Phantom-based Study Research Articles

Demonstration of real-time positron emission tomography biology-guided radiotherapy delivery to targets.

Biology-guided radiotherapy (BgRT) is a novel technology that uses positron emission tomography (PET) data to direct radiotherapy delivery in real-time. BgRT enables the precise delivery of radiation doses based on the PET signals emanating from PET-avid tumors on the fly. In this way, BgRT uniquely utilizes radiotracer uptake as a biological beacon for controlling and adjusting dose delivery in real-time to account for target motion. To demonstrate using real-time PET for BgRT delivery on the RefleXion X1 radiotherapy machine. The X1 radiotherapy machine is a rotating ring-gantry radiotherapy system that generates a nominal 6MV photon beam, PET, and computed tomography (CT) components. The system utilizes emitted photons from PET-avid targets to deliver effective radiation beamlets or pulses to the tumor in real-time. This study demonstrated a real-time PET BgRT delivery experiment under three scenarios. These scenarios included BgRT delivering to (S1 ) a static target in a homogeneous and heterogeneous environment, (S2 ) a static target with a hot avoidance structure and partial PET-avid target, and (S3 ) a moving target. The first step was to create stereotactic body radiotherapy (SBRT) and BgRT plans (offline PET data supported) using RefleXion's custom-built treatment planning system (TPS). Additionally, to create a BgRT plan using PET-guided delivery, the targets were filled with 18F-Fluorodeoxyglucose (FDG), which represents a tumor/target, that is, PET-avid. The background materials were created in the insert with homogeneous water medium (for S1 ) and heterogeneous water with styrofoam mesh medium. A heterogeneous background medium simulated soft tissue surrounding the tumor. The treatment plan was then delivered to the experimental setups using a pre-commercial version of the X1 machine. As a final step, the dosimetric accuracy for S1 and S2 was assessed using the ArcCheck analysis tool-the gamma criteria of 3%/3mm. For S3 , the delivery dose was quantified using EBT-XD radiochromic film. The accuracy criteria were based on coverage, where 100% of the clinical target volume (CTV) receives at least 97% of the prescription dose, and the maximum dose in the CTV was ≤130% of the maximum planned dose (97%≤CTV≤130%). For the S1, both SBRT and BgRT deliveries had gamma pass rates greater than 95% (SBRT range: 96.9%-100%, BgRT range: 95.2%-98.9%), while in S2 , the gamma pass rate was 98% for SBRT and between 95.2% and 98.9% for BgRT plan delivering. For S3 , both SBRT and BgRT motion deliveries met CTV dose coverage requirements, with BgRT plans delivering a very high dose to the target. The CTV dose ranges were (a) SBRT:100.4%-120.4%, and (b) BgRT: 121.3%-139.9%. This phantom-based study demonstrated that PET signals from PET-avid tumors can be utilized to direct real-time dose delivery to the tumor accurately, which is comparable to the dosimetric accuracy of SBRT. Furthermore, BgRT delivered a PET-signal controlled dose to the moving target, equivalent to the dose distribution to the static target. A future study will compare the performance of BgRT with conventional image-guided radiotherapy.

Correlation Between Volume and Pressure of Intracranial Space With Craniectomy Surface Area and Brain Herniation: A Phantom-Based Study.

