David Christopher Medich

Worcester Polytechnic Institute | WPI · Department of Physics

Purpose: We propose an alternative to LDR brachytherapy for the treatment of ocular melanomas by coupling intensity modulation, through the use of a gold shielded ring applicator, with a middle energy HDR brachytherapy source, Se-75. In this study, we computationally test this proposed design using MCNP6. Methods and materials: An array of discr...

We propose an approach for treating ocular melanoma using a new type of brachytherapy treatment device. This device couples Yb-169, a middle-energy HDR brachytherapy source, with a gold shielded ring applicator to better conform radiation exposures to the tumor. In this study, we computationally test the dosimetric output of our proposed shielded r...

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...

Inhalation of airborne radionuclides, particularly alpha-emitters such as Am-241, delivers an internal dose of ionizing radiation proportional to the cumulative exposure to air activity. Dose coefficients of biokinetic models enable the calculation of organ dose through different pathways such as inhalation and ingestion following an exposure event...

Airborne radionuclides deliver a dose of radiation when inhaled or ingested proportional to exposure to air activity. Predicting the resuspended air concentration following a surface deposit is difficult given the number of complicating factors present which influence the resuspension mechanism, especially outdoors. The currently accepted model use...

For patients with an ostomy, a poor fitting appliance may cause leakage, peristomal dermatitis, and frequent appliance changes. Purpose: The purpose of this case study was to report the outcome of fat grafting to augment peristomal soft tissue and improve appliance fit. Case study: A 57-year-old woman with a history of Crohn's disease presented...

Modern CT systems seek to evaluate patient‐specific dose by converting the CT dose index generated during a procedure to a size‐specific dose estimate using conversion factors that are related to patient attenuation properties. The most accurate way to measure patient attenuation is to evaluate a full‐field‐of‐view reconstruction of the whole scan...

A recent analysis of historical radionuclide resuspension datasets confirmed the general applicability of the Anspaugh and modified Anspaugh models of resuspension factors following both controlled and disastrous releases. While observations appear to have larger variance earlier in time, previous studies equally weighted the data for statistical f...

Inhalation of airborne radionuclides, particularly alpha-emitters such as Am-241, delivers an internal dose of ionizing radiation proportional to the cumulative air activity. While biokinetic models enable the calculation of organ dose via ingestion pathways through dose coefficients, predicting the fraction of particulates resuspended from a surfa...

Inhalation of airborne radionuclides, particularly alpha-emitters such as Am-241, delivers an internal dose of ionizing radiation proportional to the cumulative air activity. While biokinetic models enable the calculation of organ dose via ingestion pathways through dose coefficients, predicting the fraction of particulates resuspended from a surfa...

A statistical pilot study was retrospectively performed to analyze potential changes in occupational radiation exposures to Interventional Radiology (IR) staff at Lawrence General Hospital after implementation of the i2 Active Radiation Dosimetry System (Unfors RaySafe Inc, 6045 Cochran Road Cleveland, OH 44139- 3302). In this study, the monthly OS...

A recent analysis of historical radionuclide resuspension datasets confirmed the general applicability of the Anspaugh and modified Anspaugh models of resuspension factors following both controlled and disastrous releases. The observations appear to increase in variance earlier in time, however all points were equally weighted in statistical fit ca...

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...

Background: Immediately after a radiological dispersion event or nuclear disaster, a method is needed to quickly assay the large amount of people for internal contamination. While no such method exists presently, we propose to adapt a Nuclear Medicine Gamma Camera and use internal dosimetric calculations to enable the high-throughput screening of u...

Background: Radiation exposures to Interventional Radiology (IR) staff continues to increase as the use of IR increases. To address this, Lawrence General Hospital (LGH) has incorporated the i2 active dosimetry system (RaySafe, Hopkington MA) into their IR department. This system monitors personnel exposures and displays them in real-time on the IR...

Immediately after a radiologist dispersion event or nuclear disaster, a method is needed to quickly assay a large number of people for internal contamination. While no such method exists presently, we propose to adapt a Nuclear Medicine Gamma Camera and use internal dosimetric calculations to enable the high-throughput screening of urine bioassay s...

Because of continual increases in the rate of Interventional Radiology (IR) procedures, Lawrence General Hospital (LGH), Lawrence, MA, has incorporated the RaySafe i2 real-time dose monitoring system (RaySafe, Hopkinton MA) into their radiation safety program. This system monitors and displays personnel exposures in real-time on the IR screen durin...

The Source Production & Equipment Co. (SPEC) model M-15 is a new Iridium-192 brachytherapy source model intended for use as a temporary high-dose-rate (HDR) brachytherapy source for the Nucletron microSelectron Classic afterloading system. The purpose of this study is to characterize this HDR source for clinical application by obtaining a complete...

The MCNP5 radiation transport code was used to quantify changes in the absorbed dose conversion factor for LiF, Al2O3, and silicon-based electronic dosimeters calibrated in-air using standard techniques and summarily used to measure absorbed dose to water when placed in a water phantom. A mono-energetic photon source was modeled at energies between...

A novel technique is presented for obtaining a single in-vivo image containing both functional and anatomical information in a small animal model such as a mouse. This technique, which incorporates appropriate image neutron-scatter rejection and uses a neutron opaque contrast agent, is based on neutron radiographic technology and was demonstrated t...

Purpose: A novel (169)Yb low dose rate permanent implant brachytherapy source, the GammaClip™, was developed by Source Production & Equipment Co. (New Orleans, LA) which is designed similar to a surgical staple while delivering therapeutic radiation. In this report, the brachytherapy source was characterized in terms of "Dose calculation for photo...

