Diffusion-weighted Magnetic Resonance Imaging Technique Research Articles

Diffusion Weighted Magnetic Resonance Imaging of Spinal Cord Injuries After Instrumented Fusion Stabilization.

Diffusion-weighted magnetic resonance imaging (DW-MRI) is a promising technique for assessing spinal cord injury (SCI) that has historically been challenged by the presence of metallic stabilization hardware. This study leverages recent advances in metal-artifact resistant multi-spectral DW-MRI to enable diffusion quantification throughout the spinal cord even after fusion stabilization. Twelve participants with cervical spinal cord injuries treated with fusion stabilization and 49 asymptomatic able-bodied control participants underwent multi-spectral DW-MRI evaluation. Apparent diffusion coefficient (ADC) values were calculated in axial cord sections. Statistical modeling assessed ADC differences across cohorts and within distinct cord regions of the SCI participants (at, above, or below injured level). Computed models accounted for subject demographics and injury characteristics. ADC was found to be elevated at injured levels compared with non-injured levels (z = 3.2, p = 0.001), with ADC at injured levels decreasing over time since injury (z = -9.2, p < 0.001). Below the injury level, ADC was reduced relative to controls (z = -4.4, p < 0.001), with greater reductions after more severe injuries that correlated with lower extremity motor scores (z = 2.56, p = 0.012). No statistically significant differences in ADC above the level of injury were identified. By enabling diffusion analysis near fusion hardware, the multi-spectral DW-MRI technique allowed intuitive quantification of cord diffusion changes after SCI both at and away from injured levels. This demonstrates the approach's potential for assessing post-surgical spinal cord integrity throughout stabilized regions.

Development and validation of cardiac diffusion weighted magnetic resonance imaging for the diagnosis of myocardial injury in small animal models

Cardiac diffusion weighted-magnetic resonance imaging (DWI) has slowly developed due to its technical difficulties. However, this limitation could be overcome by advanced techniques, including a stimulated echo technique and a gradient moment nulling technique. This study aimed to develop and validate a high-order DWI sequence, using echo-planar imaging (EPI) and second-order motion-compensated (M012) diffusion gradient applied to cardiac imaging in small-sized animals with fast heart and respiratory rates, and to investigate the feasibility of cardiac DWI, diagnosing acute myocardial injury in isoproterenol-induced myocardial injury rat models. The M012 diffusion gradient sequence was designed for diffusion tensor imaging of the rat myocardium and validated in the polyvinylpyrrolidone phantom. Following sequence optimization, 23 rats with isoproterenol-induced acute myocardial injury and five healthy control rats underwent cardiac MRI, including cine imaging, T1 mapping, and DWI. Diffusion gradient was applied using a 9.4-T MRI scanner (Bruker, BioSpec 94/20, gradient amplitude = 440 mT/m, maximum slew rate = 3440 T/m/s) with double gating (electrocardiogram and respiratory gating). Troponin I was used as a serum biomarker for myocardial injury. Histopathologic examination of the heart was subsequently performed. The developed DWI sequence using EPI and M012 provided the interpretable images of rat hearts. The apparent diffusion coefficient (ADC) values were significantly higher in rats with acute myocardial injury than in the control group (1.847 ± 0.326 * 10–3 mm2/s vs. 1.578 ± 0.144 * 10–3 mm2/s, P < 0.001). Troponin I levels were increased in the blood samples of rats with acute myocardial injury (P < 0.001). Histopathologic examinations detected myocardial damage and subendocardial fibrosis in rats with acute myocardial injury. The newly developed DWI technique has the ability to detect myocardial injury in small animal models, representing high ADC values on the myocardium with isoproterenol-induced injury.

Advanced Diffusion-Weighted MRI for Cancer Microstructure Assessment in Body Imaging, and Its Relationship With Histology.

