West Michigan Cancer Center

Michigan Center, MI, United States

West Michigan Cancer Center

Michigan Center, MI, United States
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Garcia A.A.,University of Southern California | Sill M.W.,Roswell Park Cancer Institute | Lankes H.A.,Roswell Park Cancer Institute | Godwin A.K.,University of Kansas Medical Center | And 6 more authors.
Gynecologic Oncology | Year: 2012

Objective: Activation and dimerization of the ERBB family play a role in the pathogenesis and progression of ovarian cancer. We conducted a phase II trial to evaluate the activity and tolerability of lapatinib in patients with recurrent or persistent epithelial ovarian cancer (EOC) and to explore the clinical value of expression levels of epidermal growth factor receptors (EGFR), phosphorylated EGFR, HER-2/neu, and Ki-67, and the presence of EGFR mutations. Methods: Eligible patients had recurrent or persistent EOC or primary peritoneal carcinoma, measurable disease, and up to 2 prior chemotherapy regimens for recurrent disease. Patients were treated with lapatinib 1500 mg/day. The primary endpoint of efficacy was 6-month progression free survival (PFS). Results: Twenty-five of 28 patients were eligible and evaluable for analysis of efficacy and toxicity. Two (8.0%) were alive and progression-free at 6 months. No objective responses were observed. There were 1 grade 4 toxicity (fatigue) and few grade 3 toxicities. Associations between Ki-67 with prior platinum-free interval, PFS, and a polymorphism in EGFR were suggested. Conclusions: Lapatinib has minimal activity in recurrent ovarian cancer. Ki-67 expression may be associated with prior PFS and a polymorphism in EGFR exon 20 (2361G>A, Q787Q). © 2011 Published by Elsevier Inc.


PubMed | West Michigan Cancer Center and Western Michigan University
Type: | Journal: Case reports in infectious diseases | Year: 2015

The Kytococcus genus formerly belonged to Micrococcus. The first report of a Kytococcus schroeteri infection was in 2002 in a patient diagnosed with endocarditis. We report a case of central line associated Kytococcus schroeteri bacteremia in a patient with underlying Hairy Cell Leukemia. Kytococcus schroeteri is an emerging infection in the neutropenic population and in patients with implanted artificial tissue. It is thought to be a commensal bacterium of the skin; however, attempts to culture the bacteria remain unsuccessful. There have been a total of 5 cases (including ours) of K. schroeteri bacteremia in patients with hematologic malignancies and neutropenia and only 18 documented cases in any population. Four of the cases of bacteria in neutropenic patients have been fatal, but early detection and treatment could make a difference in clinical outcomes.


Purpose: For external beam in vivo measurements, the dosimeter is normally placed on the patient's skin, and the dose to a point of interest inside the patient is derived from surface measurements. In order to obtain accurate and reliable measurements, which correlate with the dose values predicted by a treatment planning system, a dosimeter needs to be at a point of electronic equilibrium. This equilibrium is accomplished by adding material (buildup) above the detector. This paper examines the use of buildup caps in a clinical setting for two common detector types: OSLDs and diodes. Clinically built buildup-caps and commercially available hemispherical caps are investigated. The effects of buildup cap thickness and fabrication material on field-size correction factors, C FS, are reported, and differences between the effects of thickness and fabrication material are explained based on physical parameters. Methods: Measurements are made on solid water phantoms for 6 and 15 MV x-ray beams. Two types of dosimeters are used: OSLDs, InLightOSL Nanodot dosimeters (Landauer, Inc., Glenwood, IL) and a P-type surface diode (Standard Imaging, Madison, WI). Buildup caps for these detectors were fabricated out of M3, a water-equivalent material, and sheet-metal stock of Al, Cu, and Pb. Also, commercially available hemispherical buildup caps made of plastic water and brass (Landauer, Inc., Glenwood, IL) were used with Nanodots. OSLDs were read with an InLight microStar reader (Landauer, Inc., Glenwood, IL). Dose calculations were carried out with the XiO treatment planning system (CMSElekta, Stockholm) with tissue heterogeneity corrections. Results: For OSLDs and diodes, when measurements are made with no buildup cap a change in C FS of 200 occurs for a field-size change from 3 cm × 3 cm to 30 cm × 30 cm. The change in C FS is reduced to about 4 when a buildup cap with wall thickness equal to the depth of maximum dose is used. Buildup caps with larger wall thickness do not cause further reduction in C FS. The buildup cap fabrication material has little or no effect on C FS. The perturbation to the delivered dose caused by placing a detector with a buildup cap on the surface of a patient is measured to be 4%-7%. A comparison between calculated dose and dose measured with a Nanodot and a diode for 6 and 15 MV x-rays is made. When C FS factors are carefully determined and applied to measurements made on a phantom, the differences between measured and calculated doses were found to be between ±1.3%. Conclusions: OSLDs and diodes with appropriate buildup caps can be used to measure dose on the surface of a patient and predict the delivered dose to depth dmax in a range of ±1.3% for 100 cGy. The buildup cap: can be fabricated from any material examined in this work, is best with wall thickness dmax, and causes a perturbation to the delivered dose of 4%-7% when the wall thickness is dmax. OSLDs and diodes with buildup caps can both give accurate measurements of delivered dose. © 2011 American Association of Physicists in Medicine.


