Increase In Apparent Diffusion Coefficient Research Articles

Quantitative PET-MRI for early treatment response assessment in pancreatic ductal adenocarcinoma.

520 Background: There is an unmet need for improved non-invasive markers to assess early treatment response in pancreatic ductal adenocarcinoma (PDAC). Assessing early treatment response using tumor size on anatomic imaging or serum carbohydrate antigen 19-9 (CA19-9) level is unreliable. In contrast, metabolic and functional imaging is a promising new tool that may differentiate responders from non-responders early on during therapy. Therefore, the objective of this pilot study was to explore the potential of integrated positron emission tomography-magnetic resonance imaging (PET-MRI) to provide imaging biomarkers of early (4 weeks post treatment initiation) response in patients with advanced PDAC. Methods: 13 patients with biopsy-proven locally advanced or metastatic PDAC underwent integrated 18F-fluorodeoxyglucose PET-MRI through the abdomen prior to, and again at 4 weeks post, treatment initiation. Patients also had computed tomography (CT) imaging of the chest, abdomen, and pelvis and serum CA19-9 levels measured, as per standard of care. Patients were classified as responders or non-responders according to RECIST (Response Evaluation Criteria In Solid Tumors) on delayed CT, at 8-12 weeks interval post treatment initiation. Changes in metabolic tumor volume (MTV) and total lesion glycolysis (TLG) from PET, and apparent diffusion coefficient (ADC) from diffusion-weighted MRI at 4 weeks were compared between responders and non-responders. Results: Of the 13 patients, there were 7 responders (partial response by RECIST) and 6 non-responders (progressive or stable disease by RECIST). After 4 weeks of therapy, responders had a significantly greater decrease in MTV (p = 0.003) and TLG (p = 0.006) compared to non-responders. Responders also had a significantly greater increase in mean and minimum ADC (p = 0.004 and p = 0.024, respectively) compared to non-responders. Change in tumor size at 4 weeks was not significantly different between responders and non-responders (p = 0.11). Conclusions: Integrated PET-MRI can provide early assessment of treatment response in patients with advanced PDAC.

Short Diffusion Time Diffusion-Weighted Imaging With Oscillating Gradient Preparation as an Early Magnetic Resonance Imaging Biomarker for Radiation Therapy Response Monitoring in Glioblastoma: A Preclinical Feasibility Study

Toinvestigate a novel alternative diffusion-weighted imaging (DWI) approach using oscillating gradients preparation (OGSE) to obtain much shorter effective diffusion times (Δeff) for tumor response monitoring by apparent diffusion coefficient (ADC) mapping in a glioblastoma mouse model. Twenty-four BALB/c nude mice inoculated with U87 glioblastoma cells were randomized into a control group and an irradiation group, which underwent a 15-day fractioned radiation therapy (RT) course with 2Gy/d. Therapy response was assessed by mapping of ADCs at 6 time points using an in-house implementation of a cos-OGSE DWI sequence with Δeff=1.25ms and compared with a standard pulsed gradient DWI protocol (PGSE) with typical clinical diffusion time Δeff=18ms. Longitudinal ADC changes in tumor and contralateral white matter (WM) were statistically assessed using repeated-measures analysis of variance and post hoc (Sidak) testing. On short Δeff OGSE maps tumor ADC was generally 30%-50% higher than in surrounding WM. Areas correlated well with histology. Tumor identification was generally more difficult on PGSE maps owing to nonsignificant WM/tumor contrast. During RT, OGSE maps also showed significant tumor ADC increase (approximately 15%) in response to radiation, consistently seen after 14-Gy RT dose. The clinical reference (PGSE) showed lower sensitivity to radiation changes, and no significant response across the radiation group and time course could be detected. Our short Δeff DWI method using OGSE better reflected histologically defined tumor areas and enabled more consistent and earlier detection of microstructural radiation changes than conventional methods. Oscillating gradients preparation offers significant potential as a robust microstructural RT response biomarker, potentially helping to shift important therapy decisions to earlier stages in the RT time course.

Early Changes in Apparent Diffusion Coefficient for Salivary Glands during Radiotherapy for Nasopharyngeal Carcinoma Associated with Xerostomia.

