicine and Biology - November 8, 2017 Category: Physics Authors: Zheng C, Wang X, Zeng S, Zhou J, Yin Y, Feng D, Fulham M Tags: Phys Med Biol Source Type: research

An interdimensional correlation framework for real-time estimation of six degree of freedom target motion using a single x-ray imager during radiotherapy.
Conclusion: The first method to directly estimate real-time 6DoF target motion from segmented marker positions on a 2D imager was devised. The algorithm was evaluated using 81 motion traces from 19 liver patients and found to have sub-mm and sub-degree accuracy. . PMID: 29106377 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - November 6, 2017 Category: Physics Authors: Nguyen DT, Bertholet J, Kim J, O'Brien RT, Booth JT, Poulsen PR, Keall PJ Tags: Phys Med Biol Source Type: research

Two-argument total scatter factor for small fields simultaneously collimated by MLC and jaws: application to stereotactic radiosurgery and radiotherapy.
Abstract Direct use of the total scatter factor (S&lt;sub&gt;tot&lt;/sub&gt;) for independent monitor unit (MU) calculations can be a good alternative approach to the traditional separate treatment of head/collimator scatter (S&lt;sub&gt;c&lt;/sub&gt;) and phantom scatter (S&lt;sub&gt;p&lt;/sub&gt;), especially for stereotactic small fields under the simultaneous collimation of secondary jaws and tertiary multileaf collimators (MLC). We have carried out the measurement of S&lt;sub&gt;tot&lt;/sub&gt; in water for field sizes down to 0.5 × 0.5 cm&...
Source: Physics in Medicine and Biology - November 6, 2017 Category: Physics Authors: Han Z, Friesen S, Hacker FL, Zygmanski P Tags: Phys Med Biol Source Type: research

PDT dose dosimetry for photofrin-mediated pleural photodynamic therapy (pPDT).
In this study, we have developed a four-channel PDT dose dosimetry system to simultaneously acquire light dosimetry and photosensitizer fluorescence data. We measured PDT dose at four sites in the pleural cavity during pleural PDT. We have determined an empirical optical property correction function using Monte Carlo (MC) simulations as well as measurements of fluorescence for a range of physiologically relevant tissue optical properties. Parameters of the optical property correction function for Photofrin fluorescence were determined experimentally. In-vivo measurements of photosensitizer fluorescence showed negligible ph...
Source: Physics in Medicine and Biology - November 6, 2017 Category: Physics Authors: Ong YH, Kim MM, Finlay JC, Dimofte A, Singhal S, Glatstein E, Cengel KA, Zhu TC Tags: Phys Med Biol Source Type: research

Gold nanoparticle nucleated cavitation for enhanced high intensity focused ultrasound therapy.
In this study, a combination of pulse laser illumination (839nm), HIFU exposures (3.3MHz) and plasmonic gold nanorods (AuNR) was demonstrated as a new approach for the guidance and enhancement of HIFU treatments. For imaging, short duration HIFU pulses (10μs) demonstrated broadband acoustic emissions from AuNR nucleated cavitation with a signal-to-noise ranging from 5-35dB for peak negative pressures between 1.19-3.19±0.01MPa. In the absence of either AuNR or laser illumination these emissions were either not present or lower in magnitude (e.g. 5dB for 3.19MPa). Continuous wave (CW) HIFU exposures for 15s, were t...
Source: Physics in Medicine and Biology - November 3, 2017 Category: Physics Authors: McLaughlan JR, Cowell DMJ, Freear S Tags: Phys Med Biol Source Type: research

Derivation of mean dose tolerances for new fractionation schemes and treatment modalities.
Conclusions: The dose shape effect should be accounted for to avoid overestimation of mean dose tolerances, particularly when estimating constraints for hypofractionated regimens. Additionally, tolerances established for one treatment modality cannot necessarily be applied to other modalities with drastically different dose distributions, such as proton therapy. Last, protons may only allow marginal (5-10%) dose escalation if a fraction-size adjusted organ mean dose is constraining instead of a physical dose. PMID: 29099720 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - November 3, 2017 Category: Physics Authors: Perkó Z, Bortfeld TR, Hong TS, Wolfgang J, Unkelbach J Tags: Phys Med Biol Source Type: research