There are proponents of decompressive craniectomy (DC) and its various modifications who claim reasonable clinical outcomes for each of them. Clinical outcome in cases of traumatic brain injury, managed conservatively or aided by different surgical techniques, depends on multiple factors, which vary widely among patients and have complex interplay, making it difficult to compare one case with another in absolute terms. This forms the basis of the perceived necessity to have a standard model to study, compare, and strategize in this field. We designed a phantom-based model and present the findings of the study aimed at establishing a correlation of the volume of intracranial space and changes in intracranial pressure (ICP) with surface area of the craniectomy defect created during DC and brain herniation volume. A roughly hemispherical radio-opaque container was scanned on a 128-slice computed tomography scanner. Craniectomies of different sizes and shapes were marked on the walls of the phantom. Two spherical sacs of stretchable materials were subsequently placed inside the phantom, fixed to three-way connectors, filled with water, and connected with transducers. The terminals of the transducer cables were coupled with the display monitor through a signal amplifier and processor module. Parts of the wall of the phantom were removed to let portions of the sac herniate through the defect, simulating a DC. Volume measurements using AW volume share 7® software were done. Resection of a 12.7 × 11.5 cm part of the wall resulted in a 10-cm-diameter defect in the wall. Volume differential of 35 mL created a midline shift of 5 mm to the side with lesser volume. When measuring pressure in two stretchable sacs contained inside the phantom, there always remained a pressure differential ranging from 1 to 2 mm Hg in different recordings, even with sacs on both sides containing an equal volume of fluids. Creating a circular wall defect of 10 cm in diameter with an intracavitary pressure of 35 mm Hg on the ipsilateral sac and 33 mm on the contralateral sac recorded with intact walls, resulted in a true volume expansion of 48.411 cm3. The herniation resulted in a reduction of pressure in both sacs, with the pressure recorded as 25 mm in the ipsilateral sac and 24 mm in the contralateral sac. The findings closely matched those of the other model-based studies. Refinement of the materials used is likely to provide a valid platform to study cranial volume, ICP, craniectomy size, and brain prolapse volume in real time. The model will help in pre-operatively choosing the most appropriate technique between a classical DC, a hinge craniotomy, and an expansive cranioplasty technique in cases of refractory raised ICP.

A Compact and Novel Photoacoustic Sensing Technique for In Vitro Characterization of Blood Viscosity: A Phantom-Based Study

A Compact and Novel Photoacoustic Sensing Technique for In Vitro Characterization of Blood Viscosity: A Phantom-Based Study

Customization of neonatal functional magnetic resonance imaging: A preclinical phantom-based study.

Over the past few decades, the use of functional magnetic resonance imaging (fMRI) on neonates and very young children has increased dramatically in research and clinical settings. However, the specific characteristics of this population and the MRI standards largely derived from adult studies, pose serious practical challenges. The current study aims to provide general methodological guidelines for customized neonatal fMRI by assessing the performance of various fMRI hardware and software applications. Specifically, this article focuses on MR equipment (head coils) and MR sequences (singleband vs. multiband). We computed and compared the signal-to-noise ratio (SNR) and the temporal SNR (tSNR) in different fMRI protocols using a small-size spherical phantom in three different commercial receiver-only head-neck coils. Our findings highlight the importance of coil selection and fMRI sequence planning in optimizing neonatal fMRI. For SNR, the prescan normalize filter resulted in significantly higher values overall, while in general there was no difference between the different sequences. In terms of head coil performance, the 20-channel head coil showed slightly but significantly higher values compared to the others. For tSNR, there was no difference in the usage of the prescan normalize filter, but the values were significantly higher in the singleband EPI sequences compared to the multiband. In contrast to the SNR, the pediatric head coil seems to have an advantage for tSNR. We provide five practical guidelines to assist researchers and clinicians in developing fMRI studies in neonates and young infants. These recommendations are especially relevant considering ethical constraints and exogenous challenges of neonatal fMRI.

Impact of uterine deformation induced by applicator on brachytherapy dosimetric value: an uterine-mimicking-phantom study

Brachytherapy (BT) is subjected to uncertainties from imaging, treatment planning, and anatomical variations. It is necessary to identify the uncertainties, their magnitude, and their impact on the overall uncertainty of dose delivery. The aim of the present phantom-based study is to investigate the deformation of the uterus anatomy induced by BT applicator insertion and the relationship between dose and location of the inserted applicator. A novel flexible phantom was designed based on female pelvic anatomy by the 3D printing process to simulate the deformation and movement of the uterine during the BT process. The applicator was inserted into the uterus and in order to simulate the uterus motion, the phantom was moved in four directions, right, left, down, and up. The CT and ultrasound images were obtained. A two-stage registration algorithm was designed to register the ultrasound and CT images in order to calculate the applicator displacements map. This map was used to calculate delivered dose error to uterus and rectum and to correct the planned dose values in treatment planning procedure. The results showed that in a planned D90 (dose) of 9.4 Gy for the uterus and maximum dose of 1.8 Gy to the rectum, movement of applicator leads to a big deviation in final delivered doses. After the applicator moved to the right and left directions, the D90 delivered to the uterus was 6.2 Gy and 5.6 Gy, respectively. Moreover, by moving downwards and upwards, the uterus received 0.4 and 1.2 Gy lower than 9.4 Gy. Similarly, the maximum dose to the rectum in right, left, down, and up directions after applicator movement were 3.4 Gy, 3.3 Gy, 3.7 Gy and 3.2 Gy, respectively which highlighted the higher delivered dose to the rectum. The results of the study demonstrate that applicator displacement can lead to uterine underdosing and also increase the risk of rectum irradiation. Ultimately, image-guided brachytherapy and using image registration can increase the accuracy of treatment and reduce the errors of delivered dose to target volume and organs at risk, especially in uterus cancer.

