Query: cbct breast con  clips

title: A randomised trial of supine versus prone breast radiotherapy (SuPr study) comparing set up errors and respiratory motion.
abstract: To test a prone position against the international standard supine position in women undergoing whole breast radiotherapy (WBRT) after wide local excision (WLE) of early breast cancer (BC) in terms of feasibility, set up errors, and respiratory motion.  Following WLE of BC with insertion of tumour bed clips, patients underwent 4D CT for WBRT planning in supine and prone positions (the latter using an in house designed platform) Patients were randomised to undergo WBRT fractions 1 7 in one position, switching to the alternate position for fractions 8 15 (40Gy/15 fractions total) Cone beam CT images (CBCT) were acquired prior to fractions 1, 4, 7, 8, 11 and 14. CBCT data were matched to planning CT data using (i) chest wall and (ii) clips. Systematic and random errors were calculated. Maximal displacement of chest wall and clips with respiration was measured on 4D CT. Clinical to planning target volume (CTV PTV) margins were calculated. Patient comfort scores and treatment times were evaluated.  Twenty five patients were randomized. 192/192 (100% planned supine fractions and 173/192 (90% prone fractions were completed. 3D population systematic errors were 1.3 1.9mm (supine) and 3.1 4.3mm (prone) (p=0.02) and random errors 2.6 3.2mm (supine) and 3.8 5.4mm (prone) (p=0.02) Prone positioning reduced chest wall and clip motion (0.5+ 0.2mm (prone) versus 2.7+ 0.5mm (supine) (p<0.001) with respiration. Calculated CTV PTV margins were greater for prone (12 16mm) than for supine treatment (10mm) Patient comfort scores and treatment times were comparable (p=0.06) CONCLUSIONS Set up errors were greater using our prone technique than for our standard supine technique, resulting in the need for larger CTV PTV margins in the prone position. Further work is required to optimize the prone treatment platform and technique before it can become a standard treatment option at our institution.

title: SU E J 12: Evaluation of Setup Uncertainties for Electron Boost Field Treated Using Compression Device for Breast Cancer Irradiation.
abstract: To investigate uncertainties of patient setup for electron boost field using an in house breast compression device for breast cancer irradiation.  Ten early stage breast cancer patients with deep seated tumor beds treated with post lumpectomy radiation were randomly selected. The patients underwent resimulation and treatment with the compression device to decrease the depth of tumor bed. A cone beam computed tomography (CBCT) scan was performed for each patient before treatment and fused with the simulation CT. Four surgical clips located in superior, inferior, left and right of tumor bed were identified in both CT and CBCT data sets for each patient. Set up uncertainties were estimated based on differences in the positions of the clips between scans relative to the marked isocenter.  For each patient, all clips shifted consistently in the same direction superior inferior (SI) and left right (LR) direction, but not in the anterior posterior (AP) direction because of the perturbation of the compression device. 50% of clips (20 out of 40 clips) shifted anteriorly, 60% shifted inferiorly, and 70% shifted left. Clip shifts in AP direction were smaller than in SI and LR direction. The 55% of clips shifted >1 cm, 18% of clips shifted 1.5 cm, and only one clip shifted 2cm which was out of the intended isodose coverage. The average shift of 4 clips for each patient in LR direction was correlated with the breast volume (R2=0.406) but the average shifts of 4 clips in AP and SI direction were not correlated breast volume (R2>0.02) CONCLUSION For most patients whose breast boosts were treated with a compression device, a 2cm margin was sufficient to ensure target coverage based on set up uncertainties observed in this study. A larger margin might be necessary for electron boost fields for patients with large (volume >2000cc) and/or pendulous breasts.

