In the past few years, mammography is recommended for early detection of breast cancer in Thailand. Since mammography is one of the most demanding radiologic technique, qualify radiologic technologist, low dose film, delicate machine and proper processing. Today we did not think only the best image but the examination must be done at the lowest radiation dose because the breast is one of the more radiosensitive site in the body.
In this lecture discussed the concrete method and the clinical application about two difference high voltages which divided from one high voltage generator were simultaneously use for frontal and lateral X-ray tubes. The author stress that lower price, smaller room size and easy to reconstruct an established equipment from single-plane system to biplane system were found more helpful in developing country or area.
Very low magnetic susceptibility of the air causes local distortion of magnetic gradient and results in spatial mismapping and signal change, chemical shift artifacts are produced in the frequency-encoding axis by lipid molecules because of difference of resonance frequencies of contained protons with those of protons in water. A test tube phantom study was performed in 2.0 T and 0.5 T superconducting magnetic resonance imaging systems for the investigation of natures of susceptibility and chemical shift artifacts encountered in high and medium field strength and in various imaging sequences. Both artifacts were prominent in high field MR and showed characteristic appearances. Several signal voids were noted around the air-colums in gradients echo images and MRI at 0.5 T showed more severe artifacts in T2-weighted image than those in the other sequences. Familiarity with causes, appearances and mechanisms of various artifacts helps Radiotechnologist for interpretation of MRI.
In our country, there is acute shortage of resources including trained man power. Thus the idea of a comprehensive imaging center at Bir Hospital, Kathmandu, Nepal was conceived. The resources were pooled at one place, which has proved quite convenient for the patients & staff besides being economical. Moreover, the atmospheric conditions for imaging equipments such as dust free environment, air conditioning, stabilized power supply with a standby diesel generator set could be made available at one place. This center is named as NMIC and consists of whole body CT, Gamma Camera and US machines along with few radiation monitoring equipments. The center started functioning from Oct. 1987 and since then about 12, 000 patients have been benefited. Though all the three modalities are being optimally utilized but the patients load is maximum on CT scanner. About 7000 patients have been scanned so far on CT out of which nearly 80% constitute Head Scanning. Comma finding in paediatric patients has been tuberculoma and Medulloblastoma. Astrocytoma & Glioma have been found in adults. Patients with spinal ailments and disorders in other body organs are getting full benefit of CT scanning. This in the only center in our country where we have CT & radioisotope scanning facility. Both static and dynamic nuclear scanning in available at the center. Ultrasonography has been particularly useful in abdominal scanning. A large number of patients with gall & kidney stones are diagnosed by this modality besides liver, pancreas, pelvis etc. Patients are being optionally benefitted at our imaging center, particularly because many patients diagnosis is better achieved by using one modality first and then subjecting to second or vice verse. At times all the three modalities of US, CT and Gamma Camera are required to arrive at a comprehensive diagnosis within shortest possible time.
(Introduction) Major problems of single photon emission computed tomography (SPECT) which degrade images both qualitatively and quantitatively include attenuation, camera uniformity geometric collimator response, and scattered photons. Compton scattered photons degrade spatial resolution and reduce the accuracy and precison of quantiation in SPECT images. The majority of correction methods introduced to reduce influence of compton scatter component consider the scatter distribution function to be a symmetrical, monoexponential function of distance from source position. Here a more realistic approach has been taken to derive scatter distribution functions for usiform and nonuniform scattering geometries. (Method) Monte Carlo simulations of Tc-99m point and line sources were used to obtain detailed information on the spatial and energy distribution of scattered and non-scattered events in SPECT images. EGS4 simulation code was adapted for use with planar and SPECT imaging geometries and detection devices. Simulations were carried out in two steps : 1) photons were followed in attenuation media until they were completely absorbed or emerged. Photon energy, input and output coordinates, direction and scatter order were recorded for photons that emerged within the detector field of view. 2) The detection process was simulated in a second step which gave greater flexibility in changing detection parameters (collimator geometry, intrinsic spatial resolution, energy resolution, energy window settings etc.). Scatter in the collimator and septal penetration were not included. Energy resolution of the system was simulated by sampling from an energydependent Gaussian function. The data shown were obtained from a simulation of SPECT system with a LEHR collimator, radius of rotation of 13cm, an energy resolution of 13%, intrinsic spatial resolution of 3.6mm, an energy window of 20% centered at 140KeV and a pixel size of 1mm. Seperate images were obtained for nonscattered events and events of scatter order n=1-3, a single image was obtained for n>4. (Results) The scatter distribution function in non-uniform density media indicates that scatter correction techniqes based on single exponential scatter distribution function do not provide a valid correction for non-uniform scattering geometries. Further investigations of SDF in more complex non-uniform geometries are needed to develop accurate correction method for Compton scatter reduction in SPECT images. My results suggest that 3-D scatter correction function and reconstruction methods need to be applied.
The Film Badge was the only device used for individual monitoring for all the staff of the Radiology Department of Melake General Hospital. The staff here include the Radiologist, Radiographers, darkroom technicians, attendants, assistant nurse. The type of X-ray examinations carried out include general radiography, ward radiography, intravenous urography, myelography and barium screening (briefly). A study was made on the available records of the results of the Film Badge monitoring and a survey was done recently for all the staff whether the Film Badge were being actually used and if so where was it located. It was found that there is no necessity for the staff to be issued the Film Badge and being monitored individually for the present type of X-ray examinations being carried out. More so as now the department were supplied with equiptments to check on the compliance of the working environment to the standards for Radiation Protection. A yearly check would surfice. A yearly medical surveillance as carried out now is also sufficient and last of all, the staff must continue to be cautious during their daily work.
An outline on how AIDS is contracted and passed on from one person to another. A brief summary on the present statistics of local and global situation of HIV contracted positive cases and expected statistics for the year 2000. To bring to the awareness of the Radiographers the possibility of contracting such disease in their field of work. The important steps that need to be taken to educate Radiographers on the control of the spread of the disease in the X-ray department due to handling of patients who are HIV positive. Precaution dan special nursing care when handling such patients in the radiodiagnostic imaging department.