scholarly journals Patient individual phase gating for stereotactic radiation therapy of early stage non-small cell lung cancer (NSCLC)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
K. M. Kraus ◽  
M. Oechsner ◽  
J. J. Wilkens ◽  
K. A. Kessel ◽  
S. Münch ◽  
...  
Keyword(s):  
Early Stage ◽  
Treatment Plan ◽  
Target Volume ◽  
Surrounding Tissue ◽  
Internal Target Volume ◽  
Stereotactic Radiation ◽  
Individual Phase ◽  
4D Computed Tomography ◽  
High Doses ◽  
Definition Of

AbstractStereotactic body radiotherapy (SBRT) applies high doses and requires advanced techniques to spare surrounding tissue in the presence of organ motion. In this work patient individual phase gating is investigated. We studied peripheral and central primary lung tumors. The internal target volume (ITV) was defined including different numbers of phases picked from a 4D Computed tomography (CT) defining the gating window (gw). Planning target volume (PTV) reductions depending on the gw were analyzed. A treatment plan was calculated on a reference phase CT (rCT) and the dose for each breathing phase was calculated and accumulated on the rCT. We compared the dosimetric results with the dose calculated when all breathing phases were included for ITV definition. GWs including 1 to 10 breathing phases were analyzed. We found PTV reductions up to 38.4%. The mean reduction of the lung volume receiving 20 Gy due to gating was found to be 25.7% for peripheral tumors and 16.7% for central tumors. Gating considerably reduced esophageal doses. However, we found that simple reduction of the gw does not necessarily influence the dose in a clinically relevant range. Thus, we suggest a patient individual definition of the breathing phases included within the gw.

scholarly journals A novel index for assessing treatment plan quality in stereotactic radiosurgery

2018 ◽  
Vol 129 (Suppl1) ◽  
pp. 118-124 ◽  
Author(s):  
Alexis Dimitriadis ◽  
Ian Paddick
Keyword(s):  
Stereotactic Radiosurgery ◽  
Treatment Plan ◽  
Efficiency Index ◽  
Target Volume ◽  
Surrounding Tissue ◽  
Plan Quality ◽  
Multiple Target ◽  
Integral Dose ◽  
Plan Optimization ◽  
Dose Volume

OBJECTIVEStereotactic radiosurgery (SRS) is characterized by high levels of conformity and steep dose gradients from the periphery of the target to surrounding tissue. Clinical studies have backed up the importance of these factors through evidence of symptomatic complications. Available data suggest that there are threshold doses above which the risk of symptomatic radionecrosis increases with the volume irradiated. Therefore, radiosurgical treatment plans should be optimized by minimizing dose to the surrounding tissue while maximizing dose to the target volume. Several metrics have been proposed to quantify radiosurgical plan quality, but all present certain weaknesses. To overcome limitations of the currently used metrics, a novel metric is proposed, the efficiency index (η50%), which is based on the principle of calculating integral doses: η50% = integral doseTV/integral dosePIV50%.METHODSThe value of η50% can be easily calculated by dividing the integral dose (mean dose × volume) to the target volume (TV) by the integral dose to the volume of 50% of the prescription isodose (PIV50%). Alternatively, differential dose-volume histograms (DVHs) of the TV and PIV50% can be used. The resulting η50% value is effectively the proportion of energy within the PIV50% that falls into the target. This value has theoretical limits of 0 and 1, with 1 being perfect. The index combines conformity, gradient, and mean dose to the target into a single value. The value of η50% was retrospectively calculated for 100 clinical SRS plans.RESULTSThe value of η50% for the 100 clinical SRS plans ranged from 37.7% to 58.0% with a mean value of 49.0%. This study also showed that the same principles used for the calculation of η50% can be adapted to produce an index suitable for multiple-target plans (Gη12Gy). Furthermore, the authors present another adaptation of the index that may play a role in plan optimization by calculating and minimizing the proportion of energy delivered to surrounding organs at risk (OARη50%).CONCLUSIONSThe proposed efficiency index is a novel approach in quantifying plan quality by combining conformity, gradient, and mean dose into a single value. It quantifies the ratio of the dose “doing good” versus the dose “doing harm,” and its adaptations can be used for multiple-target plan optimization and OAR sparing.

scholarly journals Impact of 4D CT for treatment planning of moving targets: a computer-based biological evaluation

2017 ◽  
Vol 3 (2) ◽  
pp. 665-668
Author(s):  
Eike Helf ◽  
Oliver Waletzko ◽  
Christian Mehrens ◽  
Ralf Rohn ◽  
Andreas Block
Keyword(s):  
Treatment Plan ◽  
Tumour Volume ◽  
Target Volume ◽  
Biological Evaluation ◽  
Internal Target Volume ◽  
4D Ct ◽  
Tumour Control ◽  
Ct Data ◽  
Conventional Ct ◽  
The Impact

