الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Cervical lymphadenopathy has a wide differential diagnosis, but is most frequently due to local or systemic infection, although it can also be caused by a malignant disease [1].
The main aim of the clinician is to differentiate between benign and malignant cervical lymphadenopathy in patient who is not known to have primary tumor and whether the cervical lymphadenopathy is metastatic or not in patient who has a primary tumor whether this primary tumor located in the head and neck or elsewhere in the body, this is due to the importance of lymph node metastasis in staging, planning of the treatment and prognosis of the case [2].
Lymph node biopsy or dissections, followed by histopathological examination are considered the gold standard for assessment of lymph nodes. However, surgical removal of lymph nodes is an invasive procedure with associated complications. Furthermore, although ultrasound guided fine needle aspiration cytology (FNAC) is gaining popularity in the assessment of lymph nodes, it is still an invasive and operator dependent procedure with high incidence of false negative cases [2].
Modern imaging modalities such as ultrasound (US), computed tomography (CT) and magnetic resonance (MR) imaging allow reliable detection of cervical lymph nodes. However, the differentiation between benign and malignant lymph nodes remains challenging, this is because the criterion of the size of greater than 10mm in the small diameter of lymph node, morphological criteria such as a rounded shape and regional grouping of lymph nodes, extra capsular tumor spread and the presence of necrosis are just suspicious criteria of malignancy and unfortunately not absolutely reliable [3, 4].
Lymph nodes may be enlarged reactively and even small lymph nodes may be infiltrated by malignant cells. Besides the size, presence of necrosis is the strongest indicator for metastatic disease, but necrosis has been shown to occur in benign conditions as well [3, 4].
Metabolic imaging with single photon emission CT (SPECT) and photon emission tomography (PET) can help differentiation between benign and malignant lymph nodes, but they are expensive, less available, expose the patient to ionizing radiation and have low spatial resolution [59].
MRI diffusion application can also help this differentiation as the malignant lymph nodes have hypercellularity, more nuclear to cytoplasmic ratio, more macromolecular proteins and more cell membranes which represent impediment to diffusion and, consequently, a lower ADC. On the other hand, benign lymph nodes have a decrease in the restrictive cell membranes with less of an impediment to diffusion and a consequently higher ADC [5, 6].
Monitoring of response to chemotherapy and radiation therapy is the area where DW imaging has the potential to play major role in clinical management. Early results suggest that tumors that show only a small increase or decrease in ADC during treatment or in the early post treatment phase are more likely to fail treatment [6, 7].
Diffusion-weighted MR imaging has advantages over other imaging techniques. It is noninvasive, has a short examination time, and is cost-effective. Additionally, there is no ionizing radiation exposure or external tracer or contrast medium administration. Thus, it can be incorporated into routine MR imaging to improve radiologist confidence in image interpretation and follow-up of patients. Furthermore, both conventional morphologic and physiologic assessments can be made during the same examination [5].