Diffusion-weighted magnetic resonance imaging (DW-MRI) aims to disentangle multiple biological signal sources in each imaging voxel, enabling the computation of innovative maps of tissue microstructure. DW-MRI model development has been dominated by brain applications. More recently, advanced methods with high fidelity to histology are gaining momentum in other contexts, for example, in oncological applications of body imaging, where new biomarkers are urgently needed. The objective of this article is to review the state-of-the-art of DW-MRI in body imaging (ie, not including the nervous system) in oncology, and to analyze its value as compared to reference colocalized histology measurements, given that demonstrating the histological validity of any new DW-MRI method is essential. In this article, we review the current landscape of DW-MRI techniques that extend standard apparent diffusion coefficient (ADC), describing their acquisition protocols, signal models, fitting settings, microstructural parameters, and relationship with histology. Preclinical, clinical, and in/ex vivo studies were included. The most used techniques were intravoxel incoherent motion (IVIM; 36.3% of used techniques), diffusion kurtosis imaging (DKI; 16.7%), vascular, extracellular, and restricted diffusion for cytometry in tumors (VERDICT; 13.3%), and imaging microstructural parameters using limited spectrally edited diffusion (IMPULSED; 11.7%). Another notable category of techniques relates to innovative b-tensor diffusion encoding or joint diffusion-relaxometry. The reviewed approaches provide histologically meaningful indices of cancer microstructure (eg, vascularization/cellularity) which, while not necessarily accurate numerically, may still provide useful sensitivity to microscopic pathological processes. Future work of the community should focus on improving the inter-/intra-scanner robustness, and on assessing histological validity in broader contexts. LEVEL OF EVIDENCE: NA TECHNICAL EFFICACY: Stage 2.

Value of diffusion MRI versus [18F]FDG PET/CT in detection of cervical nodal metastases in differentiated thyroid cancer patients.

In differentiated thyroid cancer (DTC) patients, cervical nodal metastasis is a negative prognostic factor. Preoperative imaging plays an important role in treatment planning for nodal metastasis and recurrence. The aim of the study is to compare the diagnostic performance of the diffusion-weighted magnetic resonance imaging (DW-MRI) and the F-18 flurodeoxyglucose positron emission computed tomography ([18F]FDG PET/CT) in detection of cervical nodal deposits in DTC patients. The study was conducted on 30 patients, each performed both modalities just before the surgery. The gold standard was the pathological specimens with post-operative clinico-radiological follow-up, to assess the diagnostic performance of each modality. Based on pathological and post-operative clinico-radiological follow up data. Sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV) and accuracy were 84%, 80%, 50%, 95% and 83% for PET/CT compared to 84%, 60%, 42.8%, 91.3% and 80% for DW-MRI. On comparing the diagnostic performance of combined DW-MRI and PET/CT to each modality alone, the sensitivity and NPV were improved to 96% and 80% respectively. [18F]FDG PET/CT study is a valuable diagnostic modality for the assessment of cervical nodal deposits in DTC patients, surpassing DW-MRI. Combined PET/CT and DW-MRI techniques seemed to have synergistic performance, mainly in terms of sensitivity and NPV, for detection of nodal metastases.

Diffusion-weighted imaging and diffusion tensor imaging of the heart in vivo: major developments.

Diffusion-weighted magnetic resonance imaging (DWI) is a powerful diagnostic tool. Contrast in DWI images is dictated by the differences in diffusion of water in tissues, which depends on the tissue type, hydration and fluid composition. Therefore DWI can differentiate between hard and soft tissues, as well as visualize their condition, such as edema, necrosis or fibrosis. Diffusion tensor imaging (DTI) is a DWI technique which additionally delivers information about the microstructure. In cardiovascular applications DWI/DTI can non-invasively characterize the acute to chronic phase of the area at risk and microstructural dynamics without the need to use contrast agents. However, cardiac DWI/DTI differs from other applications due to serious anatomic and technologic challenges. Over the years, scientists have stepped up overcoming more and more advanced obstacles associated with complex 3D myocardial motions, breathing, blood flow and perfusion. The aim of this article is to review milestone technologic advances in DWI/DTI of the heart in vivo. The discussed development begins with the adjustment of the diffusion imaging block to the electrocardiogram-based most quiescent phase, next considers different pulse sequence designs for first-, second- and higher-order motion compensation and SNR improvement, and ends up with prospects for further developments. Reviewed papers show great progress in this research area, but the gap between the scientific development and common clinical practice is tremendous. Cardiac DWI/DTI has promising clinical relevance and its addition to routine imaging techniques of patients with heart disease may empower clinical diagnosis.

