الفهرس 
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Abstract
Diagnosis of the head and neck lesions is difficult due to the compli-cated anatomic structure and different histological components of the many tissues that the neck contains. SCC is the most common primary malignancy of the head and neck. It represents almost 90% of the head and neck tumors (HNSCC) and it shows different biological behaviors according to location. Malignant Lymphoma (ML) is also common, it is the second most common malignant tumor of the head and neck and represent approximately 5% of all malignant neoplasms of the head and neck area.
There are no specific characteristics for the manifestations and clinical behavior of lymphomas and SCC in the head and neck region that would help in the diagnosis without biopsy and histological evidence. Pretreatment imaging evaluation of these two malignant tumors is very important for tumor staging and treatment planning, because the management of them is radically different.
Magnetic resonance imaging (MRI) is effective for diagnosing tumors, it can not only define tumor’s locoregional extension, it provides additional information on tumor extension, muscles and lymph nodes involvement, and skull base and intracranial invasion, but, both T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI) may show equal signaling characteristics for both tumors. Thus, it is sometimes very difficult to clinically differentiate HNSCC from lymphoma on the basis of conventional MRI alone.
Functional imaging techniques such as diffusion-weighted MRI can provide information, not only on tumor size and location, but also on biological and functional aspects. DWI is a non-invasive technique that based on the amount of random (Brownian) motion that water protons undergo which causes incoherent phase shifts that result in signal attenuation, so, it analyzes the structures of biologic tissues at the microscopic level. The main advantage of DWI appeared to be the sensitivity to microscopic pathologic alterations before they became visible on conventional MRI sequences.
This study aimed to evaluate malignant lymphoma and squamous cell carcinoma in the head and neck regions with standard and high b values diffusion weighted MRI.
Twenty two patients with histologically proven HNSCC and malignant lymphoma were included in this study, all the patients were selected from the outpatient oncology clinics in El Minia University Hospital and El Minia Oncology Center. The patients were of both sexes and varying ages. All cases were subjected to history taking, thorough clinical examination, MRI with different imaging sequences (T1, T2, and T2 fat saturation) and single-shot echo-planar DW-MRI in the axial plane was obtained at the standard b value (b = 0 and 1000 s/mm2) and high b values (b= 0 and 1500 s/mm2 and b = 0 and 2000 s/mm2).
ADC maps were generated and the regions of interest (ROI) were drawn manually on the ADC maps at b=1000 s/mm2 and as far as possible on the same region of approximately similar size (about 25-30 mm2) on ADC maps of b = 1500 s/mm2 and b= 2000 s/mm2.
The result of this study showed that carcinoma group showed statistically significantly higher mean ADC values than lymphoma group whether using standard (b=1000 s/mm2), or high b values (b=1500 or b=2000 s/mm2).
The results showed that receiver operating characteristic (ROC) curve analysis of b=1000, b=1500 and b=2000 s/mm2 showed cut off values of<0.83 x 10-3 mm2/s, < 0.75 x 10-3mm2/s and < 0.67 x 10-3 mm2/s respectively which can discriminate between SCC and ML with equal diagnostic accuracy 95.5%, sensitivity of 90.9%, specificity of 100%, 100% positive and 91.7% negative predictive value.
Diffusion weighted MRI and the calculation of the ADC is useful for distinguishing head and neck squamous cell carcinoma and malignant lymphoma either using standard or high b values.