Four-Dimensional Measurement of the Displacement of Internal Fiducial and Skin Markers During 320-Multislice Computed Tomography Scanning of Breast Cancer

Considering Lumpectomy Cavity PTV Expansions: Characterization of Intrafraction Lumpectomy Cavity Motion

PURPOSE

Accelerated partial breast irradiation and lumpectomy cavity boost radiation therapy plans generally use volumetric expansions from the lumpectomy cavity clinical target volume to the planning target volume (PTV) of 1 to 1.5 cm, substantially increasing the volume of irradiated breast tissue. The purpose of this study was to quantify intrafraction lumpectomy cavity motion during external beam radiation therapy to inform the indicated clinical target volume to PTV expansion.

METHODS AND MATERIALS

Forty-four patients were treated with a whole breast irradiation using traditional linear accelerator-based radiation therapy followed by lumpectomy cavity boost using magnetic resonance (MR)-guided radiation therapy on a prospective registry study. Two-dimensional cine-MR images through the center of the surgical cavity were acquired during each boost treatment to define the treatment position of the lumpectomy cavity. This was compared with the reference position to quantify intrafraction cavity motion. Free-breathing technique was used during treatment. Clinical outcomes including toxicity, cosmesis, and rates of local control were additionally analyzed.

RESULTS

The mean maximum displacement per fraction in the anterior-posterior (AP) direction was 1.4 mm. Per frame, AP motion was <5 mm in 92% of frames. The mean maximum displacement per fraction in the superior-inferior (SI) direction was 1.2 mm. Per frame, SI motion was <5 mm in 94% of frames. Composite motion was <5 mm in 89% of frames. Three-year local control was 97%. Eight women (18%) developed acute G2 radiation dermatitis. With a median follow-up of 32.4 months, cosmetic outcomes were excellent (22/44, 50%), good (19/44, 43%), and fair (2/44, 5%).

CONCLUSIONS

In approximately 90% of analyzed frames, intrafraction displacement of the lumpectomy cavity was <5 mm, with even less motion expected with deep inspiratory breath hold. Our results suggest reduced PTV expansions of 5 mm would be sufficient to account for lumpectomy cavity position, which may accordingly reduce late toxicity and improve cosmetic outcomes.

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.

Comprehensive target geometric errors and margin assessment in stereotactic partial breast irradiation

Background

Recently developed stereotactic partial breast irradiation (S-PBI) allows delivery of a high biologically potent dose to the target while sparing adjacent critical organs and normal tissue. With S-PBI tumoricidal doses, accurate and precise dose delivery is critical to achieve high treatment quality. This study is to investigate both rigid and non-rigid components of target geometric error and their corresponding margins in S-PBI and identify correlated clinical factors.

Methods

Forty-three early-stage breast cancer patients with implanted gold fiducial markers were enrolled in the study. Fiducial positions recorded on the orthogonal kV images on a Cyberknife system during treatment were used to estimate intra-fraction errors and composite errors (including intra-fraction errors and residual errors after patient setup). Both rigid and non-rigid components of intra-fraction and composite errors were analyzed and used to estimate rigid and non-rigid margins, respectively. Univariate and multivariate linear regressions were conducted to evaluate correlations between clinical factors and errors.

Results

For the study group, the intra-fraction rigid and non-rigid errors are 2.0 ± 0.6 mm and 0.3 ± 0.2 mm, respectively. The composite rigid and non-rigid errors are 2.3 ± 0.5 mm and 1.3 ± 0.8 mm, respectively. The rigid margins in the left-right, anterior-posterior, and superior-inferior directions are estimated as 2.1, 2.4, and 2.3 mm, respectively. The estimated non-rigid margin, assumed to be isotropic, is 1.7 mm. The outer breast quadrants are more susceptible to composite errors occurrence than the inner breast quadrants. The target to chest wall distance is the clinical factor correlated with target geometric errors.

Conclusions

This is the first comprehensive analysis of breast target geometric rigid and non-rigid errors in S-PBI. Upon the estimation, the non-rigid margin is comparable to rigid margin, and therefore should be included in planning target volume as it cannot be accounted for by the Cyberknife system. Treatment margins selection also need to consider the impact of relevant clinical factor.

Electronic supplementary material

The online version of this article (10.1186/s13014-017-0889-6) contains supplementary material, which is available to authorized users.