Jursinic P.,West Michigan Cancer Center
Journal of applied clinical medical physics / American College of Medical Physics | Year: 2014

The purpose of this study was to develop new and modified tools that allow HDR brachytherapy quality assurance tests to be carried out efficiently without film, video cameras, stopwatches, and mechanical rulers; and to devise methods that use these new tools for daily and quarterly check procedures, which are efficient and provide increased accuracy compared to previous methods. The HDR brachytherapy system tested was the GammaMedplus iX, Ir-192 HDR. Various catheters and treatment applicators designed for this system were tested. To measure the absolute position of the source, a simple tool was built that uses a Plexiglas frame, a template for applicator positioning, and a diode for radiation detection. For daily reproducibility and source strength tests, modifications were made of a Model 70008, HDR brachytherapy Ir-192 quality assurance tool, which is used with the HDR-1000-Plus well-type reentrant chamber. Measurement procedures and analysis protocols were developed that use the Microsoft Excel spreadsheet program. Independent determination of source positions was made with a computer video camera and radiochromic film. Using the new tool, for a straight catheter the measured source position is found to be within ± 0.1 mm of the mechanically set distance, for a ring applicator ± 0.3 mm, for a tandem ± 0.2 mm, and for an ovoid ± 0.2 mm. Using the modified insert, daily dwell position can be determined with an accuracy of 0.3 mm and timer accuracy can be determined with an accuracy of 0.3% over a 20 s time frame. The time needed to carry out quarterly tests is estimated to be reduced by two- to four-fold compared to previous methods. New and modified equipment and procedures have been developed for measuring HDR brachytherapy dwell position and dwell times efficiently with high accuracy. The equipment described in this work can be built and modifications can be made in most clinics. Location of dwell position can be determined in straight catheters and ring and ovoid applicators. Timer linearity and accuracy can be determined. Source strength can be confirmed. Measurement efficiency is improved compared to previous methods that used film, video cameras, mechanical rulers, and stopwatches.


Sharma R.,West Michigan Cancer Center | Jursinic P.A.,West Michigan Cancer Center
Medical Physics | Year: 2013