ASSOCIATION BETWEEN APPARENT DIFFUSION COEFFICIENT AND KI67 IN BRAIN TUMORS: A SYSTEMATIC REVIEW

Certain histological variants of tumors have a correlation between the values of the apparent diffusion coefficients (AdC), cell density and the proliferative activity index MIB-I (Ki67). The results of studies on the relationship between the values of the AdC and the Ki67 index in brain tumors are ambiguous and largely contradictory. The purpose of this study was to perform a systematic review based on the results of clinical studies that examined the relationship between AdC values and the Ki67 proliferative activity index in brain tumors. Material and Methods . Clinical studies were searched in the databases pubmed, EMBASE, Cohrane Library and eLibrary published from January 2000 to January 2020, which studied the relationship between AdC values and the Ki67 proliferative activity index in brain tumors. Results . A systematic review included 17 retrospective cohort nonrandomized clinical studies. The average value of the coefficient of reliable correlation between AdC and the mitotic index Ki67 in the group of meningiomas was -0.493. The indicated dependence was more often found in groups of typical (MI) and atypical (MII) brain meningiomas. The average coefficient of statistically significant correlation between the studied parameters in the group of brain gliomas was -0.443. The relationship between the AdC values and the Ki67 proliferative activity index was observed both in the glioma group of low (GI–II) and high (GIII–IV) grade of malignancy. In groups of patients with pituitary adenomas, primary lymphomas and brain metastases, the relationship between the studied parameters was not reliably confirmed. Conclusion. The use of diffusion-weighted magnetic resonance imaging techniques with subsequent calculation of AdC values can be recommended for use in the clinical practice of oncologists in order to assess the proliferative potential of brain meningiomas and gliomas.

The role of novel motor unit magnetic resonance imaging to investigate motor unit activity in ageing skeletal muscle.

Sarcopenia is a progressive and generalized disease, more common in older adults, which manifests as a loss of muscle strength and mass. The pathophysiology of sarcopenia is still poorly understood with many mechanisms suggested. Age associated changes to the neuromuscular architecture, including motor units and their constituent muscle fibres, represent one such mechanism. Electromyography can be used to distinguish between different myopathies and produce counts of motor units. Evidence from electromyography studies suggests that with age, there is a loss of motor units, increases to the sizes of remaining units, and changes to their activity patterns. However, electromyography is invasive, can be uncomfortable, does not reveal the exact spatial position of motor units within muscle and is difficult to perform in deep muscles. We present a novel diffusion‐weighted magnetic resonance imaging technique called ‘motor unit magnetic resonance imaging (MUMRI)’. MUMRI aims to improve our understanding of the changes to the neuromuscular system associated with ageing, sarcopenia and other neuromuscular diseases. To date, we have demonstrated that MUMRI can be used to detect statistically significant differences in fasciculation rate of motor units between (n = 4) patients with amyotrophic lateral sclerosis (mean age ± SD: 53 ± 15) and a group of (n = 4) healthy controls (38 ± 7). Patients had significantly higher rates of fasciculation compared with healthy controls (mean = 99.1/min, range = 25.7–161.0 in patients vs. 7.7/min, range = 4.3–9.7 in controls; P < 0.05. MUMRI has detected differences in size, shape, and distribution of single human motor units between (n = 5) young healthy volunteers (29 ± 2.2) and (n = 5) healthy older volunteers (65.6 ± 14.8). The maximum size of motor unit territories in the older group was 12.4 ± 3.3 mm and 9.7 ± 2.7 mm in the young group; P < 0.05. MUMRI is an entirely non‐invasive tool, which can be used to detect physiological and pathological changes to motor units in neuromuscular diseases. MUMRI also has the potential to be used as an intermediate outcome measure in sarcopenia trials.