Monte Carlo simulation techniques using a Monte Carlo N-Particle code (MCNP5) analyzed six Source Production & Equipment Co., Inc., Se industrial radiography sources to determine an appropriate air kerma rate constant for Se, factoring in source encapsulation and compared to a theoretical approximation. Based on this study, an air kerma rate consta...

Purpose: In photon-brachytherapy (BT), all data for clinical dosimetry (e.g., the dose-rate constant) are not measured in water, but calculated, based on MC-simulation. To enable the measurement of absorbed dose to water, DW, in the vicinity of a source, the complex energy-dependence and other influence quantities must be considered. Methods: The d...

Eppendorf tubes often are used in biomedical research labs and contain radioactive tracers. Although the associated direct contact finger doses are typically small, it is suggested (and in line with the principle of ALARA) to handle these tubes from the cap of the tube. When containing radioactive material, handling a tube near the bottom conical s...

Ionizing radiation is used in diagnostic imaging, external-beam radiation therapy, brachytherapy, and nuclear medicine to diagnose and treat a number of common conditions. To ensure the safety of patients, providers, and surrounding staff members, it is important that the health care community become familiar with the terminology, common equipment,...

To study the effects of the breast-air and breast-lung interfaces on the absorbed dose within the planning target volume (PTV) of a MammoSite balloon dose delivery system as well as the effect of contrast material on the dose rate in the PTV. The Monte Carlo MCNP5 code was used to simulate dose rate in the PTV of a 2 cm radius MammoSite balloon dos...

Purpose: By calibrating brachytherapy (BT) sources to the TG‐43U1 reference position at 1cm in water, named the nominal absorbed dose‐rate to water, Ḋw,1, accuracy and precision for patient treatment will be increased. Traceability must be provided to Ḋw,1 ‐primary‐standards; which soon become available. Methods and Materials: Efforts have been mad...

Purpose: Proper evaluation of a stereotactic radiosurgery(SRS) plan is challenging due to lack of a comprehensive evaluation index and variation of dose prescription. In this study, a new treatment plan index is proposed to evaluate the quality of an SRS treatment plan by incorporating planning parameters that describe tumor coverage, dose to surro...

Absorbed dose energy correction factors, used to convert the absorbed dose deposited in a LiF thermoluminescent dosimeter (TLD) into the clinically relevant absorbed dose to water, were obtained for both spherical volumetric sources and for the model 4140 HDR Yb-169 source. These correction factors have a strong energy dependence below 200 keV; the...

The objective was to characterize a new Yb-169 high dose rate source for brachytherapy application. Monte Carlo simulations were performed using the MCNP5 F6 energy deposition tallies placed around the Yb-169 source at different radial distances in both air-vacuum and water environments. The calculations were based on a spherical water phantom with...

The American Journal of Neuroradiology has played a seminal role in the history of vertebral augmentation (VA). Because VA is increasingly being included in the multidisciplinary management of malignant vertebral compression fractures (VCFs), combined therapeutic approaches that include strategies to treat metastatic disease along with the fracture...

We recently reported a novel concept for combining radioactive isotope technology with polymethylmethacrylate (PMMA) cement used for vertebral augmentation and have advocated that pain physicians become aware of this new concept when treating malignant compression fractures. The use of vertebral augmentation for malignant compression fractures is s...

Radiochromic film dosimetry has been extensively used for intravascular brachytherapy applications for near field within 1 cm from the sources. With the recent introduction of new model of radiochromic films, GAFCHROMIC EBT, with higher sensitivity than earlier models, it is promising to extend the distances out to 5 cm for low dose rate (LDR) sour...

Vertebral compression fractures (VCFs), a major cause of morbidity and debilitating pain, often results from secondary tumor metastases to the skeleton. Vertebral augmentation is a palliative technique developed to treat VCFs and involves the injection of polymethyl methacrylate (PMMA) to augment the fractured vertebral body. The authors investigat...

The MCNP5 Monte Carlo code was used to simulate the dosimetry of an M-19 iridium-192 high dose rate brachytherapy source in both air/vacuum and water environments with the in-air photon spectrum filtered to remove low-energy photons below delta=10 keV. Dosimetric data was organized into an away-along table and was used to derive the updated AAPM Ta...

An ytterbium-169 high dose rate brachytherapy source, distinguished by an intensity-weighted average photon energy of 92.7 keV and a 32.015 +/- 0.009 day half-life, is characterized in terms of the updated AAPM Task Group Report No. 43 specifications using the MCNP5 Monte Carlo computer code. In accordance with these specifications, the investigati...

The SeedLink brachytherapy system is comprised from an assembly of I-Plant 3500 interstitial brachytherapy seeds and bioresorbable spacers joined together by a 6-mm-long titanium sleeve centered over each seed. This device is designed to maintain specified spacing between seeds during treatment thereby decreasing implant preparation time and reduci...

The SeedLink™ brachytherapy system is comprised from an assembly of I-Plant™ 3500 interstitial brachytherapy seeds and bioresorbable spacers joined together by a 6-mm-long titanium sleeve centered over each seed. This device is designed to maintain specified spacing between seeds during treatment thereby decreasing implant preparation time and redu...

We show that the thermal fluctuations of very soft mechanical oscillators, such as the cantilever in an atomic force microscope (AFM), can be reduced without changing the stiffness of the spring or having to lower the environment temperature. We derive a theoretical relationship between the thermal fluctuations of an oscillator and an actively cont...

The biokinetics of Iodophenylpentadecanoic acid (123I-IPPA) during a chronic period of myocardial infarction were determined and compared to 201Tl. IPPA was assessed as a perfusion and metabolic tracer in the scintigraphic diagnosis of coronary artery disease. The myocardial clearance kinetics were measured by placing a series of thermoluminescent...