Automated detection of breast cancer in resected specimens with fluorescence lifetime imaging.
This study generated a database of co-registered histologic sections and FLIm data from breast cancer specimens (N=20) and a support vector machine (SVM) classification algorithm able to automatically detect cancerous, fibrous, and adipose breast tissue. Classification accuracies were greater than 97% for automated detection of cancerous, fibrous, and adipose tissue from breast cancer specimens. The classification worked equally well for specimens scanned by hand or with a mechanical stage, demonstrating that the system could be used during surgery or on excised specimens. The ability of this technique to simply discrimina...
Source: Physics in Medicine and Biology - November 3, 2017 Category: Physics Authors: Phipps JE, Gorpas D, Unger J, Darrow M, Bold RJ, Marcu L Tags: Phys Med Biol Source Type: research

Supplemental computational phantoms to estimate out-of-field absorbed dose in photon radiotherapy.
Abstract The purpose of this study was to develop a straightforward method of supplementing patient anatomy and estimating out-of-field absorbed dose for a cohort of pediatric radiotherapy patients with limited recorded anatomy. A cohort of nine children, aged 2 to 14 years, who received three-dimensional conformal radiotherapy for low grade localized brain tumors (LBTs), were randomly selected for this study. The extents of these patients' computed tomography simulation image sets were cranial only. To approximate their missing anatomy, we supplemented the LBT patients' image sets with computed tomography images ...
Source: Physics in Medicine and Biology - November 3, 2017 Category: Physics Authors: Gallagher KJ, Tannous J, Nabha R, Feghali JA, Ayoub Z, Jalbout WT, Youssef B, Taddei PJ Tags: Phys Med Biol Source Type: research

Image reconstruction and scan configurations enabled by optimization-based algorithms in multispectral CT.
Abstract Optimization-based algorithms for image reconstruction in multispectral (or photon-counting) computed tomography (MCT) remains a topic of active research. The challenge of optimization-based image reconstruction in MCT stems from the inherently non-linear data model that can lead to a non-convex optimization program for which no mathematically exact solver seems to exist for achieving globally optimal solutions. In this work, based upon a non-linear data model, we design a non-convex optimization program, derive its first-order-optimality conditions, and propose an algorithm to solve the program for image...
Source: Physics in Medicine and Biology - November 2, 2017 Category: Physics Authors: Chen B, Zhang Z, Sidky EY, Xia D, Pan X Tags: Phys Med Biol Source Type: research

Impact of motion compensation and partial volume correction for < sup > 18 < /sup > F-NaF PET/CT imaging of coronary plaque.
In conclusion, we have built and validated a STIR framework incorporating MoCo and PVC for &lt;sup&gt;18&lt;/sup&gt;F-NaF PET imaging of coronary plaques. First results indicate an improved quantification of plaque-type lesions. PMID: 29095701 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - November 2, 2017 Category: Physics Authors: Cal-Gonzalez J, Tsoumpas CH, Lassen ML, Rasul S, Koller L, Hacker M, Schäfers KP, Beyer T Tags: Phys Med Biol Source Type: research

The incidence of the different sources of noise on the uncertainty in radiochromic film dosimetry using single channel and multichannel methods.
A, Ruiz-Morales C Abstract The influence of the various sources of noise on the uncertainty in radiochromic film (RCF) dosimetry using single channel and multichannel methods is investigated in this work. These sources of noise are extracted from pixel value (PV) readings and dose maps. Pieces of an RCF were each irradiated to different uniform doses, ranging from 0 to 1092 cGy. Then, the pieces were read at two resolutions (72 and 150 ppp) with two flatbed scanners: Epson 10000XL and Epson V800, representing two states of technology. Noise was extracted as described in ISO 15739 (2013), separating its distinct co...
Source: Physics in Medicine and Biology - November 1, 2017 Category: Physics Authors: González-López A, Vera-Sánchez JA, Ruiz-Morales C Tags: Phys Med Biol Source Type: research

