Cervix Motion in 50 Cervical Cancer Patients Assessed by Daily Cone Beam Computed Tomographic Imaging of a New Type of Marker.

Purpose: To evaluate a new type of marker and a new method of marker implantation and to assess interfraction cervix motion for a large population of patients with locally advanced cervical cancer by daily cone beam computed tomographic (CBCT) imaging.

Methods And Materials: We investigated the position of markers in 50 patients treated in prone position during at least 23 fractions. To reduce streaking artifacts in the planning CT scan, a new type of polymeric marker was used and compared with conventional gold markers.

Repeat CT-scan assessment of lymph node motion in locally advanced cervical cancer patients.

Purpose: In cervical cancer patients the nodal clinical target volume (CTV, defined using the major pelvic blood vessels and enlarged lymph nodes) is assumed to move synchronously with the bony anatomy. The aim of this study was to verify this assumption by investigating the motion of the major pelvic blood vessels and enlarged lymph nodes visible in CT scans.

Methods And Materials: For 13 patients treated in prone position, four variable bladder-filling CT scans per patient, acquired at planning and after 40 Gy, were selected from an available dataset of 9-10 CT scans.

Statistical modeling of CTV motion and deformation for IMRT of early-stage rectal cancer.

Purpose: To derive and validate a statistical model of motion and deformation for the clinical target volume (CTV) of early-stage rectal cancer patients.

Methods And Materials: For 16 patients, 4 to 5 magnetic resonance images (MRI) were acquired before each fraction was administered. The CTV was delineated on each MRI.

Clinical implementation of an online adaptive plan-of-the-day protocol for nonrigid motion management in locally advanced cervical cancer IMRT.

Purpose: To evaluate the clinical implementation of an online adaptive plan-of-the-day protocol for nonrigid target motion management in locally advanced cervical cancer intensity modulated radiation therapy (IMRT).

Methods And Materials: Each of the 64 patients had four markers implanted in the vaginal fornix to verify the position of the cervix during treatment. Full and empty bladder computed tomography (CT) scans were acquired prior to treatment to build a bladder volume-dependent cervix-uterus motion model for establishment of the plan library.

Coupling between inter-helical hydrogen bonding and water dynamics in a proton transporter.

Long-distance proton transfers by proton pumps occurs in discrete steps that may involve the direct participation of protein sidechains and water molecules, and coupling of protonation changes to structural rearrangements of the protein matrix. Here we explore the role of inter-helical hydrogen bonding in long-distance protein conformational coupling and dynamics of internal water molecules. From molecular dynamics simulations of wild type and nine different bacteriorhodopsin mutants we find that both intra- and inter-helical hydrogen bonds are important determinants of the local protein structure, dynamics, and water interactions.

A margin-of-the-day online adaptive intensity-modulated radiotherapy strategy for cervical cancer provides superior treatment accuracy compared to clinically recommended margins: a dosimetric evaluation.

Purpose: To dosimetrically evaluate a margin-of-the-day (MoD) online adaptive intensity-modulated radiotherapy (IMRT) strategy for cervical cancer patients. The strategy is based on a single planning computed tomography (CT) scan and a pretreatment constructed IMRT plan library with incremental clinical target volumes (CTV)-to-planning target volumes (PTV) margins.

Material And Methods: For 14 patients, 9-10 variable bladder filling CT scans acquired at pretreatment and after 40 Gy were available.

Intra-patient semi-automated segmentation of the cervix-uterus in CT-images for adaptive radiotherapy of cervical cancer.

For online adaptive radiotherapy of cervical cancer, fast and accurate image segmentation is required to facilitate daily treatment adaptation. Our aim was twofold: (1) to test and compare three intra-patient automated segmentation methods for the cervix-uterus structure in CT-images and (2) to improve the segmentation accuracy by including prior knowledge on the daily bladder volume or on the daily coordinates of implanted fiducial markers. The tested methods were: shape deformation (SD) and atlas-based segmentation (ABAS) using two non-rigid registration methods: demons and a hierarchical algorithm.

Toward an individualized target motion management for IMRT of cervical cancer based on model-predicted cervix-uterus shape and position.

Background And Purpose: To design and evaluate a 3D patient-specific model to predict the cervix-uterus shape and position.

Methods And Materials: For 13 patients lying in prone position, 10 variable bladder filling CT-scans were acquired, 5 at planning and 5 after 40Gy. The delineated cervix-uterus volumes in 2-5 pre-treatment CT-scans were used to generate patient-specific models that predict the cervix-uterus geometry by bladder volume.

Three-dimensional dose addition of external beam radiotherapy and brachytherapy for oropharyngeal patients using nonrigid registration.

Purpose: To develop and evaluate a method for adding dose distributions of combined external beam radiotherapy (EBRT) and brachytherapy (BT) for oropharyngeal patients.

Methods And Materials: Two computed tomography (CT) scans were used for 5 patients: the EBRT CT, used for EBRT planning, and the BT CT, acquired after catheter implantation. For each scan, the salivary glands and the chewing and swallowing muscles were contoured, and a dose distribution was calculated.

A symmetric nonrigid registration method to handle large organ deformations in cervical cancer patients.

Purpose: Modern radiotherapy requires assessment of patient anatomical changes. By using unidirectional registration methods, the quantified anatomical changes are asymmetric, i.e.

A novel flexible framework with automatic feature correspondence optimization for nonrigid registration in radiotherapy.

Technical improvements in planning and dose delivery and in verification of patient positioning have substantially widened the therapeutic window for radiation treatment of cancer. However, changes in patient anatomy during the treatment limit the exploitation of these new techniques. To further improve radiation treatments, anatomical changes need to be modeled and accounted for Nonrigid registration can be used for this purpose.