Diffusion-weighted Renal MRI at 9.4\u2009Tesla Using RARE to Improve Anatomical Integrity

Diffusion-weighted magnetic resonance imaging (DWI) is a non-invasive imaging technique sensitive to tissue water movement. By enabling a discrimination between tissue properties without the need of contrast agent administration, DWI is invaluable for probing tissue microstructure in kidney diseases. DWI studies commonly make use of single-shot Echo-Planar Imaging (ss-EPI) techniques that are prone to suffering from geometric distortion. The goal of the present study was to develop a robust DWI technique tailored for preclinical magnetic resonance imaging (MRI) studies that is free of distortion and sensitive to detect microstructural changes. Since fast spin-echo imaging techniques are less susceptible to B0 inhomogeneity related image distortions, we introduced a diffusion sensitization to a split-echo Rapid Acquisition with Relaxation Enhancement (RARE) technique for high field preclinical DWI at 9.4 T. Validation studies in standard liquids provided diffusion coefficients consistent with reported values from the literature. Split-echo RARE outperformed conventional ss-EPI, with ss-EPI showing a 3.5-times larger border displacement (2.60 vs. 0.75) and a 60% higher intra-subject variability (cortex = 74%, outer medulla = 62% and inner medulla = 44%). The anatomical integrity provided by the split-echo RARE DWI technique is an essential component of parametric imaging on the way towards robust renal tissue characterization, especially during kidney disease.

Diffusion MRI in acute nervous system injury

Diffusion weighted magnetic resonance imaging (DWI) and related techniques such as diffusion tensor imaging (DTI) are uniquely sensitive to the microstructure of the brain and spinal cord. In the acute aftermath of nervous system injury, for example, DWI reveals changes caused by injury that remains invisible on other MRI contrasts such as T2-weighted imaging. This ability has led to a demonstrated clinical utility in cerebral ischemia. However, despite strong promise in preclinical models and research settings, DWI has not been as readily adopted for other acute injuries such as traumatic spinal cord, brain, or peripheral nerve injury. Furthermore, the precise biophysical mechanisms that underlie DWI and DTI changes are not fully understood. In this report, we review the DWI and DTI changes that occur in acute neurological injury of cerebral ischemia, spinal cord injury, traumatic brain injury, and peripheral nerve injury. Their associations with the underlying biology are examined with an emphasis on the role of acute axon and dendrite beading. Lastly, emerging DWI techniques to overcome the limitations of DTI are discussed as these may offer the needed improvements to translate to clinical settings.

Diagnostic power of diffusion-weighted magnetic resonance imaging for the presence of lymph node metastasis: A meta-analysis

Present work was designed to quantitatively evaluate the performance of diffusion-weighted magnetic resonance imaging (DWI) in the diagnosis of the presence of metastasis in lymph nodes (LNs). Eligible studies were identified from systematical PubMed and EMBASE searches. Data were extracted. Meta-analyses were performed to generate pooled sensitivity and specificity on the basis of per-node, per-lesion and per-patient, respectively. Fourteen publications (2458 LNs, 404 lesions and 334 patients) were eligible. Per-node basis demonstrated the pooled sensitivity and specificity was 0.82 (P<0.0001) and 0.90 (P<0.0001), respectively. Per-lesion basis illustrated the pooled sensitivity and specificity was 0.73 (P=0.0036) and 0.85 (P<0.0001), respectively. Per-patient basis indicated the pooled sensitivity and specificity was 0.67 (P=0.0909) and 0.86 (P<0.0001), respectively. In conclusion, DWI has rather a negative predictive value for the diagnosis of LN metastasis presence. The difference of the mean apparent diffusion coefficients between benign and malignant LNs is not yet stable. Therefore, the DWI technique has to be further improved.