ObjectiveTo evaluate the early changes in the apparent diffusion coefficient (ADC) of the salivary glands during radiotherapy (RT) and their association with the degree of xerostomia at 6 months after RT in patients with nasopharyngeal carcinoma (NPC).Materials and MethodsWe enrolled 26 patients with NPC who underwent RT. Each patient underwent diffusion-weighted MRI of the salivary glands at rest and with gustatory stimulation within 1 week before RT and 2 weeks after the beginning of RT. The ADC at rest (ADCR) and increase and increase rate with stimulation (ADCI, ADCIR) of the submandibular and parotid glands were calculated. The differences in the variables' values between 2 weeks after the beginning of RT and baseline (ΔADCR, ΔADCI, and ΔADCIR) were compared to the degree of xerostomia at 6 months after RT.ResultsThe ADCR of the submandibular and parotid glands were both significantly higher at 2 weeks after the beginning of RT than found at baseline (both p < 0.01). The ADCI and ADCIR for the parotid glands were both significantly lower at 2 weeks after the beginning of RT than found at baseline (both p < 0.01). ΔADCI and ΔADCIR of the parotid glands were associated with the degree of xerostomia at 6 months after RT (r = −0.61 and −0.72, both p < 0.01).ConclusionThe ADCs of the salivary glands change early during RT. The differences in the ADC increase and increase rate of the parotid glands between 2 weeks after the beginning of RT and baseline were associated with the degree of xerostomia at 6 months after RT.

Diffusion-weighted imaging of the brains of dogs with idiopathic epilepsy

BackgroundIdiopathic epilepsy is one of the most common neurological disorders in dogs. Unfortunately, up to 30% of dogs with idiopathic epilepsy show no improvement under antiepileptic drug treatment. Diffusion-weighted imaging is used in human medicine to identify epileptogenic foci in the brain to allow for more invasive treatments such as deep brain stimulation or surgical removal.The aim of this study was to ass the feasibility of interictal diffusion-weighted MRI in dogs and to evaluate the distribution of diffusion in the brains of dogs with idiopathic epilepsy (IE) and to compare these values to previously published values from healthy beagle dogs.Client-owned dogs with the final diagnosis of IE were included in this study. MRI examination was carried out using a 1.0Tesla superconductive magnet. Diffusion-weighted images using a single shot echo planar imaging sequence (SSh-EPI) with a b value of b = 0 s/mm2 and b = 800 s/mm2 were acquired in a dorsal and transverse plane with diffusion gradients in all three planes (x-, y- and z-plane). An ADC (apparent diffusion coefficient) map of the isometric image of each acquired slice was generated.Regions of interest (ROIs) were manually drawn around the caudate nucleus, the thalamus, the piriform lobe including the amygdala, the hippocampus, the semioval center and the temporal cerebral cortex by one of the authors. ROI drawings were repeated 5 times at different time points to assess intra-obersver variability. A multi-way mixed-model analysis of variance (ANOVA) and two-way ANOVA were used during statistical analysis. A p value of p < 0.05 was considered significant.ResultsDogs with IE showed a significantly increased ADC in the amygdala within the piriform lobe and in the semioval center (p < 0.05) compared with the healthy control group.ConclusionChanges in the piriform lobe in cases of epilepsy are reported infrequently in human and veterinary medicine. Similar to our results, ADC changes in the interictal phase usually include an increase in ADC due to cell loss and increased intercellular spaces. Diffusion MRI might be a promising technique for the examination of canine epileptic patients lacking other gross neuromorphological abnormalities.

Diffusion-weighted MRI Provides a Useful Biomarker for Evaluation of Radiotherapy Efficacy in Patients with Prostate Cancer.

Diffusion-weighted imaging (DWI) with measurement of apparent diffusion coefficient (ADC) allows for assessment of tumor aggressiveness. The objective of this study was to evaluate the changes of ADC value in prostate cancer after volumetric-modulated arc radiotherapy (VMAT) and to identify magnetic resonance imaging (MRI) biomarkers for monitoring tissue changes after radiotherapy. Thirty-seven patients with biopsy-proven prostate cancer treated with VMAT underwent serial MRI examinations including DWI before radiotherapy, and at 3 and 12 months after radiotherapy. ADC values of the tumor and healthy prostate tissue were measured and compared at these three time points. The tumor ADC value increased significantly 3 months after radiotherapy (p<0.0001). There was a further increase of tumor ADC from 3 to 12 months after radiotherapy (p<0.01). The ADC of healthy prostate tissue did not show any significant changes. The ADC value is a useful biomarker for evaluating the efficacy of radiotherapy in prostate cancer.

