The signal intensity in MRI depends on the proton density, T1, T2 and T2 relaxation processes of any ensemble of the spins within each Imaging elements (vowel). Another important contrast mechanism in MRI is signal loss caused by proton rephrasing in the presence of coherent and incoherent flow. Random Diffusion of protons into areas of varying magnetic field strength leads to random phase shifts. The summation of signals from these protons with random phase shifts results in a net signal loss (hypo intensity on (DWI)). In restricted Diffusion (like acute infarction) the signal attenuation is decreased (hyper intensity on (DWI)). The observed proton Diffusion rate and direction reflect the molecular and macromolecular barriers, or hindrances that proton experiences during its translational process. As water protons diffuse and thus interact with the lattice and spin microenvironment, their traveled path along any one direction can be described. The proton displacement is expressed by an apparent Diffusion coefficient (ADC). The apparent Diffusion in tissue is slowed if the protons are "hindered," or slowed in their random motion by the presence of cell membranes, walls, and macromolecules but are not completely restricted. For example, myelin fiber and neurofibril orientation in white matter possesses a preferred direction for water proton movement. This feature causes protons to diffuse faster along the path of least resistance, causing the ADC to be anisotropic, or directionally dependent. Measurements during proper times can fully reflect these hindrances to Diffusion. DW images have become an essential part of clinical MR Imaging, providing physiological information useful in identifying early ischemic infarction. They have also been used to differentiate cysts from solid tumors, to aid in the diagnosis of inflammatory conditions such as encephalitis and abscesses, and to evaluate various white matter abnormalities, such as multiple sclerosis.

Background: Pre-operative differentiation of benign from malignant cervical adenopathies remains a challenge. Several studies indicate parameters to discriminate between benign and malignant lymph nodes, which has not yet been enough. Objectives: The aim of the current study was to assess the diagnostic efficacy of Diffusion-Weighted MR Imaging ((DWI)) to differentiate benign from malignant cervical lymph nodes. Patients and Methods: In all patients, we assessed axial and coronal fast spin echo T2 and T1-Weighted images and T1-Weighted after contrast injection. (DWI) sequences were implemented before contrast injection, in axial and coronal planes (b factor of 50, 500 and 1000 s/mm2) and the apparent Diffusion coefficient (ADC) maps were reconstructed. Data were assessed in mixed model analysis and results were compared with postoperative histopathologic findings. Results: Thirty seven subjects were enrolled, 10 with benign lymphadenopathy and 27 patients with malignant lymphadenopathies before treatment. The mean ADC of the benign neck lymph nodes was (1. 00 ± 0. 34) × 10-3 mm2/s, while it was (0. 76 ± 0. 16) × 10-3 mm2/s in malignant ones (P = 0. 058). The mean ADC of the metastatic nodes was (0. 81 ± 0. 14) × 10-3 mm2/s, while it was (0. 56 ± 0. 04) × 10-3 mm2/s in lymphoma (P < 0. 001). The mean ADC of poorly differentiated metastatic nodes was significantly lower than that of good and moderately differentiated ones [(0. 86 ± 0. 13) × 10-3 mm2/s vs. (0. 66 ± 0. 02) × 10-3 mm2/s respectively; P = 0. 001]. The area under the ROC curve of ADC was 0. 69 [95%CI = 0. 52-0. 83]. Considering cut off points of 0. 6 × 10-3, 0. 95 × 10-3, and 1. 2 × 10-3 yielded sensitivities were 15%, 92. 5%, and 100%, respectively; while, in these cutoff points, specificities were 80%, 50%, and 40%, respectively. Conclusion: (DWI) could be considered as an important diagnostic tool to differentiate enlarged cervical lymphadenopathies.