Application of neurite orientation dispersion and density imaging or diffusion tensor imaging to quantify the severity of cervical spondylotic myelopathy and to assess postoperative neurologic recovery

Background ContextSurgical outcome and the severity of cervical spondylotic myelopathy (CSM) are unpredictable and cannot be estimated by conventional anatomical magnetic resonance imaging (MRI). The utility of diffusion tensor imaging (DTI) to quantify the severity of CSM and to assess postoperative neurologic recovery has been investigated. However, whether conventional DTI should be applied in a clinical setting remains controversial. Neurite orientation dispersion and density imaging (NODDI) is a recently introduced model-based diffusion-weighted MRI technique that quantifies specific microstructural features related directly to neuronal morphology. However, there are as yet few clinical applications of NODDI reported. Indeed, there are no reports to indicate NODDI is useful for diagnosing CSM. Study DesignThis is a retrospective cohort study using consecutive patients. PurposeThe objective of this study was to evaluate the utility of NODDI and conventional DTI for detecting changes in the spinal cord microstructure. In particular, this study aimed to quantify the preoperative severity of CSM and to assess postoperative neurologic recovery from this myelopathy. Patient SampleWe included 27 consecutive patients with a nontraumatic cervical lesion from CSM who underwent laminoplasty at a single institution between April 2012 and April 2015. The patients underwent MRI before and approximately 2 weeks after surgery. Outcome MeasuresIn addition to conventional DTI metrics, we evaluated the intracellular volume fraction (ICVF) and the orientation dispersion index (ODI), which are metrics derived from NODDI. The 10-second grip and release test and the Japanese Orthopaedic Association scoring system were used before and 1 year after surgery to assess neurologic outcome. Materials and MethodsNeurite orientation dispersion and density imaging and conventional DTI values were measured at the C2–C3 intervertebral level (control value) and at the most compressed levels (C3–C7 intervertebral levels) were measured. The changes in these values pre- and postoperative were demonstrated. Correlations between NODDI and conventional DTI values and clinical outcome were determined. ResultsPreoperative fractional anisotropy was significantly correlated with the severity of neural damage, but not with postoperative neurologic recovery. No significant correlation could be found between the preoperative ICVF, the ODI, the apparent diffusion coefficient, and the severity of the preoperative neurologic dysfunction. Preoperative ICVF was most strongly correlated with the severity of neurologic dysfunction and postoperative neurologic recovery. ConclusionsConventional DTI may be applied clinically to assess the severity of myelopathy. Neurite orientation dispersion and density imaging may be more valuable than conventional DTI to predict outcome following surgery in patients with CSM.

Diffusion weighted imaging of the prostate—principles, application, and advances

This review article aims to provide an overview on the principles of diffusion-weighted magnetic resonance imaging (DW-MRI) and its applications in the imaging of the prostate. DW-MRI with regards to different applications for prostate cancer (PCa) detection and characterization, local staging as well as for active surveillance (AS) and tumor recurrence after radical prostatectomy (RP) will be discussed. Furthermore, advances in DW-MRI techniques like diffusion kurtosis imaging (DKI) will be presented.

Deficits in Neurite Density Underlie White Matter Structure Abnormalities in First-Episode Psychosis

BackgroundStructural abnormalities across multiple white matter tracts are recognized in people with early psychosis, consistent with dysconnectivity as a neuropathological account of symptom expression. We applied advanced neuroimaging techniques to characterize microstructural white matter abnormalities for a deeper understanding of the developmental etiology of psychosis. MethodsThirty-five first-episode psychosis patients, and 19 healthy controls, participated in a quantitative neuroimaging study using neurite orientation dispersion and density imaging, a multishell diffusion-weighted magnetic resonance imaging technique that distinguishes white matter fiber arrangement and geometry from changes in neurite density. Fractional anisotropy (FA) and mean diffusivity images were also derived. Tract-based spatial statistics compared white matter structure between patients and control subjects and tested associations with age, symptom severity, and medication. ResultsPatients with first-episode psychosis had lower regional FA in multiple commissural, corticospinal, and association tracts. These abnormalities predominantly colocalized with regions of reduced neurite density, rather than aberrant fiber bundle arrangement (orientation dispersion index). There was no direct relationship with active symptoms. FA decreased and orientation dispersion index increased with age in patients, but not control subjects, suggesting accelerated effects of white matter geometry change. ConclusionsDeficits in neurite density appear fundamental to abnormalities in white matter integrity in early psychosis. In the first application of neurite orientation dispersion and density imaging in psychosis, we found that processes compromising axonal fiber number, density, and myelination, rather than processes leading to spatial disruption of fiber organization, are implicated in the etiology of psychosis. This accords with a neurodevelopmental origin of aberrant brain-wide structural connectivity predisposing individuals to psychosis.