Towards an in-plane methodology to track breast lesions using mammograms and patient-specific finite-element simulations.
J, Del Palomar AP Abstract In breast cancer screening or diagnosis, it is usual to combine different images in order to locate a lesion as accurately as possible. These images are generated using a single or several imaging techniques. As x-ray-based mammography is widely used, a breast lesion is located in the same plane of the image (mammogram), but tracking it across mammograms corresponding to different views is a challenging task for medical physicians. Accordingly, simulation tools and methodologies that use patient-specific numerical models can facilitate the task of fusing information from different images...
Source: Physics in Medicine and Biology - November 1, 2017 Category: Physics Authors: Lapuebla-Ferri A, Cegoñino-Banzo J, Jiménez-Mocholí AJ, Del Palomar AP Tags: Phys Med Biol Source Type: research

Accelerating volumetric cine MRI (VC-MRI) using undersampling for real-time 3D target localization/tracking in radiation therapy: a feasibility study.
Conclusions: It is feasible to estimate VC-MRI from a single undersampled on-board 2D cine MRI. Phantom and patient studies showed that the temporal resolution of VC-MRI can potentially be improved by 5-10 times using a 2D cine image acquired with 10-20% k-space sampling. . PMID: 29087963 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 31, 2017 Category: Physics Authors: Harris W, Yin FF, Wang C, Zhang Y, Cai J, Ren L Tags: Phys Med Biol Source Type: research

Dosimetric Feasibility of Using Tungsten-Based Functional Paper for Flexible Chest Wall Protectors in Intraoperative Electron Radiotherapy for Breast Cancer.
In this study, the applicability of newly developed tungsten-based functional paper (TFP) was assessed as an alternative to the existing protective disk. The radiation-shielding performance of the TFP was verified through experimental measurements and Monte Carlo simulations. Percentage depth dose curves and lateral dose profiles with and without TFPs were measured and simulated on a dedicated IOERT accelerator. The number of piled-up TFPs was changed from 1 to 40. In the experimental measurements, the relative doses at the exit plane of the TFPs for 9 MeV were 42.7%, 9.2%, 0.2%, and 0.1% with 10, 20, 30, and 40 TFPs, resp...
Source: Physics in Medicine and Biology - October 30, 2017 Category: Physics Authors: Kamomae T, Monzen H, Kawamura M, Okudaira K, Nakaya T, Mukouyama T, Miyake Y, Ishihara Y, Itoh Y, Naganawa S Tags: Phys Med Biol Source Type: research

Electromechanical wave imaging and electromechanical wave velocity estimation in a large animal model of myocardial infarction.
Conclusions: These results indicate that EWI and EW velocity might help with the detection of infarcts and their border zones, which may be useful for characterizing arrhythmogenic substrate. . PMID: 29083316 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 30, 2017 Category: Physics Authors: Costet A, Melki L, Sayseng V, Hamid N, Nakanishi K, Wan E, Hahn R, Homma S, Konofagou EE Tags: Phys Med Biol Source Type: research

Investigating the generalisation of an atlas-based synthetic-CT algorithm to another centre and MR scanner for prostate MR-only radiotherapy.
This study suggests that the atlas-based algorithm can be generalised to MR data acquired using a different field strength at a different centre. PMID: 29076457 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 27, 2017 Category: Physics Authors: Wyatt J, Dowling JA, Kelly CG, McKenna J, Johnstone E, Speight R, Henry A, Greer PB, McCallum HM Tags: Phys Med Biol Source Type: research

Feasibility of MR-only proton dose calculations for prostate cancer radiotherapy using a commercial pseudo-CT generation method.
Abstract A magnetic resonance (MR)-only radiotherapy workflow can reduce cost, radiation exposure and uncertainties introduced by CT-MRI registration. A crucial prerequisite is generating the so called pseudo-CT (pCT) images for accurate dose calculation and planning. Many pCT generation methods have been proposed in the scope of photon radiotherapy. This work aims at verifying for the first time whether a commercially available photon-oriented pCT generation method can be employed for accurate intensity-modulated proton therapy (IMPT) dose calculation. A retrospective study was conducted on ten prostate canc...
Source: Physics in Medicine and Biology - October 27, 2017 Category: Physics Authors: Maspero M, Van den Berg CAT, Landry G, Belka C, Parodi K, Seevinck PR, Raaymakers BW, Kurz C Tags: Phys Med Biol Source Type: research

