Interobserver variability in the delineation of the tumour bed using seroma and surgical clips based on 4DCT scan for external-beam partial breast irradiation

Contouring aid tools in radiotherapy. Smoothing: the false friend

OBJECTIVE

Contouring accuracy is critical in modern radiotherapy. Several tools are available to assist clinicians in this task. This study aims to evaluate the performance of the smoothing tool in the ARIA system to obtain more consistent volumes.

METHODS

Eleven different geometric shapes were delineated in ARIA v15.6 (Sphere, Cube, Square Prism, Six-Pointed Star Prism, Arrow Prism, And Cylinder and the respective volumes at 45° of axis deviation (_45)) in 1, 3, 5, 7, and 10 cm side or diameter each. Post-processing drawing tools to smooth those first-generated volumes were applied in different options (2D-ALL vs 3D) and grades (1, 3, 5, 10, 15, and 20). These volumetric transformations were analyzed by comparing different parameters: volume changes, center of mass, and DICE similarity coefficient index. Then we studied how smoothing affected two different volumes in a head and neck cancer patient: a single rounded node and the volume delineating cervical nodal areas.

RESULTS

No changes in data were found between 2D-ALL or 3D smoothing. Minimum deviations were found (range from 0 to 0.45 cm) in the center of mass. Volumes and the DICE index decreased as the degree of smoothing increased. Some discrepancies were found, especially in figures with cleft and spikes that behave differently. In the clinical case, smoothing should be applied only once throughout the target delineation process, preferably in the largest volume (PTV) to minimize errors.

CONCLUSION

Smoothing is a good tool to reduce artifacts due to the manual delineation of radiotherapy volumes. The resulting volumes must be always carefully reviewed.

Target volumes comparison between postoperative simulation magnetic resonance imaging and preoperative diagnostic magnetic resonance imaging for prone breast radiotherapy after breast-conserving surgery

BACKGROUND

This study investigated the differences in target volumes between preoperative magnetic resonance imaging (MRIpre) and postoperative MRI (MRIpost) for breast radiotherapy after breast-conserving surgery (BCS) using deformable image registration (DIR).

METHODS AND MATERIALS

Seventeen eligible patients who underwent whole-breast irradiation in the prone position after BCS were enrolled. On MRIpre, the gross tumor volume (GTV) was delineated as GTVpre, which was then expanded by 10 mm to represent the preoperative lumpectomy cavity (LC), denoted as LCpre. The LC was expanded to the clinical target volume (CTV) and planning target volume (PTV) on the MRIpre and MRIpost, denoted as CTVpre, CTVpost, PTVpre, and PTVpost, respectively. The MIM software system was used to register the MRIpre and MRIpost using DIR. Differences were evaluated regarding target volume, distance between the centers of mass (dCOM), conformity index (CI), and degree of inclusion (DI). The relationship between CILC /CIPTV and the clinical factors was also assessed.

RESULTS

Significant differences were observed in LC and PTV volumes between MRIpre and MRIpost (p < 0.0001). LCpre was 0.85 cm3 larger than LCpost, while PTVpre was 29.38 cm3 smaller than PTVpost. The dCOM between LCpre and LCpost was 1.371 cm, while that between PTVpre and PTVpost reduced to 1.348 cm. There were statistically significant increases in CI and DI for LCpost-LCpre and PTVpost-PTVpre (CI = 0.221, 0.470; DI = 0.472, 0.635). No obvious linear correlations (p > 0.05) were found between CI and GTV, primary tumor volume-to-breast volume ratio, distance from the primary tumor to the nipple and chest wall, and body mass index.

CONCLUSIONS

Despite using DIR technology, the spatial correspondence of target volumes between MRIpre and MRIpost was suboptimal. Therefore, relying solely on preoperative diagnostic MRI with DIR for postoperative LC delineation is not recommended.

The King is in the altogether: Radiation therapy after oncoplastic breast surgery

Breast cancer is the most common malignancy, and the majority of the patients are diagnosed at an early disease stage. Breast conservation is the preferred locoregional approach, and oncoplastic breast conservation surgery is becoming more popular. This narrative review aims to discuss the challenges and uncertainties in target volume definition for postoperative radiation after these procedures, to improve radiation therapy decisions and encourage multidisciplinary.

