Shirin Abbasinejad Enger

McGill University | McGill · Gerald Bronfman Department of Oncology, Medical Physics Unit

In e-aq dosimetry, absorbed radiation dose to water is measured by monitoring the concentration of radiation-induced hydrated electrons (e-aq). However, to obtain accurate dose, the radiation chemical yield of e-aq, G(e-aq), is needed for the radiation quality/setup under investigation. The aim of this study was to investigate the time-evolution of...

Objective: Intensity modulated high dose rate brachytherapy (IMBT) is a rapidly developing application of brachytherapy where anisotropic dose distributions can be produced at each source dwell position. This technique is made possible by placing rotating metallic shields inside brachytherapy needles or catheters. By dynamically directing the radi...

Background: Intensity modulated brachytherapy (IMBT) is an emerging technology for cancer treatment, in which radiation sources are shielded to shape the dose distribution. The rotatable shields provide an additional degree of freedom, but also introduce an additional, directional, type of uncertainty, compared to conventional high dose-rate brach...

Purpose Intensity-modulated brachytherapy (IMBT) is a developing application of brachytherapy where high-density metallic shields located inside the catheters are used to modulate radiations allowing the production of anisotropic dose distributions at each source dwell position. By rotating the shields during the treatment, the radiation is directe...

Background: Dynamic positron emission tomography (dPET) is a nuclear medicine imaging technique providing functional images for organs of interest with applications in oncology, cardiology, and drug discovery. This technique requires the acquisition of the time-course arterial plasma activity concentration, called the arterial input function (AIF)...

(1) Background: The introduction of total mesorectal excision (TME) for rectal cancer has led to improvement in local recurrence (LR) outcomes. Furthermore, the addition of preoperative external beam radiotherapy to TME reduces LR to less than 6%. As a trade-off to these gradual improvements in local therapies, the oncology community’s work is now...

Purpose: To build a machine-learning (ML) classifier to predict the clinical endpoint of post-Radiation-Therapy (RT) recurrence of gynecological cancer patients, while exploring the outcome predictability of cell spacing and nuclei size pre-treatment histopathology image features and clinical variables. Materials and Methods: Thirty-six gynecolog...

Purpose/Objective: The McMedHacks workshop and presentation series was created to teach individuals from various backgrounds about deep learning (DL) for medical image analysis in May, 2021. Material/Methods: McMedHacks is a free and student-led 8-week summer program. Registration for the event was open to everyone, including a form to survey pa...

PURPOSE To automate the segmentation of treatment applicators on computed tomography (CT) images for high-dose-rate (HDR) brachytherapy prostate patients implanted with titanium needles with the goals of improving plan quality and reducing the patient's time under anesthesia. METHODS The investigation was performed using 57 retrospective, intersti...

Background Rectal cancer is curable by standard surgery with Total Mesorectal Excision (TME). However, there are well known associated long-term bowel and sexual dysfunctions. Non-operative management (NOM) is an emerging treatment for patients with operable rectal cancer. There is evidence supporting dose response for tumor control in rectal adeno...

Background Tumor delineation in endoscopy images is a crucial part of clinical diagnoses and treatment planning for rectal cancer patients. However, it is challenging to detect and adequately determine the size of tumors in these images, especially for inexperienced clinicians. This motivates the need for a standardized, automated segmentation meth...

This work presents Monte Carlo (MC) study of a novel non-invasive positron detector, hereinafter called NID, designed to measure the arterial input function (AIF) through the wrist of a patient for use with dynamic positron emission tomography (PET). The goal of the study was to optimize a previously developed NID prototype, to determine its effici...

We present a simple, continuous, cavity-enhanced optical absorption measurement technique based on high-bandwidth Pound-Drever-Hall (PDH) sideband locking. The technique provides a resonant amplitude quadrature readout that can be mapped onto the cavity’s internal loss rate and is naturally compatible with weak probe beams. With a proof-of-concept...

Background Multiple post-treatment dosimetry methods are currently under investigation for Yttrium-90 ( $$^{90}\hbox {Y}$$ 90 Y ) radioembolization. Within each methodology, a variety of dosimetric inputs exists that affect the final dose estimates. Understanding their effects is essential to facilitating proper dose analysis and crucial in the eve...

We present a simple, continuous, cavity-enhanced optical absorption measurement technique based on high-bandwidth Pound-Drever-Hall (PDH) sideband locking. The technique provides a resonant amplitude quadrature readout that can be mapped onto the cavity's internal loss rate, and is naturally compatible with weak probe beams. With a proof-of-concept...

