Diffusion Weighted MRI

ABSTRACT MRI allows optimal characterization of normal and pathological soft tissues of the female pelvis through the use of standard morphological T1W and T2W sequences, fat-suppression techniques and perfusion and diffusion weighted sequences.

Accurate radiographic diagnosis is a cornerstone of the clinical management and outcome prediction of the head-injured patient. New technological advances, such as multidetector computed tomography (MDCT) scanning and diffusionweighted magnetic resonance imaging (MRI) have influenced imaging strategy. In this article we review the impact of these developments on the neuroradiological diagnosis of acute head injury. In the acute phase, multidetector CT has supplanted plain X-ray films of the skull as the initial imaging study of choice. MRI, including fluid-attenuated inversion recovery, gradient echo T2* and diffusion-weighted sequences, is useful in determining the severity of acute brain tissue injury and may help to predict outcome. The role of MRI in showing diffuse axonal injuries is emphasized. We review the different patterns of primary and secondary extra-axial and intra-axial traumatic brain lesions and integrate new insights. Assessment of intracranial hypertension and cerebral herniation are of major clinical importance in patient management. We discuss the issue of pediatric brain trauma and stress the importance of MRI in non-accidental injury. In summary, new developments in imaging technology have advanced our understanding of the pathophysiology of brain trauma and contribute to improving the survival of patients with craniocerebral injuries.

Purpose. Our aim was to assess the overall diagnostic accuracy of magnetic resonance diffusion-weighted whole-body imaging with background signal suppression (MR-DWIBS) compared with ([ 18 F]-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT), considered the reference standard of whole-body tumour imaging modalities, in a series of consecutive patients with malignant tumour. Materials and methods. Thirty-eight patients diagnosed with a malignant tumour over a 4-month period were enrolled in this retrospective, observational study. PET/CT and MR-DWIBS images were reviewed in double-blind manner by a nuclear medicine physician and radiologists with 4 years experience. Lesion size, standard uptake value (SUV) and apparent diffusion coefficient (ADC) were measured and calculated for each lesion. Results. The qualitative analysis of MR-DWIBS and [ 18 F]-FDG-PET/CT showed that two patients were negative at both techniques. MR-DWIBS was positive in 36 patients, 34 of whom were positive and two negative at [ 18 F]-FDG-PET/CT, respectively. Two hundred and fiftyfive lesions were identified by MR-DWIBS and 184 by [ 18 F]-FDG-PET/CT, which was a significative discordance. Correlation between SUV and ADC of lesions positive at both techniques was not statistically significant. The mean difference between lesion size in [ 18 F]-FDG-PET/ Riassunto Obiettivo. L'obiettivo del nostro lavoro è stato stabilire il valore di accuratezza diagnostica della whole-body risonanza magnetica (RM)-diffusion weighted whole body imaging with background signal suppression (DWIBS) rispetto alla 18 F-fluor-deossiglucosio (FDG)-tomografia a emissione di positroni (PET)/tomografia computerizzata (TC), considerata il gold standard nell'ambito della diagnostica whole body nell'imaging dei tumori, in un gruppo di pazienti con diagnosi di neoplasia maligna. Materiali e metodi. Sono stati inclusi 38 pazienti con diagnosi di neoplasia maligna in un periodo di 4 mesi. Le immagini PET/TC e RM-DWIBS sono state rivalutate in doppio cieco da un medico nucleare e da un radiologo con 4 anni di esperienza. Per ciascuna lesione sono state valutate dimensioni, standardized uptake value (SUV) e coefficiente di diffusione apparente (ADC). Risultati. La valutazione qualitativa sia della MR-DWIBS che della 18 F-FDG-PET/TC ha riscontrato due soli pazienti negativi per entrambe le tecniche. La RM-DWIBS è risultata positiva in 36 pazienti, di cui 34 erano positivi e 2 risultavano negativi alla 18 F-FDG-PET/TC. Duecentocinquantacinque lesioni sono state identificate con la MR-DWIBS e 184 con 18 F-FDG-PET/TC. È stata dimostrata una discordanza significativa. La correlazione tra SUV e ADC nelle lesioni positive ad entrambe le tecniche non è risultata statisticamente significativa.

This paper presents brain lesion segmentation of diffusion-weighted magnetic resonance images (DW-MRI or DWI) based on thresholding technique. The lesions are solid tumour, acute infarction, haemorrhage, and abscess. Preprocessing is applied to the DWI for normalization, background removal and enhancement. Two different techniques which are Gamma-law transformation and contrast stretching are applied for the enhancement. For the image segmentation process, the DWI is divided by 8 x 8 regions. Then image histogram is calculated at each region to find the maximum number of pixels for each intensity level. The optimal threshold is determined by comparing normal and lesion regions. By using Gamma-law transformation, 0.48 is found as the optimal thresholding value whereas 0.28 for the contrast stretching. The proposed technique has been validated by using area overlap (AO), false positive rate (FPR), and false negative rate (FNR). Thresholding with gamma-law transformation algorithm provides better segmentation results with AO, FPR, FNR (0.68, 0.14, 0.18) compared to contrast stretching (0.62, 0.15, 0.23).