Magnetic Resonance Image Guided Radiation Therapy for External Beam Accelerated Partial-Breast Irradiation: Evaluation of Delivered Dose and Intrafractional Cavity Motion

PURPOSE

To use magnetic resonance image guided radiation therapy (MR-IGRT) for accelerated partial-breast irradiation (APBI) to (1) determine intrafractional motion of the breast surgical cavity; and (2) assess delivered dose versus planned dose.

METHODS AND MATERIALS

Thirty women with breast cancer (stages 0-I) who underwent breast-conserving surgery were enrolled in a prospective registry evaluating APBI using a 0.35-T MR-IGRT system. Clinical target volume was defined as the surgical cavity plus a 1-cm margin (excluding chest wall, pectoral muscles, and 5 mm from skin). No additional margin was added for the planning target volume (PTV). A volumetric MR image was acquired before each fraction, and patients were set up to the surgical cavity as visualized on MR imaging. To determine the delivered dose for each fraction, the electron density map and contours from the computed tomography simulation were transferred to the pretreatment MR image via rigid registration. Intrafractional motion of the surgical cavity was determined by applying a tracking algorithm to the cavity contour as visualized on cine MR.

RESULTS

Median PTV volume was reduced by 52% when using no PTV margin compared with a 1-cm PTV margin used conventionally. The mean (± standard deviation) difference between planned and delivered dose to the PTV (V95) was 0.6% ± 0.1%. The mean cavity displacement in the anterior-posterior and superior-inferior directions was 0.6 ± 0.4 mm and 0.6 ± 0.3 mm, respectively. The mean margin required for at least 90% of the cavity to be contained by the margin for 90% of the time was 0.7 mm (5th-95th percentile: 0-2.7 mm).

CONCLUSION

Minimal intrafractional motion was observed, and the mean difference between planned and delivered dose was less than 1%. Assessment of efficacy and cosmesis of this MR-guided APBI approach is under way.

Are fiducial markers useful surrogates when using respiratory gating to reduce motion of gastroesophageal junction tumors?

BACKGROUND

Radiation therapy (RT) is an integral component of the management of gastroesophageal junction (GEJ) tumors. We evaluated the use of implanted radiopaque fiducials as tumor surrogates to allow for more focal delivery of RT to these mobile tumors when using respiratory gating (RG) to reduce motion.

MATERIAL AND METHODS

We analyzed four-dimensional computed tomography scans of 20 GEJ patients treated with RG and assessed correlation between tumor and implanted fiducial motion over the whole respiratory cycle and within a clinically realistic gate around end-exhalation. We evaluated fiducial motion concordance in 11 patients with multiple fiducials.

RESULTS

Gating reduced anterior-posterior (AP) and superior-inferior (SI) mean tumor and fiducial motions by over 50%. Fiducials and primary tumor motions were moderately correlated: R(2) for AP and SI linear fits to the entire group were 0.54 and 0.68, respectively, but the correlation had strong inter-patient variation. For all patients with multiple fiducials, relative in-gate displacements were below 3 mm; results were similar for eight of 11 patients over the whole cycle.

CONCLUSION

Implanted fiducial and gross tumor volume (GTV) motions correlate well but the correlation is patient-specific and may be dependent on the location of the fiducials with respect to the GTV.

Differences in displacement of the proximal and distal ends of mid-upper thoracic esophageal squamous cell carcinoma

In the present study, clips were used as markers to evaluate displacement differences between proximal and distal ends of esophageal tumors and to test whether their internal target volume (ITV) margins should be determined separately. A total of 23 patients with mid-upper thoracic esophageal squamous-cell carcinoma, a tumor length of ≤8 cm and an esophageal lumen suitable for endoscopic ultrasonography were recruited for the present study. Clips were implanted endoscopically at the proximal and distal ends of the esophageal tumor (upper and lower clips). In a further exploratory study on 16 of the patients, a third clip was placed at the distal esophagus 2 cm above the gastro-esophageal junction (GEJ) (cardiac clip). The clips were contoured for all 10 phases of the four-dimensional computed tomography and the maximum displacements of the clip centroids among different breathing phases in left-right (LR), superior-inferior (SI) and anterior-posterior (AP) directions were marked as x, y and z, respectively. The ITV margins that covered 95% of the LR, SI and AP motion were 2.89, 5.00 and 2.36 mm, respectively. Axial displacement (y) was greater than radial displacement (x, z; P<0.05). It was also revealed that LR(x), SI(y) and AP(z) displacement of cardiac clips was greater than that of upper or lower clips (P<0.05). Differences in the axial and radial displacement of the upper and lower clips indicated that axial and radial ITV margins should be determined separately. However, further study is required on patients in whom the distal tumor end is located in proximity to the GEJ.

