Patterns of practice for adaptive and real-time radiation therapy (POP-ART RT) part II: Offline and online plan adaption for interfractional changes.

Purpose: The POP-ART RT study aims to determine to what extent and how intrafractional real-time respiratory motion management (RRMM), and plan adaptation for interfractional anatomical changes (ART) are used in clinical practice and to understand barriers to implementation. Here we report on part II: ART using more than one plan per target per treatment course.

Materials And Methods: A questionnaire on the current practice of ART, wishes for expansion or implementation, and barriers to implementation was distributed worldwide.

Improving the intra-fraction update efficiency of a correlation model used for internal motion estimation during real-time tumor tracking for SBRT patients: fast update or no update?

Background And Purpose: For tumor tracking, a correlation model is used to estimate internal tumor position based on external surrogate motion. When patients experience an internal/external surrogate drift, an update of the correlation model is required to continue tumor tracking. In this study, the accuracy of the internal tumor position estimation for both the clinical available update at discrete points in time (rebuild) and an in-house developed non-clinical online update approach was investigated.

Impact of inadequate respiratory motion management in SBRT for oligometastatic colorectal cancer.

Purpose: Stereotactic body radiotherapy (SBRT) in oligometastatic colorectal cancer (CRC) resulted in a disappointing 1-year local control rate of 54% in our experience. We aimed to determine the root cause(s).

Methods: 47 oligometastatic CRC patients were treated with SBRT by helical tomotherapy to a dose of 40 or 50Gy in 10 fractions, without specific respiratory motion management and PTV-margins of 10-10-12mm in all patients.

A complementary dual-modality verification for tumor tracking on a gimbaled linac system.

Background And Purpose: For dynamic tracking of moving tumors, robust intra-fraction verification was required, to assure that tumor motion was properly managed during the course of radiotherapy. A dual-modality verification system, consisting of an on-board orthogonal kV and planar MV imaging device, was validated and applied retrospectively to patient data.

Methods And Materials: Real-time tumor tracking (RTTT) was managed by applying PAN and TILT angular corrections to the therapeutic beam using a gimbaled linac.

Initial assessment of tumor tracking with a gimbaled linac system in clinical circumstances: a patient simulation study.

Purpose: To have an initial assessment of the Vero Dynamic Tracking workflow in clinical circumstances and quantify the performance of the tracking system, a simulation study was set up on 5 lung and liver patients.

Methods And Materials: The preparatory steps of a tumor tracking treatment, based on fiducial markers implanted in the tumor, were executed allowing pursuit of the tumor with the gimbaled linac and monitoring X-rays acquisition, however, without activating the 6 MV beam. Data were acquired on workflow time-efficiency, tracking accuracy and imaging exposure.

Dosimetric comparison of different treatment modalities for stereotactic radiosurgery of arteriovenous malformations and acoustic neuromas.

Purpose: We investigated the influence of beam modulation on treatment planning by comparing four available stereotactic radiosurgery (SRS) modalities: Gamma-Knife-Perfexion, Novalis-Tx Dynamic-Conformal-Arc (DCA) and Dynamic-Multileaf-Collimation-Intensity-Modulated-radiotherapy (DMLC-IMRT), and Cyberknife.

Material And Methods: Patients with arteriovenous malformation (n = 10) or acoustic neuromas (n = 5) were planned with different treatment modalities. Paddick conformity index (CI), dose heterogeneity (DH), gradient index (GI) and beam-on time were used as dosimetric indices.

Implementation of HybridArc treatment technique in preoperative radiotherapy of rectal cancer: dose patterns in target lesions and organs at risk as compared to helical Tomotherapy and RapidArc.

Purpose: HybridArc is a novel treatment technique blending aperture-enhanced optimized arcs with discrete IMRT-elements, allowing selection of arcs with a set of static IMRT-beams. This study compared this new technique to helical Tomotherapy, and RapidArc, in preoperative radiotherapy of rectal cancer.

Material And Methods: Twelve rectal cancer patients treated consecutively with Tomotherapy Hi-Art II system were simulated with HybridArc and RapidArc.