Purpose: To show the feasibility of clinical implementation of OSLDs for high dose-rate (HDR) in vivo dosimetry for gynecological and breast patients. To discuss how the OSLDs were characterized for an Ir-192 source, taking into account low gamma energy and high dose gradients. To describe differences caused by the dose calculation formalism of treatment planning systems. Methods: OSLD irradiations were made using the GammaMedplus iX Ir-192 HDR, Varian Medical Systems, Milpitas, CA. BrachyVision versions 8.9 and 10.0, Varian Medical Systems, Milpitas, CA, were used for calculations. Version 8.9 used the TG-43 algorithm and version 10.0 used the Acuros algorithm. The OSLDs (InLight Nanodots) were characterized for Ir-192. Various phantoms were created to assess calculated and measured doses and the angular dependence and self-absorption of the Nanodots. Following successful phantom measurements, patient measurements for gynecological patients and breast cancer patients were made and compared to calculated doses. Results: The OSLD sensitivity to Ir-192 compared to 6 MV is between 1.10 and 1.25, is unique to each detector, and changes with accumulated dose. The measured doses were compared to those predicted by the treatment planning system and found to be in agreement for the gynecological patients to within measurement uncertainty. The range of differences between the measured and Acuros calculated doses was -10%-14%. For the breast patients, there was a discrepancy of -4.4% to +6.5% between the measured and calculated doses at the skin surface when the Acuros algorithm was used. These differences were within experimental uncertainty due to (random) error in the location of the detector with respect to the treatment catheter. Conclusions: OSLDs can be successfully used for HDR in vivo dosimetry. However, for the measurements to be meaningful one must account for the angular dependence, volume-averaging, and the greater sensitivity to Ir-192 gamma rays than to 6 MV x-rays if 6 MV x-rays were used for OSLD calibration. The limitations of the treatment planning algorithm must be understood, especially for surface dose measurements. Use of in vivo dosimetry for HDR brachytherapy treatments is feasible and has the potential to detect and prevent gross errors. In vivo HDR brachytherapy should be included as part of the QA for a HDR brachytherapy program. © 2013 American Association of Physicists in Medicine.


Jursinic P.A.,West Michigan Cancer Center
Journal of Applied Clinical Medical Physics | Year: 2014

The purpose of this study was to develop new and modified tools that allow HDR brachytherapy quality assurance tests to be carried out efficiently without film, video cameras, stopwatches, and mechanical rulers; and to devise methods that use these new tools for daily and quarterly check procedures, which are efficient and provide increased accuracy compared to previous methods. The HDR brachytherapy system tested was the GammaMedplus iX, Ir-192 HDR. Various catheters and treatment applicators designed for this system were tested. To measure the absolute position of the source, a simple tool was built that uses a Plexiglas frame, a template for applicator positioning, and a diode for radiation detection. For daily reproducibility and source strength tests, modifications were made of a Model 70008, HDR brachytherapy Ir-192 quality assurance tool, which is used with the HDR-1000-Plus well-type reentrant chamber. Measurement procedures and analysis protocols were developed that use the Microsoft Excel spreadsheet program. Independent determination of source positions was made with a computer video camera and radiochromic film. Using the new tool, for a straight catheter the measured source position is found to be within ± 0.1 mm of the mechanically set distance, for a ring applicator ± 0.3 mm, for a tandem ± 0.2 mm, and for an ovoid ± 0.2 mm. Using the modified insert, daily dwell position can be determined with an accuracy of 0.3 mm and timer accuracy can be determined with an accuracy of 0.3% over a 20 s time frame. The time needed to carry out quarterly tests is estimated to be reduced by two- to four-fold compared to previous methods. New and modified equipment and procedures have been developed for measuring HDR brachytherapy dwell position and dwell times efficiently with high accuracy. The equipment described in this work can be built and modifications can be made in most clinics. Location of dwell position can be determined in straight catheters and ring and ovoid applicators. Timer linearity and accuracy can be determined. Source strength can be confirmed. Measurement efficiency is improved compared to previous methods that used film, video cameras, mechanical rulers, and stopwatches.