title: CBCT analysis of displacement of titanium clips for tumor bed localization after breast conserving surgery for breast cancer
abstract: To analyze the displacement of titanium clips for tumor bed localization after breast conserving surgery for breast cancer and its influential factors.  A retrospective analysis was performed on the cone beam computed tomography (CT) images of 14 patients with breast cancer who received radiotherapy after breast conserving surgery from April to October, 2016.The relative position of the chest wall and the errors of the titanium clips in radiotherapy were measured. A Pearson correlation analysis was used to analyze the correlation of the displacement of titanium clips with the relative position of titanium clips, the breast volume, the vertical distance between the titanium clips and the tangential line of the chest wall, and the maximum thickness of the breast.  The system errors of the chest wall in left right, superior inferior, and anterior posterior directions were 4.42, 3.44, and 5.13 mm, respectively, and the random errors were 3.55, 3.07, and 4.54 mm, respectively. The titanium clips had a large displacement relative to the chest wall, mainly in the left right direction. The maximum system error was 4.39 mm and the random error was 2.42 mm. The displacement of titanium clips was not significantly correlated with the breast volume and the maximum thickness of the breast (P>0.05) However, the relative position of titanium clips in superior inferior direction was significantly correlated with the displacement of the lowest, the most lateral, the most anterior, and the most posterior titanium clips (P<0.05) As to the uppermost clips, there was a significant difference in displacement between the clips close to the chest wall and the clips far from the chest wall (P=0.02)  Due to large setup error and displacement of titanium clips during radiotherapy, simultaneous integrated boost is not suitable for patients with breast cancer who are immobilized by vacuum cushion and received radiotherapy. The unstable immobilization may be the major influential factor for the displacement of titanium clips.  Tomography, X ray computed, cone beam; Breast neoplasms/surgery; Variation of surgical clips

title: The displacement of silver clips in breast cavity during kV plain film guided three dimensional con formal external beam partial breast irradiation assisted by active breathing control
abstract: To measure the displacement of the silver clips guided by kV plain film at state of moderate deep inspiration hold(mDIBH) assisted by active breathing control(ABC) and to explore the margin of clinical target volume(CTV) to planning target volume(PTV) for breast cancer patients treated with three dimensional conformal external beam partial breast irradiation (EB PBI) assisted by ABC.  The patients undertook CT simulation assisted by ABC to get the CT images on the respiratory condition of mDIBH. Four selected silver clips in breast cavity were delineated and the cavity based on all of the clips were delineated as gross tumor volume (GTV) Before each irradiation, two orthogonal kV plain films were taken for the patients in the respiratory condition of mDIBH assisted by ABC device. 2D 2D auto matie registration was performed based on pixel between the kV plain films and the digital reconstructed radi ographs(DRR) Then manual registration was undertook to get the shifts of the four clips separately at LAT, LNG,and VRT directions. Based on the shift data,the margins of CTV to PTV at LAT,LNG and VRT direc tions were calculated.  The margins from CTV to PTV were 5.00 mm,7.78 mm and 9.30 mm at LAT,LNG and VRT directions based on the clip at cephal border of the cavity. The corresponding margins were 4.40 mm,6.43 mm and 6.73 mm based on the clip at bottom of the cavity;5.04 mm,8.63 mm and 10.54 mm based on the clip at lateral border of the cavity;5.40 mm,8.59 ram and 10.81 mm based on the clip at pedal border of the cavity.  The silver clips in breast cavity can be clearly showed on the kV plain film. The displacement of the clips can be exactly measured by registration of kV plain film and planning DRR in condition of mDIBH assisted by ABC. The margins from CTV to PTV for EB PBI can be calculated based on the displacement of the clips.  Partial breast/three dimensional conformal radiation therapy Active breathing con trol; Kilovoh plain film; Silver clip displacement

