Query: partial breast irradiation CBCT

title: Measurement of dose exposure of image guidance in external beam accelerated partial breast irradiation: Evaluation of different techniques and linear accelerators.
abstract: Verifying the patient position is always an essential part of the treatment process, especially in hypofractionated treatments such as accelerated partial breast irradiation (APBI) The purpose of the study was to compare five image guidance techniques with respect to imaging dose and image quality.  We chose five types of imaging methods applicable for APBI and measured their dose exposure on four different accelerators (Synergy, TrueBeam, Artiste and CyberKnife) Absorbed dose was measured with ionization chamber in thorax phantom. Besides dose exposure image quality was also compared.  The lowest dose exposure was measured with kV kV planar imaging followed by kV CBCT, MV MV pair and MV CBCT in ascending order. Average phantom dose with kV kV image pair on CyberKnife was 0.01 cGy as the lowest and with MV CBCT on Artiste was 7.11 cGy as the highest. Average dose exposures of MV MV images with TrueBeam, Synergy and Artiste were 1.18 cGy, 2.13 cGy and 1.61 cGy, respectively, with similar image quality. For the same machines the doses of kV CT imaging were comparable: 0.65 cGy, 0.65 cGy and 0.52 cGy, with some differences in image quality. MV CBCT technique resulted in the highest dose and poorest image quality.  In APBI the position of the patient and tumour bed can be verified with many tools. When fiducials are available, often 2D imaging is enough to achieve appropriate positioning and the kV kV method is recommended. Imaging with 2.5MV can also be a good solution instead of 6MV. Without fiducials 3D images should be acquired and the recommended method is the kV CBCT.

title: Accelerated partial breast irradiation with 3 dimensional conformal and image guided intensity modulated radiotherapy following breast conserving surgery 7 Year results of a phase II trial
abstract: To present the 7 year results of accelerated partial breast irradiation (APBI) using three dimensional conformal (3D CRT) and image guided intensity modulated radiotherapy (IG IMRT) following breast conserving surgery (BCS)  Between 2006 and 2014, 104 patients were treated with APBI given by means of 3D CRT using 3 5 non coplanar, isocentric wedged fields, or IG IMRT using kV CBCT. The total dose of APBI was 36.9 Gy (9 x 4.1 Gy) using twice a day fractionation. Survival results, side effects and cosmetic results were assessed.  At a median follow up of 90 months three (2.9% local recurrences, one (0.9% regional recurrence and two (1.9% distant metastases were observed. The 7 year local (LRFS) recurrence free survival was 98.9% The 7 year disease free (DFS) metastases free (MFS) and overall survival (OS) was 94.8% 97.9% and 94.8% respectively. Late side effects included G1 skin toxicity in 15 (14.4% G1, G2, and G3 fibrosis in 26 (25% 3 (2.9% and 1 (0.9% patients respectively. Asymptomatic (G1) fat necrosis occurred in 10 (9.6% patients. No G2 or higher late side effects occurred with IMRT. The rate of excellent/good and fair/poor cosmetic results was 93.2% and 6.8% respectively.  7 year results of APBI with 3D CRT and IG IMRT are encouraging. Toxicity profile and local tumor control are comparable to other series using multicatheter interstitial brachytherapy. Therefore, these external beam APBI techniques are valid alternatives to whole breast irradiation and brachytherapy based APBI.

title: Effects of online cone beam computed tomography with active breath control in determining planning target volume during accelerated partial breast irradiation.
abstract: To test if active breath control during cone beam computed tomography (CBCT) could improve planning target volume during accelerated partial breast radiotherapy for breast cancer.  Patients who were more than 40 years old, underwent breast conserving dissection and planned for accelerated partial breast irradiation, and with postoperative staging limited to T1 2 N0 M0, or postoperative staging T2 lesion no larger than 3cm with a negative surgical margin greater than 2mm were enrolled. Patients with lobular carcinoma or extensive ductal carcinoma in situ were excluded. CBCT images were obtained pre correction, post correction and post treatment. Set up errors were recorded at left right, anterior posterior and superior inferior directions. The differences between these CBCT images, as well as calculated radiation doses, were compared between patients with active breath control or free breathing.  Forty patients were enrolled, among them 25 had active breath control. A total of 836 CBCT images were obtained for analysis. CBCT significantly reduced planning target volume. However, active breath control did not show significant benefit in decreasing planning target volume margin and the doses of organ at risk when compared to free breathing.  CBCT, but not active breath control, could reduce planning target volume during accelerated partial breast irradiation.