Determination of mean ionization potential using magnetic resonance imaging for the reduction of proton beam range uncertainties: theory and application.
We present a novel model to accurately calculate mean ionization potential from measurements acquirable by MRI and show its feasibility in a phantom. PMID: 29077570 [PubMed - in process] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 27, 2017 Category: Physics Authors: Sudhyadhom A Tags: Phys Med Biol Source Type: research

Shading correction assisted iterative cone-beam CT reconstruction.
Abstract Recent advances in total variation (TV) technology enable accurate CT image reconstruction from highly under-sampled and noisy projection data. The standard iterative reconstruction algorithms, which work well in conventional CT imaging, fail to perform as expected in cone beam CT (CBCT) applications, wherein the non-ideal physics issues, including scatter and beam hardening, are more severe. These physics issues result in large areas of shading artifacts and cause deterioration to the piecewise constant property assumed in reconstructed images. To overcome this obstacle, we incorporate a shading correcti...
Source: Physics in Medicine and Biology - October 27, 2017 Category: Physics Authors: Yang C, Wu P, Gong S, Wang J, Lyu Q, Tang X, Niu T Tags: Phys Med Biol Source Type: research

Monte Carlo simulation of radiation transport and dose deposition from locally released gold nanoparticles labeled with (111)In, (177)Lu or (90)Y incorporated into tissue implantable depots.
We report here the 3D dose distribution resulting from a NPD incorporating AuNP labeled with electron emitters ((90)Y, (177)Lu, (111)In) of different energies using Monte Carlo based voxel level dosimetry. The MCNP5 Monte Carlo radiation transport code was used to assess differences in dose distribution from simulated NPD and conventional brachytherapy sources, positioned in breast tissue simulating material. We further compare these dose distributions in mice bearing subcutaneous human breast cancer xenografts implanted with (177)Lu-AuNP NPD, or injected IT with (177)Lu-AuNP in suspension. The radioactivity distributions ...
Source: Physics in Medicine and Biology - October 27, 2017 Category: Physics Authors: Lai P, Cai Z, Pignol JP, Lechtman E, Mashouf S, Lu Y, Winnik MA, Jaffray DA, Reilly RM Tags: Phys Med Biol Source Type: research

K-edge energy-based calibration method for photon counting detectors.
Abstract In recent years, potential applications of energy-resolved photon counting detectors (PCDs) in the x-ray medical imaging field have been actively investigated. Unlike conventional x-ray energy integration detectors, PCDs count the number of incident x-ray photons within certain energy windows. For PCDs, the interactions between x-ray photons and photoconductor generate electronic voltage pulse signals. The pulse height of each signal is proportional to the energy of the incident photons. By comparing the pulse height with the preset energy threshold values, x-ray photons with specific energies are recorde...
Source: Physics in Medicine and Biology - October 26, 2017 Category: Physics Authors: Ge Y, Ji X, Zhang R, Li K, Chen GH Tags: Phys Med Biol Source Type: research

Evaluation of water-mimicking solid phantom materials for use in HDR and LDR brachytherapy dosimetry.
This study includes the HDR therapy sources Nucletron Flexisource Co-60 HDR (&lt;sup&gt;60&lt;/sup&gt;Co), Eckert und Ziegler BEBIG GmbH CSM-11 (&lt;sup&gt;137&lt;/sup&gt;Cs), Implant Sciences Corporation HDR Yb-169 Source 4140 (&lt;sup&gt;169&lt;/sup&gt;Yb) as well as the LDR therapy sources IsoRay Inc. Proxcelan CS-1 (&lt;sup&gt;131&lt;/sup&gt;Cs), IsoAid Advantage I-125 IAI-125A (&lt;sup&gt;125&lt;/sup&gt;I), and IsoAid Advantage Pd-103 IAPd-103A (&lt;sup&gt;103&lt;/sup&gt;Pd). Thereby our previous comparison between phantom ...
Source: Physics in Medicine and Biology - October 26, 2017 Category: Physics Authors: Schoenfeld AA, Thieben M, Harder D, Poppe B, Chofor N Tags: Phys Med Biol Source Type: research