Modulation of water diffusion by activation-induced neural cell swelling in Aplysia Californica

Diffusion functional magnetic resonance imaging (DfMRI) has been proposed as a method for functional neuroimaging studies, as an alternative to blood oxygenation level dependent (BOLD)-fMRI. DfMRI is thought to more directly reflect neural activation, but its exact mechanism remains unclear. It has been hypothesized that the water apparent diffusion coefficient (ADC) decrease observed upon neural activation results from swelling of neurons or neuron parts. To elucidate the origin of the DfMRI response at cellular level we performed diffusion MR microscopy at 17.2 T in Aplysia californica buccal ganglia and compared the water ADCs at cellular and ganglia levels before and after neuronal activation induced by perfusion with a solution containing dopamine. Neural cell swelling, evidenced from optical microscopy imaging, resulted in an intracellular ADC increase and an ADC decrease at ganglia level. Furthermore, the intracellular ADC increase was found to have a significant positive correlation with the increase in cell size. Our results strongly support the hypothesis that the ADC decrease observed with DfMRI upon neuronal activation at tissue level reflects activation-induced neural cell swelling.

Age-related differences in the response of the L5-S1 intervertebral disc to spinal traction

BackgroundLumbar traction is a common treatment for low back pain; however its mechanisms of action are poorly understood. It has been hypothesized that a key effect of lumbar traction is its capacity to influence fluid movement within the intervertebral disc (IVD). ObjectivesTo determine differences in the apparent diffusion coefficient (ADC) obtained with lumbar diffusion-weighted imaging (DWI) of the L5-S1 IVD before, and during, the application of lumbar traction. DesignCase series, repeated measures. MethodsA static traction load of ∼50% of body-weight was applied to the low back using a novel “MRI-safe” apparatus. DWI of the lumbar spine was performed prior to, and during the application of the traction load. ResultsParticipants were currently asymptomatic and included a young adult group (n = 18) and a middle-aged group (n = 15). The young adult group had a non-significant 2.2% increase in ADC (mean change = 0.03 × 10−3 mm2/s, SD = 0.24, 95% CI = −0.09, 0.15). The ADC for the middle-aged group significantly increased by 20% (mean change of 0.18 × 10−3 mm2/s, SD = 0.19; 95% CI = 0.07, 0.28; p = 0.003; effect size = 0.95). There was an inverse relationship between the ADC obtained before traction and the percent increase in ADC that was measured during traction. ConclusionStatic traction was associated with an increase in diffusion of water within the L5-S1 IVDs of middle-age individuals, but not in young adults, suggesting age-related differences in the diffusion response. Further study is needed to assess the relationship between these findings and the symptoms of back pain. Level of evidence4.

Hyperpolarized gas diffusion MRI of biphasic lung inflation in short- and long-term emphysema models.

During lung inflation, airspace dimensions are affected nonlinearly by both alveolar expansion and recruitment, potentially confounding the identification of emphysematous lung by hyperpolarized helium-3 diffusion magnetic resonance imaging (HP MRI). This study aimed to characterize lung inflation over a broad range of inflation volume and pressure values in two different models of emphysema, as well as in normal lungs. Elastase-treated rats (n = 7) and healthy controls (n = 7) were imaged with HP MRI. Gradual inflation was achieved by incremental changes to both inflation volume and airway pressure. The apparent diffusion coefficient (ADC) was measured at each level of inflation and fitted to the corresponding airway pressures as the second-order response equation, with minimizing residue (χ2 < 0.001). A biphasic ADC response was detected, with an initial ADC increase followed by a decrease at airway pressures >18 cmH2O. Discrimination between treated and control rats was optimal when airway pressure was intermediate (between 10 and 11 cmH2O). Similar findings were confirmed in mice following long-term exposure to cigarette smoke, where optimal discrimination between treated and healthy mice occurred at a similar airway pressure as in the rats. We subsequently explored the evolution of ADC measured at the intermediate inflation level in mice after prolonged smoke exposure and found a significant increase (P < 0.01) in ADC over time. Our results demonstrate that measuring ADC at intermediate inflation enhances the distinction between healthy and diseased lungs, thereby establishing a model that may improve the diagnostic accuracy of future HP gas diffusion studies.

Water diffusion closely reveals neural activity status in rat brain loci affected by anesthesia.