Jursinic P.A.,West Michigan Cancer Center
Medical Physics | Year: 2010

Purpose: A new type of in vivo dosimeter, an optically stimulated luminescent dosimeter (OSLD), has now become commercially available for clinical use. The OSLD is a plastic disk infused with aluminum oxide doped with carbon (Al2O3:C). Crystals of Al2O3:C, when exposed to ionizing radiation, store energy that is released as luminescence (420 nm) when the OSLD is illuminated with stimulation light (540 nm). The intensity of the luminescence depends on the dose absorbed by the OSLD and the intensity of the stimulation light. The effects of accumulated dose on OSLD response were investigated. Methods: The OSLDs used in this work were nanodot dosimeters, which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL). Dose to the OSLDs was delivered by 6 MV x rays and gamma rays from Co-60 and Ir-192. The signal on the OSLDs after irradiation is removed by optical annealing with a 150 W tungsten-halogen lamp or a 14 W compact fluorescent lamp was investigated. Results: It was found that OSLD response to dose was supralinear and this response was altered with the amount of accumulated dose to the OSLD. The OSLD response can be modeled by a quadratic and an exponential equation. For accumulated doses up to 60 Gy, the OSLD sensitivity (counts/dose) decreases and the extent of supralinear increases. Above 60 Gy of accumulated dose the sensitivity increases and the extent of supralinearity decreases or reaches a plateau, depending on how the OSLDs were optically annealed. With preirradiation of OSLDs with greater than 1 kGy, it is found that the sensitivity reaches a plateau 2.5 folds greater than that of an OSLD with no accumulated dose and the supralinearity disappears. A regeneration of the luminescence signal in the dark after full optical annealing occurs with a half time of about two days. The extent of this regeneration signal depends on the amount of accumulated dose. Conclusions: For in vivo dosimetric measurements, a precision of ±0.5% can be achieved if the sensitivity and extent of supralinearity is established for each OSLD and use. Methods are presented for accomplishing this task. © 2010 American Association of Physicists in Medicine.


Jursinic P.A.,West Michigan Cancer Center | Sharma R.,West Michigan Cancer Center | Reuter J.,West Michigan Cancer Center
Medical Physics | Year: 2010

Purpose: To measure patient-specific-QA dose distributions with a 2D array of diodes, the MapCHECK, for the dose delivered, with step-and-shoot and rotational IMRT. Methods: Two MapCHECKs were used that had different styles of diode connection. These MapCHECKs were used in their original manufactured configuration and in a modified configuration. The modification made in the clinic consists of filling air gaps with sheets of Lucite that had custom-machined slots for the diodes and by adding pieces of copper to offset the intrinsic asymmetry of the diodes. The MapCHECKs were housed in a tight-fitting phantom fabricated from solid water. Measurements were made on IMRT treatment plans delivered with Varian linear accelerators with step-and-shoot and RapidArc methods, and a TomoTherapy machine with helical delivery. Patient plans and QA plans were developed with the XiO, Eclipse, and TomoTherapy planning systems. All MapCHECK data were analyzed with its commercially available software. Results: Kilovoltage CT imaging of the MapCHECK in its phantom has streak artifacts from high atomic number components. These artifacts must be corrected in order to obtain accurate calculation of dose. The original MapCHECK is found to have an angular dependence of ±20%. A modification of the MapCHECK has been made that reduces the angular dependence to ±2%. Proper compensation for attenuation by the treatment couch is also necessary for accurate results. The modified MapCHECK has been successfully used for doing patient-specific QA for IMRT treatments delivered with step-and-shoot, TomoTherapy, and RapidArc methods. Treatment plans that require large amounts of fluence from the 90° and 270° directions have significantly better QA measurements when made with modified MapCHECKs. Conclusions: When properly modified, the MapCHECK response becomes isotropic. It can then be used for patient-specific QA measurements for IMRT treatments delivered with step-and-shoot and rotational techniques such as helical Tomotherapy and RapidArc. © 2010 American Association of Physicists in Medicine.


