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).

Stereotactic radiation treatment planning with volumetric modulated arc therapy: Impact of duodenal sparing on pancreatic tumor coverage.

2011 ◽  
Vol 29 (4_suppl) ◽  
pp. 301-301
Author(s):  
R. Kumar ◽  
J. Kang ◽  
J. M. Herman ◽  
R. Tuli ◽  
T. M. Pawlik ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Treatment Planning ◽  
Radiation Treatment ◽  
Volumetric Modulated Arc Therapy ◽  
High Dose ◽  
Stereotactic Radiation ◽  
Radiation Delivery ◽  
Delivery Times ◽  
Arc Therapy ◽  
The Difference

301 Background: Volumetric modulated arc therapy (VMAT) allows for intensity-modulated radiation delivery with faster treatment times and fewer delivered monitor units (MU). The dose-limiting structure for pancreatic stereotactic body radiation therapy (SBRT) is the duodenum. We evaluate VMAT dose distribution, delivery times, and the effect of duodenal sparing (DS) for pancreas SBRT. Methods: Plans of 15 patients with unresectable pancreatic cancer (14 head/1 tail) were selected. VMAT treatment planning with the “SmartArc” function of Pinnacle v. 8.9 was used to plan one fraction of 25 Gy to the PTV (gross tumor + 2 mm expansion) normalized to the 80% isodose line. Two VMAT SBRT plans were conducted for each case; the first did not attempt to spare the duodenum (non DS) while the second did (DS). Constraints were stomach/duodenum any point max <30 Gy (for DS plan), liver D50 < 5 Gy, ipsilateral kidney D25 < 5 Gy, cord Dmax < 5 Gy and stomach D4 < 22.5 Gy. Results: Gross tumor volume ranged from 58.4cm3 to 320.3 cm3. The average overlap volume between PTV and the duodenum was 8.4 cm3. In 10/15 non-DS plans, the duodenal Dmax exceeded 30 Gy. With DS optimization, only 1/15 plans exceeded the 30 Gy threshold. These differences were statistically significant (p<0.001). Typical MU and delivery times, as calculated by the planning software, were 5494 MU and 775 secs vs. 5296 MU and 703 secs for the DS and non-DS plans, respectively. The difference in delivery times was significant (p=0.01), but amounted to only 1.2 min on average. The average duodenal Dmax for non-DS plans was 30.4Gy, D4% was 23.4 Gy. With DS, the average Dmax was reduced to 28.1Gy and D4% to <19.7 Gy (p<0.001). As expected, VMAT plans with greater overlap between the duodenum and PTV had a higher duodenal Dmax. Conclusions: This study demonstrates the feasibility of VMAT for high-dose SBRT treatment of pancreatic cancer incorporating constraints to limit the dose to the duodenum. Future studies will evaluate whether VMAT with fractionated SBRT results in improved duodenal sparing more efficiently than traditional IMRT. No significant financial relationships to disclose.

External Stereotactic Irradiation by Linear Accelerator

Neurosurgery ◽  
1985 ◽  
Vol 16 (2) ◽  
pp. 154-160 ◽  
Author(s):  
Federico Colombo ◽  
Antonio Benedetti ◽  
Franco Pozza ◽  
Renzo Carlo Avanzo ◽  
Cristina Marchetti ◽  
...  
Keyword(s):  
Linear Accelerator ◽  
Three Dimensional ◽  
Target Volume ◽  
Radiation Doses ◽  
High Radiation ◽  
Stereotactic Irradiation ◽  
Interstitial Radiotherapy ◽  
Target Volumes ◽  
Three Dimensional Configuration ◽  
Very High

