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DOE OSTI2015

Multiattribute probabilistic prostate elastic registration (MAPPER): Application to fusion of ultrasound and magnetic resonance imaging

Purpose: Transrectal ultrasound (TRUS)-guided needle biopsy is the current gold standard for prostate cancer diagnosis. However, up to 40% of prostate cancer lesions appears isoechoic on TRUS. Hence, TRUS-guided biopsy has a high false negative rate for prostate cancer diagnosis. Magnetic resonance imaging (MRI) is better able to distinguish prostate cancer from benign tissue. However, MRI-guided biopsy requires special equipment and training and a longer procedure time. MRI-TRUS fusion, where MRI is acquired preoperatively and then aligned to TRUS, allows for advantages of both modalities to be leveraged during biopsy. MRI-TRUS-guided biopsy increases the yield of cancer positive biopsies. In this work, the authors present multiattribute probabilistic postate elastic registration (MAPPER) to align prostate MRI and TRUS imagery. Methods: MAPPER involves (1) segmenting the prostate on MRI, (2) calculating a multiattribute probabilistic map of prostate location on TRUS, and (3) maximizing overlap between the prostate segmentation on MRI and the multiattribute probabilistic map on TRUS, thereby driving registration of MRI onto TRUS. MAPPER represents a significant advancement over the current state-of-the-art as it requires no user interaction during the biopsy procedure by leveraging texture and spatial information to determine the prostate location on TRUS. Although MAPPER requires manual interaction to segment the prostate on MRI, this step is performed prior to biopsy and will not substantially increase biopsy procedure time. Results: MAPPER was evaluated on 13 patient studies from two independent datasets—Dataset 1 has 6 studies acquired with a side-firing TRUS probe and a 1.5 T pelvic phased-array coil MRI; Dataset 2 has 7 studies acquired with a volumetric end-firing TRUS probe and a 3.0 T endorectal coil MRI. MAPPER has a root-mean-square error (RMSE) for expert selected fiducials of 3.36 ± 1.10 mm for Dataset 1 and 3.14 ± 0.75 mm for Dataset 2. State-of-the-art MRI-TRUS fusion methods report RMSE of 3.06–2.07 mm. Conclusions: MAPPER aligns MRI and TRUS imagery without manual intervention ensuring efficient, reproducible registration. MAPPER has a similar RMSE to state-of-the-art methods that require manual intervention.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2019

Constraints on bosonic dark matter from ultralow-field nuclear magnetic resonance

The nature of dark matter, the invisible substance making up over 80% of the matter in the universe, is one of the most fundamental mysteries of modern physics. Ultralight bosons such as axions, axion-like particles, or dark photons could make up most of the dark matter. Couplings between such bosons and nuclear spins may enable their direct detection via nuclear magnetic resonance (NMR) spectroscopy: As nuclear spins move through the galactic dark-matter halo, they couple to dark matter and behave as if they were in an oscillating magnetic field, generating a dark-matter–driven NMR signal. As part of the cosmic axion spin precession experiment (CASPEr), an NMR-based dark-matter search, we use ultralow-field NMR to probe the axion-fermion “wind” coupling and dark-photon couplings to nuclear spins. No dark matter signal was detected above background, establishing new experimental bounds for dark matter bosons with masses ranging from 1.8 × 10 -16 to 7.8 × 10 -14 eV.

Science & Technology - Other Topics↗

DOE OSTI2013

Solid State Nuclear Magnetic Resonance Investigation of Polymer Backbone Dynamics in Poly(Ethylene Oxide) Based Lithium and Sodium Polyether-ester-sulfonate Ionomers