AbstractThis study deals with comparison of conventional and 4D CT (GE Lightspeed) planning on the tumour control probability (TCP), using the TCP model of the AAPM-Report Task Group 166. In the first step a VMAT treatment plan was calculated (Varian Eclipse 13.7) on basis of conventional CT data. This treatment plan was transferred to the complete 4D CT, which represents the tumour volume in motion. Due to the increased volume and the resulting decrease of tumour coverage the TCP went down from 97,6% to 91,2%. After adding an internal target volume (ITV, ICRU 62) to the conventional CT according to our clinical protocols (1,0 cm cc and 0,3 cm axial plane) the TCP increased to 98,0% when applying the conventional plan to the 4D CT. This finding demonstrates the need of 4D CT for moving tumours in chest and abdomen region.Average IPs with increasing width have been created to evaluate the impact on the TCP and the non-malignant tissue. Our observations had shown that heart, lung and spinal cord radiation exposure did not correlate to chosen respiration segment. This could be explained by the extremely slight ratio of the planning target volume and the irradiated normal tissue.This procedure enables us to evaluate the efficacy of treatment plans. Furthermore, optimizing trials like the influence of respiration-gated RT, setting individual margins and fitting planning objectives and parameters are still under investigation.

Abstract

2014 ◽  
Vol 14 (2) ◽  
pp. 5-5
Keyword(s):  
Three Dimensional ◽  
Absorbed Dose ◽  
Target Volume ◽  
High Dose ◽  
Stereotactic Radiation ◽  
Small Field Dosimetry ◽  
Radiation Delivery ◽  
Target Volumes ◽  
Definition Of ◽  
Three Dimensional Coordinate

Rapid developments in imaging and radiation-delivery technology have fueled the application of small photon beams in stereotactic radiation therapy (SRT). Historically, stereotaxy referred to the use of a three-dimensional coordinate system to localize intracranial targets and has been more recently extensively developed in extracranial clinical situations. SRT involves stereotactic localization techniques combined with the delivery of multiple small photon fields in a few high-dose fractions. In SRT, the therapeutic ratio is optimized through delivery of highly conformal absorbed dose distributions with steep dose fall-off ensuring optimal absorbed dose in the target volume combined with minimal normal-tissue irradiation. Consistent with previous ICRU Reports 50 (ICRU, 1993), 62, (ICRU, 1999), and 83, (ICRU, 2010), this Report recommends a strict definition of target volumes (GTV, CTV) by reviewing imaging modalities used in clinical practice. This Report covers fundamentals of small-field dosimetry, treatment-planning algorithms, commissioning, and quality assurance for the existing delivery systems, as well as the role of image guidance during delivery. Finally, it recommends a framework for prescribing, recording, and reporting stereotactic radiotherapy, and covers most of the pathologies eligible for stereotactic delivery (malignant and non-malignant).

Definition of a moving gross target volume for stereotactic radiation therapy of stented coronary arteries

2002 ◽  
Vol 52 (2) ◽  
pp. 560-565 ◽  
Author(s):  
Edward M Leter ◽  
Peter J.C.M Nowak ◽  
Koen Nieman ◽  
Pim J de Feyter ◽  
Stéphane G Carlier ◽  
...  
Keyword(s):  
Radiation Therapy ◽  
Coronary Arteries ◽  
Target Volume ◽  
Stereotactic Radiation Therapy ◽  
Stereotactic Radiation ◽  
Definition Of

A Real Time Control Architecture for Continuously Managing Patients in a Care Unit

1995 ◽  
Vol 34 (05) ◽  
pp. 475-488
Author(s):  
B. Seroussi ◽  
J. F. Boisvieux ◽  
V. Morice
Keyword(s):  
Real Time ◽  
Linear Time ◽  
Treatment Plan ◽  
Control Architecture ◽  
Real Time Control ◽  
Time Representation ◽  
Time Control ◽  
Continuous Support ◽  
Definition Of ◽  
Computerized System

Abstract:The monitoring and treatment of patients in a care unit is a complex task in which even the most experienced clinicians can make errors. A hemato-oncology department in which patients undergo chemotherapy asked for a computerized system able to provide intelligent and continuous support in this task. One issue in building such a system is the definition of a control architecture able to manage, in real time, a treatment plan containing prescriptions and protocols in which temporal constraints are expressed in various ways, that is, which supervises the treatment, including controlling the timely execution of prescriptions and suggesting modifications to the plan according to the patient’s evolving condition. The system to solve these issues, called SEPIA, has to manage the dynamic, processes involved in patient care. Its role is to generate, in real time, commands for the patient’s care (execution of tests, administration of drugs) from a plan, and to monitor the patient’s state so that it may propose actions updating the plan. The necessity of an explicit time representation is shown. We propose using a linear time structure towards the past, with precise and absolute dates, open towards the future, and with imprecise and relative dates. Temporal relative scales are introduced to facilitate knowledge representation and access.

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