Stability analysis of a deterministic dose calculation for MRI-guided radiotherapy.
Abstract Modern effort in radiotherapy to address the challenges of tumor localization and motion has led to the development of MRI guided radiotherapy technologies. Accurate dose calculations must properly account for the effects of the MRI magnetic fields. Previous work has investigated the accuracy of a deterministic linear Boltzmann transport equation (LBTE) solver that includes magnetic field, but not the stability of the iterative solution method. In this work, we perform a stability analysis of this deterministic algorithm including an investigation of the convergence rate dependencies on the magnetic field...
Source: Physics in Medicine and Biology - October 24, 2017 Category: Physics Authors: Zelyak O, Fallone BG, St Aubin J Tags: Phys Med Biol Source Type: research

Lifetime attributable risk as an alternative to effective dose to describe the risk of cancer for patients in diagnostic and therapeutic nuclear medicine.
Abstract Abstract The aim of this study is to implement lifetime attributable risk (LAR) predictions of cancer for patients of various age and gender, undergoing diagnostic investigations or treatments in nuclear medicine and to compare the outcome with a population risk estimate using effective dose and the International Commission on Radiological Protection risk coefficients. The radiation induced risk of cancer occurrence (incidence) or death from four nuclear medicine procedures are estimated for both male and female between 0 and 120 years. Estimations of cancer risk are performed using recommended admin...
Source: Physics in Medicine and Biology - October 24, 2017 Category: Physics Authors: Andersson M, Eckerman K, Mattsson LJS Tags: Phys Med Biol Source Type: research

Technical characterization of five X-ray detectors for paediatric radiography applications.
Abstract Physical image quality of five x-ray detectors used in the paediatric imaging department is characterized with the aim of establishing the range/scope of imaging performance provided by these detectors for neonatal imaging. Two computed radiography (CR) detectors (MD4.0 powder imaging plate (PIP) and HD5.0 needle imaging plate (NIP), Agfa HealthCare NV, B-2640 Mortsel, Belgium) and three flat panel detectors (FPD) (the Agfa DX-D35C and DX-D45C and the DRX-2530C (Carestream Health Inc., Rochester - NY 14608, USA)) were assessed. Physical image quality was characterized using the detector metrics given by t...
Source: Physics in Medicine and Biology - October 24, 2017 Category: Physics Authors: Marshall NW, Smet MH, Hofmans M, Pauwels H, De Clerq T, Bosmans H Tags: Phys Med Biol Source Type: research

Dosimetry and prescription in liver radioembolization with 90Y microspheres: 3D calculation of tumor-to-liver ratio from global 99mTc-MAA SPECT information.
This study presents a methodology to calculate the T/N ratio using global information from the SPECT. The T/N ratio is estimated by establishing uptake thresholds consistent with previously performed volumetry. This dose calculation method was validated against three-dimensional voxel dosimetry, and was also compared with the standard partition method based on freehand regions of interest (ROI) outlining on SPECT slices. Both comparisons were done on a sample of 20 actual cases of hepatocellular carcinoma treated with resin microspheres. The proposed method and the voxel dosimetry give very similar results. Differences are...
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Mañeru F, Abós D, Bragado L, Fuentemilla N, Caudepón F, Pellejero S, Miquelez S, Rubio A, Goñi E, Hernández-Vitoria A Tags: Phys Med Biol Source Type: research

Validation of proton stopping power ratio estimation based on dual energy CT using fresh tissue samples.
This study confirms the advantages of DECT-based SPR estimation although good results were also obtained using SECT for most tissues. PMID: 29057753 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Taasti VT, Michalak GJ, Hansen DC, Deisher A, Kruse JJ, Krauss B, Muren LP, Petersen JBB, McCollough CH Tags: Phys Med Biol Source Type: research