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 LC_CT. 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 LC_T2, LC_2T1, LC_5T1 and LC_10T1, 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

LC_CT–LC_10T1 provided the best conformal index (CI) and degree of inclusion (DI), increasing by 2.08% and 4.48% compared to LC_CT–LC_T2, 11.36% and 2.94% for LC_CT–LC_2T1, and 8.89% and 7.69% for LC_5T1–LC_CT, respectively. The center of mass (COM) of LC_CT–LC_10T1 decreased by 17.86%, 6.12% and 13.21% compared with that of LC_CT–LC_T2, LC_CT–LC_2T1 and LC_CT–LC_5T1, 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.

The status of medical physics in radiotherapy in China

PURPOSE

To present an overview of the status of medical physics in radiotherapy in China, including facilities and devices, occupation, education, research, etc. MATERIALS AND METHODS: The information about medical physics in clinics was obtained from the 9-th nationwide survey conducted by the China Society for Radiation Oncology in 2019. The data of medical physics in education and research was collected from the publications of the official and professional organizations.

RESULTS

By 2019, there were 1463 hospitals or institutes registered to practice radiotherapy and the number of accelerators per million population was 1.5. There were 4172 medical physicists working in clinics of radiation oncology. The ratio between the numbers of radiation oncologists and medical physicists is 3.51. Approximately, 95% of medical physicists have an undergraduate or graduate degrees in nuclear physics and biomedical engineering. 86% of medical physicists have certificates issued by the Chinese Society of Medical Physics. There has been a fast growth of publications by authors from mainland of China in the top international medical physics and radiotherapy journals since 2018.

CONCLUSIONS

Demand for medical physicists in radiotherapy increased quickly in the past decade. The distribution of radiotherapy facilities in China became more balanced. High quality continuing education and training programs for medical physicists are deficient in most areas. The role of medical physicists in the clinic has not been clearly defined and their contributions have not been fully recognized by the community.

Interobserver Variability of Target Volumes Delineated in the Supine and Prone Positions Based on Computed Tomography Images for External-Beam Partial Breast Irradiation After Breast-Conserving Surgery: A Comparative Study

Background: Although the supine position remains the dominant position for external-beam partial breast irradiation (EB-PBI), the advantages of administering EB-PBI in the prone position have been recognized. The interobserver variability between target volumes delineated in the different positions for EB-PBI after breast-conserving surgery needs to be investigated.

Methods: Twenty-seven patients suitable for EB-PBI were enrolled from July 2016 to April 2017. Supine and prone simulation CT images were sequentially acquired for all enrolled patients during free breathing. Five experienced radiotherapists delineated the target volumes for all patients on supine and prone simulation CT images. The selected parameters, including target volumes, the coefficient of variation (COV), the matching degree (MD), and so on, were calculated to analyze the interobserver variability.

Results: Regardless of the patient position, the interobserver variability between tumor bed (TB) and clinical target volume (CTV) measurements in supine and prone positions were statistically significant (F = 31.34, 19.467; 44.000, 41.985; P = 0.000, 0.001; 0.000, 0.001). The interobserver variability of COV_CTV was significantly greater in the supine position than in the prone position (T = 2.64, P = 0.014). Furthermore, the interobserver variabilities of MD_TB and MD_CTV were statistically lower in the supine position than in the prone position (Z = −3.460, −3.195, P = 0.000, 0.001).

Conclusion: When delineating the target volume for EB-PBI, the interobserver variability in the prone position was lower than that in the supine position. Hence, the administration of EB-PBI in the prone position during free breathing is a reasonable option.

