Automatic tracking of arbitrarily shaped implanted markers in kilovoltage projection images: A feasibility study

Regmi, Rajesh; Lovelock, D. Michael; Hunt, Margie; Zhang, Pengpeng; Pham, Hai; Xiong, Jianping; Yorke, Ellen; Goodman, Karyn A.; Mostafavi, Hassan; Mageras, G.

doi:10.1118/1.4881335

Cited by 23 publications

(45 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A planning CT of the phantom with slice spacing of 2 mm was obtained and used to generate 2D reference images at one degree gantry angle increments using a modification to the template technique described by Mostafavi et al (12) and implemented at our institution by Regmi et al (20) Briefly, generation of the reference template images involved initial segmentation of the fiducials on the planning CT, followed by the addition of a 1 mm margin to create a region of interest (ROI). In the modified version, the center-of-mass and orientation of each fiducial was then determined and used to position a template of the physical shape of the each fiducial within each ROI.…”

Section: Methodsmentioning

confidence: 99%

“…To account for changes in the relative marker positions between simulation and treatment (e.g., owing to tissue deformations or fiducial migration), the fiducial position in the template images can be adjusted based on an orthogonal kV image pair during patient setup. (20) …”

Section: Methodsmentioning

confidence: 99%

“…(20) For each individual MV and kV image, the reference image closest in angle was selected and 2D template-based autoregistration was performed using simplex-based minimization of a normalized cross-correlation cost function. In order to avoid trapping in a local minimum, a grid of starting positions was defined within the search region (10 × 10 mm initially; 5 × 5 mm on subsequent images) with 2 mm grid spacing.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Simultaneous MV‐kV imaging for intrafractional motion management during volumetric‐modulated arc therapy delivery*

Hunt

Sonnick

Pham

et al. 2016

J Applied Clin Med Phys

Self Cite

View full text Add to dashboard Cite

The purpose of this study was to evaluate the accuracy and clinical feasibility of a motion monitoring method employing simultaneously acquired MV and kV images during volumetric-modulated arc therapy (VMAT). Short-arc digital tomosynthesis (SA-DTS) is used to improve the quality of the MV images that are then combined with orthogonally acquired kV images to assess 3D motion. An anthropomorphic phantom with implanted gold seeds was used to assess accuracy of the method under static, typical prostatic, and respiratory motion scenarios. Automatic registration of kV images and single MV frames or MV SA-DTS reconstructed with arc lengths from 2° to 7° with the appropriate reference fiducial template images was performed using special purpose-built software. Clinical feasibility was evaluated by retrospectively analyzing images acquired over four or five sessions for each of three patients undergoing hypofractionated prostate radiotherapy. The standard deviation of the registration error in phantom using MV SA-DTS was similar to single MV images for the static and prostate motion scenarios (σ = 0.25 mm). Under respiratory motion conditions, the standard deviation of the registration error increased to 0.7mm and 1.7 mm for single MV and MV SA-DTS, respectively. Registration failures were observed with the respiratory scenario only and were due to motion-induced fiducial blurring. For the three patients studied, the mean and standard deviation of the difference between automatic registration using 4° MV SA-DTS and manual registration using single MV images results was 0.07±0.52mm. The MV SA-DTS results in patients were, on average, superior to single-frame MV by nearly 1 mm — significantly more than what was observed in phantom. The best MV SA-DTS results were observed with arc lengths of 3° to 4°. Registration failures in patients using MV SA-DTS were primarily due to blockage of the gold seeds by the MLC. The failure rate varied from 2% to 16%. Combined MV SA-DTS and kV imaging is feasible for intratreatment motion monitoring during VMAT of anatomic sites where limited motion is expected, and improves registration accuracy compared to single MV/kV frames. To create a clinically robust technique, further improvements to ensure visualization of fiducials at the desired control points without degradation of the treatment plan are needed.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Simultaneous MV‐kV imaging for intrafractional motion management during volumetric‐modulated arc therapy delivery*

Hunt

Sonnick

Pham

et al. 2016

J Applied Clin Med Phys

Self Cite

View full text Add to dashboard Cite

show abstract

“…Several authors have investigated the performance of such algorithms 12, 13, 14, 15, 16, 21. Compared to more general tracking algorithms aiming to find the fiducials at any imaging angle, our method only requires them to be tracked in the lateral and AP projections.…”

Section: Discussionmentioning

confidence: 99%

Automatic patient positioning and gating window settings in respiratory‐gated stereotactic body radiation therapy for pancreatic cancer using fluoroscopic imaging