title: Daily CBCT Versus Biweekly CBCT Versus Portal Imaging for Partial Breast Irradiation

title: Prone accelerated partial breast irradiation using cone beam CT (CBCT) guidance.
abstract: CTRC AACR San Antonio Breast Cancer Symposium: 2008 Abstracts  Prone external beam partial breast irradiation when used for a carefully selected subset of patients has been shown to have excellent long term control and cosmesis (Formenti et al. IJROBP 60(2) 493 504 2004) We used Cone beam CT (CBCT) to visualize the tumor bed target prior to each daily fraction of partial breast irradiation. The purpose of this study is to measure the residual error in soft tissue positioning after alignment based on skin marks and MV portal imaging for patients treated on a prospective prone APBI study (3000cGy in 5 fractions over 5 days)  Twenty five post menopausal women with pT1 breast cancer have consented on our NYU partial breast protocol using CBCT. Twenty three patients have been simulated and treated in the prone position on a specially designed mattress. After initial skin mark setup and alignment, MV portal imaging with shift using the tangent beams eye view was used to optimize setup for the first 6 patients (Group I) For all daily fractions, CBCT was performed with the Varian On Board Imager kV imaging system with a 35cm field of view and a 2.5mm slice thickness. CBCT was compared with the planning CT to shift the patient and evaluate the residual error in setup. The residual error from CBCT setup after optimal portal imaging was recorded for each patient. For the subsequent 17 patients (Group II) portal imaging was performed without shift to calculate the residual error from CBCT setup representing skin mark setup.  At the time of this report, 23 patients have been treated with all 5 fractions. The values for the residual error detected after cone beam CT for Group I (after skin mark set up and portal imaging) and for Group II (after skin mark setup alone) are compared and shown in Table 1.  In this preliminary study with a small number of patients, the residual error was minimal, around 2 mm. Therefore, for patients immobilized on our customized mattress, a reproducible and accurate prone APBI setup can be achieved with use of CBCT. However, given the very small residual error detected clinicians should be weary of indiscriminant use of CBCT for PBI. Concerns over contralateral breast dose and carcinogenic risk should limit the routine use of CBCT imaging for breast radiotherapy unless larger studies demonstrate improved accuracy of treatment delivery with CBCT.   /embed/graphic 1.gif

title: SU F J 130: Margin Determination for Hypofractionated Partial Breast Irradiation.
abstract: To determine the Planning Target Volume (PTV) margin for Hypofractionated Partial Breast Irradiation (HPBI) using the van Herk formalism (M=2.5+0.7s) HPBI is a novel technique intended to provide local control in breast cancer patients not eligible for surgical resection, using 40 Gy in 5 fractions prescribed to the gross disease.  Setup uncertainties were quantified through retrospective analysis of cone beam computed tomography (CBCT) data sets, collected prior to (prefraction) and after (postfraction) treatment delivery. During simulation and treatment, patients were immobilized using a wing board and an evacuated bag. Prefraction CBCT was rigidly registered to planning 4 dimensional computed tomography (4DCT) using the chest wall and tumor, and translational couch shifts were applied as needed. This clinical workflow was faithfully reproduced in Pinnacle (Philips Medical Systems) to yield residual setup and intrafractional error through translational shifts and rigid registrations (ribs and sternum) of prefraction CBCT to 4DCT and postfraction CBCT to prefraction CBCT, respectively. All ten patients included in this investigation were medically inoperable; the median age was 84 (range, 52 100) years.  Systematic (and random) setup uncertainties (in mm) detected for the left right, craniocaudal and anteroposterior directions were 0.4 (1.5) 0.8 (1.8) and 0.4 (1.0) net uncertainty was determined to be 0.7 (1.5) Rotations >2deg in any axis occurred on 8/72 (11.1% registrations.  Preliminary results suggest a non uniform setup margin (in mm) of 2.2, 3.3 and 1.7 for the left right, craniocaudal and anteroposterior directions is required for HPBI, given its immobilization techniques and online setup verification protocol. This investigation is ongoing, though published results from similar studies are consistent with the above findings. Determination of margins in breast radiotherapy is a paradigm shift, but a necessary step in moving towards hypofractionated regiments, which may ultimately redefine the standard of care for this select patient population.