Polymer backbone dynamics of single ion conducting poly(ethylene oxide) (PEO)-based ionomer samples with low glass transition temperatures (Tg) have been investigated using solid-state nuclear magnetic resonance (NMR). Experiments detecting 13C with 1H decoupling under magic angle spinning (MAS) conditions identified the different components of the polymer backbone (PEO spacer and isophthalate groups) and their relative mobilities for a suite of lithium- and sodium-containing ionomer samples with varying cation contents. Variable temperature (203-373 K) 1H-13C cross-polarization MAS (CP-MAS) experiments also provided qualitative assessment of the differences in the motions of the polymer backbone components as a function of cation content and identity. Each of the main backbone components exhibit distinct motions, following the trends expected for motional characteristics based on earlier Quasi Elastic Neutron Scattering and 1H spin-lattice relaxation rate measurements. Previous 1H and 7Li spin-lattice relaxation measurements focused on both the polymer backbone and cation motion on the nanosecond timescale. The studies presented here assess the slower timescale motion of the polymer backbone allowing for a more comprehensive understanding of the polymer dynamics. The temperature dependences of 13C linewidths were used to both qualitatively and quantitatively examine the effects of cation content and identity on PEO spacer mobility. Variable contact time 1H-13C CP-MAS experiments were used to further assess the motions of the polymer backbone on the microsecond timescale. The motion of the PEO spacer, reported via the rate of magnetization transfer from 1H to 13C nuclei, becomes similar for T ≳ 1.1 Tg in all ionic samples, indicating that at similar elevated reduced temperatures the motions of the polymer backbones on the microsecond timescale become insensitive to ion interactions. These results present an improved picture, beyond those of previous findings, for the dependence of backbone dynamics on cation density (and here, cation identity as well) in these amorphous PEO-based ionomer systems.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Improved reconstruction stability for chemical shift encoded hyperpolarized 13 C magnetic resonance spectroscopic imaging using k‐t spiral acquisitions

Purpose A multiecho, field of view (FOV)‐oversampled k‐t spiral acquisition and direct iterative decomposition of water and fat with echo asymmetry and least‐squares estimation reconstruction is demonstrated to improve the stability of hyperpolarized 13 C magnetic resonance spectroscopic imaging (MRSI) in the presence of signal ambiguities attributed to low‐SNR (signal‐to‐noise‐ratio) species, local uncertainties in metabolite peaks, and echo‐to‐echo signal inconsistencies. Theory k‐t spiral acquisitions redistribute readout points to be more densely spaced radially in k‐space by acquiring an FOV and matrix that are oversampled by η . These more densely spaced spiral turns constitute effective intraspiral echoes and can supplement conventional interspiral echoes to improve spectral separation and reduce spectral cross‐talk to better resolve 13 C‐labeled species for spectroscopic imaging. Methods Digital simulations and imaging phantom experiments were performed for a range of interspiral echo spacings and η using multiecho, k‐t spiral acquisitions. Image spectral cross‐talk artifacts were evaluated both qualitatively and quantitatively as the percent error in measured metabolite ratios. In vivo murine experiments evaluated the feasibility of multiecho, k‐t spiral [1‐ 13 C]pyruvate MRSI to reduce spectral cross‐talk for 3 scenarios of different expected reconstruction stability. Results Digital simulations and imaging phantom experiments both demonstrated reduced or comparable image spectral cross‐talk and percent errors in measured metabolite ratios with increasing η and better choices of echo spacings. In vivo images displayed markedly reduced spectral cross‐talk in lactate images acquired with η = 7 versus η = 1. Conclusion The precision of hyperpolarized 13 C metabolic imaging and quantification in the presence of low‐SNR species, local uncertainties in metabolite resonances, and echo‐to‐echo signal inconsistencies can be improved with the use of FOV‐oversampled k‐t spiral acquisitions.

Macdonald, Erin B.↗

DOE OSTI2019

Magnetic resonance imaging as a non-invasive method for the assessment of pancreatic fibrosis (MINIMAP): a comprehensive study design from the consortium for the study of chronic pancreatitis, diabetes, and pancreatic cancer

