title: Value of diffusion-weighted magnetic resonance imaging on the follow-up of nasopharyngeal carcinoma after radiotherapy.
abstract: OBJECTIVE
  To explore the value of diffusion-weighted imaging (DWI) and magnetic resonance imaging (MRI) on the follow-up of nasopharyngeal carcinoma (NPC) after radiotherapy.
  
  
  METHODS
  Eighty-three NPC patients after radiotherapy were divided into two groups: 4 cases of residual tumor and 33 cases of non-residual within 6 months, the cases of recurrent and non-recurrent were 5 and 41 over 6 months, respectively. MRI and DWI imaging of these cases were closely analyzed, and the apparent diffusion coefficient (ADC) of the nasopharyngeal residual mass and nasopharyngeal wall thickening, skull base destruction and lateral pterygoid muscle were measured.
  
  
  RESULTS
  The ADC of the lateral pterygoid muscle was (1.501 ± 0.069) × 10<formula>^{ - 3}</formula> mm<formula>^{2}</formula>/s in 83 cases. The ADCs of the non-residual group, residual group, non-recurrent group and recurrent group were (1.843 ± 0.133.4) × 10<formula>^{ - 3}</formula> mm<formula>^{2}</formula>/s, (1.097 ± 0.183) × 10<formula>^{ - 3}</formula> mm<formula>^{2}</formula>/s, (1.884 ± 0.134) × 10<formula>^{ - 3}</formula> mm<formula>^{2}</formula>/s and (0.787 ± 0.067) × 10<formula>^{ - 3}</formula> mm<formula>^{2}</formula>/s respectively.The ADCs of the residual group and recurrent group were lower than that of the lateral pterygoid muscle, while the ADCs of the non-residual group and non-recurrent group were higher than that of the lateral pterygoid muscle.The differences were statistically significant (P < 0.05).
  
  
  CONCLUSIONS
  DWI can provide qualitative and quantitative information about the tumor cellular level; it can also identify residual, local fibrosis and recurrence after NPC radiotherapy sensitively and accurately by measuring the ADC of the region of interest.
authors.affiliation: Department of Radiation Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China.
authors.forename: Ji-Fei
authors.initials: JF
authors.lastname: Xu
authors.affiliation: Department of Radiology, the First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China.
authors.forename: Xing-Wang
authors.initials: XW
authors.lastname: Wu
authors.affiliation: Department of Radiology, the First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China.
authors.forename: Wan-Qin
authors.initials: WQ
authors.lastname: Wang
authors.affiliation: Department of Radiation Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China.
authors.forename: Ling-Ling
authors.initials: LL
authors.lastname: Kong
authors.affiliation: Department of Radiation Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China.
authors.forename: Li-Ming
authors.initials: LM
authors.lastname: Wu
authors.affiliation: Department of Radiation Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei, Anhui, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002277:Carcinoma; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D009305:Nasopharynx / Q000473:pathology; D055815:Young Adult
keywords: Magnetic resonance imaging; diffusion; nasopharyngeal neoplasms; radiotherapy