Fiducial marker guided stereotactic liver radiotherapy: Is a time delay between marker implantation and planning CT needed?

To minimize the risk of marker migration in fiducial marker guided liver SBRT it is common to add a delay of a week between marker implantation and planning CT. This study found that such a delay is unnecessary and could be avoided to minimize the treatment preparation time.

Time-Resolved Intrafraction Target Translations and Rotations During Stereotactic Liver Radiation Therapy: Implications for Marker-based Localization Accuracy.

Purpose: Image guided liver stereotactic body radiation therapy (SBRT) often relies on implanted fiducial markers. The target localization accuracy decreases with increased marker-target distance. This may occur partly because of liver rotations.

Setup error and motion during deep inspiration breath-hold breast radiotherapy measured with continuous portal imaging.

Background: The position and residual motion of the chest wall of breast cancer patients during treatment in deep inspiration breath-hold (DIBH) were investigated.

Material And Methods: The study included 58 left-sided breast cancer patients treated with DIBH three-dimensional (3D) conformal radiotherapy in 15 or 25 fractions. The DIBH levels were monitored using an external marker block placed on the chest, either shifted 5 cm to the right at the level of the xiphoid process (Group 1, 27 consecutive patients) or placed medially on the inferior part of the sternum (Group 2, 31 consecutive patients).

The first clinical treatment with kilovoltage intrafraction monitoring (KIM): a real-time image guidance method.

Purpose: Kilovoltage intrafraction monitoring (KIM) is a real-time image guidance method that uses widely available radiotherapy technology, i.e., a gantry-mounted x-ray imager.

Moving metal artifact reduction in cone-beam CT scans with implanted cylindrical gold markers.

Purpose: Implanted gold markers for image-guided radiotherapy lead to streaking artifacts in cone-beam CT (CBCT) scans. Several methods for metal artifact reduction (MAR) have been published, but they all fail in scans with large motion. Here the authors propose and investigate a method for automatic moving metal artifact reduction (MMAR) in CBCT scans with cylindrical gold markers.

Kilovoltage intrafraction motion monitoring and target dose reconstruction for stereotactic volumetric modulated arc therapy of tumors in the liver.

Purpose: To use intrafraction kilovoltage (kV) imaging during liver stereotactic body radiotherapy (SBRT) delivered by volumetric modulated arc therapy (VMAT) to estimate the intra-treatment target motion and to reconstruct the delivered target dose.

Methods: Six liver SBRT patients with 2-3 implanted gold markers received SBRT in three fractions of 18.75 Gy or 25 Gy.

Inter- and intra-fraction geometric errors in daily image-guided radiotherapy of free-breathing breast cancer patients measured with continuous portal imaging.

Background: Daily image-guided radiotherapy (IGRT) using two orthogonal setup images may be inaccurate for breast cancer patients treated in free breathing because the setup images may capture the patient in a breathing phase that is not representative of the mean anatomy. The aim of this study was to quantify the setup errors in breast radiotherapy after image-guided setup correction based on two orthogonal setup images acquired in free breathing.

Methods And Materials: For 16 breast cancer patients with daily image-pair based IGRT, continuous portal imaging (7.

Variations in magnitude and directionality of respiratory target motion throughout full treatment courses of stereotactic body radiotherapy for tumors in the liver.

Purpose: To investigate the stability of target motion amplitude and motion directionality throughout full stereotactic body radiotherapy (SBRT) treatments of tumors in the liver.

Material And Methods: Ten patients with gold markers implanted in the liver received 11 courses of 3-fraction SBRT on a conventional linear accelerator. A four-dimensional computed tomography (4DCT) scan was obtained for treatment planning.

A method of dose reconstruction for moving targets compatible with dynamic treatments.

Purpose: To develop a method that allows a commercial treatment planning system (TPS) to perform accurate dose reconstruction for rigidly moving targets and to validate the method in phantom measurements for a range of treatments including intensity modulated radiation therapy (IMRT), volumetric arc therapy (VMAT), and dynamic multileaf collimator (DMLC) tracking.

Methods: An in-house computer program was developed to manipulate Dicom treatment plans exported from a TPS (Eclipse, Varian Medical Systems) such that target motion during treatment delivery was incorporated into the plans. For each treatment, a motion including plan was generated by dividing the intratreatment target motion into 1 mm position bins and construct sub-beams that represented the parts of the treatment that were delivered, while the target was located within each position bin.

Kilovoltage intrafraction monitoring for prostate intensity modulated arc therapy: first clinical results.