System requirements to improve adaptive 4-dimensional computed tomography (4D CT) imaging

Four-Dimensional Computed Tomography (4D CT) is of increasing importance in stereotactic body radiotherapy (SBRT) treatments affected by respiratory motion. However, 4D CT images are commonly impacted by irregular breathing, causing image artifacts that can propagate through to treatment, negatively effecting local control. REspiratory Adaptive CT (REACT) is a real-time gating method demonstrated to reduce motion artifacts by avoiding imaging during irregular respiration. Despite artifact reduction seen through in silico and clinical phantom-based studies, REACT has not been able to remove all artifacts. Here, we explore several hardware and software latencies (gantry rotation time, couch shifts, acquisition delays and phase calculation method) inherently linked to REACT and 4D CT in general and investigate their contribution to artifacts beyond those caused by irregular breathing. Imaging was simulated using the digital extended cardiac-torso (XCAT) phantom for fifty patient-measured respiratory traces. Imaging protocols included conventional cine 4D CT and five REACT scans with systematically varied parameters to test the effect of different latencies on artifacts. Artifacts were quantified by comparing the image normalized cross correlation across couch transition points and determining the volume error compared to a static phantom ground truth both as a total error and individually across pixel rows in the main plane of motion. Artifacts were determined for each lung, the whole heart and lung tumour and were compared back to conventional 4D CT and REACT with standard clinical scanning parameters. The gantry rotation time and acquisition delay were found to have the largest impact on reducing image artifacts and should be the focus of future development. The phase calculation method was also found to influence motion artifacts and should potentially be assessed on a patient-to-patient basis. Finally, the correlation between an increase in artifacts and baseline drift suggests that longer scan times allowing drift to occur may impact image quality.

Usage of augmented reality for interventional neuraxial procedures: A phantom-based study.

Neuraxial access is necessary for an array of procedures in anaesthesia, interventional pain medicine and neurosurgery. The commonly used anatomical landmark technique is challenging and requires practical experience. We aimed to evaluate the technical feasibility of an augmented reality-guided approach for neuraxial access and tested the hypothesis that its use would improve success as the primary outcome. As secondary outcomes, we measured accuracy and the procedural duration compared with the classical landmark approach. A randomised phantom-based study. The three-dimensional image of a thoracolumbar phantom spine model with the surrounding soft tissue was created with a neurosurgical planning workstation and ideal trajectories to the epidural space on the levels T10-L1 were planned using a paramedian approach. Both the three-dimensional holographic image of the spine and the trajectories were transferred to an augmented reality-headset. Four probands (two anaesthesiologists, one neuroradiologist and one stereotactic neurosurgeon) performed 20 attempts, 10 each of either conventional landmark or augmented reality-guided epidural punctures, where anatomical level, side and sequence of modality were all randomised. Accuracy was assessed by measuring Euclidean distance and lateral deviation from the predefined target point. Success of epidural puncture on the first attempt was compared between the conventional and the augmented reality-guided approaches. Success was achieved in 82.5% of the attempts using augmented reality technique, compared with 40% with the conventional approach [ P = 0.0002, odds ratio (OR) for success: 7.07]. Euclidean distance (6.1 vs. 12 mm, P < 0.0001) and lateral deviation (3.7 vs. 9.2 mm, P < 0.0001) were significantly smaller using augmented reality. Augmented reality-guided puncture was significantly faster than with the conventional landmark approach (52.5 vs. 67.5 s, P = 0.0015). Augmented reality guidance significantly improved the accuracy and success in an experimental phantom model of epidural puncture. With further technical development, augmented reality guidance might prove helpful in anatomically challenging neuraxial procedures.

