Radiography in india

 Ultrasound transducer A typical source of ultrasound is a transducer, which works on the principle of piezoelectric effect. Transducer is a device which convert energy from one form to another.. In transducer the piezoelectric crystal like quartz converts electrical energy into US energy and vise versa. Piezoelectric material or crystal Piezoelectric means pressure electricity. Piezoelectric materials have molecular dipoles containing + & - electric charges, and the net charges is zero. If electrical voltage is applied across the crystal, the dipole orientation changes, resulting in variation of crystal thickness. The crystal undergoes compression and expression, and ultrasound waves are produce. Natural piezoelectric material is quartz crystal and synthetic ceremic material is most commonly used as crystal e.g. lead zirconate titanate (PZT) or polyvinylidene difluoride. Transducer design US transducer consist five main components  1.Piezoelectric crystal 2. Matching la...

 It is also called ultra Sonography (USG). Sound is a form of energy resulting in form transmission of mechanical vibrations through a  medium. Ultrasound is a sound having frequencies greater than20,000 Hz, which can't be detected by human ear. Ultrasound used to formation of images from static and moving organs. Basic of ultrasound  Propagation of ultrasound US is produced by piezoelectric effect and it travels in straight line in a medium, in the form of wave with compression and rarefaction. Diagnostic ultrasound uses 1-20 MHz frequency. Sound waves travel faster in solids and slower in gases. The average velocity in soft tissue is 1540 m/sec. The intensity of ultrasound is a measure of beam energy and is proportional to the square of the amplitude. It expressed in watts per mm². Relative intensity is measured in a lograthmic scale in bels .                     1B = 10 decibels (dB ) Interaction of ultrasound with medi...

 Image quality :-  Ct image quality is mainly controlled by four factors, namely - →Spatial resolution  spatial resolution is the ability to discriminate between adjacent objects, that is expressed in lp/cm  It depends on pixel size, detector size, choice of image reconstruction filter and sampling frequency. The range of spatial resolution in CT is 5 to 15 lp/cm. →Noise  Noise is the fundamental limit to the quality of CT image. It reduces contrast resolution of small objects. There are three sources of noise-  1 quantum noise  2 electronic noise 3 structural noise  The typical noise level in CT scan is 3 HU. →contrast   Ct contrast is the difference in the HU values between the adjacent tissues. It increase as tube voltage decreases, not affected by tube current or scan times. →artifacts Artifacts -  Artifacts are the one which not only degrade image quality, but also leads to wrong or miss diagnosis. The typical artifacts in CT i...

 Generations of CT scan :-  Ct scan have gone many design changes since 1970. A variety of CT geometries have been developed to acquire the x ray transmission data for image reconstruction.  There are seven generations of ct scan... (1) first generation -  translate rotate system There are pencil x ray beam used in first generation. It is designed for brain imaging. There are a total of 180×160= 28,800 rays are measured . This combination of linear translation followed by incremental rotation is called translate - rotate motion. Disadvantage:-  →Water bath acted as a bolus →Afterglow of Nal (2) second generation- narrow fan beam →Narrow fan beam & multiple detectors (linear array of 30 detectors). →With 10° rotation increment only 18 translation would be required for 180° Image acquisition. →Data 600 per projection and no. of projection. (3) third generation - rotate/rotate Third generation scanner uses increased number of detectors ( up to about 750 detecto...

 CT scan :- A commonly use word in medical field. It takes x ray imaging to a step away from 2D to 3D imaging. When We are going to discuss conventional x ray imaging we take only a plain radiograph of a 2D plane where as we talk CT scan it is 3D study of an object or human body in multi sliced form. CT invention -  First commercial viable CT scanner designed by Sir Godfrey Newbold Housfield in 1971 in london, to over come the visual representation challenges in radiography and convention tomography. Basic principal of CT -  The basic principle behind CT is that the internal structure of an object that can be reconstructed from multiple projection of object. To carry out the reconstruction the ,u (mu) of the object is base.  Where mu is linear attenuation coefficient. Various principle parameters in CT scan -  (1)slice   (2)matrix  (3)pixel   (4)voxel  (5) CT number (6) window (7) pitch Note - we describe these parameters in another...