title: Image guided radiotherapy for breast cancer patients: surgical clips as surrogate for breast excision cavity.
abstract: To determine the use of surgical clips as a surrogate for localization of the excision cavity and to quantify the stability of the clips' positions during the course of external beam radiotherapy for breast cancer patients, using cone beam computed tomography (CBCT) scans.  Twenty one breast cancer patients with surgical clips placed in the breast excision cavity were treated in a supine position with 28 daily fractions. CBCT scans were regularly acquired for a setup correction protocol. Retrospectively, the CBCT scans were registered to the planning CT scans, using gray value registration of the excision cavity region and chamfer matching of the clips. Subsequently, residual setup errors (systematic [S] and random [s] of the excision cavity were estimated relative to the clips' registration. Finally, the stability of the clips' positions were quantified as the movement of each separate clip according to the center of gravity of the excision cavity.  When clips were used for online setup corrections, the residual errors of the excision cavity were S(left right) 1.2, s(left right) 1.0; S(cranial caudal) 1.3, s(cranial caudal) 1.2; and S(anterior posterior) 0.7, s(anterior posterior) 0.9 mm. Furthermore, the average distance (over all patients) between the clips and centers of gravity of the excision cavities was 18.8 mm (on the planning CT) and was reduced to 17.4 mm (measured on the last CBCT scan) CONCLUSION Clips move in the direction of the center of gravity of the excision cavity, on average, 1.4 mm. The clips are good surrogates for locating the excision cavity and providing small residual errors.

title: Accuracy and efficiency of image guided radiation therapy (IGRT) for preoperative partial breast radiosurgery.
abstract: To analyze and evaluate accuracy and efficiency of IGRT process for preoperative partial breast radiosurgery.  Patients were initially setup with skin marks and 5 steps were performed: (1) Initial orthogonal 2D kV images, (2) pre treatment 3D CBCT images, (3) verification orthogonal 2D kV images, (4) treatment including mid treatment 2D kV images (for the final 15 patients only) and (5) post treatment orthogonal 2D kV or 3D CBCT images. Patient position was corrected at each step to align the biopsy clip and to verify surrounding soft tissue positioning.  The mean combined vector magnitude shifts and standard deviations at the 5 imaging steps were (1) 0.96 0.69, (2) 0.33 0.40, (3) 0.05 0.12, (4) 0.15 0.17, and (5) 0.27 0.24 in cm. The mean total IGRT time was 40.2 13.2 minutes. Each step was shortened by 2 to 5 minutes with improvements implemented. Overall, improvements in the IGRT process reduced the mean total IGRT time by approximately 20 minutes. Clip visibility was improved by implementing oblique orthogonal images.  Multiple imaging steps confirmed accurate patient positioning. Appropriate planning and imaging strategies improved the effectiveness and efficiency of the IGRT process for preoperative partial breast radiosurgery.

title: EP 1737: Intrafraction motion and ITV dose coverage in thoracic SBRT: preliminary analysis of 101 CBCT images
abstract: Ten patients with early stage breast cancer were enrolled. All patients had undergone breastconserving surgery and implantation of 4 surgical clips on the tumor bed, 2 of which had been placed in the nipple side of the tumor bed and 2 on each medial and lateral side of the tumor bed. Computed tomography (CT) was performed during free breathing (FB) After the FB CT data set acquisition, 2 additional CT scans were obtained during a held breath after light inhalation (IN) and light exhalation (EX) Based on the FB CT images, 2 different treatment plans (FIF plan and PWplan) were created for the entire breast for each patient and copied to the IN CT and EX CT images. The prescribed dose was 50 Gy in 25 fractions. The amount of change of in the volume of the target receiving 107% 95% and 90% of the prescription dose (V107% V95% and V90% respectively) on the IN plan and EX plan compared with the FB plan were evaluated. The length of movement of each surgical clip from EX CT to IN CT in 3 directions (horizontal, anteroposterior, and craniocaudal) and three dimensional vector displacement were measured.

title: Comparison of displacement of the silver clips in the cavity determined by KV plain film and cone beam computed tomography for the breast cancer patients treated by three dimensional conformal external beam partial breast irradiation assisted by active breathing control
abstract: 11585  To compare the margins of CTV extended to PTV depending on the displacement of the silver clips in the cavity determined by KV plain film and cone beam computed tomography for the breast cancer patients treated by external beam partial breast irradiation (EB PBI) assisted by active breathing control (ABC)  Ten patients were enrolled in the study. The patients received CT simulated positioning assisted by ABC to get the CT image sets based on the respiratory condition of moderate deep inspiration breath hold (mDIBH) and the clips located at the cephal, pedal, lateral border and bottom of the cavity were delineated respectively. Before each irradiation, twice CBCT and KV plain film were received assisted by ABC device, and then 3D 3D automatic registration based on pixel between the CBCT image and the planning CT image and 2D 2D automatic registration based on pixel between KV plain film and the planning digitally reconstructed radiograph (DRR) were finished, and then the margins.