Intravoxel Incoherent Motion Imaging in Small Vessel Disease: Microstructural Integrity and Microvascular Perfusion Related to Cognition.

Cerebral small vessel disease (SVD) is associated with cognitive impairment. This may be because of decreased microstructural integrity and microvascular perfusion, but data on these relationships are scarce. We determined the relationship between cognition and microvascular perfusion and microstructural integrity in SVD patients, using intravoxel incoherent motion imaging-a diffusion-weighted magnetic resonance imaging technique designed to determine microvascular perfusion and microstructural integrity simultaneously. Seventy-three patients with SVD and 39 controls underwent intravoxel incoherent motion imaging and neuropsychological assessment. Parenchymal diffusivity D (a surrogate measure of microstructural integrity) and perfusion-related measure fD* were calculated for the normal appearing white matter, white matter hyperintensities, and cortical gray matter. The associations between cognitive performance and D and fD* were determined. In SVD patients, multivariable analysis showed that lower fD* in the normal appearing white matter and cortical gray matter was associated with lower overall cognition (P=0.03 and P=0.002, respectively), lower executive function (P=0.04 and P=0.01, respectively), and lower information-processing speed (P=0.04 and P=0.01, respectively). D was not associated with cognitive function. In controls, no association was found between D, fD*, and cognition. In SVD patients, lower cognitive performance is associated with lower microvascular perfusion in the normal appearing white matter and cortical gray matter. Our results support recent findings that both cortical gray matter and normal appearing white matter perfusion may play a role in the pathophysiology of cognitive dysfunction in SVD. URL: http://www.trialregister.nl. Unique identifier: NTR3786.

Four-dimensional diffusion-weighted MR imaging (4D-DWI): a feasibility study.

Diffusion-weighted Magnetic Resonance Imaging (DWI) has been shown to be a powerful tool for cancer detection with high tumor-to-tissue contrast. This study aims to investigate the feasibility of developing a four-dimensional DWI technique (4D-DWI) for imaging respiratory motion for radiation therapy applications. Image acquisition was performed by repeatedly imaging a volume of interest (VOI) using an interleaved multislice single-shot echo-planar imaging (EPI) 2D-DWI sequence in the axial plane. Each 2D-DWI image was acquired with an intermediately low b-value (b=500s/mm2 ) and with diffusion-encoding gradients in x, y, and z diffusion directions. Respiratory motion was simultaneously recorded using a respiratory bellow, and the synchronized respiratory signal was used to retrospectively sort the 2D images to generate 4D-DWI. Cine MRI using steady-state free precession was also acquired as a motion reference. As a preliminary feasibility study, this technique was implemented on a 4D digital human phantom (XCAT) with a simulated pancreas tumor. The respiratory motion of the phantom was controlled by regular sinusoidal motion profile. 4D-DWI tumor motion trajectories were extracted and compared with the input breathing curve. The mean absolute amplitude differences (D) were calculated in superior-inferior (SI) direction and anterior-posterior (AP) direction. The technique was then evaluated on two healthy volunteers. Finally, the effects of 4D-DWI on apparent diffusion coefficient (ADC) measurements were investigated for hypothetical heterogeneous tumors via simulations. Tumor trajectories extracted from XCAT 4D-DWI were consistent with the input signal: the average D value was 1.9mm (SI) and 0.4mm (AP). The average D value was 2.6mm (SI) and 1.7mm (AP) for the two healthy volunteers. A 4D-DWI technique has been developed and evaluated on digital phantom and human subjects. 4D-DWI can lead to more accurate respiratory motion measurement. This has a great potential to improve the visualization and delineation of cancer tumors for radiotherapy.

