Head And Neck Cancer Radiation Therapy, Image Guidance

PART 1 The dosimetric impacts on targets and normal volumes by reduction PTV of primary disease margins in patients with locally advanced or recurrent nasopharyngeal carcinomaObjective To analyze the impact on dose distribution of targets and organs-at-risk by reducing plan target volume (PTV) margins in patients with locally advanced or recurrent nasopharyngeal carcinoma.Methods Thirty patients with locally advanced (11cases) and recurrent (2 cases) were enrolled to this study. All patients treated with intensity modulated radiotherapy (IMRT) technique to irradiate the primary diseases with 70.4Gy/32F(locally advanced disease)or 70Gy/35F(recurrent tumor)。PTV margins were reduced for clinical target volume (PTV-C) from 3mm to 2mm and gross target volume (PTV-G) from 5mm to 2mm after delivery 23-25 fraction. All patients had three plans:Plan 1:Without reducing PTV margins; plan 2:With (7-10 fractions) and without reducing PTV margins (25 fractions); plan 3:With reducing PTV margins (32-35 fractions). Dosimetric changes were analyzed among three plans.Results Between March 2008 and October 2009,13 patients with locally advanced or recurrent NPC were enrolled in this study. There were no significant qualitative dosimetric differences for maximum dose (Dmax) of spinal cord and mean dose of PTV-G. between the plan 1 and the plan 2. Dose to brain stem, optic nerve, temporal lobe and chiasm were decreased, especially high dose regions of brain lobe and brain stem were increased dramatically, P=0.000. The dose distribution of plan 3 compared to plan 2 showed there were no significant differences for Dmax of spinal cord and brain stem. There were significant dosimetric differences between the plan 1 and the plan 3 except Dmax of spinal cord, even improve dose distribution of PTV-G, P=0.022.Conclusions Reduction PTV margins from 3mm to 2mm for PTV-C and PTV-G from 5mm to 2mm in patients with locally advanced or recurrent nasopharyngeal carcinoma can reduce does to normal tissues without comprising targets dose distribution. PART 2 Set-up errors in the treatment of head and neck cancer and brain tumor:Investigated by megavoltage cone-beam CT(1) Regularity of isocenter displacements located superior C2 in treatment of head and neck cancer and brain tumorObjective To explore regularity of isocenter displacements located superior C2 in treatment of head and neck cancer by megavoltage cone-beam CT.Methods From Apr.2007 to Mar.2008,22 patients with head and neck cancer and brain tumor treated by three dimensional conformal radiotherapy (3DCRT) or intensity modulated radiotherapy (IMRT),56-70.4Gy/28-32/6-7 week. Megavoltage cone-beam scan was performed once a week before radiation. The isocenter displacement distance of megavoltage cone-beam CT opposite in planning CT in the three dimensional direction, left-right, cranio-caudal and anterior-posterior, were analyzed.Results All together 129 megavoltage cone-beam CT images were obtained in 22 patients. The number and percentage of isocenter displacements more than 0.3cm,0.4cm and 0.5cm were 28 (21.7%),15 (11.6%) and 9 (7.0%) respectively. The biggest mean shift, about 0.1cm more than that in the left-right and anterior-posterior was found in cranio-caudal direction. Calculation of CTV-PTV margins was based on the formula 2∑+0.7σ. The CTV-PTV margins were 0.38cm,0.36cm and 0.47cm in the left-right, anterior-posterior and cranio-caudal directions, respectively.The frequency of isocenter shift direction was almost identical in the left-right and cranio-caudal, while prone to shifting to posterior direction, about acconting for 75%.Conclusions During the course of radiation of head and neck cancer, the set-up errors have the enlargement tendency in three directions. The frequency of isocenter shift direction in anterior-posterior was prone to posterior direction. PART 2 Set-up errors in the treatment of head and neck cancer and brain tumor:Investigated by megavoltage cone-beam CT(2) Set-up errors in the treatment of nasopharyngeal carcinoma with isocenter located around inferior border of the cricoid cartilageObjective To explore set-up errors in the treatment of nasopharyngeal carcinoma with isocenter located around inferior border of the cricoid cartilage by megavoltage cone-beam CT.Methods From Dec.2008 to Mar.2009,8 patients with nasopharyngeal carcinoma treated by intensity modulated radiotherapy (IMRT),66-70.4Gy/30-32/6-7 week. Megavoltage cone-beam scan was performed weekly before radiation. The isocenter shift distance, i.e. set-up errors, of megavoltage cone-beam CT opposite in planning CT in the three dimensional direction, left-right, cranio-caudal and anterior-posterior, were analyzed. These results were compared with those from partl.Results All together 46 megavoltage cone-beam CT images were obtained in 8 patients. The frequency and percentage of isocenter shifts more than 0.3cm,0.4cm and 0.5cm were 5,2 and 2 respectively. The biggest random set-up errors, about 0.16cm was found in the left-right direction. The frequency