Pettersson

Simpson

Atwood

et al. 2018

J Applied Clin Med Phys

View full text Add to dashboard Cite

Before treatment delivery of respiratory‐gated radiation therapy (RT) in patients with implanted fiducials, both the patient position and the gating window thresholds must be set. In linac‐based RT, this is currently done manually and setup accuracy will therefore be dependent on the skill of the user. In this study, we present an automatic method for finding the patient position and the gating window thresholds. Our method uses sequentially acquired anterior–posterior (AP) and lateral fluoroscopic imaging with simultaneous breathing amplitude monitoring and intends to reach 100% gating accuracy while keeping the duty cycle as high as possible. We retrospectively compared clinically used setups to the automatic setups by our method in five pancreatic cancer patients treated with hypofractionated RT. In 15 investigated fractions, the average (±standard deviation) differences between the clinical and automatic setups were −0.4 ± 0.8 mm, −1.0 ± 1.1 mm, and 1.8 ± 1.3 mm in the left–right (LR), the AP, and the superior–inferior (SI) direction, respectively. For the clinical setups, typical interfractional setup variations were 1–2 mm in the LR and AP directions, and 2–3 mm in the SI direction. Using the automatic method, the duty cycle could be improved in six fractions, in four fractions the duty cycle had to be lowered to improve gating accuracy, and in five fractions both duty cycle and gating accuracy could be improved. Our automatic method has the potential to increase accuracy and decrease user dependence of setup for patients with implanted fiducials treated with respiratory‐gated RT. After fluoroscopic image acquisition, the calculated patient shifts and gating window thresholds are calculated in 1–2 s. The method gives the user the possibility to evaluate the effect of different patient positions and gating window thresholds on gating accuracy and duty cycle. If deemed necessary, it can be used at any time during treatment delivery.

show abstract

“…The RPM system records the anterior-posterior (AP) motion of the block. The internal breathing signal was obtained using a purpose-built computer program 19 to track the implanted markers visualized in the projection images acquired for the CBCT. The program tracked the centroid of the markers assuming rigid body motion, rather than tracking the differential motion of individual markers.…”

Section: Methodsmentioning

confidence: 99%

Technical Note: Intrafractional changes in time lag relationship between anterior-posterior external and superior-inferior internal motion signals in abdominal tumor sites

et al. 2015

Self Cite

View full text Add to dashboard Cite

Purpose: To investigate constancy, within a treatment session, of the time lag relationship between implanted markers in abdominal tumors and an external motion surrogate. Methods: Six gastroesophageal junction and three pancreatic cancer patients (IRB-approved protocol) received two cone-beam CTs (CBCT), one before and one after treatment. Time between scans was less than 30 min. Each patient had at least one implanted fiducial marker near the tumor. In all scans, abdominal displacement (Varian RPM) was recorded as the external motion signal. Purpose-built software tracked fiducials, representing internal signal, in CBCT projection images. Time lag between superior-inferior (SI) internal and anterior-posterior external signals was found by maximizing the correlation coefficient in each breathing cycle and averaging over all cycles. Time-lag-induced discrepancy between internal SI position and that predicted from the external signal (external prediction error) was also calculated. Results: Mean ± standard deviation time lag, over all scans and patients, was 0.10 ± 0.07 s (range 0.01-0.36 s). External signal lagged the internal in 17/18 scans. Change in time lag between pre-and post-treatment CBCT was 0.06 ± 0.07 s (range 0.01-0.22 s), corresponding to 3.1% ± 3.7% (range 0.6%-10.8%) of gate width (range 1.6-3.1 s). In only one patient, change in time lag exceeded 10% of the gate width. External prediction error over all scans of all patients varied from 0.1 ± 0.1 to 1.6 ± 0.4 mm. Conclusions: Time lag between internal motion along SI and external signals is small compared to the treatment gate width of abdominal patients examined in this study. Change in time lag within a treatment session, inferred from pre-to post-treatment measurements is also small, suggesting that a single measurement of time lag at the session start is adequate. These findings require confirmation in a larger number of patients. C 2015 American Association of Physicists in Medicine.

show abstract

Automatic tracking of arbitrarily shaped implanted markers in kilovoltage projection images: A feasibility study

Cited by 23 publications

References 22 publications

Simultaneous MV‐kV imaging for intrafractional motion management during volumetric‐modulated arc therapy delivery*

Simultaneous MV‐kV imaging for intrafractional motion management during volumetric‐modulated arc therapy delivery*

Automatic patient positioning and gating window settings in respiratory‐gated stereotactic body radiation therapy for pancreatic cancer using fluoroscopic imaging

Technical Note: Intrafractional changes in time lag relationship between anterior-posterior external and superior-inferior internal motion signals in abdominal tumor sites

Contact Info

Product

Resources

About