Muon capture in ²⁸Si

A measurement has been made of the angular correlation of the neutrino with a specific nuclear de-excitation γ-ray following exclusive muon capture on ²⁸Si , in order to determine the size of the induced-pseudoscalar coupling constant gp of the weak hadronic current. The correlation is observed via the Doppler-broadened line shape of the 1229 keV ²⁸ Al γ-ray, which is measured using a pair of Comptonsuppressed intrinsic Ge detectors. Significant background suppression is achieved through the use of a coincidence technique in which the 1229 keV γ-ray of interest is 'tagged' by the subsequent 942 keV γ-ray in the cascade, which is detected in an array of 24 NaI(Tl) scintillators. Through a detailed attention to the detectors' response functions as well as the use of background-subtracted spectra, the γ — v correlation coefficient a is found to be 0.360±0.059 i n good agreement with a recent measurement at Dubna. The result obtained yields the value of gp/gA = 0.0±3.2 when compared to the latest calculation of the γ — v angular correlation, suggesting a massive quenching of the induced-pseudoscalar coupling constant in 2 8 S i in comparison with the value expected for a free nucleon. However other available calculations give the values gp/gA — 5.3±2.0 and gp/gA = 4.2±2.5, but the model-dependence of these intriguing results has yet to be assessed fully. A measurement of the correlation coefficient a of the 2171 keV ( 1⁺ → 2⁺) γ-ray has solved the enigma of the unphysical result that was found by a previous experiment. In addition, the lifetime of the 2201 keV ²⁸ Al level has been measuredScience, Faculty ofPhysics and Astronomy, Department ofGraduat

A study of X and gamma rays following muon capture in 28Si

Negative muons produced via the backward decay of pions in the M9b beam channel at TRIUMF were stopped in a ²⁸Si target. The energies of the muonic X-rays and nuclear γ-rays following the muon capture were measured in order to identify a Doppler broadened γ ray line in ²⁸A1 which is suitable for analysis in terms of a γ — ν angular correlation to determine a value for the induced-pseudoscalar coupling constant (gp ). The muon beam was also stopped in 6 other background targets ( polythene, A1, stainless steel, Cu, Pb and BGO ) and their X- and γ-ray energies have been studied so as to fully understand the backgrounds associated with such a transition.Science, Faculty ofPhysics and Astronomy, Department ofGraduat

Advantages of inflatable multichannel endorectal

applicator in the neo-adjuvant treatment of patients with locally advanced rectal cancer with HDR brachytherap

Characterisations of a fibre optic dosimetry system for source tracking during HDR Brachytherapy

Brachytherapy is a complex treatment procedure where radioactive sources are inserted in or close to the tumours to destroy the cancerous cells. Due to the unique properties of scintillation plastic detectors, this study was aimed to characterise an innovative fibre optic dosimetry system as a quality assurance tool during HDR Brachytherapy. Scintillating plastic fibres with different scintillation lengths were prepared and then optically coupled to non-scintillating fibres for light transmission. A transimpedance photodiode amplifier was used to detect positional sensitivities of different fibre probes placed within a solid-water phantom at varying distances above an 192-Ir brachytherapy source located within the catheter. Monte Carlo simulation has validated the expected response of the scintillating plastic fibres for multiple dwell positions with demonstrating the variance of detector response with source location. It showed the ability of shorter scintillating fibre lengths to distinguish between varying source locations when the SNR maintained high. However, fully scintillating plastic fibre showed flat response for most dwell positions. The proposed system proved to be appropriate for further clinical investigations, such as simultaneous dose measurement, and providing 3D position reconstruction through in-vivo source tracking

Image-Guided Brachytherapy for Rectal Cancer: Reviewing the Past Two Decades of Clinical Investigation

(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 focusing on mitigating treatment-related toxicities. In other words, if a small proportion of 4–6% of rectal cancer patients benefit from additional local therapy beyond TME, the burden of acute and long-term side effects must be considered with care. (2) Methods: With the introduction of better-quality imaging for tumor visualization and treatment planning, a new conformed radiation treatment was introduced with high-dose-rate endorectal brachytherapy. The treatment concept was tested in phase I and II studies: first in the pre-operative setting, and then as a boost after external beam radiation therapy, as a dose-escalation study, to achieve higher local tumor control. (3) Results: HDREBT is safe and effective in achieving a high tumor regression rate and was well tolerated in a phase II multicenter and two matched-pair studies. (4) Conclusions: HDREBT is a conformed radiation therapy that is safe and effective, and is presently explored in a phase III dose-escalation study in the NOM of patients with operable rectal cancer

