Development of a randomised contrast detail digital phantom for observer detectability study

The accuracy and the efficacy of radiological diagnosis depend, to a large extent, on the conditions under which radiographs and images are viewed. This mainly involves the luminance of the display devices and the ambient room illumination. We report a perceptual study to investigate the relationship between detectability and monitor luminance as well as ambient illuminance. A statistical test pattern was used in this study, and the test pattern was developed using Microsoft® Visual Basic 6. The test pattern contained a set of randomised contrast detail objects, that is, disks of different diameters (0.7, 1.0, 1.4, and 2.0 mm) and contrasts against a black background (2.7, 3.9, 5.5, and 7.8%), simulating lesions in digital images. The receiver operating characteristic (ROC) analysis was used in this study. The results indicated that a set of optimal viewing conditions exists and that it has a significant effect on detectability performance

Environment Influence On Pspl-based Digital Dental Radiology Systems

Photo-stimulable phosphor luminescence technology (PSPL) has been used in Digora (Soredex, Finland) and Denoptix (CEDH Gendex, Italy) digital dental radiology imaging systems. PSPL plates store X-ray energy during exposition, being later processed by a laser reader and digitizer. Afterward they are erased and re-used. The large band of energy absorption provides PSPL systems with an extensive dynamic scale but at the same time a high sensibility to the incoming noise of environmental radiations. We have measured environment influences (electromagnetic radiation) for Digora and Denoptix plates after X-ray exposure and before digital processing. We have first compared the processing of PSPL plates "in dark" against "in light" environments. In another experiment, the exposed plates were also processed after being positioned 10 cm away from a 17 inches video monitor screen and to its laterals for 5, 10, 15, 20, 25 and 30 minutes (plates protected against light). The acquired images were used to calculate the noise power spectra (NPS) in each case. We have noticed that there was an increase in the noise spectra energy of "in light" processing compared to "in dark" processing. There was also an increment in the NPS energy when the images were processed after the exposition of the plates to the radiation emanated from video monitor.4320219226Huda, W., Comparison of a photostimulable phosphor system with film for dental radiology (1997) Oral Surgery Oral Medicine Oral Pathology, 84, pp. 725-731Brettle, D.S., The imaging performance of a storage phosphor system for dental radiography (1996) The British Journal of Radiology, 69, pp. 256-261Xinhua, A novel algorithm for measuring the MTF of a digital radiographic system with a CCD array detector (2000) SPIE, 3977, pp. 580-587Knüpfer, W., Novel X-ray detectors for medical imaging (1999) Nuclear Physics, 78, pp. 610-615Hildebold, C.F., Dental photostimulable phosphor radiology (2000) Dental Clinics of North America, 44 (2), pp. 273-297Stamatakis, Dose response of a storage phosphor system for intraoral radiography (1999) Dentomaxillofacial Radiology, 28, pp. 272-276Yoshiura, K., Physical evaluation of a system for direct digital intra-oral radiography based on a charged-coupled device (1999) Dentomaxillofacial Radiology, 28, pp. 277-283Workman, A., Brettle, D.S., Physical performance measures of radiographic imaging systems (1997) Dentomaxillofacial Radiology, 26, pp. 139-146Granfors, P.R., Performance characteristics of an amorphous silicon flat panel X-ray imaging detector (1999) SPIE, 3659, pp. 480-490Yoshiura, K., Physical evaluation of a system for direct digital intra-oral radiography based on a charged-coupled device (1999) Dentomaxillofacial Radiology, 28, pp. 277-283Kengyelics, S.M., Image quality evaluation of a direct digital radiology detector operating in a UK radiology department (1999) SPIE, 3659, pp. 24-35Granfords, P.R., Aufrichtig, P.R.R., DQE(f) of an amorphous silicon flat panel X-ray detector: Detector parameter influences and measurement methodology (2000) SPIE, 3977, pp. 2-13Dobbins III, J.T., DQE(f) of four generations of computed radiography devices (1995) Medical Physics, 22, pp. 1581-1593Cowen, A.R., Workman, A., A physical image quality evaluation of a digital spot flurography system (1992) Phys. Med. Biol., 37, pp. 325-342Daint, J.C., Shaw, R., (1976) Image Science - Principles, Analyses and Evaluation of Photographic-Type Imaging Process, , Academic Press, London, UKBethea, R.M., Duran, B.S., Benllion, T.L., (1995) Statistical Methods for Engineers and Scientists, , Mc Hill Reckker, New York, NYZanella, G., Zannoni, R., DQE of imaging detectors in terms of spatial frequency (1999) Nuclear Instruments and Methods Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 437, pp. 163-167Zanella, G., Zannoni, R., The role of the quantum efficiency on the DQE of an imaging detector (1996) Nuclear Instruments and Methods in Physics Research A, 381, pp. 157-160Costa, S., DQE measurement in a scintillating glass optical fiber detector for X-ray imaging (1996) Nuclear Instruments and Methods in Physics Research A, 380, pp. 568-571Meyer, R.R., Experimental characterization of CCD cameras for HREM at 300kV (2000) Ultramicroscopy, 85, pp. 9-13Onttonello, P., MTF and DQE measurement in imaging detectors by their single-event response (1998) Nuclear Instruments and Methods in Physics Research Section A, 419, pp. 731-735Kandarakis, I., An experimental method for the determination of spatial-frequency-dependent detective quantum efficiency (DQE) of scintillators used in X-ray imaging detectors (1997) Nuclear Instruments and Methods in Physics Research Section A, 399, pp. 335-34