Assessment of respiration-induced displacement of canine abdominal organs in dorsal and ventral recumbency using multislice computed tomography

Respiratory-induced organ displacement during image acquisition can produce motion artifacts and variation in spatial localization of an organ in diagnostic computed tomography (CT) examinations. The purpose of this prospective study was to quantify respiratory-induced abdominal organ displacement in dorsal and ventral recumbency using five normal dogs. All dogs underwent CT examinations using 64 multidetector row CT (64-MDCT). A "3-dimensional (3D) apneic CT exam" of the abdomen was acquired followed by a "4-dimensional (4D) ventilated CT exam." The liver, pancreas, both kidneys, both medial iliac lymph nodes, and urinary bladder were delineated on the 3D-apneic examination and the organ outlines were compared to the maximum alteration in organ position in the 4D-ventilated examination. Displacement was measured in dorsal-to-ventral (DV), right-to-left (RL), and cranial-to-caudal (CC) directions. Respiratory-induced displacement of canine abdominal organs was not predictable and showed large variability in the three directions evaluated. For most canine abdominal organs, dorsal recumbency provided overall the least amount of displacement among all directions evaluated except for liver and urinary bladder. For liver, a large variability was found for all directions and a statistically significant difference was found only in the RL direction with ventral recumbency exhibiting less displacement (P = 0.0099). For the urinary bladder, ventral recumbency also provided less displacement but this was statistically significant only in the RL direction (P < 0.0001). Findings from this study indicated that dorsal recumbency may be preferred for minimizing respiratory motion artifacts in whole abdomen studies, but ventral recumbency may be preferred for liver and urinary bladder studies when respiration cannot be controlled.

A comparative study on the volume and localization of the internal gross target volume defined using the seroma and surgical clips based on 4DCT scan for external-beam partial breast irradiation after breast conserving surgery

Background

To explore the volume and localization of the internal gross target volume defined using the seroma and/or surgical clips based on the four-dimensional computed tomography (4DCT) during free-breathing.

Methods

Fifteen breast cancer patients after breast-conserving surgery (BCS) were recruited for EB-PBI. On the ten sets CT images, the gross target volume formed by the clips, the seroma, both the clips and seroma delineated by one radiation oncologist and defined as GTVc, GTVs and GTVc + s, respectively. The ten GTVc, GTVs and GTVc + s on the ten sets CT images produced the IGTVc, IGTVs, IGTVc + s, respectively. The IGTV volume and the distance between the center of IGTVc, IGTVs, IGTVc + s were all recorded. Conformity index (CI), degree of inclusion (DI) were calculated for IGTV/IGTV, respectively.

Results

The volume of IGTVc + s were significantly larger than the IGTVc and IGTVs (p < 0.05). There was significant difference between the DIs of IGTVc vs IGTVc + s, the DIs of IGTVs vs IGTVc + s. There was significant difference among the CIs of IGTV/IGTV. The DIs and CIs of IGTV/IGTV were negatively correlated with their centroid distance (r < 0, p < 0.05).

Conclusions

There were volume difference and spatial mismatch between the IGTVs delineated based on the surgical clips and seroma. The IGTV defined as the seroma and surgical clips provided the best overall representation of the ‘true’ moving GTV.

Individually wide range of renal motion evaluated by four-dimensional computed tomography

Objectives

Assessment of physiologic renal motion in order to optimize abdominal intensity-modulated radiation therapy and stereotactic body radiation therapy.

Methods and materials

Twenty patients with a median age of 47 years underwent computed tomography simulation and four-dimensional computed tomography acquisition. Thirty-nine kidneys were contoured during ten phases of respiration to estimate renal motion.