Diffusion functional MRI (DfMRI) reveals neuronal activation even when neurovascular coupling is abolished, contrary to blood oxygenation level—dependent (BOLD) functional MRI (fMRI). Here, we show that the water apparent diffusion coefficient (ADC) derived from DfMRI increased in specific rat brain regions under anesthetic conditions, reflecting the decreased neuronal activity observed with local field potentials (LFPs), especially in regions involved in wakefulness. In contrast, BOLD signals showed nonspecific changes, reflecting systemic effects of the anesthesia on overall brain hemodynamics status. Electrical stimulation of the central medial thalamus nucleus (CM) exhibiting this anesthesia-induced ADC increase led the animals to transiently wake up. Infusion in the CM of furosemide, a specific neuronal swelling blocker, led the ADC to increase further locally, although LFP activity remained unchanged, and increased the current threshold awakening the animals under CM electrical stimulation. Oppositely, induction of cell swelling in the CM through infusion of a hypotonic solution (−80 milliosmole [mOsm] artificial cerebrospinal fluid [aCSF]) led to a local ADC decrease and a lower current threshold to wake up the animals. Strikingly, the local ADC changes produced by blocking or enhancing cell swelling in the CM were also mirrored remotely in areas functionally connected to the CM, such as the cingulate and somatosensory cortex. Together, those results strongly suggest that neuronal swelling is a significant mechanism underlying DfMRI.

Diffusion-weighted (DW) MRI in lung cancers: ADC test-retest repeatability.

To determine the test-retest repeatability of Apparent Diffusion Coefficient (ADC) measurements across institutions and MRI vendors, plus investigate the effect of post-processing methodology on measurement precision. Thirty malignant lung lesions >2cm in size (23 patients) were scanned on two occasions, using echo-planar-Diffusion-Weighted (DW)-MRI to derive whole-tumour ADC (b = 100, 500 and 800smm-2). Scanning was performed at 4 institutions (3 MRI vendors). Whole-tumour volumes-of-interest were copied from first visit onto second visit images and from one post-processing platform to an open-source platform, to assess ADC repeatability and cross-platform reproducibility. Whole-tumour ADC values ranged from 0.66-1.94x10-3mm2s-1 (mean = 1.14). Within-patient coefficient-of-variation (wCV) was 7.1% (95% CI 5.7-9.6%), limits-of-agreement (LoA) -18.0 to 21.9%. Lesions >3cm had improved repeatability: wCV 3.9% (95% CI 2.9-5.9%); and LoA -10.2 to 11.4%. Variability for lesions <3cm was 2.46 times higher. ADC reproducibility across different post-processing platforms was excellent: Pearson's R2 = 0.99; CoV 2.8% (95% CI 2.3-3.4%); and LoA -7.4 to 8.0%. A free-breathing DW-MRI protocol for imaging malignant lung tumours achieved satisfactory within-patient repeatability and was robust to changes in post-processing software, justifying its use in multi-centre trials. For response evaluation in individual patients, a change in ADC >21.9% will reflect treatment-related change. • In lung cancer, free-breathing DWI-MRI produces acceptable images with evaluable ADC measurement. • ADC repeatability coefficient-of-variation is 7.1% for lung tumours >2cm. • ADC repeatability coefficient-of-variation is 3.9% for lung tumours >3cm. • ADC measurement precision is unaffected by the post-processing software used. • In multicentre trials, 22% increase in ADC indicates positive treatment response.

PD55-01 DUTASTERIDE AND ACTIVE SURVEILLANCE IN PROSTATE CANCER: ARE VISIBLE LESIONS LESS CONSPICUOUS AT MAGNETIC RESONANCE IMAGING? A PILOT RANDOMIZED CONTROLLED TRIAL

