Radiation-induced CT number changes in GTV and parotid glands during the course of radiation therapy for nasopharyngeal cancer. Br J Radiol 2016 Jun;89(1062):20140819
Date
04/02/2016Pubmed ID
27033059Pubmed Central ID
PMC5258137DOI
10.1259/bjr.20140819Scopus ID
2-s2.0-84989908321 (requires institutional sign-in at Scopus site) 8 CitationsAbstract
OBJECTIVE: To investigate the changes in CT number (CTN) in gross tumour volume (GTV) and organs at risk (OARs) during the course of radiation therapy (RT) for nasopharyngeal cancer (NPC).
METHODS: Daily megavoltage CT (MVCT) data collected from 30 patients with NPC treated with a prescription dose of 70 Gy in 30-33 fractions using helical tomotherapy were retrospectively analyzed. The contours of GTV and OARs on daily MVCTs were obtained by populating the planning contours from planning CT to daily MVCTs with manual editing, if necessary. The changes of GTV and OAR volumes and the histograms of CTN in the GTV and OARs during the course of RT delivery were analyzed.
RESULTS: Volumes of GTV and parotid glands were reduced during the course of radiation treatment, with an average shrinkage rate of 0.23% per day (range, 0.02-0.8%) and 1.2% per day (range, 0.2-2.3%), respectively. The mean CTN changes in GTV and ipsilateral and contralateral parotid glands were reduced by 52 ± 35 HU, 18 ± 20 HU and 17 ± 22 HU, respectively. For GTV, the CTN and GTV volume decreases were found to be correlated with each other (p < 0.0001). No noticeable CTN change was found in the spinal cord and non-specified tissue irradiated with low doses.
CONCLUSION: The CTN changes in GTV and parotids are measurable during the delivery of fractionated radiotherapy for NPC, were associated with the doses received (the number of fractions delivered) and were patient specific.
ADVANCES IN KNOWLEDGE: The CTN change during radiotherapy is dose dependent and is measurable for NPC.
Author List
Xu S, Wu Z, Yang C, Ma L, Qu B, Chen G, Yao W, Wang S, Liu Y, Li XAAuthor
Guang-Pei Chen PhD Associate Professor in the Radiation Oncology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AdolescentAdult
Child
Female
Humans
Male
Middle Aged
Nasopharyngeal Neoplasms
Organ Sparing Treatments
Organs at Risk
Parotid Gland
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Radiotherapy, Image-Guided
Tomography, X-Ray Computed
Treatment Outcome
Tumor Burden
Young Adult