Grading of Glioma Tumors by Analysis of Minimum Apparent Diffusion Coefficient and Maximum Relative Cerebral Blood Volume

Article type: Original Article Background: Gliomas are the most common primary neoplasms of the central nervous system. Relative cerebral blood volume (rCBV) could estimate high-grade Gliomas computed with dynamic susceptibility contrast MR imaging which it is artificially lowered by contrast extravasation through a disrupted blood-brain barrier. Objectives: Our intent was to clarify the usefulness of diffusion-weighted magnetic resonance imaging (DWI) and perfusion weighted magnetic resonance imaging (PWI) in the grading of Gliomas. Materials and Methods: Both PWI and DWI with a three-tesla scanner investigated nineteen consecutive patients with Gliomas. The means of rCBV and ADC values have been compared among the tumor groups with t-test and ROC curve analysis to determine threshold values of Gliomas grading. Results: Mean maximum rCBV were 2.71±1.41 for low grades (I & II), and 8.14±2.58 for high grades (III & IV) Gliomas (p=0.001). Mean minimum ADC were 1.47±.46 ×10 3 mm 2 /s for low grades (I & II), and .47±.38×10 3 mm 2 /s for high grades (III & IV) Gliomas (p=0.001). We can get 0.94×10 3 mm 2 /s for minimum ADC and 3.85 for maximum rCBV as a difference cutoff point between low and high-grade Gliomas. Conclusion: Combination of both DWI and PWI techniques, with measurement of minimum ADC and maximum rCBV can be used to distinguish between high grade and low-grade Glioma tumors.

Does Diffusion-Weighted MR Imaging Change the Follow-Up Strategy in Cases with Residual Cholesteatoma?

To analyze the effectiveness of diffusion-weighted magnetic resonance imaging (DW-MRI) in the evaluation of recurrent cholesteatomas. Twenty-three patients undergoing second-look surgery were included in our study. There were 14 men and 9 women with ages ranging from 10 to 50. All patients underwent DW-MRI prior to second-look surgery. All magnetic resonance imaging (MRI) examinations were performed with a 1.5-T MRI unit using a standard 8-channel neurovascular coil. DW-MRI and apparent diffusion coefficient maps were included in the examination. Cholesteatoma was diagnosed on the DW-MRI as a marked hyperintense signal in comparison with brain tissue. All cases were classified as positive or negative. The sensitivity and specificity of DW-MRI were 86% and 87%, respectively. The positive predictive value of DW-MRI was 92%, while the negative predictive value was 77%. The DW-MRI technique is an important and effective technique in the evaluation of residual cholesteatoma. It can be an alternative method to second-look surgery, which can spare patients repeat operations.

Updates in advanced diffusion-weighted magnetic resonance imaging techniques in the evaluation of prostate cancer.

Diffusion-weighted magnetic resonance imaging (DW-MRI) is considered part of the standard imaging protocol for the evaluation of patients with prostate cancer. It has been proven valuable as a functional tool for qualitative and quantitative analysis of prostate cancer beyond anatomical MRI sequences such as T2-weighted imaging. This review discusses ongoing controversies in DW-MRI acquisition, including the optimal number of b-values to be used for prostate DWI, and summarizes the current literature on the use of advanced DW-MRI techniques. These include intravoxel incoherent motion imaging, which better accounts for the non-mono-exponential behavior of the apparent diffusion coefficient as a function of b-value and the influence of perfusion at low b-values. Another technique is diffusion kurtosis imaging (DKI). Metrics from DKI reflect excess kurtosis of tissues, representing its deviation from Gaussian diffusion behavior. Preliminary results suggest that DKI findings may have more value than findings from conventional DW-MRI for the assessment of prostate cancer.