A novel, adaptable, radiographically opaque, multi-plane continuous filament marker for optimizing tissue identification, radiation planning, and radiographic follow-up

Background

In breast cancer treatment, marking the tumor bed is an important aspect of the surgical component of therapy. Clear delineation of the tumor bed allows radiation oncologists a defined target for planning and delivering postoperative radiation therapy (XRT). Tumor bed marking also allows radiographic follow-up of the tumor bed on subsequent breast imaging. The aim of this assessment is to evaluate the ease and feasibility of utilizing a tumor bed filament marker (VeraFormÒ, Videra Surgical inc., USA) as a marker in post-operative benign surgical sites and malignant breast surgical tumor beds in breast cancer surgery.

Methods

The filament marker is a novel radiopaque surgical filament that in lieu of clips and other markers is implanted in the surgical tumor bed during breast surgery. Following development of the filament marker, the researchers used breast phantoms and radiographic images to develop a series of geometric patterns of placement options that optimize comprehensive multi-plane radiographic interpretation of the exact tumor bed or surgical margin. Three breast surgeons at 3 separate institutions then used this filament as a continuous multi-plane marker in 20 patients during breast conservation surgery. In these patients, the filament marker was thus used to mark the tumor bed (breast cancer surgery) or surgical site (benign breast disease) instead of the more traditional devices such as clips or other metallic open framework devices. We then assessed 2 important factors related to this device; (I) the ease, feasibility, and accuracy of in vivo placement with oncoplastic and non-oncoplastic breast conservation surgery techniques; (II) the radiographic footprint this device left on standard imaging protocols of post-operative mammogram (MMG), computed tomography (CT) scan, breast magnetic resonance imaging (MRI) examinations, and ultrasounds (USs) for both routine follow-up imaging and for standard radiation planning.

Results

There were no adverse events reported with the use of this device. The cases were then reviewed by a multidisciplinary team that included the original surgeon, a breast radiologist, and radiation oncologist. Their unanimous evaluation was that the filament marker clearly delineated all sides and planes of the tumor bed (cancer surgery) or surgical site (benign disease). Regardless of surgical technique utilized, this information provided precise 3D guidance for radiation planning and delivery as well as radiographic follow-up. The surgeons involved reported that delineating the bed with the filament marker was a quick and easy procedure and did not interfere with performing the planned surgical technique. Radiologists, surgeons, and radiation oncologists found that the filament marker was not only radiographically opaque on CT and MMG, but also caused no significant artifact on CT, MRI, US, or MMG.

Conclusions

The continuous multi-plane filament marker is a new device that fulfills the heretofore unmet need for safe and improved tumor bed and tissue site marking. It is an easy to place, non-palpable continuous multi-plane radiographic opaque tissue marker that seems to better delineate the tumor bed, regardless of type of breast surgery performed, while providing a more accurate 3D image for radiation planning and radiographic follow-up on MMG MRI, CT and US.

Analysis of the variability among radiation oncologists in delineation of the postsurgical tumor bed based on 4D-CT

OBJECTIVE

This study investigated interobserver and intraobserver variability in radiation oncologists' definition of the tumor bed (TB) after breast-conserving surgery (BCS).

RESULTS

The TB volume, CVS and number of surgical clips were not significantly related to intraobserver variability. Moreover, no correlation was noted between CT slice thickness and interobserver variability (Δinter, DSCinter) in TB delineation, and no significant difference was noted among the three groups. The TB volume was negatively correlated with Δinter. DSCinter improved significantly with increased TB volume and decreased Δinter. DSCinter also increased significantly in patients with a CVS of 3 to 5 compared with patients with a CVS of 1 to 2. DSCinter was thus positively correlated with the CVS, with a correlation coefficient of 0.451. The use of 7 to 9 surgical clips neither decreased Δinter nor increased DSCinter.

MATERIALS AND METHODS

Five or more surgical clips were placed at the TB during lumpectomy. The TB was delineated on the end expiration scan. The data were stratified based on the cavity visualization score (CVS), CT slice thickness and surgical clip number. The Dice similarity coefficient (DSC) and inter(intra)observer variability (Δinter and Δintra) in different groups were evaluated and compared.

CONCLUSIONS

Inter(intra)observer variability in TB delineation was decreased for breast cancer patients implanted with 5 or more surgical clips in the cohort with a higher CVS and a larger TB. The use of more than 6 surgical clips did not significantly improve TB delineation, so 5 to 6 surgical clips are likely adequate to delineate the TB.