Summary: We report the use of diffusion-weighted MR imaging in the early diagnosis and monitoring of the pro- gression of a histopathologically proved case of sporadic Creutzfeldt-Jakob disease. Ribbon-like areas of hyperin- tensity in the cerebral cortex on diffusion-weighted images corresponded to the localization of periodic sharp-wave complexes on the electroencephalogram. Sporadic Creutzfeldt-Jakob disease (CJD) is a rare fatal dementing

This paper presents an automated segmentation of brain lesion from Diffusion-weighted magnetic resonance images (DW-MRI or DWI) based on region and boundary information in gray level co-occurrence matrix (GLCM). The lesions are hyperintense lesion from tumour, acute infarction, haemorrhage and abscess, and hypointense lesion from chronic infarction and haemorrhage. Pre-processing is applied to the DWI for intensity normalization, background removal and intensity enhancement. Then, GLCM is computed to segment the lesions. Different peaks from the GLCM cross-section indicate the present of normal brain region, cerebral spinal fluid (CSF), hyperintense or hypointense lesions. Minimum and maximum threshold values are computed from the GLCM cross-section. Region and boundary information from the GLCM are introduced as the statistical features for segmentation of hyperintense and hypointense lesions. The proposed method provides very good segmentation results even in a small brain lesion.

PurposeThe objective of this study was to assess the value of high-resolution computed tomography (HRCT) and that of magnetic resonance imaging (MRI), including postcontrast T1-weighted images and echo-planar diffusion-weighted (EP-DW) images, in the detection of residual cholesteatomas after primary bony obliteration of the mastoid.

An effective method for in vivo detection of early therapeutic response of patients with non-Hodgkin's lymphoma would enable personalized clinical management of cancer therapy and facilitate the design of optimal treatment regimens. This study evaluates the feasibility of T 2 -weighted MRI (T2WI) and diffusion-weighted MRI (DWI) for in vivo detection of response of human diffuse large B-cell lymphoma xenografts in severe combined immunodeficient mice to chemotherapy. Each cycle of combination chemotherapy with cyclophosphamide, hydroxydoxorubicin, Oncovin, prednisone, and bryostatin 1 (CHOPB) was administered to tumor-carrying mice weekly for up to four cycles. T2WI and DWI were performed before the initiation of CHOPB and after each cycle of CHOPB. In order to corroborate the MRI results, histological analyses were carried out on control tumors and treated tumors after completion of all MRI studies. DWI revealed a significant (P < 0.03) increase in the mean apparent diffusion coefficient in CHOPB-treated tumors as early as 1 week after initiation of CHOPB. However, a significant (P < 0.03) decrease in mean T 2 was observed only after two cycles of CHOPB. Both MRI methods produced high-resolution (0.1 Â 0.1 Â 1.0 mm 3 ) maps of regional therapeutic response in the treated tumors based on local apparent diffusion coefficient and T 2 . Only a specific region of the tumors (in 3 of the 5 tumors) corresponding to about one third of the tumor volume exhibited a response-associate increase in ADC and decrease in T 2 . An adjacent region exhibited an increase in T 2 and no change in ADC. The rest of the tumor was indistinguishable from shamtreated controls by MRI criteria. The therapeutic response of the treated tumors detected by MRI was accompanied by changes in tumor cell density, proliferation and apoptosis revealed by histological studies performed upon completion of the longitudinal study. The mechanism producing the regional response of the tumor remains to be elucidated.

Recent improvements in MR gradient technology allow significant increases in diffusion weighting without prohibitive signal-to-noise degradation. The purpose of our investigation was to establish normative references for the signal intensity characteristics and apparent diffusion coefficient values of the adult brain at high b values. Fifty adults underwent diffusion-weighted single-shot spin-echo echo-planar MR imaging. Isotropic diffusion-weighted images were obtained with b values of 0, 1,000, 2,000, 2,500, 3,000, and 3,500 s/mm2. Qualitative assessments were made in multiple regions of interest in gray and white matter. Three apparent diffusion coefficient maps were generated for each of six patients with a 2-point technique at a b value of 0 and at b values of 1,000, 2,000, and 3,000 s/mm2. Increasing b values result in a progressive decrease in the gray to white matter signal intensity ratio. Isointensity between gray and white matter results at b values between 1,000 and 2,00...

Diffusion tensor imaging (DTI) and tractographic reconstruction may be applied for in vivo clinical spinal cord studies. However, this structure represents a challenge to current acquisition and reconstruction strategies, due to its small size, motion artifacts, partial volume effects and low signal-to-noise-ratio (SNR). Aims of this work were to select the best approach for the estimate of SNR and to use it for spinal cord diffusion weighted (DW) sequence optimization.