Abstract Stereotactic radiotherapy has two advantages: (a) the possibility of giving high radiation doses to small but spatially well-defined target volumes and (b) the presence of a stepped dose gradient between the target volume and the surrounding healthy tissues. To utilize these advantages, the authors built a new stereotactic head frame by which the intracranial target is fixed to the rotational isocenter of a 4-MV linear accelerator. The collimator openings are selected according to the volume and the three-dimensional configuration of the target, and the radiation dose is based on the radiosensitivity of the lesion. After the patient is fixed to the frame, the radiation source and the patient are rotated so that the target is irradiated through infinite portals distributed over the convexity of the skull. It is thereby possible to obtain very high radiation doses centered into the target with a stepped dose gradient. The preliminary radiodosimetric tests and the operative technique are described. The advantages of this technique compared to interstitial radiotherapy and Leksell's radiosurgery are emphasized. This noninvasive procedure has been used to treat a series of intracranial tumors.

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

scholarly journals Modern development of high-dose-rate brachytherapy

2020 ◽  
Vol 50 (5) ◽  
pp. 490-501
Author(s):  
Jun Itami
Keyword(s):  
Radiation Therapy ◽  
Dose Rate ◽  
Radiation Source ◽  
Three Dimensional ◽  
Target Volume ◽  
High Dose Rate ◽  
High Dose ◽  
High Dose Rate Brachytherapy ◽  
Radiation Oncologists ◽  
Modern Development

Abstract Brachytherapy is an invasive therapy with placement of radiation source into or near the tumor. The difference between planning target volume and clinical target volume is minimal, and the dose out of the tumor reduces rapidly due to the inverse-square law. High-dose-rate brachytherapy enables three-dimensional image guidance, and currently, tumor dose as well as doses of the surrounding normal structures can be evaluated accurately. High-dose-rate brachytherapy is the utmost precision radiation therapy even surpassing carbon ion therapy. Biological disadvantages of high-dose rate have been overcome by the fractional irradiation. High-dose-rate brachytherapy is indispensable in the definitive radiation therapy of cervical cancer. Also in prostate cancer and breast cancer, high-dose-rate brachytherapy plays a significant role. Brachytherapy requires techniques and skills of radiation oncologists at the time of invasive placement of the radiation source into the tumor area. Education of young radiation oncologists is most urgent and important.

Clinical dosimetry optimization in spinal metastases

2009 ◽  
Vol 8 (1) ◽  
pp. 35-40
Author(s):  
P. Pedrosa ◽  
C. Lucena ◽  
I.J. Sainz
Keyword(s):  
Organs At Risk ◽  
Three Dimensional ◽  
Spinal Metastases ◽  
Target Volume ◽  
The Body ◽  
High Dose ◽  
Prescription Dose ◽  
The Mean ◽  
Posterior Anterior ◽  
Anterior Posterior

AbstractIntroduction: Radiotherapy is commonly used to treat spinal metastases. The aim of this study was to compare conventional dosimetry (posterior–anterior fields) with an optimized three-dimensional conformal plan (using oblique fields).Material and Methods: Fifteen patients were selected, and split into three groups of five based on tumour localization: cervical, dorsal and lumbar. Reference planning comprised of two fields: anterior–posterior. The planning target volume (PTV) was covered with 90% of the prescribed doses, minimizing anterior field weight and not exceeding 120%. The alternative consisted of three fields: two oblique posterior fields with wedge and anterior field. The PTV was covered with 95% of the prescription dose, minimizing the anterior field weight with 107% of overdose as a limit. The patient received 8 Gy in one fraction; retreatment with an additional fraction was feasible, safe and effective if persistent or recurrent bone pain was present. Five fractions of 4 Gy were used for cervical cases. To consider the future patients toxicity we evaluated the mean dose, V90 and V70 parameters in each plan.Results: Dosimetric parameters of organs at risk were not significantly different from one trial to another. The optimized plan followed ICRU criteria, reaching PTV coverage of 95–107% range of the prescription dose. In the conventional plan, high dose had to be accepted to obtain 90% of coverage in the target.Conclusions: In contrast with the anterior–posterior configuration, oblique fields improve dose conformity and limit high dose all of the body except the spinal cord.

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