Purpose: A type of in vivo dosimeter, an optically stimulated luminescent dosimeter, OSLD, may have dose sensitivity that depends on the angle of incidence of radiation. This work measures how angular dependence of a nanoDot changes with the geometry of the phantom in which irradiation occurs and with the intrinsic structure of the nanoDot. Methods: The OSLDs used in this work were nanoDot dosimeters (Landauer, Inc., Glenwood, IL), which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL). Dose to the OSLDs was delivered by 6 MV x-rays. NanoDots with various intrinsic sensitivities were irradiated in numerous phantoms that had geometric shapes of cylinders, rectangles, and a cube. Results: No angular dependence was seen in cylindrical phantoms, cubic phantoms, or rectangular phantoms with a thickness to width ratio of 0.3 or 1.5. An angular dependence of 1% was observed in rectangular phantoms with a thickness to width of 0.4330.633. A group of nanoDots had sensitive layers with mass density of 2.422.58 g/cm3 and relative sensitivity of 0.921.09 and no difference in their angular dependence. Within experimental uncertainty, nanoDot measurements agree with a parallel-plate ion chamber at a depth of maximum dose. Conclusions: When irradiated in cylindrical, rectangular, and cubic phantoms, nanoDots show a maximum angular dependence of 1% or less at an incidence angle of 90°. For a sample of 78 new nanoDots, the range of their relative intrinsic sensitivity is 0.921.09. For a sample of ten nanoDots, on average, the mass in the sensitive layer is 73.1% Al2O3:C and 26.9% polyester. The mass density of the sensitive layer of a nanoDot disc is between 2.42 and 2.58 g/cm3. The angular dependence is not related to Al2O3:C loading of the nanoDot disc. The nanoDot at the depth of maximum dose has no more angular dependence than a parallel-plate ion chamber. © 2015 American Association of Physicists in Medicine.


Jursinic P.A.,West Michigan Cancer Center
Medical Physics | Year: 2013

Purpose: It has been reported that diode sensitivity decreases by as much as 2% when the average dose rate set at the accelerator console was decreased from 600 to 40 MU/min. No explanation was given for this effect in earlier publications. This work is a detailed investigation of this phenomenon: the change of diode sensitivity versus the rate of delivery of dose pulses in the milliseconds and seconds range. Methods: X-ray beams used in this work had nominal energies of 6 and 15 MV and were generated by linear accelerators. The average dose rate was varied from 25 to 600 MU/min, which corresponded to time between microsecond-long dose pulses of 60-2.7 ms, respectively. The dose-per-pulse, dpp, was changed by positioning the detector at different source-to-detector distance. A variety of diodes fabricated by a number of manufacturers were tested in this work. Also, diodes in three different MapCHECKs (Sun Nuclear, Melbourne, FL) were tested. Results: For all diodes tested, the diode sensitivity decreases as the average dose rate is decreased, which corresponds to an increase in the pulse period, the time between radiation pulses. A sensitivity decrease as large as 5% is observed for a 60-ms pulse period. The diode sensitivity versus the pulse period is modeled by an empirical exponential function. This function has a fitting parameter, teff, defined as the effective lifetime. The values of teff were found to be 1.0-14 s, among the various diodes. For all diodes tested, teff decreases as the dpp decreases and is greater for 15 MV than for 6 MV x rays. The decrease in diode sensitivity after 20 s without radiation can be reversed by as few as 60 radiation pulses. Conclusions: A decrease in diode sensitivity occurs with a decrease in the average dose rate, which corresponds to an increase in the pulse period of radiation. The sensitivity decrease is modeled by an empirical exponential function that decreases with an effective lifetime, teff, of 1.0-14 s. teff varies widely for different diodes, dpp, and x-ray energy. It is hypothesized that the capture of excess minority carriers by charge traps, cause the observed decrease in diode sensitivity. Also, it is hypothesized that the slow reopening of these traps occurs in the hundreds of milliseconds to seconds range at ambient temperature and this underlies the slow decrease in the diode sensitivity. Calibration of a diode is best done at the average dose rate with which it will be used. This is easily accomplished for radiation deliveries in which the average dose rate is a constant. However, for a VMAT delivery the average dose rate is a variable. For measurements made under these conditions diodes can be calibrated with a median or average dose rate which splits the difference in diode sensitivity that is known to occur with changes in average dose rate. © 2013 American Association of Physicists in Medicine.

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