A phantom-based study and clinical implementation of brainlab’s treatment planning system for radiosurgical treatments of arteriovenous malformations

Purpose. Development of a simple, phantom-based methodology allowing for pilot applications for the Elements TPS cranio-vascular module and clinical implementation prior to AVM treatments. Methods. A customized phantom was developed to be visible in MRI and CT images. High resolution digital subtraction angiograms (DSAs) and CT images of the phantom were acquired and imported into the Brainlab Elements treatment planning system. A clinical treatment plan with 5 arcs was generated in cranial vascular planning module and delivered to the phantom using a Varian TrueBeam STx Linac equipped with HD-MLCs and Brainlab ExacTrac imaging system for non-coplanar setup verification. The delivered dose was verified using a calibrated ionization chamber placed in the phantom. Upon verification of the TPS workflow, three patients with AVM who have been treated to date at our center using the Brainlab’s cranial vascular module for AVM are presented here for retrospective review. Results. The difference between the planed and measured dose by the ionization chamber was found to be less than 1%. Following a successful dose verification study, a clinical workflow was created. Currently, three AVM patients have been treated successfully. Clinical aspects of imaging and treatment planning consideration are presented in retrospective setting. Conclusions. Dose verification of the Brainlab Elements cranial vascular planning module for intracranial SRS treatments of AVM on Varian TrueBeam was successfully implemented using a custom-made phantom with <1% discrepancy. The Brainlab Elements’ cranial vascular module was successfully implemented in clinical workflow to treat patients with AVM. This manuscript provides a guideline for clinical implementation of frameless Linac-based AVM treatment using the Brainlab Elements TPS.

Factors Affecting Image Resolution in a Modern Angiographic Suite: A Phantom-Based Study

BackgroundImprovements in angiographic imaging systems technology provide options to decrease radiation exposure. The effect of these variations on image resolution is unknown. MethodsUsing an American National Standards Institution phantom, a high-contrast (line-pair) and low contrast (Gammex 151) phantoms, 5 second images were acquired using a Phillips Allure angiographic suite, using fluoroscopic capture (FC) as well as cineangiography (CA) in posterior anterior (PA) and left anterior oblique (LAO) projections as well as high and low table positions. Image resolutions were measured as ranked by three independent trained observers blinded to the purpose of the assessments. Comparative analyses were performed. Interobserver agreement was evaluated. ResultsHigh contrast image resolution was significantly lower with FC compared to CA (median [interquartile range], 1.69 [1.52–1.69] mm, vs 2.09 [1.88–2.09] mm, P < 0.001). No significant differences were observed in between PA and LAO projections as well as low and high table positions. Low contrast resolution was also lower with FC compared to CA (5 [6.5–5] vs 3 [5–3] mm, P < 0.001). No significant differences in high-contrast or low-contrast resolution were noted between PA and LAO projections, or high and low table positions. Both low and high-contrast image resolution improved with higher radiation exposure. Good interobserver agreement was noted (Fleiss-Kappa ranging from 0.69–0.74). ConclusionImage resolution was perceived to be better with CA compared to FC, although not significantly affected by beam angulation or table height. Aligning resolution needs with imaging modality and maximizing table height may improve procedural efficacy and safety.

Cellular Damage in the Target and Out-Of-Field Peripheral Organs during VMAT SBRT Prostate Radiotherapy: An In Vitro Phantom-Based Study.