Comparison of rigid and deformable registration through the respiratory phases of four-dimensional computed tomography image data sets for radiotherapy after breast-conserving surgery

BACKGROUND

The aim of this study was to compare the geometric differences in gross tumor volume (GTV) and surgical clips propagated by rigid image registration (RIR) and deformable image registration (DIR) using a four-dimensional computed tomography (4DCT) image data set for patients treated with boost irradiation or accelerated partial breast irradiation after breast-conserving surgery (BCS).

METHODS

The 4DCT data sets of 44 patients who had undergone BCS were acquired. GTV and selected clips were manually delineated on end-inhalation phase (CT0) and end-exhalation phase (CT50) images of 4DCT data sets. Subsequently, the GTV and selected clips from CT0 images were transformed and propagated to CT50 images using RIR and DIR, respectively. The geometric differences in GTV and surgical clips from DIR were compared with those of RIR.

RESULTS

The mean Dice similarity coefficient (DSC) index was 0.860 ± 0.042 for RIR and 0.870 ± 0.040 for DIR for GTV (P = .000). The three-dimensional distance to the center of mass (COM) of the GTV from RIR was longer than that from DIR (1.22 mm and 1.10 mm, respectively, P = .000). Moreover, in the anterior-posterior direction, displacements from RIR were significantly greater than those from DIR for both GTV (0.70 mm and 0.50 mm, respectively) and selected clips (upper clip, 0.45 mm vs 0.20 mm; inner clip, 0.55 mm vs 0.30 mm; outer clip, 0.40 mm vs 0.20 mm; lower clip, 0.50 mm vs 0.25 mm) (P = .000). However, in the left-right and superior-inferior directions, there were no significant displacement differences between RIR and DIR for GTV and the selected clips (all P > .050).

CONCLUSION

DIR can improve the overlap for GTV registration from CT0 to CT50 images from 4DCT scanning. Furthermore, DIR is superior to RIR in reflecting the displacement of GTV and selected clips in the anterior-posterior direction induced by respiratory movement.

A comparison study between gross tumor volumes defined by preoperative magnetic resonance imaging, postoperative specimens, and tumor bed for radiotherapy after breast-conserving surgery

BACKGROUND

The identification and contouring of target volume is important for breast-conserving therapy. The aim of the study was to compare preoperative magnetic resonance imaging (MRI), postoperative pathology, excised specimens' (ES) size, and tumor bed (TB) delineation as methods for determining the gross tumor volume (GTV) for radiotherapy after breast-conserving surgery (BCS).

METHODS

Thirty-three patients with breast cancer who underwent preoperative MRI and radiotherapy after BCS were enrolled. The GTVs determined by MRI, pathology, and the ES were defined as GTVMRI, GTVPAT, and GTVES, respectively. GTVMRI+1 was defined as a 1.0-cm margin around the GTVMRI. The radiation oncologist delineated GTV of the TB (GTVTB) using planning computed tomography according to ≥5 surgical clips placed in the lumpectomy cavity (LC).

RESULTS

The median GTVMRI, GTVMRI+1, GTVPAT, GTVES, and GTVTB were 0.97 cm (range, 0.01-6.88), 12.58 cm (range, 3.90-34.13), 0.97 cm (range, 0.01-6.36), 15.46 cm (range, 1.15-70.69), and 19.24 cm (range, 4.72-54.33), respectively. There were no significant differences between GTVMRI and GTVPAT, GTVMRI+1 and GTVES, GTVES and GTVTB (P = 0.188, 0.070, and 0.264, respectively). GTVMRI is positively related with GTVPAT. However, neither GTVES nor GTVTB correlated with GTVMRI (P = 0.071 and 0.378, respectively). Furthermore, neither GTVES nor GTVTB correlated with GTVMRI+1 (P = 0.068 and 0.375, respectively).