Characteristic features of chronic pancreatitis (CP) may be absent on standard imaging studies. Quantitative Magnetic Resonance Imaging (MRI) techniques such as T{sub 1} mapping, extracellular volume (ECV) fraction, diffusion-weighted imaging (DWI) with apparent diffusion coefficient map (ADC), MR elastography (MRE), and T{sub 1}-weighted signal intensity ratio (SIR) have shown promise for the diagnosis and grading severity of CP. However, radiologists still use the Cambridge classification which is based on traditional ductal imaging alone. There is an urgent need to develop new diagnostic criteria that incorporate both parenchymal and ductal features of CP seen by MRI/MRCP. Designed to fulfill this clinical need, we present the MINIMAP study, which was funded in September 2018 by the National Institutes of Health. This is a comprehensive quantitative MR imaging study which will be performed at multiple institutions in well-phenotyped CP patient cohorts. We hypothesize that quantitative MRI/MRCP features can serve as valuable non-invasive imaging biomarkers to detect and grade CP. We will evaluate the role of T{sub 1} relaxometry, ECV, T{sub 1}-weighted gradient echo SIR, MRE, arteriovenous enhancement ratio, ADC, pancreas volume/atrophy, pancreatic fat fraction, ductal features, and pancreatic exocrine output following secretin stimulation in the assessment of CP. We will attempt to generate a multi-parametric pancreatic tissue fibrosis (PTF) scoring system. We anticipate that a quantitative scoring system may serve as a biomarker of pancreatic fibrosis; hence this imaging technique can be used in clinical practice as well as clinical trials to evaluate the efficacy of agents which may slow the progression or reverse measures of CP.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

NASA NTRS1984

In vivo nuclear magnetic resonance imaging

A number of physiological changes have been demonstrated in bone, muscle and blood after exposure of humans and animals to microgravity. Determining mechanisms and the development of effective countermeasures for long duration space missions is an important NASA goal. The advent of tomographic nuclear magnetic resonance imaging (NMR or MRI) gives NASA a way to greatly extend early studies of this phenomena in ways not previously possible; NMR is also noninvasive and safe. NMR provides both superb anatomical images for volume assessments of individual organs and quantification of chemical/physical changes induced in the examined tissues. The feasibility of NMR as a tool for human physiological research as it is affected by microgravity is demonstrated. The animal studies employed the rear limb suspended rat as a model of mucle atrophy that results from microgravity. And bedrest of normal male subjects was used to simulate the effects of microgravity on bone and muscle.

Leblanc, A.↗

DOE OSTI2017

{sup 18}F-Choline Positron Emission Tomography/Computed Tomography and Multiparametric Magnetic Resonance Imaging for the Detection of Early Local Recurrence of Prostate Cancer Initially Treated by Radiation Therapy: Comparison With Systematic 3-Dimensional Transperineal Mapping Biopsy

Purpose: To compare the diagnostic performance of {sup 18}F-fluorocholine positron emission tomography/computed tomography (FCH-PET/CT), multiparametric prostate magnetic resonance imaging (mpMRI), and a combination of both techniques for the detection of local recurrence of prostate cancer initially treated by radiation therapy. Methods and Materials: This was a retrospective, single-institution study of 32 patients with suspected prostate cancer recurrence who underwent both FCH-PET/CT and 3T mpMRI within 3 months of one another for the detection of recurrence. All included patients had to be cleared for metastatic recurrence. The reference procedure was systematic 3-dimensional (3D)-transperineal prostate biopsy for the final assessment of local recurrence. Both imaging modalities were analyzed by 2 experienced readers blinded to clinical data. The analysis was made per-patient and per-segment using a 4-segment model. Results: The median prostate-specific antigen value at the time of imaging was 2.92 ng/mL. The mean prostate-specific antigen doubling time was 14 months. Of the 32 patients, 31 had a positive 3D-transperineal mapping biopsy for a local relapse. On a patient-based analysis, the detection rate was 71% (22 of 31) for mpMRI and 74% (23 of 31) for FCH-PET/CT. On a segment-based analysis, the sensitivity and specificity were, respectively, 32% and 87% for mpMRI, 34% and 87% for FCH-PET/CT, and 43% and 83% for the combined analysis of both techniques. Accuracy was 64%, 65%, and 66%, respectively. The interobserver agreement was κ = 0.92 for FCH-PET/CT and κ = 0.74 for mpMRI. Conclusions: Both mpMRI and FCH-PET/CT show limited sensitivity but good specificity for the detection of local cancer recurrence after radiation therapy, when compared with 3D-transperineal mapping biopsy. Prostate biopsy still seems to be mandatory to diagnose local relapse and select patients who could benefit from local salvage therapy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2015