Microscopic energy deposition distributions from ionizing radiation are used to predict the biological effects of an irradiation and vary depending on biological target size. Ionizing radiation is thought to kill cells or inhibit cell cycling mainly by damaging DNA in the cell nucleus. The size of cells and nuclei depends on tissue type, cell cycle...

BACKGROUND AND PURPOSE Despite the excellent clinical outcomes from brachytherapy treatments compared with other modalities and the low associated costs, there have been reports of a decline in utilization of brachytherapy. The aim of this study was to investigate in detail the trend in utilization of brachytherapy in the province of Québec, Canada...

Purpose: The purpose of this study was to evaluate the impact of dose reporting schemes and tissue/applicator heterogeneities for 192 Ir-, 75 Se- and 169 Yb-based MRI guided conventional and intensity modulated brachytherapy METHODS AND MATERIALS: Treatment plans using a variety of dose reporting and tissue/applicator segmentation schemes were gen...

The goal of this study was (i) to use artificial intelligence to automate the traditionally labor-intensive process of manual segmentation of tumor regions in pathology slides performed by a pathologist and (ii) to validate the use of a deep learning architecture. Automation will reduce the human error involved in the manual process, increase effic...

The biological effects of ionizing radiation depend on the tissue, tumor type, radiation quality, and patient-specific factors. Inter-patient variation in cell/nucleus size may influence patient-specific dose response. However, this variability in dose response is not well investigated due to lack of available cell/nucleus size data. The aim of thi...

Purpose: To present a novel, MRI-compatible dynamic-shield intensity modulated brachytherapy (IMBT) applicator and delivery system using 192 Ir, 75 Se and 169 Yb radioisotopes for the treatment of locally advanced cervical cancer. Needle-free IMBT is a promising technique for improving target coverage and organ at risk (OAR) sparing. Methods and...

Kinetic modeling of positron emission tomography (PET) data can assess index rate of uptake, metabolism and predict disease progression more accurately than conventional static PET. However, it requires knowledge of the time-course of the arterial blood radioactivity concentration, called the arterial input function (AIF). The gold standard to acqu...

The purpose of this work was to develop an efficient quadratic mixed integer programming algorithm for high dose rate (HDR) brachytherapy treatment planning problems and integrate the algorithm into an open-source Monte Carlo based treatment planning software, RapidBrachyMCTPS. The mixed-integer algorithm yields a globally optimum solution to the d...

We have previously described RapidBrachyMCTPS, a brachytherapy treatment planning toolkit consisting of a graphical user interface (GUI) and a Geant4-based Monte Carlo (MC) dose calculation engine. This work describes the tools that have recently been added to RapidBrachyMCTPS, such that it now serves as the first stand-alone application for MC-bas...

A prototype Yb source was developed in combination with a dynamic rotating platinum shield system (AIM‐Brachy) to deliver intensity modulated brachytherapy (IMBT). The purpose of this study was to evaluate the dosimetric characteristics of the bare/shielded Yb source using Monte Carlo (MC) simulations and perform an independent dose verification us...

Purpose Detailed and accurate absorbed dose calculations from radiation interactions with the human body can be obtained with the Monte Carlo (MC) method. However, the MC method can be slow for use in the time-sensitive clinical workflow. The aim of this study was to provide a solution to the accuracy-time trade-off for ¹⁹²Ir -based high dose rate...

Purpose Intensity modulated brachytherapy (IMBT) with rotating metal shields enables dose modulation that can better conform to the tumor while reducing OAR doses. In this work, we investigate novel rotating shields, compatible with MRI-compatible tandems used for cervix brachytherapy. Three unique shields were evaluated using the traditional ¹⁹²Ir...

Purpose: Several radionuclides with high (60Co, 75Se) and intermediate (169Yb, 153Gd) energies have been investigated as alternatives to 192Ir for high-dose-rate brachytherapy. The purpose of this study was to evaluate the impact of tissue heterogeneities for these five high- to intermediate-energy sources in prostate and head & neck brachytherapy....

The purpose of this study was to review the limitations of dose calculation formalisms for photon-emitting brachytherapy sources based on the American Association of Physicists in Medicine (AAPM) Task Group No. 43 (TG-43) report and to provide recommendations to transition to model-based dose calculation algorithms. Additionally, an overview of the...

We present a simple, high-duty-cycle, cavity-enhanced optical absorption measurement technique based on delay-limited Pound-Drever-Hall (PDH) sideband locking. The chosen circuit naturally provides realtime readout of the amplitude quadrature of the PDH error signal, which can be mapped onto the cavity’s internal loss rate while using the phase qua...