Computer-aided analysis of star shot films for high-accuracy radiation therapy treatment units.

As mechanical stability of radiation therapy treatment devices has gone beyond sub-millimeter levels, there is a rising demand for simple yet highly accurate measurement techniques to support the routine quality control of these devices. A combination of using high-resolution radiosensitive film and computer-aided analysis could provide an answer. One generally known technique is the acquisition of star shot films to determine the mechanical stability of rotations of gantries and the therapeutic beam.

Clinical evaluation of a robotic 6-degree of freedom treatment couch for frameless radiosurgery.

Purpose: To evaluate the added value of 6-degree of freedom (DOF) patient positioning with a robotic couch compared with 4DOF positioning for intracranial lesions and to estimate the immobilization characteristics of the BrainLAB frameless mask (BrainLAB AG, Feldkirchen, Germany), more specifically, the setup errors and intrafraction motion.

Methods And Materials: We enrolled 40 patients with 66 brain metastases treated with frameless stereotactic radiosurgery and a 6DOF robotic couch. Patient positioning was performed with the BrainLAB ExacTrac stereoscopic X-ray system.

Setup accuracy of the Novalis ExacTrac 6DOF system for frameless radiosurgery.

Purpose: Stereotactic radiosurgery using frame-based positioning is a well-established technique for the treatment of benign and malignant lesions. By contrast, a new trend toward frameless systems using image-guided positioning techniques is gaining mainstream acceptance. This study was designed to measure the detection and positioning accuracy of the ExacTrac/Novalis Body (ET/NB) for rotations and to compare the accuracy of the frameless with the frame-based radiosurgery technique.

Geometric accuracy of a novel gimbals based radiation therapy tumor tracking system.

Purpose: VERO is a novel platform for image guided stereotactic body radiotherapy. Orthogonal gimbals hold the linac-MLC assembly allowing real-time moving tumor tracking. This study determines the geometric accuracy of the tracking.

Daily megavoltage computed tomography in lung cancer radiotherapy: correlation between volumetric changes and local outcome.

Purpose: To assess the predictive or comparative value of volumetric changes, measured on daily megavoltage computed tomography during radiotherapy for lung cancer.

Patients And Methods: We included 80 patients with locally advanced non-small-cell lung cancer treated with image-guided intensity-modulated radiotherapy. The radiotherapy was combined with concurrent chemotherapy, combined with induction chemotherapy, or given as primary treatment.

The effect of tomotherapy imaging beam output instabilities on dose calculation.

A radiotherapy treatment plan is based on an anatomical 'snapshot' of the patient acquired during the preparation stage using a kVCT (kilovolt computed tomography) scanner. Anatomical changes will occur during the treatment course, in some cases requiring a new treatment plan to deliver the prescribed dose. With the introduction of 3D volumetric on-board imaging devices, it became feasible to use the produced images for dose recalculation.

Volumetric imaging by megavoltage computed tomography for assessment of internal organ motion during radiotherapy for cervical cancer.

Purpose: To assess the internal organ motion of the cervix and uterus by megavoltage computed tomography (MVCT) during intensity-modulated radiotherapy (IMRT).

Methods And Materials: Ten patients with Stage IIB-IVA cervical cancer underwent daily MVCT imaging. Internal organ motion was evaluated on 150 pretreatment MVCT images by measuring shifts in their boundaries between the MVCT and kilovoltage (kV) planning CT scan in the anterior, posterior, left and right lateral, and superior and inferior direction.

An in-house developed resettable MOSFET dosimeter for radiotherapy.

The purpose of this note is to report the feasibility and clinical validation of an in-house developed MOSFET dosimetry system and describe an integrated non-destructive reset procedure. Off-the-shelf MOSFETs are connected to a common PC using an 18 bit/analogue-input and 16 bit/output data acquisition card. A reading algorithm was developed defining the zero-temperature-coefficient point (ZTC) to determine the threshold voltage.

Toxicity and outcome results of a class solution with moderately hypofractionated radiotherapy in inoperable Stage III non-small cell lung cancer using helical tomotherapy.