Application of Magnetic Resonance Imaging and Three-Dimensional Treatment Planning in the Treatment of Orbital Lymphoma

Radiotherapy for lymphoma of the orbit must be individualized for each patient and clinical setting. Most techniques focus on optimizing the dose to the tumor while sparing the lens. This study describes a technique utilizing magnetic resonance imaging (MRI) and three dimensional (3D) planning in the treatment of orbital lymphoma. A patient presented with an intermediate grade lymphoma of the right orbit. The prescribed tumor dose was 4050 cGy in 18 fractions. Three D planning was carried out and tumor volumes, retina, and lens were subsequently outlined. Dose calculations including dose volume histograms of the target, retina, and lens were then performed. Part of the retina was outside of the treatment volume while 50% of the retina received 90% or more of the prescribed dose. The patient was clinically NED when last seen 2 years following therapy with no treatment-related morbidity. Patients with lymphomas of the orbit can be optimally treated using MRI based 3D treatment planning.

61 RADIATION PROTECTION AND DOSIMETRY↗

DOE OSTI2013

Magnetic Resonance Imaging (MRI) Markers for MRI-Guided High-Dose-Rate Brachytherapy: Novel Marker-Flange for Cervical Cancer and Marker Catheters for Prostate Cancer

Purpose: To present a novel marker-flange, addressing source-reconstruction uncertainties due to the artifacts of a titanium intracavitary applicator used for magnetic resonance imaging (MRI)-guided high-dose-rate (HDR) brachytherapy (BT); and to evaluate 7 different MRI marker agents used for interstitial prostate BT and intracavitary gynecologic HDR BT when treatment plans are guided by MRI. Methods and Materials: Seven MRI marker agents were analyzed: saline solution, Conray-60, copper sulfate (CuSO{sub 4}) (1.5 g/L), liquid vitamin E, fish oil, 1% agarose gel (1 g agarose powder per 100 mL distilled water), and a cobalt–chloride complex contrast (C4) (CoCl{sub 2}/glycine = 4:1). A plastic, ring-shaped marker-flange was designed and tested on both titanium and plastic applicators. Three separate phantoms were designed to test the marker-flange, interstitial catheters for prostate BT, and intracavitary catheters for gynecologic HDR BT. T1- and T2-weighted MRI were analyzed for all markers in each phantom and quantified as percentages compared with a 3% agarose gel background. The geometric accuracy of the MR signal for the marker-flange was measured using an MRI-CT fusion. Results: The CuSO{sub 4} and C4 markers on T1-weighted MRI and saline on T2-weighted MRI showed the highest signals. The marker-flange showed hyper-signals of >500% with CuSO{sub 4} and C4 on T1-weighted MRI and of >400% with saline on T2-weighted MRI on titanium applicators. On T1-weighted MRI, the MRI signal inaccuracies of marker-flanges were measured <2 mm, regardless of marker agents, and that of CuSO{sub 4} was 0.42 ± 0.14 mm. Conclusion: The use of interstitial/intracavitary markers for MRI-guided prostate/gynecologic BT was observed to be feasible, providing accurate source pathway reconstruction. The novel marker-flange can produce extremely intense, accurate signals, demonstrating its feasibility for gynecologic HDR BT.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2017

Study of the impact of resonant magnetic perturbation fields on gross tungsten erosion using DiMES samples in DIII-D