You have accessJournal of UrologyProstate Cancer: Localized: Active Surveillance III1 Apr 2017PD55-01 DUTASTERIDE AND ACTIVE SURVEILLANCE IN PROSTATE CANCER: ARE VISIBLE LESIONS LESS CONSPICUOUS AT MAGNETIC RESONANCE IMAGING? A PILOT RANDOMIZED CONTROLLED TRIAL Francesco Giganti, Caroline Moore, Nicola Robertson, Alex Freeman, Mark Emberton, Clare Allen, and Alex Kirkham Francesco GigantiFrancesco Giganti More articles by this author , Caroline MooreCaroline Moore More articles by this author , Nicola RobertsonNicola Robertson More articles by this author , Alex FreemanAlex Freeman More articles by this author , Mark EmbertonMark Emberton More articles by this author , Clare AllenClare Allen More articles by this author , and Alex KirkhamAlex Kirkham More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.2424AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Dutasteride 0.5mg daily is licensed for lower urinary tract symptoms (LUTS) in men with an enlarged prostate, and some men on active surveillance will be taking dutasteride for LUTS. This study was designed to describe the effects of daily 0.5 mg dutasteride for 6 months, compared to placebo, on men with biopsy proven prostate cancer and an MR lesion at baseline. We report here the effect of dutasteride on the conspicuity of tumor on diffusion-weighted imaging (DWI) sequences to answer the question: does dutasteride make visible lesions less conspicuous on DWI? METHODS Institutional review board approval and patient informed consent were obtained. We retrospectively analyzed 37 men, randomized to 6 months of daily dutasteride 0.5 mg (n=18) or placebo (n=19), undergoing 3T multi-parametric Magnetic Resonance Imaging (mpMRI) scans at baseline and 6 months. Images were reviewed by 2 experienced uro-radiologists in consensus blind to treatment allocation and clinical information. Mean apparent diffusion coefficient (ADC) from DWI of peripheral (PZ) and transition (TZ) zones, and MR-suspicious lesions were compared between the dutasteride and placebo groups at baseline and 6 months (T test; p < 0.05 significant). We defined the term conspicuity as the mean ADC of the PZ divided by the mean ADC of the lesion. We assessed the change in conspicuity over 6 months and analyzed the differences in the dutasteride and placebo groups. RESULTS All men had at least one visible lesion at baseline and 6 months on DWI. There were no significant differences at 6 months for ADC values in the PZ, TZ and lesions between the two groups (placebo vs dutasteride). There was a significant decrease in mean conspicuity in the dutasteride group (1.54 at baseline vs 1.38 after 6 months; p = 0.025). Changes in mean absolute tumor ADC and conspicuity between the placebo and dutasteride groups were demonstrated (- 0.03 vs 0.08, p =0.033) and (0.11 vs - 0.16, p = 0.012), respectively. There was a significant percentage increase in tumor ADC and a significant decrease in the conspicuity for the dutasteride group when compared to men in the placebo group (8.6% vs - 2.3%, p = 0.048) and (- 9.9% vs 9.3, p = 0.013), respectively. CONCLUSIONS Dutasteride reduces tumor ADC and conspicuity. A lower biopsy threshold would make sense in men who are on dutasteride for LUTS and are undergoing MRI assessment for prostate cancer. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e1051 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Francesco Giganti More articles by this author Caroline Moore More articles by this author Nicola Robertson More articles by this author Alex Freeman More articles by this author Mark Emberton More articles by this author Clare Allen More articles by this author Alex Kirkham More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Predicting Treatment Response of Colorectal Cancer Liver Metastases to Conventional Lipiodol-Based Transarterial Chemoembolization Using Diffusion-Weighted MR Imaging: Value of Pretreatment Apparent Diffusion Coefficients (ADC) and ADC Changes Under Therapy.

To use absolute pretreatment apparent diffusion coefficients (ADC) derived from diffusion-weighted MR imaging (DWI) to predict response to repetitive cTACE for unresectable liver metastases of colorectal carcinoma (CRLM) at 1 and 3months after start of treatment. Fifty-five metastases in 34 patients were examined with DWI prior to treatment and 1 month after initial cTACE. Treatment was performed in 4-week intervals. Response was evaluated at 1 and 3months after start of therapy. Metastases showing a decrease of ≥30% in axial diameter were classified as responding lesions. One month after initial cTACE, seven lesions showed early response. There was no significant difference in absolute pretreatment ADC values between responding and non-responding lesions (p=0.94). Three months after initial cTACE, 17 metastases showed response. There was a significant difference (p=0.021) between absolute pretreatment ADC values of lesions showing response (median 1.08×10-3mm2/s) and no response (median 1.30×10-3mm2/s). Pretreatment ADC showed fair diagnostic value to predict response (AUC 0.7). Lesions showing response at 3months also revealed a significant increase in ADC between measurements before treatment and at one month after initial cTACE (p<0.001). Applying an increase in ADC of 12.17%, response at 3months after initial cTACE could be predicted with a sensitivity and specificity of 77 and 74%, respectively (AUC 0.817). Furthermore, there was a strong and significant correlation (r=0.651, p<0.001) between percentage change in size after third cTACE and percentage change in ADC. In patients with CRLM, ADC measurements are potential biomarkers for assessing response to cTACE.

Functional MRI for quantitative treatment response prediction in locally advanced rectal cancer.