Small composite field correction factors for the CyberKnife radiosurgery system: clinical and PCSR plans.
Abstract A formalism has been proposed for small and non-standard photon fields in which k&lt;sup&gt;fclin, fmsr&lt;/sup&gt; &lt;sub&gt;Qclin, Qmsr&lt;/sub&gt; correction factors are used to correct dosimeter response in small fields (static or composite) relative to that in a larger machine-specific reference (MSR) field. For composite fields, a plan-class specific reference (PCSR) field can also be defined, serving as an intermediate calibration field between the MSR and clinical fields within a certain plan-class. In this work, the formalism was applied in the calculation of k&am...
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Christiansen EJ, Muir BR, Belec J, Vandervoort EJ Tags: Phys Med Biol Source Type: research

Study for online range monitoring with the Interaction Vertex Imaging method.
Abstract Ion beam therapy enables a highly accurate dose conformation delivery to the tumor due to the finite range of charged ions in matter (i.e., Bragg Peak (BP)). Consequently, the dose profile is very sensitive to patients anatomical changes as well as minor mispositioning, and so it requires improved dose control techniques. Proton Interaction Vertex Imaging (IVI) could offer an online range control in carbon ion therapy. In this paper, a statistical method was used to study the sensitivity of the IVI technique on experimental data obtained from the Heidelberg Ion-Beam Therapy Center. The vertices of se...
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Finck C, Karakaya Y, Reithinger V, Rescigno R, Baudot J, Constanzo J, Juliani D, Krimmer J, Rinaldi I, Rousseau M, Testa E, Vanstalle M, Ray C Tags: Phys Med Biol Source Type: research

Planning, guidance, and quality assurance of pelvic screw placement using deformable image registration.
Abstract Percutaneous pelvic screw placement is challenging due to narrow bone corridors surrounded by vulnerable structures and difficult visual interpretation of complex anatomical shapes in 2D x-ray projection images. To address these challenges, a system for planning, guidance, and quality assurance (QA) is presented, providing functionality analogous to surgical navigation, but based on robust 3D-2D image registration techniques using fluoroscopy images already acquired in routine workflow. Two novel aspects of the system are investigated: automatic planning of pelvic screw trajectories and the ability to acc...
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Goerres J, Uneri A, Jacobson MW, Ramsay B, De Silva T, Ketcha MD, Han R, Manbachi A, Vogt S, Kleinszig G, Wolinsky JP, Osgood GM, Siewerdsen JH Tags: Phys Med Biol Source Type: research

Extension of the Fermi-Eyges most likely path in heterogeneous medium with prior knowledge information.
In conclusion, the introduction of prior-knowledge in the MLP formalism decreases the RMS uncertainty to the MC path, but no further than the use of a simpler Hull contour algorithm. The use of this Hull algorithm is suggested for future particle imaging applications. PMID: 29059051 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Collins-Fekete CA, Bär E, Volz L, Bouchard H, Beaulieu L, Seco J Tags: Phys Med Biol Source Type: research

Correspondence model-based 4D VMAT dose simulation for analysis of local metastasis recurrence after extracranial SBRT.
Abstract The purpose of this study is to introduce a novel approach to incorporate patient-specific breathing variability information into 4D dose simulation of volumetric arc therapy (VMAT)-based stereotactic body radiotherapy (SBRT) of extracranial metastases. Feasibility of the approach is illustrated by application to treatment planning and motion data of lung and liver metastasis patients. The novel 4D dose simulation approach makes use of a regression-based correspondence model that allows representing patient motion variability by breathing signal-steered interpolation and extrapolation of defor...
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Sothmann T, Gauer T, Wilms M, Werner R Tags: Phys Med Biol Source Type: research