Purpose: Intensity modulated brachytherapy (IMBT) is a novel high dose rate brachytherapy (HDR BT) technique which incorporates static or dynamic shielding to increase tumor coverage and/or spare healthy tissues. The purpose of this study is to present a novel delivery system (AIM-Brachy) design that can enable dynamic-shield IMBT for prostate can...

Radioembolization gains continuous traction as a primarily palliative radiation treatment for hepatic tumours. A form of nuclear medicine therapy, Yttrium-90 containing microspheres are catheter guided and injected into the right, left, or a specifically selected hepatic artery. A multitude of comprehensive planning steps exist to ensure a thorough...

PURPOSE: Manual and automatic blood sampling at different time intervals is considered the gold standard to determine the arterial input function (AIF) in dynamic positron emission tomography (PET). However, blood sampling is characterized by poor time resolution and is an invasive procedure. The aim of this study was to characterize the scintillat...

Purpose: To evaluate the TG-43 parameters for a new 169Yb source design for high dose rate brachytherapy. 169Yb has an average energy of 93 keV and a half-life of 32.0 days. The 169Yb source has physical dimensions and dosimetric characteristics that make it suitable as an intermediate energy source for intensity modulated brachytherapy (IMBT). Mat...

Objectives: Kinetic modelling of dynamic PET data requires knowledge of the time-course of the arterial blood activity concentration. This is normally acquired by invasive means [1] and is called the arterial input function (AIF). Kinetic modelling of PET data can predict disease progression more accurately than conventional static PET [2]. The pur...

Purpose: Intensity modulated brachytherapy (IMBT) is a novel high dose rate brachytherapy (HDR-BT) technique which incorporates rotating metallic shields inside brachytherapy catheters to dynamically direct the radiation towards the tumor and away from healthy tissues. A delivery system that can enable IMBT for prostate cancer was proposed in a pre...

Despite being considered the gold standard for brachytherapy dosimetry, Monte Carlo (MC) has yet to be implemented into a software for brachytherapy treatment planning. The purpose of this work is to present RapidBrachyMCTPS, a novel treatment planning system (TPS) for brachytherapy applications equipped with a graphical user interface (GUI), optim...

Purpose: Clinical standards of brachytherapy (BT) dose calculation have traditionally been based on report number 43 issued in 1995 by the American Association of Physicists in Medicine (AAPM) termed TG-43. In the TG-43 based dose calculation process the affected malignant tissue, the surrounding radiation sensitive healthy organs, BT seeds, needle...

Purpose: Several gamma emitting radionuclides with high (60Co, 75Se) and intermediate (169Yb, 153Gd) energies have been investigated as alternatives to 192Ir for high dose rate (HDR) brachytherapy. The purpose of this study was to evaluate the effect of tissue heterogeneities for 60Co, 192Ir, 75Se, 169Yb and 153Gd for prostate and oral tongue HDR b...

Purpose: Conventional brachytherapy often results in less than ideal tumor dose conformity due to the non-symmetrical shape of the tumors, resulting in dose spillage to radiation sensitive organs at risk (OARs). Intensity modulated brachytherapy (IMBT) can dynamically direct the radiation towards the tumor and away from OARs by incorporating metall...

Purpose: Renewed interest is being expressed in intravascular brachytherapy (IVBT). A number of unresolved issues exist in the discipline. Providing a homogeneous and adequate dose to the target remains difficult in IVBT. The guidewire that delivers the device to the target, arterial plaques, and stent struts are all known to reduce the dose deliv...

Background and purpose: Model-based dose calculation algorithms (MBDCAs) have evolved from serving as a research tool into clinical practice in brachytherapy. This study investigates primary sources of tissue elemental compositions used as input to MBDCAs and the impact of their variability on MBDCA-based dosimetry. Materials and methods: Releva...

Purpose/Objectives: Conventional brachytherapy often results in less than ideal tumor dose conformity due to the non-symmetrical shape of the tumors, resulting in dose spillage to radiation sensitive healthy tissues. Intensity modulated brachytherapy (IMBT) can dynamically direct the radiation towards the tumor and away from healthy tissues by inco...

Purpose Recent studies have identified and proposed gamma emitting radionuclides (⁷⁵Se, ¹⁶⁹Yb, ¹⁵³Gd) with intermediate energy (50 keV < E < 200 keV) as an alternative to ¹⁹²Ir for HDR brachytherapy. The impact of tissue composition and density on the treatment plan quality was studied in a retrospective evaluation for a prostate cancer patient usi...