Here, an experiment was conducted in DIII-D to compare gross tungsten (W) erosion on samples exposed to outer strike point (OSP) sweeps in L-mode plasmas for three conditions. These included two phases of resonant magnetic perturbations (RMPs), and a set with no perturbations. Upon RMP application, lobe structures indicative of strike point splitting of the OSP were evident in divertor camera data and on Langmuir probes. Gross W erosion flux, ${{\rm{\Gamma }}}_{{\rm{W}}},$ inferred spectroscopically using the S/XB method applied to the 400.9 nm W-I line, was generally in the range ${{\rm{\Gamma }}}_{{\rm{W}}}/{{\rm{\Gamma }}}_{{\rm{D}}+,\perp }=2\times {10}^{-4}$ referenced to incident deuterium ion flux ${{\rm{\Gamma }}}_{{\rm{D}}+,\perp },$ and was increased in the RMP cases by no more than 30% of the level observed in unperturbed discharges. A large reduction in gross erosion (50%) was observed in the private flux region at the W sample for one specific toroidal phase of the RMP field.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2017

Interaction of a magnetic island chain in a tokamak plasma with a resonant magnetic perturbation of rapidly oscillating phase

An investigation is made here into the interaction of a magnetic island chain, embedded in a tokamak plasma, with an externally generated magnetic perturbation of the same helicity whose helical phase is rapidly oscillating. The analysis is similar in form to the classic analysis used by Kapitza [Sov. Phys. JETP 21, 588 (1951)] to examine the angular motion of a rigid pendulum whose pivot point undergoes rapid vertical oscillations. The phase oscillations are found to modify the existing terms, and also to give rise to new terms, in the equations governing the secular evolution of the island chain's radial width and helical phase. An examination of the properties of the new secular evolution equation reveals that it is possible to phase-lock an island chain to an external magnetic perturbation with an oscillating helical phase in a stabilizing phase relation provided that the amplitude, ϵ, of the phase oscillations (in radians) is such that | J 0 ( ϵ ) | << 1 , and the mean angular frequency of the perturbation closely matches the natural angular frequency of the island chain.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2016

Audiovisual Biofeedback Improves Cine–Magnetic Resonance Imaging Measured Lung Tumor Motion Consistency

Purpose: To assess the impact of an audiovisual (AV) biofeedback on intra- and interfraction tumor motion for lung cancer patients. Methods and Materials: Lung tumor motion was investigated in 9 lung cancer patients who underwent a breathing training session with AV biofeedback before 2 3T magnetic resonance imaging (MRI) sessions. The breathing training session was performed to allow patients to become familiar with AV biofeedback, which uses a guiding wave customized for each patient according to a reference breathing pattern. In the first MRI session (pretreatment), 2-dimensional cine-MR images with (1) free breathing (FB) and (2) AV biofeedback were obtained, and the second MRI session was repeated within 3-6 weeks (mid-treatment). Lung tumors were directly measured from cine-MR images using an auto-segmentation technique; the centroid and outlier motions of the lung tumors were measured from the segmented tumors. Free breathing and AV biofeedback were compared using several metrics: intra- and interfraction tumor motion consistency in displacement and period, and the outlier motion ratio. Results: Compared with FB, AV biofeedback improved intrafraction tumor motion consistency by 34% in displacement (P=.019) and by 73% in period (P<.001). Compared with FB, AV biofeedback improved interfraction tumor motion consistency by 42% in displacement (P<.046) and by 74% in period (P=.005). Compared with FB, AV biofeedback reduced the outlier motion ratio by 21% (P<.001). Conclusions: These results demonstrated that AV biofeedback significantly improved intra- and interfraction lung tumor motion consistency for lung cancer patients. These results demonstrate that AV biofeedback can facilitate consistent tumor motion, which is advantageous toward achieving more accurate medical imaging and radiation therapy procedures.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2019

Combined Nuclear Magnetic Resonance and Molecular Dynamics Study of Methane Adsorption in M 2 (dobdc) Metal–Organic Frameworks

We investigate the diffusion of methane in the metal-organic frameworks M 2 (dobdc) (M = Mg, Ni, Zn; dobdc 4- = 2,5-dioxido-1,4-benzenedicarboxylate) as a function of methane loading through a combination of nuclear magnetic resonance and molecular dynamics simulations. At low gas densities, our results suggest that favorable CH 4 -CH 4 interactions lower the free energy barrier for methane hopping between coordinatively unsaturated metal sites and thus enhance the translational motion of methane down the c -axis. At higher gas densities, CH 4 -CH 4 interactions become more significant, CH 4 -CH 4 collisions become more frequent, and the gas self-diffusion begins to decrease. Lastly, we determine that the self-diffusion coefficient of methane is inversely related to the binding energy at the coordinatively unsaturated metal sites, such that diffusion is most rapid in the Zn 2 (dobdc) framework.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2019

