Specific Features of the Use of Microfocal Roentgenography in Medical Diagnosis

Abstract

Microfocal roentgenography is a method of X ray imaging using sources with focal spot size of less than 0.1 mm called microfocal X ray radiation sources (MXRS).Domestic manufacturers offer MXRS models with anode voltage 50, 70, 100, 125, and 150 kV and X ray apparatuses based on these sources [5]. Although radia tion intensity of MXRS is low because of small beam size, the area of their use in medicine is steadily widening.Microfocal roentgenography is being used in trau matology, rheumatology, orthopedics, prosthetics, etc.[3]. The microfocal X ray apparatus Pardus 150 is used for ward X ray in children's hospitals [9]. The microfocal dental X ray apparatus Pardus 02 developed in 2003 is used in dentistry and maxillofacial surgery [10,11].Our experience in development and use of microfo cal X ray apparatuses has revealed a number of advan tages of this method over conventional radiography.For example, it was shown in [3] that soft tissue imaging contrast provided by microfocal radiography was two times higher than in the case of conventional radio graphy. The image contrast between cortical bone and soft tissues provided by microfocal radiography was virtu ally the same as in the case of conventional radiography.Studies performed at the Vreden Research Institute of Traumatology and Orthopedics (St. Petersburg) demonstrated that with otherwise identical imaging qual ity, X ray image background in case of microfocal radio graphy and in case of conventional radiography was light gray and black, respectively. Background color also affects imaging quality.Therefore, it is safe to conclude that radiation load on the patient during MXRS microfocal radiography is lower than in the case of conventional radiography. This conclusion was confirmed by the results of comparative assessment of radiation dose at object site in Pardus 150 and RUM 20 apparatuses. The following equation was used:where D is the dose; k is the scaling factor; U is the X ray tube anode voltage; I is the X ray tube anode current; and R is the distance between the focal spot and object. Exposure time and exposure dose per frame normal ized to anode voltage and focal distance in microfocal radiography of various objects (foot, hand, knee) were found to be four to five times lower in comparison with conventional radiography. Additional research was car ried out in collaboration with the Research Institute of Radiation Hygiene (St. Petersburg) to determine the radiation load on patients during microfocal X ray exam ination. Exposure doses were measured in patients of dif ferent age groups subjected to chest and pelvis X ray with Pardus 150 and RUM 20 apparatuses. The results of the tests revealed that the effective exposure dose in the microfocal apparatus Pardus 150 was significantly (4 13 times) lower [6].Quantum efficiency of radiation detection is a func tion of spatial frequency spectrum of the image. This pro vides a methodological approach to quantitative descrip tion of imaging efficiency. In this work we applied this approach to images of bone st...

Generalized Detective Quantum Efficiency of Digital X-Ray Apparatuses

“…(6), (7), and (8) detector quantum efficiency at low spatial frequency is η d (0) = 0.333; gen eral quantum efficiency of apparatus without or with raster at δ = 5, η 0 (0) = 0.056 or Т P = 0.59 and Т S = 0.07η 0 p (0) = 0.123, respectively. Therefore, the raster induces a 2.2 fold increase in the general quantum efficiency.…”