Purpose: Most linear accelerators purchased today are equipped with a gantry-mounted kilovoltage X-ray imager which is typically used for patient imaging prior to therapy. A novel application of the X-ray system is kilovoltage intrafraction monitoring (KIM), in which the 3-dimensional (3D) tumor position is determined during treatment. In this paper, we report on the first use of KIM in a prospective clinical study of prostate cancer patients undergoing intensity modulated arc therapy (IMAT).

On-line use of three-dimensional marker trajectory estimation from cone-beam computed tomography projections for precise setup in radiotherapy for targets with respiratory motion.

Purpose: To develop and evaluate accurate and objective on-line patient setup based on a novel semiautomatic technique in which three-dimensional marker trajectories were estimated from two-dimensional cone-beam computed tomography (CBCT) projections.

Methods And Materials: Seven treatment courses of stereotactic body radiotherapy for liver tumors were delivered in 21 fractions in total to 6 patients by a linear accelerator. Each patient had two to three gold markers implanted close to the tumors.

Image-based dynamic multileaf collimator tracking of moving targets during intensity-modulated arc therapy.

Purpose: Intensity-modulated arc therapy (IMAT) enables efficient and highly conformal dose delivery. However, intrafraction motion may compromise the delivered target dose distribution. Dynamic multileaf collimator (DMLC) tracking can potentially mitigate the impact of target motion on the dose.

Robust automatic segmentation of multiple implanted cylindrical gold fiducial markers in cone-beam CT projections.

Purpose: Implanted fiducial markers, which are used to correct for day-to-day variations, may potentially also be used to correct for intrafraction motion measurements. However, before any treatment can make use of, and react to, the position of the inserted markers they have to be segmented, either manually through expert user intervention or automatically from an imaging system. In the current study, we aimed to establish a robust and autonomous segmentation method for implanted cylindrical gold markers in a single set of projections from a cone-beam computed tomography (CBCT).

Tracking latency in image-based dynamic MLC tracking with direct image access.

Purpose: Target tracking is a promising method for motion compensation in radiotherapy. For image-based dynamic multileaf collimator (DMLC) tracking, latency has been shown to be the main contributor to geometrical errors in tracking of respiratory motion, specifically due to slow transfer of image data from the image acquisition system to the tracking system via image file storage on a hard disk. The purpose of the current study was to integrate direct image access with a DMLC tracking system and to quantify the tracking latency of the integrated system for both kV and MV image-based tracking.

Geometric accuracy of dynamic MLC tracking with an implantable wired electromagnetic transponder.

Background: Tumor motion during radiotherapy delivery can substantially deteriorate the target dose distribution. A promising method to overcome this problem is dynamic multi-leaf collimator (DMLC) tracking. The purpose of this phantom study was to integrate a wired electromagnetic (EM) transponder localization system with DMLC tracking and to investigate the geometric accuracy of the integrated system.

A method for robust segmentation of arbitrarily shaped radiopaque structures in cone-beam CT projections.

Purpose: Implanted markers are commonly used in radiotherapy for x-ray based target localization. The projected marker position in a series of cone-beam CT (CBCT) projections can be used to estimate the three dimensional (3D) target trajectory during the CBCT acquisition. This has important applications in tumor motion management such as motion inclusive, gating, and tumor tracking strategies.

Megavoltage image-based dynamic multileaf collimator tracking of a NiTi stent in porcine lungs on a linear accelerator.

Purpose: To investigate the accuracy and potential limitations of MV image-based dynamic multileaf collimator (DMLC) tracking in a porcine model on a linear accelerator.

Methods And Materials: A thermo-expandable NiTi stent designed for kilovoltage (kV) X-ray visualization of lung lesions was inserted into the bronchia of three anaesthetized Göttingen minipigs. A four-dimensional computed tomography scan was used for planning a five-field conformal treatment with circular multileaf collimator (MLC) apertures.

Influence of suture regularity on corneal astigmatism after penetrating keratoplasty.

Purpose: To investigate whether suture regularity affects corneal astigmatism after keratoplasty.

Methods: Twenty-one patients undergoing penetrating keratoplasty for various corneal diseases were included in the study. The grafts were sutured in place using a single-running Nylon 10-0 suture, taking 24 bites.

Three-year changes in epithelial and stromal thickness after PRK or LASIK for high myopia.

Purpose: To compare 3-year changes in corneal sublayer thickness after photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK).

Methods: Forty-six patients with spheroequivalent refraction of -6.0 to -8.

Comparison of performance of conventional and minimally invasive surgery acetabular reamers.

Unlabelled: Acetabular reaming in minimally invasive surgery can be done using a newly designed minimally invasive reamer. The new minimally invasive reamer is narrower and chamfered, which results in two sharp edges. This design may result in acetabular cavities with less ideal spheres than those achieved with conventional reaming.