Feasibility of markerless 3D position monitoring of the central airways using kilovoltage projection images: Managing the risks of central lung stereotactic radiotherapy.

Background And Purpose: Central lung stereotactic body radiotherapy (SBRT) can cause proximal bronchial tree (PBT) toxicity. Information on PBT position relative to the high-dose could aid risk management. We investigated template matching + triangulation for high-frequency markerless 3D PBT position monitoring.

First Experience With Markerless Online 3D Spine Position Monitoring During SBRT Delivery Using a Conventional LINAC.

Purpose: The purpose was to report our initial experience with online markerless 3-dimensional (3D) spine position monitoring. We used template matching plus triangulation of fluoroscopic kilovoltage images acquired with the gantry-mounted imager during flattening filter-free volumetric modulated arc spine stereotactic body radiation therapy delivery on a conventional linear accelerator.

Methods And Materials: Kilovoltage images were acquired at 7 frames per second and streamed to a stand-alone computer.

Toward planning target volume margin reduction for the prostate using intrafraction motion correction with online kV imaging and automatic detection of implanted gold seeds.

Purpose: The imaging application Auto Beam Hold (ABH) allows for the online analysis of 2-dimensional kV images acquired during treatment. ABH can automatically detect fiducial markers and initiate a beam interrupt. In this study, we investigate the practical use and results of this intrafraction monitoring tool for patients with prostate cancer who have implanted gold seeds treated with a RapidArc technique.

Markerless positional verification using template matching and triangulation of kV images acquired during irradiation for lung tumors treated in breath-hold.

Lung tumors treated in breath-hold are subject to inter- and intra-breath-hold variations, which makes tumor position monitoring during each breath-hold important. A markerless technique is desirable, but limited tumor visibility on kV images makes this challenging. We evaluated if template matching  +  triangulation of kV projection images acquired during breath-hold stereotactic treatments could determine 3D tumor position.

Subsecond and Submillimeter Resolution Positional Verification for Stereotactic Irradiation of Spinal Lesions.

Purpose: Spine stereotactic body radiation therapy (SBRT) requires highly accurate positioning. We report our experience with markerless template matching and triangulation of kilovoltage images routinely acquired during spine SBRT, to determine spine position.

Methods And Materials: Kilovoltage images, continuously acquired at 7, 11 or 15 frames/s during volumetric modulated spine SBRT of 18 patients, consisting of 93 fluoroscopy datasets (1 dataset/arc), were analyzed off-line.

Digital tomosynthesis (DTS) for verification of target position in early stage lung cancer patients.

Purpose: The ability to verify intrafraction tumor position is clinically useful for hypofractionated treatments. Short arc kV digital tomosynthesis (DTS) could facilitate more frequent target verification. The authors used DTS combined with triangulation to determine the mean temporal position of small-volume lung tumor targets treated with stereotactic radiotherapy.

Feasibility of using anatomical surrogates for predicting the position of lung tumours.

We studied the use of internal anatomical surrogates (carina and diaphragm) for the purpose of predicting the 3D position of lung tumours in 41 patients, in whom repeat 4DCT scans were available. Despite using two surrogates, significant prediction errors were observed, which varied depending on tumour position, baseline tumour motion and respiratory phase.

Use of megavoltage cine-images for studying intra-thoracic motion during radiotherapy for locally advanced lung cancer.

Background And Purpose: Use of planning 4-dimensional CT (4DCT) scans often permits use of smaller target volumes for thoracic tumors but this assumes a reproducible pattern of motion during radiotherapy. We compared cranio-caudal (CC) motion on MV cine-images acquired during treatment with that seen on planning 4DCT.

Methods And Materials: A pre-programmable respiratory motion phantom and a software tool for motion assessment were used to validate the use of MV cine-images for motion detection.

Early detection of local RFA site recurrence using total liver volume perfusion CT initial experience.

Rationale And Objectives: The aim of this study was to prospectively evaluate the feasibility of a novel total liver volume perfusion computed tomographic technique in demonstrating treatment-site recurrence of liver metastases after radiofrequency ablation (RFA).

Materials And Methods: Eleven patients considered to be at increased risk for local RFA-site tumor recurrence underwent both positron emission tomography (PET) and perfusion computed tomography (CTP): a 12-phase scan of the entire liver acquired before and 11 times after contrast injection. After coregistration, blood flow maps were created using the maximum slope method.

Subtraction-multiphase-CT unbeneficial for early detection of colorectal liver metastases.

Purpose: To assess the value of multiphase-subtraction-CT for early detection of colorectal-liver-metastases (CRLM).

Methods And Materials: In 50 patients suspected of CRLM a routine pre-operative 4-phase-CT-scan of the upper abdomen was obtained. All 12 possible image subtractions between two different phases were constructed applying 3D-image-registration to decrease distortion artefacts induced by differences in inspiration volume.

Total-liver-volume perfusion CT using 3-D image fusion to improve detection and characterization of liver metastases.

The purpose of this study was to evaluate the feasibility of a total-liver-volume perfusion CT (CTP) technique for the detection and characterization of liver metastases. Twenty patients underwent helical CT of the total liver volume before and 11 times after intravenous contrast-material injection. To decrease distortion artifacts, all phases were co-registered using 3-D image fusion before creating blood-flow maps.

Analysis of carina position as surrogate marker for delivering phase-gated radiotherapy.

Purpose: Respiratory gating can mitigate the effect of tumor mobility in radiotherapy (RT) for lung cancer. Because the tumor is generally not visualized, external surrogates of tumor position are used to trigger respiration-gated RT. We evaluated the suitability of the carina position as a surrogate in respiration-gated RT.