Simple SummaryNew developments show that patients with prostate cancer can benefit from radiotherapy delivered with a hypo-fractionated regimen. The aim of our study was to investigate the effect of hypo-fractionated stereotactic body radiation therapy (SBRT) of prostate cancer on out-of-field organs. We used a humanoid phantom to irradiate prostate cells in conditions similar to patient therapy, using SBRT planning. Our results show that radiation doses in the location of the intestine and lung resulted in significantly higher radiation doses than the further locations. We observed a high radiotoxic effect in the cells irradiated in the prostate, and a small increase in DNA damage and cell killing in the intestine location. Gene expression analysis revealed significant enrichment of the biological processes related to the radiation response in the prostate. In the lung and thyroid, the enrichment of several gene groups was revealed, however the processes were not clearly related to the response to radiation. Our study provides extensive data on out-of-field safety of prostate SBRT.Hypo-fractionated stereotactic body radiation therapy (SBRT) is an effective treatment for prostate cancer (PCa). Although many studies have investigated the effects of SBRT on the prostate and adjacent organs, little is known about the effects further out-of-field. The aim of this study was to investigate, both in vitro and in a quasi-humanoid phantom, the biological effects (using a dose-scaling approach) of radiation in the out-of-field peripheral organs delivered by 6 MV volumetric modulated arc therapy (VMAT) SBRT in a prostate cancer model. Healthy prostate cells were irradiated in a phantom at locations corresponding to the prostate, intestine, lung, thyroid, and brain. Seven 10 Gy fractions of VMAT SBRT were delivered to the target in a single session without intermission (scaled-up method). Radiochromic films were used to measure the doses. The radiobiological response was assessed by measuring DNA breaks, the cell survival fraction, and differences in gene expression profile. Our results showed a strong, multiparametric radiobiological response of the cells in the prostate. Outside of the radiation field, the highest doses were observed in the intestine and lung. A small increase (not statistically significant) in DNA damage and cell death was observed in the intestines. Several gene groups (cell cycle, DNA replication) were depleted in the lung and thyroid (DNA replication, endocytosis), but further analysis revealed no changes in the relevant biological processes. This study provides extensive evidence of the types and extent of radiobiological responses during VMAT SBRT in a prostate cancer model. Additional research is needed to determine whether the radiobiological effects observed in the peripheral organs are validated in a clinical context.

Geometric distortion assessment in 3T MR images used for treatment planning in cranial Stereotactic Radiosurgery and Radiotherapy.

Magnetic Resonance images (MRIs) are employed in brain Stereotactic Radiosurgery and Radiotherapy (SRS/SRT) for target and/or critical organ localization and delineation. However, MRIs are inherently distorted, which also impacts the accuracy of the Magnetic Resonance Imaging/Computed Tomography (MRI/CT) co-registration process. In this phantom-based study, geometric distortion is assessed in 3T T2-weighted images (T2WIs), while the efficacy of an MRI distortion correction technique is also evaluated. A homogeneous polymer gel-filled phantom was CT-imaged before being irradiated with 26 4-mm Gamma Knife shots at predefined locations (reference control points). The irradiated phantom was MRI-scanned at 3T, implementing a T2-weighted protocol suitable for SRS/SRT treatment planning. The centers of mass of all shots were identified in the 3D image space by implementing an iterative localization algorithm and served as the evaluated control points for MRI distortion detection. MRIs and CT images were spatially co-registered using a mutual information algorithm. The inverse transformation matrix was applied to the reference control points and compared with the corresponding MRI-identified ones to evaluate the overall spatial accuracy of the MRI/CT dataset. The mean image distortion correction technique was implemented, and resulting MRI-corrected control points were compared against the corresponding reference ones. For the scanning parameters used, increased MRI distortion (>1mm) was detected at areas distant from the MRI isocenter (>5cm), while median radial distortion was 0.76mm. Detected offsets were slightly higher for the MRI/CT dataset (0.92mm median distortion). The mean image distortion correction improves geometric accuracy, but residual distortion cannot be considered negligible (0.51mm median distortion). For all three datasets studied, a statistically significant positive correlation between detected spatial offsets and their distance from the MRI isocenter was revealed. This work contributes towards the wider adoption of 3T imaging in SRS/SRT treatment planning. The presented methodology can be employed in commissioning and quality assurance programmes of corresponding treatment workflows.

Phantom-based prospective analysis of the accuracy of photo registration technology in electromagnetic navigation of the frontal skull base.

This prospective study compared the accuracy of two different company-specific registration methods (Fiagon GmbH, Hennigsdorf, Germany) in the electromagnetic navigation of the frontal skull base. A newly developed photo registration technology (Fiagon tracey©) promises an increase in accuracy and user-friendliness, but there is no phantom-based prospective study comparing the new method with the classic approach of tactile surface registration. A phantom skull was prepared with 27 markers in the sagittal, axial and coronary planes, and their reference coordinates were determined using a navigational CT (low dose, slice 0.6 mm). Subsequently, 20 runs of automatic photo registration and tactile surface registration were carried out, and the resulting marker coordinates were compared with the reference coordinates. The target registration error (TRE) of the 27 markers was assessed and compared between the two methods using a 2-factor ANOVA with repeated measures. The mean TRE using surface registration was 1.97 mm ± 0.57, while the mean TRE of the automatic photo registration was 1.54 mm ± 0.24 (p < 0.001). In a subgroup analysis limited to markers in anatomical regions of clinical relevance in terms of paranasal sinus surgery, the mean TRE for the photo registration procedure can even be reduced to 1.29 mm (± 0.43) compared to tactile registration (1.80 mm; ±0.50; p=0.01). Photo registration is a promising new technology in the field of electromagnetic navigation in paranasal sinus surgery. This prospective phantom-based study showed that the photo registration method achieves a significantly lower target registration error (1.29 mm) compared to the surface-based tactile registration procedure (1.80 mm).