Curriculum guide to teach computed radiography at El Camino College

The purpose of the project was to design a curriculum guideline for educators to teach computed radiography. This project can be used as a stand-alone course, or integrated into existing radiologic technology courses

Intensity modulated radiation therapy and arc therapy: validation and evolution as applied to tumours of the head and neck, abdominal and pelvic regions

Intensiteitsgemoduleerde radiotherapie (IMRT) laat een betere controle over de dosisdistributie (DD) toe dan meer conventionele bestralingstechnieken. Zo is het met IMRT mogelijk om concave DDs te bereiken en om de risico-organen conformeel uit te sparen. IMRT werd in het UZG klinisch toegepast voor een hele waaier van tumorlocalisaties. De toepassing van IMRT voor de bestraling van hoofd- en halstumoren (HHT) vormt het onderwerp van het eerste deel van deze thesis. De planningsstrategie voor herbestralingen en bestraling van HHT, uitgaande van de keel en de mondholte wordt beschreven, evenals de eerste klinische resultaten hiervan. IMRT voor tumoren van de neus(bij)holten leidt tot minstens even goede lokale controle (LC) en overleving als conventionele bestralingstechnieken, en dit zonder stralingsgeïnduceerde blindheid. IMRT leidt dus tot een gunstiger toxiciteitprofiel maar heeft nog geen bewijs kunnen leveren van een gunstig effect op LC of overleving. De meeste hervallen van HHT worden gezien in het gebied dat tot een hoge dosis bestraald werd, wat erop wijst dat deze “hoge dosis” niet volstaat om alle clonogene tumorcellen uit te schakelen. We startten een studie op, om de mogelijkheid van dosisescalatie op geleide van biologische beeldvorming uit te testen. Naast de toepassing en klinische validatie van IMRT bestond het werk in het kader van deze thesis ook uit de ontwikkeling en het klinisch opstarten van intensiteitgemoduleerde arc therapie (IMAT). IMAT is een rotationele vorm van IMRT (d.w.z. de gantry draait rond tijdens de bestraling), waarbij de modulatie van de intensiteit bereikt wordt door overlappende arcs. IMAT heeft enkele duidelijke voordelen ten opzichte van IMRT in bepaalde situaties. Als het doelvolume concaaf rond een risico-orgaan ligt met een grote diameter, biedt IMAT eigenlijk een oneindig aantal bundelrichtingen aan. Een planningsstrategie voor IMAT werd ontwikkeld, en type-oplossingen voor totaal abdominale bestraling en rectumbestraling werden onderzocht en klinisch toegepast

Focal Spot, Summer 1994

https://digitalcommons.wustl.edu/focal_spot_archives/1067/thumbnail.jp

Spinal Stereotactic Body Radiotherapy (SBRT) Planning Techniques

Stereotactic body radiotherapy (SBRT) delivers a highly conformal and hypofractionated radiation dose to a small target with minimal radiation applied to the surrounding areas. The spine is an ideal site for SBRT owing to its relative immobility, the potential clinical benefits of high-dose delivery to this area, and the presence of adjacent critical structures such as the spinal cord, esophagus, and bowel. However, with the potential for radiation myelopathy if the dose is delivered inaccurately or if the spinal cord dose limit is set too high, proper treatment planning techniques for SBRT are important. Intensity modulation techniques are useful for spinal SBRT because of a rapid dose falloff and spinal cord avoidance. In this chapter, various planning techniques will be discussed and reviewed

The influence of ambient lighting on the detection of small contrast elements in digital dental radiographs

Objectives: The aim of this study was to evaluate the effect of ambient light on the detection of contrast elements in digital dental radiographs. Materials and methods: A high-contrast standardized digital radiograph of an aluminum step wedge containing 32 boreholes of different depth was cut into 40 isometric images. Images were presented at random on a 17-in cathode ray tube (CRT) monitor at different ambient background illuminations of 0, 50, 200, and 500lx. Twenty observers stated twice their blinded decision whether or not they could perceive a dark spot on a five-point confidence scale. Areas (Az) under receiver operating characteristic curves were calculated and compared between the four different ambient illuminations using the Friedman test. Statistical significance was set at p < 0.05. Overall agreement was estimated determining the intraclass correlation coefficient. Results: The Az values (0.735 for 0lx, 0.728 for 50lx, 0.735 for 200lx, and 0.788 for 500lx) did not significantly differ (p = 0.796) between the four ambient lighting levels. Conclusions: The detection of small contrast features in digital dental radiographs on a CRT monitor seems to be comparable over a wide range of ambient background illumination. Clinical relevance: The ambient light in dental offices of <500lx may not negatively impact the diagnostic performance of digital dental radiograph