Results

Kidney motion was not related to age (p = 0.42), sex (p = 0.28), height (p = 0.75), or body weight (p = 0.63). The average +/- standard deviation (SD) of movement of the center of gravity for all subjects was 11.1 +/- 4.8 mm in the cranio-caudal (CC) direction (range, 2.5-20.5 mm), 3.6 +/- 2.1 mm in the anterior-posterior (AP) direction (range, 0.6-8.0 mm), and 1.7 +/- 1.4 mm in the right-left (RL) direction (range, 0.4-5.9 mm). Renal motion strongly correlated with the respiratory phases (r > 0.97 and p < 0.01 in all three directions).

Conclusions

Renal motion was independent of age, sex, height, or body weight. Renal motion in all directions was strongly respiration dependent, but motion in the cranio-caudal direction showed wide individual variation. In a clinical setting, it will be necessary to evaluate renal respiratory motion separately in each individual.

Displacement of the lumpectomy cavity defined by surgical clips and seroma based on 4D-CT scan for external-beam partial breast irradiation after breast-conserving surgery: a comparative study

OBJECTIVE

To compare the displacements of the lumpectomy cavity delineated by the surgical clips and the seroma based on four-dimensional CT (4D-CT) for external-beam partial breast irradiation (EB-PBI) after breast-conserving surgery (BCS).

METHODS

14 breast cancer patients after BCS were recruited for EB-PBI and undertook 4D-CT simulation. On the 10 sets of the 4D-CT images, all the surgical clips in the cavity were delineated. The gross tumour volume (GTV) formed by the clips, the seroma, and both the clips and the seroma were defined as GTVc, GTVs and GTVc+s, respectively. The displacements of the centre of mass (COM) of the clips, GTVc, GTVs, GTVc+s and the selected clips in the three-dimensional (3D) directions were recorded and compared.

RESULTS

In the left-right, anterior-posterior and superior-inferior directions, the displacements were 2.20, 1.80 and 2.70 mm for the clip COM; 0.90, 1.05 and 1.20 mm for GTVc; 0.80, 1.05 and 0.80 mm for GTVs; and 0.90, 1.20 and 1.40 mm for GTVc+s, respectively. In the 3D directions, the displacements of the clip COM were greater than the GTVc, GTVs, GTVc+s, and the displacements of the clip COM, GTVc+s, GTVc and GTVs were significantly greater than the displacements of the selected clips (p<0.05).

CONCLUSION

The displacements of the clip COM were greater than that of the GTVc, GTVs, GTVc+s and the four selected clips. The optimal internal target volume should be defined based on the boundary displacements.

ADVANCES IN KNOWLEDGE

When the GTV was delineated using the clips and/or the seroma, there was displacement difference between the lumpectomy cavity centre and the boundary for the EB-PBI. The optimal internal target volume should be defined based on the boundary displacements of the lumpectomy cavity.

Four-dimensional measurement of the displacement of metal clips or postoperative surgical staples during 320-multislice computed tomography scanning of gastric cancer

Purpose

To investigate the respiratory motion of metal clips or surgical staples placed in the gastric wall for planning of radiation therapy in gastric cancer patients.

Methods

This study examined 15 metal markers in the gastric walls of 12 patients with gastric cancer treated with external-beam photon RT. Motion assessment was analyzed in 41 respiratory phases covering 20 s acquired with computed tomography (CT) in the RT position using 320-multislice CT. The intra-fraction displacement was assessed in the cranio-caudal (CC), antero-posterior (AP), and right-left (RL) directions.

Results

Motion in the CC direction showed a very strong correlation (R² > 0.7) with the respiratory curve in all 15 markers. The mean (+/− SD) intra-fractional gastric motion (maximum range of displacement) was 12.5 (+/− 3.4) mm in the CC, 8.3 (+/− 2.2) mm in the AP, and 5.5 (+/− 3.0) mm in the RL direction. No significant differences in magnitude of motion were detected in the following: a) among the upper (n = 6), middle (n = 4), and lower (n = 5) stomach regions; b) between metal clips (n = 5) and surgical staples (n = 10); and c) between full (n = 9) and empty (n = 6) stomachs.

Conclusions

Motion in primary gastric tumor was evaluated with 320-multislice CT. According to this study, the 95th percentile values from the cumulative distributions of the RL, AP, and CC direction were 6.3 mm, 9.0 mm, and 13.6 mm, respectively.