Diffusion-weighted magnetic resonance imaging for the diagnosis of patients with lumbar nerve root entrapment syndromes: results from a pilot study.

Lumbar nerve root entrapment syndromes cause radicular signs and symptoms in the affected leg. The applicability of diffusion-weighted imaging (DWI) for the assessment of lower lumbar nerves (L4-S1) has been demonstrated. The purpose of this pilot study was to establish DWI reference data for the all lumbosacral nerve roots (L1-S1) in a healthy, asymptomatic study population and to determine its potential as a diagnostic tool for patients with lumbar radicular syndromes. 20 asymptomatic healthy volunteers were included (average age 39 years (24-59 years; n = 10 female, n = 10 male). The lumbosacral spine was scanned twice in a standardized fashion (1.5 T Magnetom Avanto and 3 T Magnetom Skyra, Siemens AG Healthcare, Erlangen, Germany). A spin-echo type echo-planar (SE-EPI) sequence was used to determine axial ADC maps and measurements (length, width, and angulation) of the dorsal root ganglion (DRG) and distal spinal nerves (DSN). Disc pathology, lumbar foraminal stenosis and nerve root compromise were classified. Using 3 T images 218 (91%) lumbar nerve roots had no pathologic finding [1.5 T: 226 (94%)]. All DRG and DSN could be visualized and identified on axial apparent diffusion coefficient (ADC). On average we measured ADC values of 1,231 mm(2)/s (SD 308 mm(2)/s) at the DRG for the 1.5 T scanner and 1,756 mm(2)/s (SD 465 mm(2)/s) for the 3 T scanner. There were no statistically significant gender or side differences in the 1.5 and 3 T images (p > 0.05). We noted an increase of the ADC values starting from cranial (L1: 1,444 mm(2)/s) to caudal (S1: 1,918 mm(2)/s). The average ADC value at the DSN was 1,018 mm(2)/s for the 1.5 T scanner compared to 1,589 mm(2)/s for the 3 T scanner (p < 0.001). For the first time, we have established data for the DRG and DSN in human lumbosacral spinal nerves (L1-S1), using diffusion-weighted magnetic resonance imaging techniques. 3 T ADC maps have a higher signal to noise ratio, thus offering better image quality. Results from this study suggest that DWI has added value as new diagnostic tools for patients with symptomatic lumbar nerve root entrapment syndromes as well.

Comparison of the results of computerized tomographic and diffusion-weighted magnetic resonance imaging techniques in inflammatory bowel diseases.

To compare the findings obtained by computerised tomography (CT) enterography, which uses oral neutral contrast material and non-contrasted diffusion-weighted magnetic resonance imaging (DW-MRI) technique and reveal the diagnostic value of DW-MRI in patients with inflammatory bowel diseases. Patients with established or clinically suspect diagnosis of inflammatory bowel disease were included in the study. CT enterography and DW-MRI obtained from the patients were evaluated by a radiologist blinded to the endoscopic and/or histopathological results. Duodenum, jejunum, ileal loops, ascending, transverse, descending colon, sigmoid colon and rectum were evaluated in that order as for general imaging quality, luminal distension and adequate visualization of the intestinal wall. Image qualities of neutral contrast CT-enterography and DW-MRI were compared. The study included 31 patients. Based on statistical analyses, the best correlation between the results of CT-enterography and diffusion-weighted imaging (DWI) were observed in the evaluation of transverse colon, ileum and duodenum in order of decreasing frequency and with an almost perfect compatibility. Radiological findings of sigmoid colon, jejunum and descending colon were completely compatible. However, a moderate degree of compatibility was estimated between radiological findings of rectum and cecum. Though conventional enteroclysis is the gold standard method among radiological imaging techniques used for the evaluation of inflammatory small intestinal abnormalities, CT enterography and DW-MRI are alternative methods that can be used effectively to obtain useful information.