Despite advances in multimodality treatment strategies for locally advanced rectal cancer and improvements in locoregional control, there is still a considerable variation in response to neoadjuvant chemoradiotherapy (CRT). Accurate prediction of response to neoadjuvant CRT would enable early stratification of management according to good responders and poor responders, in order to adapt treatment to improve therapeutic outcomes in rectal cancer. Clinical studies in diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE) MRI have shown promising results for the prediction of therapeutic response in rectal cancer. DWI allows for assessment of tumour cellularity. DCE-MRI enables evaluation of factors of the tumour microvascular environment and changes in perfusion in response to treatment. Studies have demonstrated that predictors of good response to CRT include lower tumour pre-CRT apparent diffusion coefficient (ADC), greater percentage increase in ADC during and post CRT, and higher pre-CRT Ktrans. However, the mean ADC and Ktrans values do not adequately reflect tumour heterogeneity. Multiparametric MRI using quantitative DWI and DCE-MRI in combination, and a histogram analysis technique can assess tumour heterogeneity and its response to treatment. This strategy has the potential to improve the accuracy of therapeutic response prediction in rectal cancer and warrants further investigation.

Diffusion radiomics analysis of intratumoral heterogeneity in a murine prostate cancer model following radiotherapy: Pixelwise correlation with histology.

To investigate the biological meaning of apparent diffusion coefficient (ADC) values in tumors following radiotherapy. Five mice bearing TRAMP-C1 tumor were half-irradiated with a dose of 15 Gy. Diffusion-weighted images, using multiple b-values from 0 to 3000 s/mm2 , were acquired at 7T on day 6. ADC values calculated by a two-point estimate and monoexponential fitting of signal decay were compared between the irradiated and nonirradiated regions of the tumor. Pixelwise ADC maps were correlated with histological metrics including nuclear counts, nuclear sizes, nuclear spaces, cytoplasmic spaces, and extracellular spaces. As compared with the nonirradiated region, the irradiated region exhibited significant increases in ADC, extracellular space, and nuclear size, and a significant decrease in nuclear counts (P < 0.001 for all). Optimal ADC to differentiate the irradiated from nonirradiated regions was achieved at a b-value of 800 s/mm2 by the two-point method and monoexponential curve fitting. ADC positively correlated with extracellular spaces (r = 0.74) and nuclear sizes (r = 0.72), and negatively correlated with nuclear counts (r = -0.82, P < 0.001 for all). As a radiomic biomarker, ADC maps correlating with histological metrics pixelwise could be a means of evaluating tumor heterogeneity and responses to radiotherapy. 1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:483-489.

Recent advances in magnetic resonance neuroimaging of lumbar nerve to clinical applications: A review of clinical studies utilizing Diffusion Tensor Imaging and Diffusion-weighted magnetic resonance neurography.

Much progress has been made in neuroimaging with Magnetic Resonance neurography and Diffusion Tensor Imaging (DTI) owing to higher magnetic fields and improvements in pulse sequence technology. Reports on lumbar nerve DTI have also increased considerably. Many studies have shown that the use of DTI in lumbar nerve lesions, such as lumbar foraminal stenosis and lumbar disc herniation, makes it possible to capture images of interruptions of tractography at stenotic sties, enabling the diagnosis of stenosis. DTI can also reveal significant decreases in fractional anisotropy (FA) with significant increases in apparent diffusion coefficient (ADC) values in compression lesions. FA values have higher accuracy than ADC values. Furthermore, strong correlations exist between FA values and indications of neurological severity, including the Japanese Orthopedic Association (JOA) score, the Oswestry Disability Index (ODI), and the Roland-Morris Disability Questionnaire (RDQ) in patients with lumbar disc herniation-induced radiculopathy. Most lumbar DTI has become 3T; 3T MRI has made it possible to take high-resolution DTI measurements in a short period of time. However, increased motion artifacts in the magnetic susceptibility effect lead to signal irregularities and image distortion. In the future, high-resolution DTI with reduced field-of-view may become useful in clinical applications, since visualization of nerve lesions and quantification of DTI parameters could allow more accurate diagnoses of lumbar nerve dysfunctions. Future translational studies will be necessary to successfully bring MR neuroimaging of lumbar nerve into clinical use.

