الفهرس 
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Abstract
Detection of neck lymph nodes and their differentiation into benign or malignant are important especially in patients with head and neck cancer for staging, treatment planning and follow-up of cancer. Ultrasound (US), computed tomography (CT) and magnetic resonance (MR) can be used in the detection of enlarged cervical nodes; however, they cannot accurately differentiate benign from malignant lymph nodes. Metabolic imaging using single photon emission-CT (SPECT) and positron emission tomography (PET) can help in this differentiation but they are limited by low spatial resolution and variable physiological fluro-deoxyglucose(FDG) uptake in anatomical structures and inflammatory lymph nodes.
Ultrasound guided fine needle aspiration cytology (FNAC) is invasive with false negative results due to operator-dependency. DWI can provide excellent tissue contrast and may be able to demonstrate malignant lymph node. ADC values may be valuable in distinguishing between malignant and benign lymph nodes.
Magnetic resonance specteroscopy also provides a non-invasive means of determining the chemical composition of tissue and thus has a unique potential as a method for localizing and characterizing cancer.
Additional advantage of DWI and MRS include its completely non-invasive nature and its cost effectiveness. Both techniques do not involve a radiation exposure, oral and intravenous administration of contrast material and do not elicit patient discomfort. They can be easily added to MR study protocols and lose no time to the injection of contrast material. These new MRI techniques play an important role in the diagnosis and follow up of patient with enlarged lymph node.
Our study included 106 patients (71 male and 35 female patients) with their age (18-78 years) with clinically enlarged neck lymph nodes before they underwent histopathological examination.
Examination was done on a 1.5-T MR with a standard head and neck coil .Axial, coronal and sagittal localizer images were obtained first then conventional study was completed including:
T1-weighted images.
T2-weighted fast spin echo images.
Diffusion-weighted images were obtained in the axial plane before contrast administration.
Magnetic resonance spectroscopy was done for all patients and dominant solid node was selected for the analysis.
Apparent diffusion coefficient (ADC) maps were automatically calculated by MRI machine software.
Our study included 106 patients with enlarged neck lymph nodes. The patient’s age was ranging from 18 to 78 years and mean age of 47.5 years.
Results of histopathological findings of benign and malignant nodes revealed that out of 25patients (23.6%) of them had benign nodes and81 patients (76.4%) had malignant ones (66metastasis and15 lymphoma).
The mean ADC value of the benign lymphadenopathy (1.31±0.27 x10-3 mm2/s) was higher than that of malignant lymphadenopathy (0.72±0.28 x10-3 mm2/s) (T=7.96, p <0.001). These two major group had been subdivided into further subgroups. The 25 benign enlarged lymph nodes had been subdivided into simple nonspecific lymphadenitis (15 patients) & T.B lymphadenitis (7 patients) & Sarcoid lymphadenitis (3 patients).
The mean ADC value of the simple lymphadenitis (1.47±0.12 x10-3 mm2/s) was higher than that of T.B lymphadenitis (0.95±0.01 x10-3 mm2/s) (T= 2.320, p <0.001). The 81 malignant lymphadenopathy had been subdivided also into 66 metastatic & 15 lymphomatous enlarged lymph nodes & also the mean ADC value of the metastasis (0.75±0.35 x10-3 mm2/s) was higher than that of lymphoma (0.66±0.8x10-3 mm2/s) (T= 0.265, p= 0.04). The lymphomatous enlarged lymph nodes (15 cases) had been further more divided into 9 Hodgkin & 6 Non- Hodgkin lymphoma.
The best ADC threshold value for distinguishing benign and malignant nodes was 0.85x10-3 mm2/s with sensitivity, specificity, PPV, NPV, accuracy and 91.0 %, 85.0 %, 90.0%, 87.0%, 89.0% respectively.
In our study, as regard MRS, the mean Cho/Cr was significantly higher in malignant nodes in comparison to benign ones (2.35±0.96 versus 1.07±0.025) (p <0.0001), furthermore it was significantly higher in lymphoma compared to metastatic lymph nodes (4.2±0.35 versus 1.98±0.3).
In our study the combination of both DWI and MRS showed a higher diagnostic value (sensitivity, specificity, PPV, NPV and accuracy of 98, 96, 98, 97and 97% respectively and p value <0.0001) in comparison to the using any of DWI or MRS alone in differentiating benign and malignant cervical lymph nodes. The sensitivity, specificity, PPV, NPV and accuracy of DWI were 91, 85, 90, 87 and 89% with p value =0.001 while with MRS the sensitivity, specificity, PPV, NPV and accuracy were 96.0, 90, 95, 91 and 93% and p value =0.001.