PURPOSE: To determine if image-guided radiotherapy (IGRT) ensures dose coverage to the target, and to assess the dosimetric impact of anatomic changes using megavoltage cone-beam CT (MVCBCT) for patient positioning during head and neck IMRT. METHODS AND MATERIALS: Forty-eight MVCBCT from 10 head and neck IMRT/IGRT patients were analyzed off-line. Target volumes and organs at risk (OARs) contours delineated on CT were transferred and adjusted on MVCBCT images. Each MVCBCT was processed to allow dose recalculation, resulting in 469 dose-volume histograms (DVHs). The concept of dosimetric latitude was introduced to provide a clinical perspective. RESULTS: MVCBCT target DVHs showed a moderate level of difference in D95 (dose to ≥95% of volume), generally less than a 5% difference from the planned dose. Delivered-dose increases to the spinal cord and brainstem showed no apparent time trend. The 4mm margin around OARs was a useful precaution to prevent exceeding critical dose thresholds. The parotid glands showed progressive increases in mean dose related to shrinkage of the external contours. CONCLUSION: IGRT repositioning ensured target volume coverage, but significant dose variations were observed for OARs. The dosimetric impact of anatomic changes during radiotherapy was of lesser importance than the effects of IGRT repositioning.
PURPOSE: To determine if image-guided radiotherapy (IGRT) ensures dose coverage to the target, and to assess the dosimetric impact of anatomic changes using megavoltage cone-beam CT (MVCBCT) for patient positioning during head and neck IMRT. METHODS AND MATERIALS: Forty-eight MVCBCT from 10 head and neck IMRT/IGRT patients were analyzed off-line. Target volumes and organs at risk (OARs) contours delineated on CT were transferred and adjusted on MVCBCT images. Each MVCBCT was processed to allow dose recalculation, resulting in 469 dose-volume histograms (DVHs). The concept of dosimetric latitude was introduced to provide a clinical perspective. RESULTS: MVCBCT target DVHs showed a moderate level of difference in D95 (dose to ≥95% of volume), generally less than a 5% difference from the planned dose. Delivered-dose increases to the spinal cord and brainstem showed no apparent time trend. The 4mm margin around OARs was a useful precaution to prevent exceeding critical dose thresholds. The parotid glands showed progressive increases in mean dose related to shrinkage of the external contours. CONCLUSION: IGRT repositioning ensured target volume coverage, but significant dose variations were observed for OARs. The dosimetric impact of anatomic changes during radiotherapy was of lesser importance than the effects of IGRT repositioning.
Authors: Mika Kapanen; Marko Laaksomaa; Tapio Tulijoki; Pirkko-Liisa Kellokumpu-Lehtinen; Simo Hyödynmaa Journal: Rep Pract Oncol Radiother Date: 2015-04-01
Authors: Mika Kapanen; Marko Laaksomaa; Tapio Tulijoki; Seppo Peltola; Tuija Wigren; Simo Hyödynmaa; Pirkko-Liisa Kellokumpu-Lehtinen Journal: Radiat Oncol Date: 2013-09-10 Impact factor: 3.481
Authors: David J Noble; Ping-Lin Yeap; Shannon Y K Seah; Karl Harrison; Leila E A Shelley; Marina Romanchikova; Amy M Bates; Yaolin Zheng; Gillian C Barnett; Richard J Benson; Sarah J Jefferies; Simon J Thomas; Raj Jena; Neil G Burnet Journal: Radiother Oncol Date: 2018-07-23 Impact factor: 6.280
Authors: Louise Belshaw; Christina E Agnew; Denise M Irvine; Keith P Rooney; Conor K McGarry Journal: Radiat Oncol Date: 2019-11-01 Impact factor: 3.481