CONCLUSION

When ≥5 surgical clips were placed in the LC for BCS, the volume of TB was consistent with the volume of ES. Neither the volume of TB nor the volume of ES correlated significantly with the volume of tumor defined by preoperative MRI.

A comparison of dosimetric variance for external-beam partial breast irradiation using three-dimensional and four-dimensional computed tomography

Purpose

To investigate the potential dosimetric benefits from four-dimensional computed tomography (4DCT) compared with three-dimensional computed tomography (3DCT) in radiotherapy treatment planning for external-beam partial breast irradiation (EB-PBI).

Patients and methods

3DCT and 4DCT scan sets were acquired for 20 patients who underwent EB-PBI. The volume of the tumor bed (TB) was determined based on seroma or surgical clips on 3DCT images (defined as TB_3D) and the end inhalation (EI) and end exhalation (EE) phases of 4DCT images (defined as TB_EI and TB_EE, respectively). The clinical target volume (CTV) consisted of the TB plus a 1.0 cm margin. The planning target volume (PTV) was the CTV plus 0.5 cm (defined as PTV_3D, PTV_EI, and PTV_EE). For each patient, a conventional 3D conformal plan (3D-CRT) was generated (defined as EB-PBI_3D, EB-PBI_EI, and EB-PBI_EE).

Results

The PTV_3D, PTV_EI, and PTV_EE were similar (P=0.549), but the PTV coverage of EB-PBI_3D was significantly less than that of EB-PBI_EI or EB-PBI_EE (P=0.001 and P=0.025, respectively). There were no significant differences in the homogeneity or conformity indexes between the three treatment plans (P=0.125 and P=0.536, respectively). The EB-PBI_3D plan resulted in the largest organs at risk dose.

Conclusion

There was a significant benefit for patients when using 3D-CRT based on 4DCT for EB-PBI with regard to reducing nontarget organ exposure. Respiratory motion did not affect the dosimetric distribution during free breathing, but might result in poor dose coverage when the PTV is determined using 3DCT.

Harmonization of the Volume of Interest Delineation among All Eleven Radiotherapy Centers in the North of France

Background

Inter-observer delineation variation has been detailed for many years in almost every tumor location. Inadequate delineation can impair the chance of cure and/or increase toxicity. The aim of our original work was to prospectively improve the homogeneity of delineation among all of the senior radiation oncologists in the Nord-Pas de Calais region, irrespective of the conditions of practice.

Methods

All 11 centers were involved. The first studied cancer was prostate cancer. Three clinical cases were studied: a low-risk prostate cancer case (case 1), a high-risk prostate cancer case (pelvic nodes, case 2) and a case of post-operative biochemical elevated PSA (case 3). All of the involved physicians delineated characteristically the clinical target volume (CTV) and organs at risk. The volumes were compared using validated indexes: the volume ratio (VR), common and additional volumes (CV and AV), volume overlap (VO) and Dice similarity coefficient (DSC). A second delineation of the same three cases was performed after discussion of the slice results and the choice of shared guidelines to evaluate homogenization. A comparative analysis of the indexes before and after discussion was conducted using the Wilcoxon test for paired samples. A p-value less than 0.05 was considered to indicate statistical significance.

Results

The indexes were not improved in case 1, for which the inter-observer agreement was considered good after the first comparison (DSC = 0.83±0.06). In case 2, the second comparison showed homogenization of the CTV delineation with a significant improvement in CV (81.4±11.7 vs. 88.6±10.26, respectively, p = 0.048), VO (0.41±0.09 vs. 0.47±0.07, respectively; p = 0.009) and DSC (0.58±0.09 vs. 0.63±0.07, respectively; p = 0.0098). In case 3, VR and AV were significantly improved: VR: 1.71(±0.6) vs. 1.34(±0.46), respectively, p = 0.0034; AV: 46.58(±14.50) vs. 38.08(±15.10), respectively, p = 0.0024. DSC was not improved, but it was already superior to 0.6 in the first comparison.

Conclusion

Our prospective work showed that a collaborative discussion about clinical cases and the choice of shared guidelines within an established framework improved the homogeneity of CTV delineation among the senior radiation oncologists in our region.