Dosimetric Performance Evaluation of MLC-based and Cone-based 3D Spatially Fractionated LATTICE Radiotherapy.

This study aims to dosimetrically compare multi-leaf collimator (MLC)-based and cone-based 3D LATTICE radiotherapy (LRT) plans. Valley-peak ratios were evaluated using seven different 3D LATTICE designs. Target volumes of 8 cm and 12 cm were defined on the RANDO phantom.

Planning and dosimetric evaluation of three total body irradiation techniques: Standard SSD VMAT, Extended SSD VMAT and Extended SSD Field-in-Field.

The aim of this study was to dosimetrically compare three total body irradiation (TBI) techniques which can be delivered by a standard linear accelerator, and to deduce which one is preferable. Specifically, Extended Source to Surface Distance (SSD) Field-in-Field (FiF), Extended SSD Volumetric Modulated Arc Therapy (VMAT), and Standard SSD VMAT TBI techniques were dosimetrically evaluated. Percent depth dose and dose profile measurements were made under treatment conditions for each specified technique.

Determination of inflection points of CyberKnife dose profiles within acceptability criteria of deviations in measurements.

Aim: The aim of this study was to determine the Inflection Points (IPs) of flattening filter free (FFF) CyberKnife dose profiles for cone-based streotactic radiotherapy. In addition, dosimetric field sizes were determined.

Background: The increased need for treatment in the early stages of cancer necessitated the treatment of smaller tumors.

Evaluation of NanoDot Optically Stimulated Luminescence Dosimeter for Cone-shaped Small-field Dosimetry of Cyberknife Stereotactic Radiosurgery Unit: A Monte Carlo Simulation and Dosimetric Verification Study.

Aim: The aim of this study was to investigate the adequacy of nanoDot optically stimulated luminescence (OSL) dosimeter for small field dosimetry before its applications in CyberKnife SRS unit.

Materials And Methods: A PTW 60018 SRS Diode, 60019 microDiamond, and Gafchromic EBT3 films were used along with a nanoDot carbon-doped aluminum oxide OSL dosimeter to collect and compare beam data. In addition, the EGSnrc/BEAMnrc code was employed to simulate 6-MV photon beams of CyberKnife SRS system.

Performance evaluation of the X-sight spine tracking system for abdominal tumors distal to spine: A 2D dosimetric analysis.

The X-sight spine tracking system was integrated with Cyberknife unit to deliver radiosurgery treatments for spinal tumors without fiducial placement. However the tracking system can also be used for the treatment of abdominal tumors located in a certain distance from the spine. The aim of our study is to evaluate the tracking performance of the X-sight spine system for abdominal tumors distal to spine based on the 3 factors: tumor distance from the reference vertebra, the angle of tumor with the vertebra, and the amplitude of tumor motion due to respiration.

Fully automated blink detection for uveal melanoma radiotherapy.

Uveal melanoma is a widespread neoplasm in the eye that cause vision defects. The disease may result in loss of eye, even loss of life with a risk of metastasis to other tissues. There have been proposed various treatment methods to overcome the disease including enucleation and radiotherapy.

Investigating the surface dose contribution of intrafractional kV imaging in CyberKnife-based stereotactic radiosurgery.

CyberKnife treatment consists of hundreds of noncoplanar beams and numerous intrafractional images that can be taken during a single treatment fraction; thus, doses because of imaging should be considered in this technique. The aim of this study is to investigate the in-field and out-of-field surface doses induced from kV imaging system during stereotactic radiosurgery (SRS) treatment. The imaging-induced surface doses were measured at the center of the imaging field and within ±15-cm distance from the center in both craniocaudal and lateral directions.

Evaluation of MLC leaf positioning accuracy for static and dynamic IMRT treatments using DAVID in vivo dosimetric system.

Accuracy and precision of leaf positioning in multileaf collimators (MLCs) are significant factors for the accuracy of IMRT treatments. This study aimed to inves-tigate the accuracy and repeatability of the MLC leaf positioning via the DAVID invivo dosimetric system for dynamic and static MLC systems. The DAVID system was designed as multiwire transmission ionization chamber which is placed in accessory holder of linear accelerators.

Evaluation of Photoneutron Dose Measured by Bubble Detectors in Conventional Linacs and Cyberknife Unit: Effective Dose and Secondary Malignancy Risk Estimation.

This study aims to reduce the uncertainty about the photoneutron dose produced over a course of radiotherapy with high-energy photon beams and evaluate photoneutron contamination-based secondary malignancy risk for different treatment modalities. Dosimetric measurements were taken in Philips SL25/75, Elekta Synergy Platform (Elekta AB, Stockholm, Sweden), Varian Clinac DHX High Performance systems (Varian Medical Systems, Palo Alto, CA), and Cyberknife Robotic Radiosurgery Unit (Accuray Inc., Sunnyvale, CA) using bubble detector for neutron dosimetry.

Investigating in-field and out-of-field neutron contamination in high-energy medical linear accelerators based on the treatment factors of field size, depth, beam modifiers, and beam type.