Purpose The aim of this study was to calculate microdosimetric distributions for low energy electrons simulated using the Monte Carlo track structure code Geant4-DNA. Materials and Methods Tracks for monoenergetic electrons with kinetic energies ranging from 100 eV to 1 MeV were simulated in an infinite spherical water phantom using the Geant4-DNA...

The goal of this study was to investigate the production, purification and immobilization techniques for a (153)Gd brachytherapy source. We have investigated the maximum attainable specific activity of (153)Gd through the irradiation of Gd2O3 enriched to 30.6% (152)Gd at McMaster Nuclear Reactor. The advantage of producing (153)Gd through this prod...

Purpose: Radioisotopes such as (75)Se, (169)Yb, and (153)Gd have photon energy spectra and half-lives that make them excellent candidates as alternatives to (192)Ir for high-dose-rate brachytherapy. The aim of the present study was to evaluate the relative biological effectiveness (RBE) of current ((192)Ir, (125)I, (103)Pd) and alternative ((75)Se...

The aim of this study was to calculate microdosimetric distributions for low energy electrons simulated using the Monte Carlo track structure code Geant4-DNA. Tracks for monoenergetic electrons with kinetic energies ranging from 100 eV to 1 MeV were simulated in an infinite spherical water phantom using the Geant4-DNA extension included in Geant4 t...

Purpose: Conventional brachytherapy often results in less than ideal tumor dose conformity due to the non-symmetrical shape of the tumors resulting in dose spillage to radiation sensitive healthy tissues. Intensity modulated Brachytherapy (IMBT) gives a possibility to dynamically direct the radiation towards the tumor and away from healthy tissues...

Purpose: Recent studies have identified and proposed gamma emitting radionuclides in the intermediate energy region that can provide optimal depth dose distributions while reducing shielding requirements compared to 192Ir. The impact of source energy on the treatment plan quality was studied in a retrospective evaluation for a prostate cancer patie...

Purpose or Objective: Recent interest in alternative radionuclides for use in high dose rate brachytherapy (Se-75, Yb-169, Gd-153) with average energies lower than Ir-192 has triggered the investigation of the microdosimetric properties of these radionuclides. A combination of Monte Carlo Track Structure (MCTS) simulations and track sampling algori...

Purpose: Coronary artery disease involves the deposition of plaque along the walls of a coronary artery leading to narrowed or blocked vessels (stenosis) and is one of the main causes of death in developed countries. Percutaneous transluminal coronary angioplasty (PTCA) is used to reverse stenosis. Restenosis (renarrowing) of the treated vessel is...

We describe the measurements of neutron spectra that we undertook around a scanning proton beam at the Skandion proton therapy clinic in Uppsala, Sweden. Measurements were undertaken using an extended energy range Nested Neutron Spectrometer (NNS, Detec Inc., Gatineau, QC) operated in pulsed and current mode. Spectra were measured as a function of...

Purpose: To present and characterize a Monte Carlo(MC) tool for the simulation of the relative biological effectiveness for the induction of direct DNA double strand breaks (RBEDSBdirect) for protons and light ions.

Introduction: In photon brachytherapy (BT), experimental dosimetry is needed to verify treatment plans if planning algorithms neglect varying attenuation, absorption or scattering conditions. The detector's response is energy dependent, including the detector material to water dose ratio and the intrinsic mechanisms. The local mean photon energy E...

Purpose: Brachytherapy (BT) can be administrated by low (E < 50 keV), intermediate (50 keV < E < 200 keV) or high (E > 200 keV) energy sources. For the lower energy sources, the photoelectric effect dominates the energy deposition and the dose distribution decreases rapidly as the inverse of the distance from the source. For the intermediate and hi...

Abstract

Understanding the fundamental mechanisms involved in the induction of biological damage by ionizing radiation remains a major challenge of today's radiobiology research. The Monte Carlo simulation of physical, physicochemical and chemical processes involved may provide a powerful tool for the simulation of early damage induction. The Geant4-DNA ext...

To introduce rotating shield brachytherapy (RSBT) for different cancer sites with (1)⁵(3)Gd and ⁷⁵Se isotopes. RSBT is a form of intensity modulated brachytherapy, using shielded rotating catheters to provide a better dose distribution in the tumour while protecting healthy tissue. BrachySource, a Geant4-based Monte Carlo dose planning system was d...