Ultrashort echo time time-spatial labeling inversion pulse magnetic resonance angiography with denoising deep learning reconstruction for the assessment of abdominal visceral arteries.

Current contrast-enhanced magnetic resonance angiography (MRA) and non-contrast-enhanced balanced steady-state free precession (bSSFP) MRA cause susceptibility artifacts from metallic devices in assessing endovascular visceral-artery interventions. The aims of this study are to investigate and compare image quality (IQ) and susceptibility artifacts of three-dimensional (3D) ultrashort echo time (UTE) time-spatial labeling inversion pulse (Time-SLIP) with those of 3D bSSFP Time-SLIP and to assess denoising deep learning reconstruction (dDLR) for the improvement of the signal-to-noise ratio (SNR) in 3D UTE with sparse sampling in phantoms and human subjects. This is a prospective type of study. Pulsatile glycerin-water flow phantom with platinum-tungsten-alloy coil, stainless-steel, nitinol, and cobalt-alloy stents were used. Ten healthy volunteers (seven males) and three patients (two males) were included in this study. 3D UTE Time-SLIP and 3D bSSFP Time-SLIP at 3T were used. The phantom-based study compared the signal-intensity ratio of the device levels (SRdevice ) and distal segments (SRdistal ) to the proximal segments. The volunteer-based study measured SNR, contrast ratio (CR), and IQ. The patient study evaluated local artifacts from metallic devices. Statistical tests included paired t-tests, Wilcoxon-signed rank tests, and Kruskal-Wallis tests. In the phantom-based study, SRdevice was small with UTE Time-SLIP, except the stainless-steel stent. SRdistal was greater (49.1%-90.4%) on bSSFP images than UTE images (-11.1% to 9.6%). Among volunteers, dDLR in UTE images improved SNR (p < 0.05) and IQ (p < 0.05), but CR was unaffected. UTE Time-SLIP showed inferior SNR and IQ than bSSFP Time-SLIP in images with and without dDLR (p < 0.05 for each). However, among patients, UTE Time-SLIP showed reduced metal artifacts compared to bSSFP Time-SLIP. Irrespective of the lower SNR and IQ of 3D UTE Time-SLIP than those of 3D bSSFP Time-SLIP, the former appeared to better depict flow after stenting or coiling. This indicates the potential of 3D UTE Time-SLIP to provide suitable diagnostic images of target vessels. dDLR improved SNR with reducing artifacts related to radial sampling, while maintaining the contrast. LEVEL OF EVIDENCE: 2. TECHNICAL EFFICACY STAGE: 2.

Using singular value distribution of backscattered ultrasound waves for tracking the pulmonary edema caused by COVID-19 in lung: A phantom-based study

A condition caused by COVID-19, pulmonary edema is an abnormal buildup of fluid in lungs. B-lines tracking of ultrasound images is a common way to track lung abnormality, however due to multiple scattering this method tracks the air volume change only on the lung surface. The aim of this phantom-based study is to assess the pulmonary edema in lungs using multiple scattering of ultrasonic waves in MHz range. A 128-element array transducer is used to form an Inter-elements Response Matrix (IRM) by firing a 5.2 MHz broadband pulse, element by element and receiving the backscattered signal by the whole array. The distribution of singular values of IRM in frequency domain is then analyzed for polymer sponges (n = 4) with different Water Volume Content (WVC) ranging from 5 to 25 ml mimicking pulmonary edema. The results of Random Matrix Theory are used to show that the mode of the Probability Density Function of singular values increases as the WVC increases in sponge indicating the change in scattering regime. The B-mode image of sponges with different WVC did not represent neither A nor B lines, however our results shows that there is a correlation between the WVC in sponge and the strongest singular value of IRM (R = 0.89) indicating the potential of using quantitative ultrasound in lung for early diagnosis of COVID-19.

