The clinical translation of plastic scintillation dosimetry

Contemporary radiotherapy focuses on achieving the best patient outcomes by delivering highly targeted treatments that often include small fields and high dose gradients. Plastic scintillators outperform traditional dosimeters in these fields as they are close to water-equivalent. However, the translation of scintillation dosimeters into the clinic has been limited by three roadblocks. The generation of Cerenkov radiation in an optic fibre irradiated by megavoltage radiation contaminates the scintillation signal. Two Cerenkov removal methods (spectral discrimination and air core) were found to be accurate in accounting for Cerenkov radiation and their clinical robustness was improved. The light readout system is often the limiting factor for the accuracy of scintillators. PMTs outperform camera-based systems, though their implementation for array dosimetry is complex. A novel system with a multianode PMT was constructed and enabled multiple light signals from an array to be simultaneously measured. Arrays of scintillation dosimeters are difficult to create due to the complex arrangement of detectors and their optical pathways. Two innovative approaches (square waveguides and 3D printing) were used to build prototype scintillation dosimeter arrays. These arrays showed that scintillation dosimeters can measure dose distributions with high spatial and temporal resolution. Addressing these roadblocks has enabled the clinical translation of scintillation dosimeters. In small field dosimetry, an air core dosimeter was used as a reference to calculate and predict correction factors for existing dosimeters. For brachytherapy, an array of scintillators provided real-time dose measurements that improved the safety of the treatment. For rotational treatments, a cylindrical array was used to verify the dose delivered during simulated stereotactic treatments. Traditional dosimeters cannot be used in these applications and this demonstrates the potential of scintillation dosimetry

Respiratory consequences of abdominal hernia in a patient with severe chronic obstructive pulmonary disease

The diaphragm is the most important muscle in respiration. It is believed that the abdominal contents affect diaphragmatic contraction by helping determine its length tension state and by acting as a fulcrum for this muscle to lift the rib cage and thereby increase lung volume. In support of these concepts we describe a patient with severe chronic obstructive pulmonary disease and a large midline hernia of the abdomen who, when standing, had a gastric pressure (Pg) of 4 cm H2O and a maximal transdiaphragmatic pressure (Pdi(max)) of 14 cm H2O. This was associated with an O2 saturation of 82%, lower thoracic and upper abdominal paradoxical breathing, and severe dyspnea. Once the hernia was reduced there was a rise in Pg to 12 cm H2O, of Pdi(max) to 27 cm H2O, and of O2 saturation to 89%. There was normalization of the breathing pattern and a decrease in dyspnea. Reduction of this patient\u27s abdominal hernia resulted in an increase in her exercise tolerance

Muscle strength and exercise kinetics in COPD patients with a normal fat-free mass index are comparable to control subjects.

Item does not contain fulltextSTUDY OBJECTIVE: This study was designed to investigate the extent of clinical muscle dysfunction in stable patients with COPD who were attending an out-patient pulmonary clinic compared with that of age-matched control subjects without COPD. Design and subjects: Respiratory muscle and hand grip strength, steady-state O(2) kinetics, and body composition were measured in 32 patients with COPD (19 women) [mean (+/- SD) FEV(1), 38 +/- 11% predicted] and 36 age-matched control subjects (13 women). RESULTS: Measurements of handgrip force (mean, 97 +/- 32% vs 106 +/- 26% predicted, respectively), maximal expiratory pressure (mean, 57 +/- 33% vs 61 +/- 22% predicted, respectively), steady-state O(2) kinetics (mean tau, 72 +/- 34 s vs 78 +/- 37 s, respectively) and steady-state CO(2) kinetics (mean tau, 77 +/- 38 s vs 65 +/- 32 s, respectively) at submaximal exercise were similar in patients and control subjects. All the subjects, except for one female COPD patient, had a normal fat-free mass index (FFMI), although on average the FFMI was lower in male patients (19.8 +/- 2.8) than in male control subjects (23.0 +/- 2.8; p < 0.01). CONCLUSIONS: In patients with COPD who were attending a regular outpatient pulmonary clinic, there was no evidence of reduced upper extremity and expiratory muscle strength or prolonged O(2) and CO(2) kinetics during isowork submaximal cardiopulmonary exercise compared to healthy, age-matched control subjects. Also, a normal body composition was found in nearly all COPD patients. This argues against the existence of a clinically significant systemic myopathy in most stable patients with severe COPD and normal FFMI