Purpose: We analysed the effects of field size, depth, beam modifier and beam type on the amount of in-field and out-of-field neutron contamination for medical linear accelerators (linacs).

Methods: Measurements were carried out for three high-energy medical linacs of Elekta Synergy Platform, Varian Clinac DHX High Performance and Philips SL25 using bubble detectors. The photo-neutron measurements were taken in the first two linacs with 18 MV nominal energy, whereas the electro-neutrons were measured in the three linacs with 9 MeV, 10 MeV, 15 MeV and 18 MeV.

Verification of dose distribution for volumetric modulated arc therapy total marrow irradiation in a humanlike phantom.

Purpose: Volumetric modulated arc therapy (VMAT) treatment planning studies have been reported to provide good target coverage and organs at risk (OARs) sparing in total marrow irradiation (TMI). A comprehensive dosimetric study simulating the clinical situation as close as possible is a norm in radiotherapy before a technique can be used to treat a patient. Without such a study, it would be difficult to make a reliable and safe clinical transition especially with a technique as complicated as VMAT-TMI.

Total marrow irradiation with RapidArc volumetric arc therapy.

Purpose: To develop a volumetric arc therapy (VMAT)-total marrow irradiation (TMI) technique for patients with hematologic malignancies.

Methods And Materials: VMAT planning was performed for 6 patients using RapidArc technology. The planning target volume consisted of all the bones in the body from the head to the mid-femur, excluding the extremities, except for the humerus, plus a 3.

Linear accelerator-based intensity-modulated total marrow irradiation technique for treatment of hematologic malignancies: a dosimetric feasibility study.

Purpose: To investigate the dosimetric feasibility of linear accelerator-based intensity-modulated total marrow irradiation (IM-TMI) in patients with hematologic malignancies.

Methods And Materials: Linear accelerator-based IM-TMI treatment planning was performed for 9 patients using the Eclipse treatment planning system. The planning target volume (PTV) consisted of all the bones in the body from the head to the mid-femur, except for the forearms and hands.

Probing the existence of medium pulmonary crackles via model-based clustering.

The objective of this study is to probe the existence of a third crackle type, medium, besides the traditionally accepted types, namely, fine and coarse crackles and, furthermore, to explore the representative parameter values for each crackle type. A set of clustering experiments have been conducted on pulmonary crackles to this end. A model-based clustering algorithm, the Expectation-Maximization algorithm, is used and the resulting cluster numbers are validated with Bayesian Inference Criterion.

Normal tissue complication probability modeling of acute hematologic toxicity in cervical cancer patients treated with chemoradiotherapy.

Purpose: To test the hypothesis that increased pelvic bone marrow (BM) irradiation is associated with increased hematologic toxicity (HT) in cervical cancer patients undergoing chemoradiotherapy and to develop a normal tissue complication probability (NTCP) model for HT.

Methods And Materials: We tested associations between hematologic nadirs during chemoradiotherapy and the volume of BM receiving≥10 and 20 Gy (V10 and V20) using a previously developed linear regression model. The validation cohort consisted of 44 cervical cancer patients treated with concurrent cisplatin and pelvic radiotherapy.

Feature extraction for pulmonary crackle representation via wavelet networks.

In this study, wavelet networks have been used to parameterize and quantify pulmonary crackles with an aim to depict the waveform with a small set of meaningful parameters. Complex Morlet wavelets are used at the nodes of both single and double-node networks to model the waveforms with the double-node rendering smaller modeling error. The features extracted from the model parameters have been compared with the conventional time domain features in a two-class clustering experiment with nearly 90% matching between the clusters of different parameter sets and with the model parameters forming clusters more closely distributed around their means and better separated from each other.

Elimination of vesicular sounds from pulmonary crackle waveforms.

Pulmonary crackles and their parameters are very useful in the diagnosis of pulmonary disorders. A new automatic method has been proposed for the elimination of background vesicular sound from crackle signal with a view to introduce minimum distortion to crackle parameters. A region of interest is designated and a distortion metric based on the correlation between raw and filtered waveforms in that region is defined.

Sensitivity of pulmonary crackle parameters to filter cut-off frequency.

Pulmonary crackles are very important indicators in the diagnosis of pulmonary disorders. Parameters derived from their waveforms, such as initial deflection width and two-cycle duration width, are useful in classifying a crackle and correlating it with various disorders. To obtain a crackle waveform, the background vesicular sound is filtered out and the crackle parameters are very sensitive to filter cut-off frequency.

Classifying respiratory sounds with different feature sets.

In this study, different feature sets are used in conjunction with (k-nearest neighbors) k-NN and artificial neural network (ANN) classifiers to address the classification problem of respiratory sound signals. A comparison is made between the performances of k-NN and ANN classifiers with different feature sets derived from respiratory sound data acquired from one microphone placed on the posterior chest area. Each subject is represented by a single respiration cycle divided into sixty segments from which three different feature sets consisting of 6th order AR model coefficients, wavelet coefficients and crackle parameters in addition to AR model coefficients are extracted.