Residual Image Registration Error by Fiducial Markers in Accelerated Partial Breast Irradiation Using C-Arm Linac: A Phantom Study

Introduction: External beam accelerated partial breast irradiation (APBI) is an alternative treatment for patients with early-stage breast cancer. The efficacy of image-guided radiotherapy (IGRT) using fiducial markers, such as gold markers or surgical clips, has been demonstrated. However, the effects of respiratory motion during a single fraction have not been reported. This study aimed to evaluate the residual image registration error of fiducial marker-based IGRT by respiratory motion and propose a suitable treatment strategy.Materials & Methods: We developed an acrylic phantom embedded with surgical clips to verify the registration error under moving conditions. The frequency of the phase difference in the respiratory cycle due to sequential acquisition was verified in a preliminary study. Fiducial marker-based IGRT was then performed in 10 scenarios. The residual registration error (RRE) was calculated on the basis of the differences in the coordinates of clips between the true position if not moved and the last position.Results: The frequencies of the phase differences in 0.0–0.99, 1.0–1.99, 2.0–2.99, 3.0–3.99, and 4.0–5.0 mm were 23%, 24%, 22%, 20%, and 11%, respectively. When assuming a clinical case, the mean RREs for all directions were within 1.0 mm, even if respiratory motion of 5 mm existed in two axes.Conclusions: For APBI with fiducial marker-based IGRT, the introduction of an image registration strategy that employs stepwise couch correction using at least three orthogonal images should be considered.

The role of surgical clips in Breast Conserving Therapy: Systematic review of the Literature

Introduction Conservative breast therapy consists of wide local excision followed by local control of the breast cancer by boost radiotherapy. For radiologists, identification of breast tumor bed (TB) is an essential first step for them to start their radiotherapy. There is number of ways to identify the tumor bed, one of them is inserting the metallic clips in the tumor bed cavity intraoperative. They mark the tumor cavity against the whole breast normal tissue as they appear radioopaque during radiotherapy. Purpose The primary aim of this study is to investigate the need & validity of surgical clips insertion in breast tumor bed and its effect on further breast radiotherapy through a systematic review that includes all published studies which used clips for marking the breast tumor bed. The secondary aim is to define the needed number of surgical clips to define the breast tumor bed clearly and obviously and what are the best types of surgical clips to be used for this purpose. Methods The literature review was done by searching on different databases using the keywords for only English studies reporting using surgical clips for localization in breast surgeries. There was no restriction to specific period or study design. Assessment of included studies was done by 2 independent researchers. Results 54 articles (n = 3427 patients) were the total number of studies that met our inclusion criteria. These studies were of different study designs. Cohort studies were the most representing type about 40 articles. The most common used clips type (21 study, n = 1444 patient) was metallic hemostatic clips according to the sum of operated patients and count of studies. Although all studies confirmed the importance and effectiveness of using clips for tumor bed localization, there was no standard optimum number of clips that can be used for localization. However, most studies used definite number of clips as 4 or 5 clips or used number ranging from 1-5 clips. The same for inserted clips margins at tumor bed, only few studies mentioned definite cavity margins. The 4 main margins (anterior, posterior, superior, inferior) were the commonest reported sites. Conclusion Using surgical clips whatever their type is very helpful for radiologists to define breast tumor bed especially with the obvious increase in using oncoplastic techniques. It’s recommended to use more than 5 clips at tumor bed cavity with special concern to insert them at least 4 margins of tumor bed.

Novel Breast Specimen Orientation Approach through 3D Visualizations for Relocating Inadequate Margins based on the Surgical Clips: Feasibility Study.

Purpose: The current breast specimen orientation method after breast-conserving surgery is potentially inaccurate due to deformability and mobility of the extracted breast tissue. This complicates targeted relocation during re-excision or radiation. Therefore, we propose a new 3D-visualization method to communicate the breast specimen orientation to instantly provide an intuitive overview of the resection margins in relation to the surgical clips on the wound bed.Methods: In 15 female patients undergoing breast-conserving surgery, the surgeon labeled the surgical clips on the specimen and the wound bed. During pathologic assessment, after inking, a 3D scan was made of the specimen. Tumor tissue was annotated on the histological image and transposed to the respective location inside the 3D model. The transposed resection margins with respect to the labeled surgical clips were calculated and visualized. Intuitivity of the visualization was tested (face validity) as well as the quality of displayed resection margins and labeled clips.Results: Average face validity score for 3D-visualization was between ‘++’ and ‘+’ for surgeons and between ‘+’ and ‘+/-’ for pathologists. Average difference between computed resection margins and reported histologic margins was 1 mm. In 8 cases not all clips could be labeled in situ. In 5 cases not all labeled clips could be retrieved by pathology. Conclusion: The visualizations appeared valuable in interdisciplinary communications. The displayed resection margins approximated the reported margins. Consistent accurate surgical clip labelling proved challenging.