To assess the depth of myometrial invasion in patients with endometrial cancer by contrasting the diagnostic efficacy of dynamic contrast enhanced (DCE) magnetic resonance Imaging with Diffusion-Weighted ((DWI)) MRI. 64 Patients with endometrial cancer who had preoperative 3.0 Tesla MRI in sagittal planes, including T2-Weighted (T2W), (DWI) (b=0 and 1000 s/mm2), and dynamic contrast enhanced (DCE) MRI, were retrospectively evaluated. Results of surgical pathology were linked with the depth of myometrial invasion on MRI. A radiologist determined the definitive histologic grade (G1-G2; G3) and compared it with the mean ADC of the tumor and peritumoral zone. The evaluation of myometrial invasion was enhanced when using (DWI) or DCE Imaging values were combined with T2W Imaging. Sensitivity, specificity, accuracy, positive predictive value, negative predictive value, and area under the receiver operating characteristic (ROC) curve were measured for determining the depth of myometrial invasion: T2W-(DWI) / T2W-DCE Imaging; 96.15%/92.31%, 85.19%/85.19%, 90.57%/86.68%, 86.21%/85.71%, 95.81%/92%, and 0.91/0.89. The average ADC offered accurate and valuable information for estimating the tumors' histopathological grade. The area under the ROC curve, sensitivity, specificity, accuracy, negative predictive value, and positive predictive value in our series were 64%, 87.18%, 76.19%, 79.07%, 78.13%, and 0.763, respectively, for a cutoff value of 0.638 x 10-3 mm2/s. T2W-(DWI) is a potential replacement for DCE in the assessment of the depth of myometrial invasion of endometrial cancer, especially useful for patients with contraindications to contrast agents. The combination of T2W and (DWI) has high diagnostic high accuracy in the assessment of the depth of myometrial invasion.

Background: Magnetic resonance Imaging (MRI) offers higher diagnostic accuracy for brain lesions caused by heroin abuse compared to compute tomography (CT) scan. These lesions have a low signal on T1-Weighted (T1W) images and a high signal on T2-Weighted (T2W) and fluid-attenuated inversion recovery (FLAIR) images. This study aimed to evaluate the role of Diffusion-Weighted MRI ((DWI)-MRI) in heroin addicts.Methods: This cross-sectional study was conducted on 20 patients with heroin addiction (vapor inhalation/injection) referring to Imam Reza Hospital of Mashhad, Iran. Patients in whom heroin abuse was only cause of consciousness, loss and neurological symptoms were enrolled in this study. Demographic data of the patients were recorded, including MRI, FLAIR, T1W and T2W images. In addition, (DWI) of axial and sagittal sections of the brain was performed in the following sequences.Results: In this study, mean age of patients was 40.15±7.673 years, and 95% of patients were male. The most common mode of heroin use was inhalation, and mean duration of addiction was 5.48±3.393 years. Mean daily intake of heroin was 13.4±15.30 grams, and mean duration of heroin abuse was 10.3 and 4.6 years in patients with and without MRI changes, respectively. A significant correlation was observed between MRI changes and duration of heroin use (r=0.721) (p=0.001). In addition, a significant correlation was observed between MRI changes and daily intake of heroin (p=0.006).Conclusion: According to the results of this study, brain lesions caused by heroin abuse have a low signal on T1W images and a high signal on T2W and FLAIR images. Therefore, it could be concluded that heroin intake has significant effects on the brain of users.

Rhabdomyosarcoma is a common primary childhood malignancy that rarely metastasizes to the breast. We report a patient with a primary sinonasal rhabdomyosarcoma metastasizing to the breast, with no distant spread. We describe the Imaging appearance of rhabdomyosarcoma on magnetic resonance Imaging (MRI), particularly on Diffusion-Weighted Imaging ((DWI)) and apparent Diffusion coefficient (ADC) sequences. Rhabdomyosarcoma metastasis has a variable appearance on ultrasound and MRI, and may mimic common benign tumors. However, it appears hyperintense on (DWI) and produces a low value on the ADC, which may be more accurate for determining its malignant nature.