of isocenter shift direction was almost identical in the three directions.Conclusions During the course of radiation of nasopharyngeal carcinoma treated with IMRT plan with isocenter located around inferior border of the cricoid, the biggest random set-up errors, which has the enlargement during first three week, was found in the left-right direction. PART 3 Kilo-voltage cone-beam computed tomography guided radiotherapy of head and neck cancer and brain tumor(1)Analysis of difference between grey and bone registrationObjective To study the differences between bone and grey registration of kilo-voltage cone-beam computed tomography (KVCBCT) guided radiotherapy of head and neck cancer, as well as put forward recommendations for applications.Methods From Apr.2007 to Jul.2008,11 patients with head and neck cancers treated by three dimensional conformal radiotherapy (3DCRT) or intensity modulated radiotherapy (IMRT),56-70Gy/28-35/5.6-7 week. KVCBCT scan was performed 1-3 weekly before delivery. Radiation treatment plan was fused on the KVCBCT imaging, and then defined the CLIPBOX, i.e. areas of registration. Bone and grey registration were performed respectively. The axial and rotation displacements of kilo-voltage cone-beam CT opposite in planning CT in the three dimensional direction, left-right, cranio-caudal and anterior-posterior were analyzed. Paired t test was used to test the differences of two registration methods.Results Eighty seven KVCBCT images were obtained in 11 patients. Regardless of methods of registration, the displacements of axes and rotations in cranio-caudal direction were more than those in the directions of left-right and anterior-posterior. The translational displacements obtained by bone registration were 0.18cm,0.14cm and 0.21cm in the left-right, anterior-posterior and cranio-caudal directions, respectively. Rotations set-up errors were 0.91°,0.90°,1.31°,respectively. The translational displacements obtained by grey registration were 0.15cm,0.11cm and 0.15cm in the left-right, anterior-posterior and cranio-caudal directions, respectively.Rotations set-up errors were 0.47°,0.65°,1.21 respectively. Overall, the set-up errors obtained by grey registration were less than those obtained by bone registration.There were no significant difference between bone and grey registration in cranio-caudal direction, axial displacement P=0.832, rotation displacement P=0.177. While in the directions of left-right and anterior-posterior, there were significant difference between bone and grey registration, the axial displacement P=0.000 and P=0.000, the rotations displacement P=0.000 and P=0.008.Conclusions Based on the data of KVCBCT technology guided radiotherapy of the head and neck cancer in our hospital, it is proposed to select bone registration. If set-up errors meet requirements, delivery can be performed immediately. Otherwise, in the direction of left-right and anterior-posterior, consider the selection of gray registration, while in the direction of cranio-caudal, immediate on-line correction of displacement is recommended. (2) Rotational set-up errors in the treatment of head and neck cancer investigated by kilo-voltage cone-beam computed tomographyObjective To analyze the rotational set-up errors in the treatment of kilo-voltage cone-beam computed tomography (KVCBCT) guided radiotherapy of head and neck cancer.Methods From Apr.2007 to Jul.2008,11 patients with head and neck cancers treated by three dimensional conformal radiotherapy (3DCRT) or intensity modulated radiotherapy (IMRT),56-70Gy/28-35/5.6-7 week. KVCBCT scan was performed 1-3 times weekly before delivery. Radiation treatment plan was fused on the KVCBCT imaging, and then defined the CLIPBOX, i. e. areas of registration. Bone and grey registration were performed with same registration areas respectively. The translational and rotational displacements of kilo-voltage cone-beam CT opposite in planning CT in the three dimensional direction, left-right, cranio-caudal and anterior-posterior were analyzed. Spearman analysis was used to test the correlates of translational set-up errors and rotational set-up errors.Results Altogether 87 KVCBCT images were obtained in 11 patients. The rotational set-up errors of X,Y and Z axis were 0.91°,0.90°,1.31°for bone registration and 0.47°,0.65°,1.21°for grey registration, respectively. The maximal rotations of x, y, and z axes was 3.7°,5°and 6°for bone registration, and 2°,4°and 4°for grey registration, respectively. The number and percentage of rotational set-up errors more than2°and 3°was 26 (29.9%),9(10.4%) for bone registration,16(18.4%) and 3 (3.5%) for grey registration, respectively. There were no significant correlations between rotational set-up errors and translational set-up errors, P>0.05.Conclusions There were insignificant correlations between rotational set-up errors and translational set-up errors.The dosimetric effect of rotational set-up errors was dependent on magnitude of rotational set-up errors, shapes of target volume and organ-at-risk and distance between isocenter and targets.