DE-MR simulation imaging for prone radiotherapy after breast-conserving surgery: assessing its application in lumpectomy cavity delineation based on deformable image registration

Background The application of delayed-enhancement magnetic resonance (DE-MR) simulation imaging in lumpectomy cavity (LC) delineation for prone radiotherapy in patients with an invisible seroma or a low seroma clarity score (SCS) after breast-conserving surgery (BCS) based on deformable image registration (DIR) was assessed. Methods Twenty-six patients who were suitable for radiotherapy in prone positions after BCS were enrolled, and both computed tomography (CT) and DE-MR simulation scans were acquired. The LC delineated based on titanium surgical clips on CT images was denoted as LCCT. The LC delineated based on the signal of cavity boundaries on fat-suppressed T2-weighted imaging (T2WI) and multiphase delayed-enhancement T1-weighted imaging (DE-T1WI), which was performed at 2 min, 5 min and 10 min postinjection, were denoted as LCT2, LC2T1, LC5T1 and LC10T1, respectively. Afterwards, DIR was performed to compare the volumes and locations of the LCs with MIM software. The generalized conformity index (CIgen) of inter (intra) observer (Inter-CIgen and Intra-CIgen) was also used to explore the inter(intra) observer variation for LC delineation on each image modality. Results LCCT–LC10T1 provided the best conformal index (CI) and degree of inclusion (DI), increasing by 2.08% and 4.48% compared to LCCT–LCT2, 11.36% and 2.94% for LCCT–LC2T1, and 8.89% and 7.69% for LC5T1–LCCT, respectively. The center of mass (COM) of LCCT–LC10T1 decreased by 17.86%, 6.12% and 13.21% compared with that of LCCT–LCT2, LCCT–LC2T1 and LCCT–LC5T1, respectively. The agreement of LC delineation was strongest for 10th min DE-TIWI (coefficient of variation, COV = 2.30%, Inter-CIgen = 87.06%, Intra-CIgen = 92.64%). Conclusion For patients with a low SCS (SCS ≤ 2) after BCS, it is feasible to contour the LC based on prone DE-MR simulation images. Furthermore, the LC derived from prone DE-T1WI at 10 min was found to be most similar to that derived from prone CT simulation scans using titanium surgical clips regardless of the volume and location of the LC. Inter (intra) variability was minimal for the delineation of the LC based on 10th min DE-TIWI.

Delayed-enhancement magnetic resonance simulation imaging for prone radiotherapy after breast-conserving surgery: Assessing its application in lumpectomy cavity delineation based on deformable image registration

Background The application of delayed-enhancement magnetic resonance (DE-MR) simulation imaging in lumpectomy cavity (LC) delineation for prone radiotherapy in patients with an invisible seroma or a low seroma clarity score (SCS) after breast-conserving surgery (BCS) based on deformable image registration (DIR) was assessed. Methods Twenty-six patients who were suitable for radiotherapy in prone positions after BCS were enrolled, and both computed tomography (CT) and DE-MR simulation scans were acquired. The LC delineated based on titanium surgical clips on CT images was denoted as LCCT. The LC delineated based on the signal of cavity boundaries on fat-suppressed T2-weighted imaging (T2WI) and multiphase delayed-enhancement T1-weighted imaging (DE-T1WI), which was performed at 2 min, 5 min and 10 min postinjection, were denoted as LCT2, LC2T1, LC5T1 and LC10T1, respectively. Afterwards, DIR was performed to compare the volumes and locations of the LCs with MIM software. The generalized conformity index (CIgen) of inter (intra) observer (Inter-CIgen and Intra-CIgen) was also used to explore the inter(intra) observer variation for LC delineation on each image modality. Results LCCT-LC10T1 provided the best conformal index (CI) and degree of inclusion (DI), increasing by 2.08% and 4.48% compared to LCCT-LCT2, 11.36% and 2.94% for LCCT-LC2T1, and 8.89% and 7.69% for LC5T1-LCCT, respectively. The center of mass (COM) of LCCT-LC10T1 decreased by 17.86%, 6.12% and 13.21% compared with that of LCCT-LCT2, LCCT-LC2T1 and LCCT-LC5T1, respectively. The agreement of LC delineation was strongest for 10th min DE-TIWI (coefficient of variation, COV = 2.30%, Inter-CIgen = 87.06%, Intra-CIgen = 92.64%). Conclusion For patients with a low SCS (SCS ≤ 2) after BCS, it is feasible to contour the LC based on prone DE-MR simulation images. Furthermore, the LC derived from prone DE-T1WI at 10 min was found to be most similar to that derived from prone CT simulation scans using titanium surgical clips regardless of the volume and location of the LC. Inter(intra)variability was minimal for the delineation of the LC based on 10th min DE-TIWI.

Finding an Alternative for the Surgical Clips-based Delineation of Tumor Bed Boost Volume for Radiotherapy after Breast Conserving Surgery: A Prospective Comparative Study

Background: Radiotherapy after breast conserving surgery includes irradiation of whole breast and regional lymphatic areas which is followed by a boost to the tumor bed. Several different techniques have been proposed for delineation of tumor bed for boost. The purpose of the study was to identify the best method for localizing the tumor bed. Methods: 21 patients with histologically proven stage I and II infiltating ductal carcinoma of breast who underwent breast conserving surgery were included in the study. We delineated the boost volumes using five different techniques viz., patients’ self-localization, surgeon’s localization, pre-op CT based, scar-based and surgical clips based. The surgical clips-based volume is taken as a standard volume and the other volumes were compared with it. The outcome measures studied were the mean overlap volumes, the mean volume of surgical clips based volume missed by the other PTVs, the mean volumes of breast tissue outside the clips based PTV that could have been irradiated by the other PTVs. Results: None of the PTV volumes had good concordance with the surgical clips-based volume (PTV1). The best volume overlap was with patient’s self-localization (PTV3) albeit only being 34%. The scar-based localization volume had the least overlap with PTV1 (23%). The patients’ self-localization volume (PTV3) had the highest amount of breast tissue included outside PTV1 (64cc) and preop CT based volume (PTV4) included the least (42cc). Conclusion: Delineation of boost volume using surgical clips augmented by the simulation CT should be the standard technique for boost bed irradiation.