Determination of absorbed dose to water from a miniature kilovoltage X-ray source using a parallel-plate ionization chamber.
This article presents a formalism for calculating and independently verifying the absorbed dose to water from a kV x-ray source (The INTRABEAM System) measured in a water phantom with an ionization chamber calibrated in terms of air-kerma. This formalism uses a Monte Carlo (MC) calculated chamber conversion factor, &lt;i&gt;C&lt;sub&gt;Q&lt;/sub&gt;&lt;/i&gt;, to convert from air-kerma in a reference beam to absorbed dose to water in the measurement beam. In this work &lt;i&gt;C&lt;sub&gt;Q&lt;/sub&gt;&lt;/i&gt; was determined for a PTW 34013 parallel-plate io...
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Watson PGF, Popovic M, Seuntjens J Tags: Phys Med Biol Source Type: research

Lateral response heterogeneity of Bragg peak ionization chambers for narrow-beam photon and proton dosimetry.
This study highlights the need for chamber-dependent response maps when using LAICs for absolute and relative dosimetry with proton pencil beams or small photon beams. PMID: 29059057 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - October 23, 2017 Category: Physics Authors: Kuess P, Böhlen TT, Lechner W, Elia A, Georg D, Palmans H Tags: Phys Med Biol Source Type: research

Ultrasound functional imaging in an < i > ex vivo < /i > beating porcine heart platform.
In this study, an isolated beating pig heart setup was adapted and used for performance assessment of UFI techniques such as volume assessment and ultrasound strain imaging. The potential of performing verification and reproducibility studies was demonstrated. For proof-of-principle, validation of UFI in pathological hearts was examined. Ex vivo porcine hearts (n = 6, slaughterhouse waste) were resuscitated and attached to a mock circulatory system. Radio frequencyt ultrasound data of the left ventricle were acquired in five short axis views and one long axis view. Based on these slices, the cardiac outputCO was measu...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Petterson NJ, Fixsen LS, Rutten MCM, Pijls NHJ, van de Vosse FN, Lopata RGP Tags: Phys Med Biol Source Type: research

Theoretically exact backprojection filtration algorithm for multi-segment linear trajectory.
Abstract A theoretically exact backprojection filtration algorithm is proved and implemented for image reconstruction from a multi-segment linear trajectory assuming fan-beam geometry. The reconstruction formula is based on a concept of linear PI-line (L-PI) proposed in our previous work. The proof is completed in two consecutive steps. In the first step, it is proved that theoretically exact image reconstruction can be obtained on an arbitrary L-PI line from an infinite straight line trajectory. In the second step, it is shown that accurate image reconstruction can be achieved from a multi-segment line trajectory...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Wu W, Yu H, Cong W, Liu F Tags: Phys Med Biol Source Type: research

Biological and dosimetric characterisation of spatially fractionated proton minibeams.
Abstract The biological effectiveness of proton beams varies with depth, spot size and lateral distance from the beam central axis. The aim of this work is to incorporate proton relative biological effectiveness (RBE) and equivalent uniform dose (EUD) considerations into comparisons of broad beam and highly modulated proton minibeams. A Monte Carlo model of a small animal proton beamline is presented. Dose and variable RBE is calculated on a per-voxel basis for a range of energies (30-109 MeV). For an open beam, the RBE values at the beam entrance ranged from 1.02-1.04, at the Bragg peak (BP) from 1.3 to 1.6, and ...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Meyer J, Stewart RD, Smith D, Eagle J, Lee E, Cao N, Ford E, Hashemian R, Schuemann J, Saini J, Marsh S, Emery R, Dorman E, Schwartz JL, Sandison GA Tags: Phys Med Biol Source Type: research

Issues in quantification of registered respiratory gated PET/CT in the lung.
Abstract PET/CT quantification of lung tissue is limited by several difficulties: the lung density and local volume changes during respiration, the anatomical mismatch between PET and CT and the relative contributions of tissue, air and blood to the PET signal (the tissue fraction effect). Air Fraction Correction (AFC) has been shown to improve PET image quantification in the lungs. Methods to correct for the movement and anatomical mismatch involve respiratory gating and image registration techniques. While conventional registration methods only account for spatial mismatch, the Jacobian determinant of the deform...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Cuplov V, Holman BF, McClelland JR, Modat M, Hutton BF, Thielemans K Tags: Phys Med Biol Source Type: research