Integrating Density Functional Theory Calculations with Vibrational and Nuclear Magnetic Resonance Spectroscopy

This review focuses on the complementary nature of density functional theory calculations and spectroscopic studies related to cellulose and its interactions within plant cell walls (PCWs). The complexity, structural disorder, and nanoscale nature of PCWs make them difficult to analyze and understand, but advances in sum-frequency generation and nuclear magnetic resonance spectroscopies as well as in density functional theory have made it possible to elucidate structure not observable previously. Combined with other techniques such as wide-angle X-ray scattering and neutron diffraction, details of PCW components (e.g., cellulose, lignin, pectin) and their interactions with one another can be elucidated. Furthermore, these techniques provide new insight into biological and biochemical studies and provide a basis for creating improved models of the PCWs.

36 MATERIALS SCIENCE↗

DOE OSTI2012

Urinary Tract Effects After Multifocal Nonthermal Irreversible Electroporation of the Kidney: Acute and Chronic Monitoring by Magnetic Resonance Imaging, Intravenous Urography and Urinary Cytology

Purpose: The nonthermal irreversible electroporation (NTIRE) is a novel potential ablation modality for renal masses. The aim of this study was the first evaluation of NTIRE's effects on the renal urine-collecting system using intravenous urography (IVU) and urinary cytology in addition to histology and magnetic resonance imaging (MRI). Methods: Eight percutaneous NTIRE ablations of the renal parenchyma, including the calyxes or pelvis, were performed in three male swine. MRI, IVU, histology, and urinary cytology follow-ups were performed within the first 28 days after treatment. Results: MRI and histological analysis demonstrated a localized necrosis 7 days and a localized scarification of the renal parenchyma with complete destruction 28 days after NTIRE. The urine-collecting system was preserved and showed urothelial regeneration. IVU and MRI showed an unaltered normal morphology of the renal calyxes, pelvis, and ureter. A new urinary cytology phenomenon featured a temporary degeneration by individual vacuolization of detached transitional epithelium cells within the first 3 days after NTIRE. Conclusions: This first urographical, urine-cytological, and MRI evaluation after porcine kidney NTIRE shows multifocal parenchyma destruction while protecting the involved urine-collecting system with regenerated urothelial tissue. NTIRE could be used as a targeted ablation method of centrally located renal masses.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2016

Decline of Tumor Vascular Function as Assessed by Dynamic Contrast-Enhanced Magnetic Resonance Imaging Is Associated With Poor Responses to Radiation Therapy and Chemotherapy

Purpose: To investigate whether changes in the volume transfer coefficient (K{sup trans}) in a growing tumor could be used as a surrogate marker for predicting tumor responses to radiation therapy (RT) and chemotherapy (CT). Methods and Materials: Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was consecutively performed on tumor-bearing mice, and temporal and spatial changes of K{sup trans} values were measured along with tumor growth. Tumor responses to RT and CT were studied before and after observed changes in K{sup trans} values with time. Results: Dynamic changes with an initial increase and subsequent decline in K{sup trans} values were found to be associated with tumor growth. When each tumor was divided into core and peripheral regions, the K{sup trans} decline was greater in core, although neither vascular structure or necrosis could be linked to this spatial difference. Tumor responses to RT were worse if applied after the decline of K{sup trans}, and there was less drug distribution and cell death in the tumor core after CT. Conclusion: The K{sup trans} value in growing tumors, reflecting the changes of tumor microenvironment and vascular function, is strongly associated with tumor responses to RT and CT and could be a potential surrogate marker for predicting the tumor response to these treatments.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2019