Assessment of early treatment response to neoadjuvant chemotherapy in breast cancer using non-mono-exponential diffusion models: a feasibility study comparing the baseline and mid-treatment MRI examinations

ObjectivesTo assess the feasibility of the mono-exponential, bi-exponential and stretched-exponential models in evaluating response of breast tumours to neoadjuvant chemotherapy (NACT) at 3 T.MethodsThirty-six female patients (median age 53, range 32–75 years) with invasive breast cancer undergoing NACT were enrolled for diffusion-weighted MRI (DW-MRI) prior to the start of treatment. For assessment of early response, changes in parameters were evaluated on mid-treatment MRI in 22 patients. DW-MRI was performed using eight b values (0, 30, 60, 90, 120, 300, 600, 900 s/mm2). Apparent diffusion coefficient (ADC), tissue diffusion coefficient (Dt), vascular fraction (ƒ), distributed diffusion coefficient (DDC) and alpha (α) parameters were derived. Then t tests compared the baseline and changes in parameters between response groups. Repeatability was assessed at inter- and intraobserver levels.ResultsAll patients underwent baseline MRI whereas 22 lesions were available at mid-treatment. At pretreatment, mean diffusion coefficients demonstrated significant differences between groups (p < 0.05). At mid-treatment, percentage increase in ADC and DDC showed significant differences between responders (49 % and 43 %) and non-responders (21 % and 32 %) (p = 0.03, p = 0.04). Overall, stretched-exponential parameters showed excellent repeatability.ConclusionDW-MRI is sensitive to baseline and early treatment changes in breast cancer using non-mono-exponential models, and the stretched-exponential model can potentially monitor such changes.Key points• Baseline diffusion coefficients demonstrated significant differences between complete pathological responders and non-responders.• Increase in ADC and DDC at mid-treatment can discriminate responders and non-responders.• The ƒ fraction at mid-treatment decreased in responders whereas increased in non-responders.• The mono- and stretched-exponential models showed excellent inter- and intrarater repeatability.• Treatment effects can potentially be assessed by non-mono-exponential diffusion models.

DWI in Pediatric Small-Bowel Crohn Disease: Are Apparent Diffusion Coefficients Surrogates for Disease Activity in Patients Receiving Infliximab Therapy?

The purpose of this study was to determine prospectively whether bowel wall apparent diffusion coefficient (ADC) measurements can be used to monitor treatment response to infliximab therapy in the setting of pediatric small-bowel Crohn disease. Twenty-eight pediatric subjects with newly diagnosed biopsy-proven Crohn disease of the distal or terminal ileum treated with infliximab were enrolled. Subjects underwent MR enterography at baseline, 1 month after therapy, and 6 months after therapy. Imaging features were documented, including bowel wall ADC and arterial or enteric phase contrast-enhanced signal intensity normalized to that of unenhanced imaging. A linear mixed model assessed the relationship between ADC and time; patient age and sex and azathioprine combination therapy were covariates. The diagnostic performance (with 95% CIs) of an increase in bowel wall ADC of 20% or more for identifying response to infliximab was calculated using a decrease in normalized contrast-enhanced bowel wall signal intensity of 20% or more as the reference standard. Bowel wall ADC increased over time (mean [± SD], 1180 ± 200 × 10-6 mm2/s at baseline, 1420 ± 420 × 10-6 mm2/s at 1 month, and 1450 ± 450 × 10-6 mm2/s at 6 months; p = 0.0003); azathioprine therapy modulated this rate of change (p = 0.003). There was a statistically significant negative correlation between change in ADC and change in normalized contrast-enhanced signal intensity over time (ρ = -0.36; p < 0.001). The diagnostic performance of change in ADC for identifying response to infliximab therapy was sensitivity of 0.58 (95% CI, 0.34-0.80), specificity of 0.52 (95% CI, 0.31-0.72), positive predictive value of 0.48 (95% CI, 0.27-0.69), and negative predictive value of 0.62 (95% CI, 0.38-0.82). Bowel wall ADC increases over time in pediatric subjects receiving infliximab, but the diagnostic performance of ADC is likely insufficient for reliable treatment monitoring.

Electrochemical behavior of zirconium(IV) in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ionic liquid

Zirconium is a constituent of metallic fuel in a nuclear reactor. The electrochemical behavior of Zr(IV) in the room temperature ionic liquid, 1-butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl) imide (C4mimNTf2), was studied by various transient electrochemical techniques. The cyclic voltamogram of Zr(IV) in C4mimNTf2 consisted of a scant cathodic wave occurring at the potential of +0.2V(Vs Pd), due to the reduction of Zr(IV) to Zr(II), and a prominent reduction occurring at the onset of −1.3V (Vs Pd), due to Zr(II) to Zr(0). The metallic deposit was characterized by SEM-EDX and XRD analysis. A nucleation loop was observed at −1.6V (Vs Pd). The cathodic peak current increased and marginally shifted cathodically with the increase of scan rate. The apparent diffusion coefficient of Zr(IV) in C4mimNTf2 was determined to be 10−10cm2/s and a five-order increase in apparent diffusion coefficient (10−5cm2/s) was observed with the onset of nucleation at −1.6V (Vs Pd). The nucleation growth and decay of chronocurrent transient was fitted into instantaneous and progressive nucleation models. The nucleation phenomenon also altered the nature of chronopotentiogram of Zr(IV) with a drop from rest potential followed by increase in the potential of working electrode in the early part of the transient. The study indicated the possibility of electrodeposition of zirconium from C4mimNTf2 ionic liquid.