Fixing Acceleration and Image Resolution Issues of Nuclear Magnetic Resonance

Lately, Magnetic Resonance scans have struggled with their own inherent limitations, such as spatial resolution as well as long examination times. A novel, rapid compressively-sensed magnetic resonance high-resolution image resolution algorithm is presented in this research paper. This technique addresses these two key issues by employing a highly-sparse sampling scheme and super-resolution reconstruction (SRR) method. Due to highly challenging requirements for the accuracy of diagnostic images registration, the presented technique exploits image priors, deblurring, parallel imaging, and a deformable human body motion analysis. Clinical trials as well as a phantom-based study have been conducted. It has been proven that the proposed algorithm can enhance image spatial resolution and reduce motion artefacts and scan times.

Utilisation of the chemiluminescence method to measure the radiation dose enhancement caused by gold nanoparticles: A phantom-based study

Gold nanoparticles (AuNPs) are being investigated extensively for their role as radiosensitisers. Studies have shown that they are effective dose enhancing agents. One of the main factors that enables AuNPs to function as dose enhancing agents is their ability to generate reactive oxygen species under X-ray irradiation. In this study, we investigated this issue utilising a chemiluminescence technique with 3’-(p-aminophenyl) fluorescein (APF) in a phantom. First, we examined the time variation and dose response of the fluorescence intensity of APF for spherical 50 nm AuNPs exposed to a 6 MV photon beam. The APF reagent was added to the AuNPs suspension in a small tube fixed in a water phantom. The fluorescence intensities of APF were measured using a microplate reader. Next, based on the APF response, we evaluated the dose enhancements caused by AuNPs in a 6 MV flattening filter (FF) and flattening filter-free (FFF) photon beams and doses of either 2, 4, or 6 Gy. While the time variation of APF fluorescence intensity without AuNPs was less than 5% after X-ray irradiation, we observed an increase in the fluorescence intensity over time in the presence of AuNPs without the radiation. The APF signals had a linear response to X-ray irradiation in a dose-dependent manner. The measured dose enhancement ratios for the FFF beam were significantly higher than that for the FF beam in the presence of 30 μg/ml AuNPs. This result shows APF can successfully detect differences in dose enhancement between the FF and FFF beams using AuNPs. In conclusion, the chemiluminescence technique using APF is a useful and simple method to estimate the level of dose enhancement caused by nanoparticles in a phantom.

A Brain Phantom Study of a Noncontact Single Inductive Coil Device and the Attendant Algorithm for First Stage Diagnosis of Internal Bleeding in the Head

Abstract Hemorrhagic stroke is one of the leading causes of premature death among economically disadvantaged populations. Treatments of these conditions require an early diagnosis. While computed tomography and magnetic resonance imaging are the medical gold standard for early diagnosis, these imaging modalities are rarely available in low- and middle-income countries. We present an unsophisticated noncontact single coil inductive device and a simple algorithm for detection of changes in fluid/tissue ratio in the head which simulates blood vessel bursting in the brain. Experiments were performed on a typical phantom model of the head and internal bleeding was simulated by injection of physiological saline at two locations in the head phantom. The primary motivation for this work is the need for a simple and robust detection device and algorithm for diagnosis of hemorrhagic stroke in low- and middle-income countries. This phantom-based study shows that the technology and in particular the algorithm introduced here are robust and could replace conventional imaging for first stage diagnosis of internal bleeding in the head, and thereby save millions of lives every year. Clinical studies are required to further examine the technology and the algorithm.

Compared vulnerabilities to small cardiac motions between different cameras used for myocardial perfusion imaging