Purpose: To prospectively assess the feasibility, toxicity, and local control of a class solution protocol of moderately hypofractionated tomotherapy in Stage III, inoperable, locally advanced non-small-cell lung cancer patients.

Methods And Materials: Eligible patients were treated according to a uniform class solution (70.5 Gy in 30 fractions) with fixed constraints and priorities using helical tomotherapy.

Toxicity report of a phase 1/2 dose-escalation study in patients with inoperable, locally advanced nonsmall cell lung cancer with helical tomotherapy and concurrent chemotherapy.

Background: The objective of the current study was to evaluate the feasibility and toxicity of radiation dose escalation with concurrent chemotherapy using helical tomotherapy (HT) in patients with inoperable, locally advanced, stage III nonsmall cell lung cancer (LANSCLC) (grading determined according to the American Joint Committee on Cancer 6th edition grading system).

Methods: This phase 1/2 study was designed to determine the maximum tolerated dose (MTD) of radiotherapy in patients with LANSCLC administered concurrently with docetaxel and cisplatin. Radiotherapy was delivered using HT.

A diagnostic tool for basic daily quality assurance of a Tomotherapy Hi*Art machine.

To investigate and evaluate the use of an in-house developed diagnostic software tool using the imaging detector data for a quick daily quality assurance check of the output (dose) and lateral profile (cone) of a tomotherapy Hi*Art system. The Hi*Art treatment system is a radiation therapy machine for delivering intensity modulated radiation therapy (IMRT) in a helical fashion with an integrated CT scanner used for improved patient positioning before treatment. Since the system was developed specifically for IMRT, flat fields can be obtained by modulating the beam and therefore the flattening filter could be omitted.

Dosimetric assessment of static and helical TomoTherapy in the clinical implementation of breast cancer treatments.

Background And Purpose: Investigation of the use of TomoTherapy and TomoDirect versus conventional radiotherapy for the treatment of post-operative breast carcinoma. This study concentrates on the evaluation of the planning protocol for the TomoTherapy and TomoDirect TPS, dose verification and the implementation of in vivo dosimetry.

Materials And Methods: Eight patients with different breast cancer indications (left/right tumor, axillary nodes involvement (N+)/no nodes (N0), tumorectomy/mastectomy) were enrolled.

Treatment delivery time optimization of respiratory gated radiation therapy by application of audio-visual feedback.

Purpose: The feasibility to use visually guided voluntary breath-hold with and without audio assistance to reduce the total treatment time was evaluated.

Materials And Methods: Patients referred for gated SBRT received hypofractionation schedules for lung or liver treatments. The patients were treated with the Novalis system (BrainLAB AG, Feldkirchen, Germany) and IGRT was performed with ExacTrac5.

Volumetric response analysis during chemoradiation as predictive tool for optimizing treatment strategy in locally advanced unresectable NSCLC.

Purpose: To study the feasibility of measuring volumetric changes in the primary tumor on megavoltage-computed tomography (MVCT) during chemoradiation and to examine the correlation with local response.

Patients And Methods: Fifteen consecutive patients with stage III, inoperable, locally advanced non-small cell lung cancer (NSCLC) were treated in a prospective dose escalation study protocol of concurrent chemoradiation. They were monitored for acute toxicity and evaluated with daily MVCT imaging.

Assessment of intrafractional movement and internal motion in radiotherapy of rectal cancer using megavoltage computed tomography.

Purpose: The aim of this study was to provide estimates of setup and internal margins of patients treated for rectal carcinoma using helical tomotherapy and to assess possible margin adaptations. Using helical tomotherapy, highly conformal dose distributions can be created, and the integrated megavoltage computed tomography (MVCT) modality allows very precise daily patient positioning. In clinical protocols, however, margins originating from traditional setup procedures are still being applied.

An assessment of the use of skin flashes in helical tomotherapy using phantom and in-vivo dosimetry.

Background And Purpose: In helical tomotherapy the nature of the optimizing and planning systems allows the delivery of dose on the skin using a build-up compensating technique (skin flash). However, positioning errors or changes in the patient's contour can influence the correct dosage in these regions. This work studies the behavior of skin-flash regions using phantom and in-vivo dosimetry.