Value of diffusion-weighted imaging after transient taste stimulation in evaluation of salivary gland function before and after radiotherapy: a preliminary study

Objective To investigate the value of diffusion-weighted imaging (DWI) after transient taste stimulation in evaluating salivary gland function before and after radiotherapy (RT), as well as the correlation between apparent diffusion coefficient (ADC) and other evaluation methods. Methods A total of 30 patients with nasopharyngeal carcinoma (NPC) underwent dynamic DWI after taste stimulation before and after RT from 2010 to 2014. The characteristics of ADC changing curves for each salivary gland were analyzed. The paired t-test was used for comparison of the time to ADC peak, resting ADC, maximum ADC after stimulation, and maximum ADC increase rate. Pearson correlation analysis was used to investigate the correlation between ADC of the salivary gland and salivary flow rate, as well as the correlation of ADC of the salivary gland after RT with Common Terminology Criteria for Adverse Events (CTCAE) grade and visual analog scale (VAS) score. Results Before and after RT, ADCs of each salivary gland reached the peak value at the first scan after taste stimulation (30 s). The resting ADCs and maximum ADC after stimulation of each salivary gland increased significantly after RT (P=0.000, 0.000, 0.000 and 0.001.0.000, 0.000), while the maximum ADC increase rate after stimulation showed no significant differences between the salivary glands (P=0.213, 0.122, and 0.839). Before RT, the resting ADC of submandibular gland was positively correlated with salivary flow rate of all glands (r=0.364, P=0.048). Conclusions DWI after transient taste stimulation can effectively show the dynamic changes in ADCs of all salivary glands after RT for NPC and has a great potential in evaluating salivary hypofunction and dynamically monitoring functional changes of the salivary glands. Key words: Gustatory stimulation; Salivary glands; Diffusion weighted imaging; Magnetic resonance imaging; nasopharyngeal neoplasms/radiotherapy; Xerostomia

WE-FG-202-08: Assessment of Treatment Response Via Longitudinal Diffusion MRI On A MRI-Guided System: Initial Experience of Quantitative Analysis

Purpose: To report our initial experience of systematic monitoring treatment response using longitudinal diffusion MR images on a Co-60 MRI-guided radiotherapy system. Methods: Four patients, including 2 head-and-necks, 1 sarcoma and 1 GBM treated on a 0.35 Tesla MRI-guided treatment system, were analyzed. For each patient, 3D TrueFISP MRIs were acquired during CT simulation and before each treatment for treatment planning and patient setup purposes respectively. Additionally, 2D diffusion-weighted MR images (DWI) were acquired weekly throughout the treatment course. The gross target volume (GTV) and brainstem (as a reference structure) were delineated on weekly 3D TrueFISP MRIs to monitor anatomy changes, the contours were then transferred onto the corresponding DWI images after fusing with the weekly TrueFISP images. The patient-specific temporal and spatial variations during the entire treatment course, such as anatomic changes, target apparent diffusion coefficient (ADC) distribution were evaluated in a longitudinal pattern. Results: Routine MRI revealed progressive soft-tissue GTV volume changes (up to 53%) for the H&N cases during the treatment course of 5–7 weeks. Within the GTV, the mean ADC values varied from −44% (ADC decrease) to +26% (ADC increase) in a week. The gradual increase of ADC value was inversely associated with target volume variation for one H&N case. The maximal changes of mean ADC values within the brainstem were 5.3% for the H&N cases. For the large size sarcoma and GBM tumors, spatial heterogeneity and temporal variations were observed through longitudinal ADC analysis. Conclusion: In addition to the superior soft-tissue visualization, the 0.35T MR system on ViewRay showed the potential to quantitatively measure the ADC values for both tumor and normal tissues. For normal tissue that is minimally affected by radiation, its ADC values are reproducible. Tumor ADC values show temporal and spatial fluctuation that can be exploited for personalized adaptive therapy.