This phantom-based study was aimed to determine whether cardiac CZT-cameras, which provide an enhanced spatial resolution and image contrast compared to Anger cameras, are similarly affected by small cardiac motions. Translations of a left ventricular (LV) insert at half-SPECT acquisitions through six possible orthogonal directions and with 5- or 10-mm amplitude were simulated on the Discovery NM-530c and DSPECT CZT-cameras and on an Anger Symbia T2 camera equipped with an astigmatic (IQ.SPECT) or conventional parallel-hole collimator (Conv.SPECT). SPECT images were initially reconstructed as currently recommended for clinical routine. The heterogeneity in recorded activity from the 17 LV segments gradually increased between baseline and motions simulated at 5- and 10-mm amplitudes with all cameras, although being higher for Anger- than CZT-cameras at each step and resulting in a higher mean number of artifactual abnormal segments (at 10-mm amplitude, Conv.SPECT: 3.7; IQ.SPECT: 1.8, Discovery: 0.7, DSPECT: 0). However, this vulnerability to motion was markedly (1) decreased for Conv.SPECT reconstructed without the recommended Resolution Recovery algorithm and (2) increased for DSPECT reconstructed without the recommended cardiac model. CZT-cameras and especially the DSPECT appear less vulnerable to small cardiac motions than Anger-cameras although these differences are strongly dependent on reconstruction parameters.

Sensitivity of low-frequency axial transmission acoustics to axially and azimuthally varying cortical thickness: A phantom-based study.

PurposeCortical thickness (cTh) is one of the main factors determining a bone’s mechanical properties, and its quantification is therefore critical for understanding and monitoring bone pathologies such as osteoporosis. Axial quantitative acoustics (ax-QA) offers a non-radiative, non-invasive method to measure cTh. Even though previous works have ascertained ax-QA’s ability to measure azimuthally varying cTh, the effect of axially varying cTh remains unclear. Furthermore, previous experiments and theoretical predictions indicate that measurement of the fundamental flexural mode at low frequencies in the kHz range could increase sensitivity to cTh. However, due to the associated long wavelengths, the approximation of bone geometry as a tube could break down at such frequencies. The presented study therefore investigates a) the sensitivity of ax-QA measurements to cTh in the kHz-regime, b) the applicability of tube theory in this regime, and c) the effect of varying cTh along the long axis on the bone.Materials and methodsAxial-transmission acoustic measurements were performed at 3kHz on 14 bone phantoms with a femur-like cross-section and a) axially varying cortical thickness or b) axially and azimuthally varying cortical thickness (cTh-range: 1.5mm-7.5mm). Experimental results were compared to theoretical predictions based on an exact elastic tube theory.Results and discussionPhase velocity measurements using low-frequency ax-QA exhibited a high sensitivity to local cTh less than 4mm, albeit with a complex, not yet understood pattern. Tube theory failed to predict the wave’s behavior in the kHz range, indicating that due to the corresponding long wavelengths the bone can no longer be approximated by a tube, thus requiring more faithful modelling of the bone geometry. The fact that results from both types of phantoms were similar (Pearson correlation coefficient: 0.94) further indicates that the slowly varying cTh along the bone’s long axis did not strongly affect wave propagation as measured by ax-QA measurements.

A four-alternative forced choice (4AFC) methodology for evaluating microcalcification detection in clinical full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT) systems using an inkjet-printed anthropomorphic phantom.

The advent of three-dimensional breast imaging systems such as digital breast tomosynthesis (DBT) has great promise for improving the detection and diagnosis of breast cancer. With these new technologies comes an essential need for testing methods to assess the resultant image quality. Although randomized clinical trials are the gold standard for assessing image quality, phantom-based studies can provide a simpler and less burdensome approach. In this work, a complete framework is presented for task-based evaluation of microcalcification (MCs) detection performance for DBT imaging systems. The framework consists of three parts. The first part is a realistic anthropomorphic physical breast phantom created through inkjet printing, with parchment paper and iodine-doped ink. The second is a method for inserting realistic MCs fabricated from calcium hydroxyapatite. The reproducibility and stability of the phantom materials were investigated through multiple samples of parchment and ink over 6 months. The final part is an analysis using a four-alternative forced choice (4AFC) reader study. To demonstrate the framework, a task-based 4AFC study was conducted using a clinical system to compare performance from DBT, synthetic mammography (SM), and full-field digital mammography (FFDM). Nine human observers read images containing MC clusters imaged with all three modalities and tried to correctly locate the MCs. The proportion correct (PC) was measured as the number of correctly detected clusters out of all trials. Overall, readers scored the highest with FFDM, (PC=0.95±0.03) then DBT (0.85±0.04), and finally SM (0.44±0.06). For the parchment and ink samples, the linear attenuation properties were very stable over 6 months. In addition, little difference was found between the various parchment and ink samples, indicating good reproducibility. This framework presents a promising methodology for evaluating diagnostic task performance of clinical breast DBT systems.