title: Study to Compare the Effect of Different Registration Methods on Patient Setup Uncertainties in Cone beam Computed Tomography during Volumetric Modulated Arc Therapy for Breast Cancer Patients
abstract: This study compared three different methods used in registering cone beam computed tomography (CBCT) image set with planning CT image set for determining patient setup uncertainties during volumetric modulated arc therapy (VMAT) for breast cancer patients.  Seven breast cancer patients treated with 50 Gy in 25 fractions using VMAT technique were chosen for this study. A total of 105 CBCT scans were acquired by image guidance protocol for patient setup verification. Approved plans' CT images were used as the reference image sets for registration with their corresponding CBCT image sets. Setup errors in mediolateral, craniocaudal, and anteroposterior direction were determined using gray scale matching between the reference CT images and onboard CBCT images. Patient setup verification was performed using clip box registration (CBR) method during online imaging. Considering the CBR method as the reference, two more registrations were performed using mask registration (MR) method and dual registration (DR) (CBR MR) method in the offline mode. For comparison, systematic error random error (s) mean displacement vector (R) mean setup error (M) and registration time (Rt) were analyzed. Post hoc Tukey's honest significant difference test was performed for multiple comparisons.  Systematic and random errors were less in CBR as compared to MR and DR (P 0.05) The mean displacement error and mean setup errors were less in CBR as compared to MR and DR (P 0.05) Increased Rtwas observed in DR as compared to CBR and MR (P 0.05) In addition, multiple comparisons did not show any significant difference in patient setup error (P 0.05)  For breast VMAT plan delivery, all three registration methods show insignificant variation in patient setup error. One can use any of the three registration methods for patient setup verification.

title: [P175] Simultaneous boost in breast radiotherapy requires increased margins or revised match strategy
abstract: In radiotherapy simultaneous boost compared to sequential boost allows shortening of the overall treatment time. Challenges remain in obtaining good image match concurrently within the boost volume and total target volume. The present study evaluated the difference between match based on boost volume and total target volume, with the overall aim to suggest treatment margins if treating both boost and total target volume using the same registration.  A total of 358 cone beam CT (CBCT) s from 55 patients were analysed retrospectively. Of these 250 CBCTs were performed before each fraction on 16 patients receiving radiotherapy after breast conserving surgery and with lymph node involvement, and 39 patients receiving radiotherapy after breast conserving surgery without lymph node involvement were scheduled for CBCT once a week, and reached a total of 108 CBCTs. Two matches were performed with each CBCT: A chest wall match where CBCTs were auto registered to the planning CT, lymph nodes included if relevant (a match on the total volume) Further a boost specific match using manual registration of surgical clips.  Based on the systematic (S) and random errors (s) between the chest wall match and the boost match the CTV to PTV margins of the boost volume were calculated. Margins needed for the boost volume to receive the prescribed dose using a match based on the total target volume are (lateral, longitudinal, vertical) (7.3, 8.4, 8.5) mm and (5.1, 7.5, 4.3) mm, for the patients with lymph node involvement and without lymph node involvement data, respectively.  CTV to PTV margin for the boost area are normally set to 5 mm when using a sequential boost strategy. Our study suggests that with simultaneous boost radiotherapy larger margins are required. Further, patients with lymph node involvement compared to patients with only the breast involved requires a larger CTV to PTV margin. Another solution can be to use an adaptive protocol for daily IGRT which can reduce the required CTV to PTV margin for the boost region by re scanning and re matching the boost region for patients where the two regions differ by more than a pre set threshold.