title: SU E J 37: Feasibility of Utilizing Carbon Fiducials to Increase Localization Accuracy of Lumpectomy Cavity for Partial Breast Irradiation
abstract: To investigate the feasibility of utilizing carbon fiducials to increase localization accuracy of lumpectomy cavity for partial breast irradiation (PBI)  Carbon fiducials were placed intraoperatively in the lumpectomy cavity following resection of breast cancer in 11 patients. The patients were scheduled to receive whole breast irradiation (WBI) with a boost or 3D conformal PBI. WBI patients were initially setup to skin tattoos using lasers, followed by orthogonal kV on board imaging (OBI) matching to bone per clinical practice. Cone beam CT (CBCT) was acquired weekly for offline review. For the boost component of WBI and PBI, patients were setup with lasers, followed by OBI matching to fiducials, with final alignment by CBCT matching to fiducials. Using carbon fiducials as a surrogate for the lumpectomy cavity and CBCT matching to fiducials as the gold standard, setup uncertainties to lasers, OBI bone, OBI fiducials, and CBCT breast were compared.  Minimal imaging artifacts were introduced by fiducials on the planning CT and CBCT. The fiducials were sufficiently visible on OBI for online localization. The mean magnitude and standard deviation of setup errors were 8.4mm 5.3 mm (n=84) 7.3mm 3.7mm (n=87) 2.2mm 1.6mm (n=40) and 4.8mm 2.6mm (n=87) for lasers,more OBI bone, OBI fiducials and CBCT breast tissue, respectively. Significant migration occurred in one of 39 implanted fiducials in a patient with a large postoperative seroma.  OBI carbon fiducial based setup can improve localization accuracy with minimal imaging artifacts. With increased localization accuracy, setup uncertainties can be reduced from 8mm using OBI bone matching to 3mm using OBI fiducial matching for PBI treatment. This work demonstrates the feasibility of utilizing carbon fiducials to increase localization accuracy to the lumpectomy cavity for PBI. This may be particularly attractive for localization in the setting of proton therapy and other scenarios in which metal clips are contraindicated.

title: Prospective Study of Cone beam CT (CBCT) Guidance for Prone Accelerated Partial Breast Irradiation (APBI)

title: Using corrected Cone Beam CT image for accelerated partial breast irradiation treatment dose verification: the preliminary experience
abstract: BackgroundAccurate target localization is mandatory in the accelerated partial breast irradiation (APBI) delivery. Dosimetric verification for positional error will further guarantee the accuracy of treatment delivery. The purpose of this study is to evaluate the clinical feasibility of a cone beam computer tomographic (CBCT) image correction method in APBI.MethodsA CBCT image correction method was developed. First, rigid image registration was proceeded for CTs and CBCTs; second, these images were separated into four parts; then, ratio images for each of the four parts of planning CTs/CBCTs were calculated and filtered to reduce the high spatial frequency; finally, the enhanced CBCT images were generated combing the four parts. An anthropomorphic thorax rando phantom was used to evaluate the feasibility and accuracy of the CBCT correction method. The CBCT images of consecutive 10 patients receiving APBI were corrected using the above method and dosimetric variations were evaluated. Each set of CBCT is composed of three images: one acquired after skin marker setup, one after online setup correction and one after treatment delivery.ResultsThe phantom study showed the improved accuracy of dose calculation with corrected CBCT. The Dose Volume Histogram (DVH) difference between the planning CT and corrected CBCT is less than the difference between the planning CT and original CBCT. The maximum dose difference between the corrected CBCT and planning CT is 0.8% in PTV_EVAL V100, which is 3.8% between original CBCT and planning. In the patient study, 67.4% of fractions benefit from CBCT setup corrections in PTV_EVAL D95, while in 47.4% of the fractions, reduced dose coverage was found on the post treatment CBCT. Overall, the CBCT based initial setup correction guaranteed target dose coverage in 9 patients.ConclusionsA generic CBCT image correction algorithm was created and proved to be easily implemented in clinic. Compared to the original CBCT, the corrected CBCT has more accuracy in dose calculation. The CBCT guided APBI based on initial skin setup is not sufficient to guarantee the accurate dose delivery throughout each fraction. The long treatment delivery time may compromise the target coverage benefits in some patients.

title: CBCT Enabled Reconstruction of Inter fraction Variation of Dose Distribution for Partial Breast Irradiation