Quality assurance of Cyberknife robotic stereotactic radiosurgery using an angularly independent silicon detector

Purpose: The aim of this work was to evaluate the use of an angularly independent silicon detector (edgeless diodes) developed for dosimetry in megavoltage radiotherapy for Cyberknife in a phantom and for patient quality assurance (QA). Method: The characterization of the edgeless diodes has been performed on Cyberknife with fixed and IRIS collimators. The edgeless diode probes were tested in terms of basic QA parameters such as measurements of tissue-phantom ratio (TPR), output factor and off-axis ratio. The measurements were performed in both water and water-equivalent phantoms. In addition, three patient-specific plans have been delivered to a lung phantom with and without motion and dose measurements have been performed to verify the ability of the diodes to work as patient-specific QA devices. The data obtained by the edgeless diodes have been compared to PTW 60016, SN edge, PinPoint ionization chamber, Gafchromic EBT3 film, and treatment planning system (TPS). Results: The TPR measurement performed by the edgeless diodes show agreement within 2.2% with data obtained with PTW 60016 diode for all the field sizes. Output factor agrees within 2.6% with that measured by SN EDGE diodes corrected for their field size dependence. The beam profiles\u27 measurements of edgeless diodes match SN EDGE diodes with a measured full width half maximum (FWHM) within 2.3% and penumbra widths within 0.148 mm. Patient-specific QA measurements demonstrate an agreement within 4.72% in comparison with TPS. Conclusion: The edgeless diodes have been proved to be an excellent candidate for machine and patient QA for Cyberknife reproducing commercial dosimetry device measurements without need of angular dependence corrections. However, further investigation is required to evaluate the effect of their dose rate dependence on complex brain cancer dose verification

Abdomen and pelvis computed tomography procedure: Effective dose assessment and establishment of a local diagnostic reference level

Exposure to ionizing radiation may induce cancer risk to the patients proportional to the radiation absorbed dose and the organ sensitivity. Therefore protection of radiation exposure is essential to minimize the radiation cancer risk and prevent the deterministic effects. The International Atomic Energy Agency (IAEA) encourages member countries to establish national diagnostic reference levels (DRLs) to reduce unjustified radiation exposure. This study establishes a local DRL for computed tomography (CT) abdomen and pelvis procedures. In total, 1444 CT abdomen procedures were carried out during nine months. CT abdomen procedures were carried out at King Faisal Specialist Hospital and research center using six CT machines from different vendors. The mean and range of patients’ weight (kg) are 50 (42–120). The recommended DRLs values in DLP (mGy.cm) and CTDIvol (mGy)were 900 and 15 per CT abdomen and pelvis procedure, respectively. 3% (41 cases) were higher than the national DRL for CT abdomen and pelvis. The proposed DRL values are slightly higher than the European and the American College of Radiologists (ACR) DRL values in DLP. The purpose of DRL in terms of CTDIvol (mGy) is comparable with the international guidelines. Thus reducing the scan length, is recommended ensuring that patients receive a minimal possible radiation dose while maintaining the image quality

International multi-institutional bench mark study on dosimetric and volumetric modulation using helical tomotherapy treatment planning for malignant pleural mesothelioma tumors

Determining the most desirable and achievable target dose and organ at risk (OAR) sparing using helical TomoTherapy planning system for mesothelioma treatment plans. A range of planning parameters was used. The reviewers’ ranking assessment (Ranking in Groups: 1 = Good, 2 = Above Average, 3 = Average, 4 = Poor).The overall rankings revealed that a plan with a balanced tradeoff among all planning objectives was preferred by most participants and reviewers. Other studies found low doses to the contralateral lung to be limiting. This was not the case in our study, with TomoTherapy we found the dose to contra lateral lung to be as low as V5Gy=0.87%. A pitch value of 0.287 or 0.43 would provide better result. A delivered modulation factor of above 1.7 and a treatment time around 500 sec will be beneficial consideration in planning