Study Of Nasopharyngeal Anatomy Concerning Clinical Dosemetry Of Radiation Treatment

Purpose To get the detail anatomical parameters of nasopharynx and have well understand of spatial relations among these important structures.To study the sectional anatomical morphology and CT/MRI features of nasopharynx on Chinese Visible Human datasets (CVH).To analyze the clinical dosemetry characteristics and advantages of different radiotherapy techniques (2D-RT, 3D-CRT, IMRT) on the treatment of nasopharyngeal carcinoma.To make the CVH2 visualization come true and study the clinical dosemetry of NPC IMRT on the sectional anatomical images of nasopharynx of CVH2.To evaluate the clinical dosemetry characteristics and indications of different boost treatment modality for NPC.Material and MethodsThe bony markers clinically important were studied, and the distances among them were measured on 30 (60 sides) adult human cadaver skulls.The nasopharynx and adjacent structures, including parapharyngeal space, infratemporal fossa and styloid diaphragm were dissected and studied by micro-neurosurgerical procedures through lateral routes in 10 adult cadaver skulls (20 sides). The morphological studies of nasopharyx and adjacent important structures were carried out on the sectional images of 5 Chinese Visible Human datasets. They were also compared with the corresponding CT and MRI images.The dose distributions of one NPC with T1a tumor treated with 2D-RT, 3D-CRT and IMRT were analyzed and evaluated with Eclipse TPS system. The CT data and anatomical images of CVH2 were processed with the STAR TPS system. The virtual NPC target volume and other important organs were outlined on the CT images and IMRT planning was made. Then the isodose distribution curves were superimposed onto the corresponding sectional images of CVH2 and evaluated.Three types of residual lesions of NPC were treated with SRT, 3D-CRT and IMRT boost techniques respectively. Their dosemetry characteristics were compared. And the clinical results of 35 patients treated with SRT were analyzed and evaluated.ResultsThe distances from pharyngeal tuberculum to the concerning structures are as follows: to the edge of left and right oval foramen are 28.31±2.70mm and 27.63±2.34mm respectively. To the edge of left and right spinous foramen are 31.75±2.62 mm and 32.05±2.71 mm respectively. To the edge of left and right lacerated foramen are 8.78±2.61 mm and 8.48±2.67 mm respectively. To the edge of left and right jugular vein canal are 27.31±2.69 mm and 26.66±2.98 mm respectively.The styloid diaphragm divides parapharyngeal space into prestyloid and retrostyloid spaces. Styloid diaphragm shields structures like internal carotid artery, internal jugular vein, lower cranial nerves and etc.The anatomical structures of CVH datasets keeps very well and no deformity, dislocation and information loses. Structures like bone, connective tissues, nerves and blood vessels can be displayed clearly. The structures had excellent correspondences with CT/MRI images.The parapharyngeal space was subdivided clearly. The boundaries of prestyloid, retrostyloid and retropharyngeal spaces were defined. MRI with superior soft-tissue resolution and ability providing images in multiple planes is superior to CT, but CT performs better than MRI in detection of lesions involving the bony structures and natural canals. IMRT had very good dose distribution and satisfactory target coverage for nasopharyngeal carcinoma. Brain stem, spinal cord and other important structures shielded well and bilateral parotids had the dose under tolerance. The main drawbacks of 2D-RT are brain stem, spinal cord and parotids had high dose exceeding their tolerance. The disadvantage of 3D-CRT is its dose inhomogenity within target volume and high dose to parotids.The visualization of CVH2 was realized on the system of Star TPS and it can be reconstructed and cut in 3 dimensions. The dose distribution of IMRT on a virtual NPC of CVH2 was transferred and superimposed onto the sectional anatomy images. Much more information about IMRT clinical dosemetry was...