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I Cornelius

Publications and source records attributed to I Cornelius.

8 recordsLinked to original sources

A method for the inter-calibration of a matrix of sensors.

We present a quick and easy method for the calibration of a matrix of sensors. The algorithm is based on a three-step irradiation procedure which relies only on the constancy of the delivered fluence at each step. With this method the gain of each sensor is derived relative to a reference detector. The algorithm has been applied to a matrix of (32 x 32) ionization chambers. After the calibration coefficients have been applied, by comparing the response of the matrix of chambers to a reference detector over a large field, we determined that the fluence measurement of individual chambers is better than 0.7%. The algorithm solves the cumbersome problem of the relative gain calibration of a matrix of a large number of sensors.

Algorithms↗

D-IMRT verification with a 2D pixel ionization chamber: dosimetric and clinical results in head and neck cancer.

Dynamic intensity-modulated radiotherapy (D-IMRT) using the sliding-window technique is currently applied for selected treatments of head and neck cancer at Institute for Cancer Research and Treatment of Candiolo (Turin, Italy). In the present work, a PiXel-segmented ionization Chamber (PXC) has been used for the verification of 19 fields used for four different head and neck cancers. The device consists of a 32x32 matrix of 1024 parallel-plate ionization chambers arranged in a square of 24x24 cm2 area. Each chamber has 0.4 cm diameter and 0.55 cm height; a distance of 0.75 cm separates the centre of adjacent chambers. The sensitive volume of each single ionization chamber is 0.07 cm3. Each of the 1024 independent ionization chambers is read out with a custom microelectronics chip.The output factors in water obtained with the PXC at a depth of 10 cm were compared to other detectors and the maximum difference was 1.9% for field sizes down to 3x3 cm2. Beam profiles for different field dimensions were measured with the PXC and two other types of ionization chambers; the maximum distance to agreement (DTA) in the 20-80% penumbra region of a 3x3 cm2 field was 0.09 cm. The leaf speed of the multileaf collimator was varied between 0.07 and 2 cm s-1 and the detector response was constant to better than 0.6%. The behaviour of the PXC was measured while varying the dose rate between 0.21 and 1.21 Gy min-1; the mean difference was 0.50% and the maximum difference was 0.96%. Using fields obtained with an enhanced dynamic wedge and a staircase-like (step) IMRT field, the PXC has been tested for simple 1D modulated beams; comparison with film gave a maximum DTA of 0.12 cm. The PXC was then used to check four different IMRT plans for head and neck cancer treatment: cervical chordoma, parotid, ethmoid and skull base. In the comparison of the PXC versus film and PXC versus treatment planning system, the number of pixels with gamma parameter<or=1 was 97.7% and 97.6%, respectively.

Chordoma↗

Simulations of silicon microdosimetry measurements in fast neutron therapy.

Experimental silicon microdosimetry measurements were performed at a Fast Neutron Therapy facility. Monte Carlo based calculations of these measurements were made using the GEANT4 toolkit. Reasonable agreement between theoretical and experimental results was obtained and the contribution of elastic and inelastic reaction products to the final microdosimetric spectrum was determined.

Computer Simulation↗

Solid state microdosimetry in hadron therapy.

A report of recent developments in silicon microdosimetry is presented. SOI based microdosemeters have shown promise as a viable alternative to traditional tissue-equivalent proportional counters. The application of these silicon microdosemeters to such radiation therapy modalities as boron neutron capture therapy (BNCT), boron neutron capture synovectomy (BNCS), proton therapy (PT), and fast neutron therapy (FNT) has been performed. Several shortcomings of the current silicon microdosemeter were identified and will be taken into account in the design of a second-generation device.

Boron Neutron Capture Therapy↗

A grounded theory study of the experience of type 2 diabetes mellitus in First Nations adults in Canada.

Diabetes among First Nations peoples has reached epidemic proportions, and diabetes prevalence, complications, and mortality rates are higher than in Whites. The purpose of this grounded theory study was to investigate the experience of Type 2 diabetes in First Nations adults. Ten individuals living in one reserve community, in southwestern Ontario, participated in this research. Participants were interviewed on two occasions by a First Nations nurse. All interviews were audiotaped and transcribed verbatim. A three-phase process of integration emerged, similar to the process of integration discovered in prior research with Type 1 diabetic Whites. However, there were some important differences in the characteristics of these three phases. In addition, there were surprising findings related to beliefs about the type of diabetes educator desired by these First Nations clients.

Adaptation, Psychological↗

Safety of gadolinium-DTPA: extended clinical experience.

This review reports data on the general and renal tolerance of the paramagnetic contrast agent Gd-DTPA after intravenous administration. Gd-DTPA was administered usually at a dose level of 0.1-0.2 mmol/kg body wt (range: 0.005-0.25 mmol/kg body wt) in cranial, spinal and body MR indications. In phase I-IIIa studies a total of 2154 healthy volunteers and patients were investigated, usually at a dose of 0.1 mmol/kg body wt. From the obtained results it was concluded that adverse events (AEs) may be expected in the order of magnitude of 1%. In phase IIIb-IV studies 13,439 patients were investigated at 0.1 or 0.2 mmol/kg body wt. Tolerance data were collected according to a standardized protocol and metaanalysis of obtained data was performed. AEs, irrespective of their drug relationship, were observed in 1.15% of the patients. The observed AEs were comparable to those after intravenous administration of iodinated nonionic X-ray contrast media. There was no correlation between patient age and the incidence of AEs. In patients with a known history of allergy the incidence of AEs increased to 2.6%. In pediatric use no added risk was observed in a total of 826 neonates, children, and adolescents up to 18 years of age. Gd-DTPA showed good renal tolerance in patients with and without preexisting impairment of renal function. A prospective open safety and pharmacokinetic study was conducted in patients with hemodialysis. Gd-DTPA was shown to be eliminated completely by hemodialysis. Fast bolus injections were tolerated without added risk. Presented data from postmarketing surveillance (up to March 31, 1991) cover an estimated total of more than 2,000,000 applications.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Tolerance data of Gd-DTPA: a review.

Gd-DTPA is the first paramagnetic contrast agent approved for clinical use in cranial and spinal MRI in the F.R.G., U.S.A., Japan and several other countries. After submission 13,439 patients were enrolled in standardized protocolled clinical trials. The observed adverse drug reactions (ADRs) after i.v. injection of Gd-DTPA were comparable to those after administration of iodinated non-ionic roentgen contrast media (CM). However, the overall incidence of ADRs after intravenous injection of 0.1 or 0.2 mmol/kg body weight Gd-DTPA was found to be even lower. Adverse events were observed in only 1.46% of the patients - or 1.14% if localized warmth is excluded. None of them was critical. There was no correlation between patient age and the incidence of ADRs. In patients with a known history of allergy the incidence of ADRs was increased by a factor 3-4, which is still lower than the incidence reported after intravenous administration of iodinated non-ionic roentgen CM to patients without known allergy. Good renal tolerance was seen in all patients, irrespective of pre-existing renal impairment. Fast bolus injections of Gd-DTPA were tolerated without added risk. The favorable safety profile is also reflected in the post marketing surveillance reports since Gd-DTPA became available as a commercial drug.

Contrast Media↗