Early Embolization After Carotid Artery Stenting with Mesh-Covered Stent: Role of Diffusion-Weighted Magnetic Resonance Imaging as Pre-procedural Predictor and Discriminant Between Intra- and Post-procedural Events

Objectives: To evaluate the incidence and the time of onset of early micro-embolism after CAS (carotid artery stenting) with two different mesh-covered stents and to assess the role of DW-MRI (Diffusion-weighted magnetic resonance imaging) in their prediction. Methods: Single-institution prospective study including 50 patients (33 male, median age 74 years) who underwent CAS with Roadsaver{sup ®} or CGuard™. All patients with primary stenosis (37/50, 74%) had carotid plaque DW-MRI pre-procedure, with both qualitative evaluation of the hyperintensity and ADC (apparent diffusion coefficient) measurement of the plaque. All patients had brain DW-MRI pre-procedure, at 1 h, 24 h and 30 days post-procedure to evaluate the appearance of hyperintense lesions over time. Imaging analysis was performed in a double-blinded fashion by two radiologists. Results: There were no statistically significant differences between the two stents both in the incidence at 1 h (P = 0.23) and 24 h (P = 0.36) and in the volume of new DWI hyperintense brain lesions at 24 h (P = 0.27). Thirty-four new asymptomatic lesions in 19 patients (38%) were reported: 4 (11.8%) at 1 h, 30 (88.2%) at 24 h. The 30-day DWI-MR showed complete resolution of all lesions and no evidence of new lesion. The incidence of new lesions at 24 h resulted significantly higher in patients with DWI hyperintense carotid plaques (12/16, 75% vs. 0/21, 0%, P < 0.0001). This result was paralleled by the difference in ADC value (0.83 ± 0.21 vs. 1.42 ± 0.52). Conclusion: The majority of early asymptomatic brain lesion occurred during the first 24 h after CAS. Pre-procedure high DWI signal of the plaque was associated with an increased incidence of post-procedure microembolizations.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2014

Threshold Doses for Focal Liver Reaction After Stereotactic Ablative Body Radiation Therapy for Small Hepatocellular Carcinoma Depend on Liver Function: Evaluation on Magnetic Resonance Imaging With Gd-EOB-DTPA

Purpose: Focal liver reaction (FLR) appears on radiographic images after stereotactic ablative body radiation therapy (SABR) in patients with hepatocellular carcinoma (HCC) and chronic liver disease. We investigated the threshold dose (TD) of FLR and possible factors affecting the TD on gadoxetate acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI). Methods and Materials: In 50 patients who were treated with SABR for small HCC and followed up by MRI for >6 months, FLR, seen as a hypointense area, was evaluated on the hepatobiliary phase of Gd-EOB-DTPA-enhanced MRI. The follow-up MRI with the largest extent of FLR was fused to the planning computed tomography (CT) image, and patients with good image fusion concordance were eligible. After delineating the border of the FLR manually, a dose–volume histogram was used to identify the TD for the FLR. Clinical and volumetric factors were analyzed for correlation with the TD. Results: A total of 45 patients were eligible for analysis with a median image fusion concordance of 84.9% (range, 71.6-95.4%). The median duration between SABR and subsequent hepatobiliary phase MRI with the largest extent of FLR was 3 months (range, 1-6 months). The median TD for FLR was 28.0 Gy (range, 22.3-36.4 Gy). On univariate analysis, pre-treatment Child-Pugh (CP) score and platelet count were significantly correlated with the TD. On multiple linear regression analysis, CP score was the only parameter that predicted TD. Median TDs were 30.5 Gy (range, 26.2.3-36.4 Gy) and 25.2 Gy (range, 22.3-27.5 Gy) for patients with CP-A and CP-B disease, respectively. Conclusion: The TD was significantly correlated with baseline liver function. We propose 30 Gy for CP-A disease and 25 Gy for CP-B disease in 5 fractions as TDs for FLR after SABR for patients with HCC and chronic liver disease. Use of these TDs will help to predict potential loss of liver tissue after SABR.

62 RADIOLOGY AND NUCLEAR MEDICINE↗