Spectral imaging using clinical megavoltage beams and a novel multi-layer imager.
Abstract We assess the feasibility of clinical megavoltage (MV) spectral imaging for material and bone separation with a novel multi-layer imager (MLI) prototype. The MLI provides higher detective quantum efficiency and lower noise than conventional electronic portal imagers. Simulated experiments were performed using a validated Monte Carlo model of the MLI to estimate energy absorption and energy separation between the MLI components. Material separation was evaluated experimentally using solid water and aluminum (Al), copper (Cu) and gold (Au) for 2.5 MV, 6 MV and 6 MV flattening filter free (FFF) clinical phot...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Myronakis ME, Fueglistaller R, Rottmann J, Hu YH, Wang A, Baturin P, Huber P, Morf D, Star-Lack JM, Berbeco RI Tags: Phys Med Biol Source Type: research

Pulsed cavitational therapy using high-frequency ultrasound for the treatment of deep vein thrombosis in an in vitro model of human blood clot.
Abstract Post-thrombotic syndrome, a frequent complication of deep venous thrombosis can be reduced with early vein recanalization. Pulsed cavitational therapy (PCT) using ultrasound is a recent non-invasive approach. We propose to test the efficacy and safety of high-frequency focused PCT for a drug-free thrombolysis (thrombotripsy) in a realistic in vitro model of venous thrombosis. To reproduce venous thrombosis conditions, human whole blood was allowed to clot by stasis in silicone tubes (6 mm internal diameter) at a 30 cmH20 pressure, maintained during the whole experiment. We engineered an ultrasound de...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Goudot G, Mirault T, Arnal B, Boisson-Vidal C, Le Bonniec B, Gaussem P, Galloula A, Tanter M, Messas E, Pernot M Tags: Phys Med Biol Source Type: research

A method for acquiring random range uncertainty probability distributions in proton therapy.
Abstract In treatment planning we depend upon accurate knowledge of geometric and range uncertainties. If the uncertainty model is inaccurate then the plan will produce under-dosing of the target and/or overdosing of OAR. We aim to provide a method for which centre and site-specific population range uncertainty due to inter-fraction motion can be quantified to improve the uncertainty model in proton treatment planning. Daily volumetric MVCT data from previously treated radiotherapy patients has been used to investigate inter-fraction changes to water equivalent path-length (WEPL). Daily image-guidance s...
Source: Physics in Medicine and Biology - October 20, 2017 Category: Physics Authors: Holloway SM, Holloway MD, Thomas SJ Tags: Phys Med Biol Source Type: research

Simulation study of light transport in laser-processed LYSO:Ce detectors with single-side readout.
t H Abstract A tightly focused pulsed laser beam can locally modify the crystal structure inside the bulk of a scintillator. The result is incorporation of so-called optical barriers with a refractive index different from that of the crystal bulk, that can be used to redirect the scintillation light and control the light spread in the detector. We here systematically study the scintillation light transport in detectors fabricated using the laser induced optical barrier technique, and objectively compare their potential performance characteristics with those of the two mainstream detector types: monolithic and mech...
Source: Physics in Medicine and Biology - October 19, 2017 Category: Physics Authors: Bläckberg L, El Fakhri G, Sabet H Tags: Phys Med Biol Source Type: research

Analysis of dose heterogeneity using a subvolume-DVH.
Abstract The dose-volume histogram (DVH) is universally used in radiation therapy for its highly efficient way of summarizing three-dimensional dose distributions. An apparent limitation that is inherent to standard histograms is the loss of spatial information, e.g. it is no longer possible to tell where low- and high-dose regions are, and whether they are connected or disjoint. Two methods for overcoming the spatial fragmentation of low- and high-dose regions are presented, both based on the gray-level size zone matrix, which is a two-dimensional histogram describing the frequencies of connected regions of simil...
Source: Physics in Medicine and Biology - October 19, 2017 Category: Physics Authors: Said M, Nilsson P, Ceberg C Tags: Phys Med Biol Source Type: research