Background: For elderly people living in nursing homes, a transport to hospital for a radiological examination can lead to increased anxiety, disorientation and other problems related to the new environment. Objective: To investigate the usefulness of a mobile radiography service for radiological assessment of patients in nursing homes from the patient and staff perspectives. Methods: Lightweight equipment with a digital flat-panel detector was used for mobile radiography on nursing home patients in their own rooms. Data on patient and staff experiences from the service were collected using a questionnaire with closed and open-ended questions. Image quality was evaluated by the radiographer and a radiologist. Results: The majority of 241 radiography examinations were of the musculoskeletal system (94%). Twelve of 123 patients had pathology that required hospital treatment, while 22 patients with radiographic pathology could be treated locally. The main beneficial factors were security and comfort, acceptance from the patients, no need for transportation, no need for staff to be absent from the nursing homes. Conclusion: Mobile radiography in nursing homes is technically feasible, with good image quality. The most beneficial results were that patients avoided unnecessary transport back and forth to the hospital, and that the majority of patients could be treated locally.
Mobile radiography can be used to examine patients in nursing homes at a lower cost than hospital-based radiography. Patients benefit from not having to transfer to a hospital for radiography, resulting in reduced anxiety for patients.
Spectra calculated for photon fields in water can be directly used for modeling the response of unshielded silicon diodes with plastic encapsulations. Unshielded diodes used together with appropriate corrections can replace shielded diodes in photon dose measurements.
Modern radiotherapy steadily utilizes more of the available degrees of freedom provided by radiotherapy equipment, raising the need for the dosimetric methods to deliver reliable measurements for situations where the spectral properties of the radiation field may also vary. A kernel-based superposition method is presented for which the spectra from any field modulation can be instantly calculated, thus facilitating the determination of dosimetric quantities at arbitrary locations. A database of fluence pencil kernels describing the fluence resulting from point monodirectional monoenergetic beams incident onto a water phantom has been calculated with the PENELOPE-2005 Monte Carlo package. Spectra calculated by means of the kernels are presented for various 6 MV fields. The spectra have been used to investigate depth and lateral variations of water-to-air stopping-power ratios. Results show that the stopping-power ratio decreases with depth, and that this effect is more pronounced for small fields. These variations are clearly connected to spectral variations. For a 10 x 10 cm(2) field, the difference between the stopping-power ratio at 2.5 cm depth and 30 cm depth is less than 0.3% while for a 0.3 x 0.3 cm(2) field this difference is 0.7%. Ratios outside the field were found to be sensitive to the collimator leakage spectral variations.
The dosimetry of small fields is important for the use of high resolution photon radiotherapy. Silicon diodes yield a high signal from a small detecting volume which makes them suitable for use in small fields and high dose gradients. Unshielded diodes used in large fields are known to give a varying dose response depending on the proportion of low energy scattered photons in the field. Response variations in small fields can be caused by both spectral variations, and disturbances of the local level of lateral electron equilibrium. We present a model that includes the effects from lack of charged particle equilibrium. The local spectra are calculated by use of fluence pencil kernels and divided into a low and a high energy component. The low energy part is treated with large cavity theory and the high energy part with the Spencer-Attix small cavity theory. Monte Carlo-derived correction factors are used to account for both the local level of electron equilibrium in the field, and deviations from this level in the silicon disk cavity. Results for field sizes ranging from 0.5 × 0.5 to 20 × 20 cm² are compared to data from full Monte Carlo simulations and measurements. The achieved dose response accuracy is for the smallest fields 1-2%, and for larger fields 0.5%. Spectral variations were of little importance for the small field response, implying that volume averaging, and to some extent interface transient effects, are of importance for use of unshielded diodes in non-equilibrium conditions. The results indicate that diodes should preferably be designed to have the thin layer of active volume padded in between inactive layers of the silicon base material.
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