Attenuation Types Of Photon Energy

AEC maxed out: GE’s automatic exposure control (AEC) tools, SmartmA and AutomA, select tube current levels during an exam between minimum and maximum tube current limits based upon the patient habitus as interpreted from the last acquired CT localizer radiograph. If the noise index requested for an image is lower than is allowed by the maximum tube current, the AEC will choose the maximum tube current throughout the scan. This infrequent occurrence can happen due to patient positioning which increases patient dose [17, 18, 31, 32], improperly chosen or set-up protocol [21, 33], or large patient size. If a scan is maxed out in mA for the entire scan, then the average and the maximum mA values will be identical. In such a case, we classify the protocol as having either a manual mA technique or being “maxed out”. If the maximum mA and the average are not equal, then we classify the irradiation event as having utilized

“Breath normally and stay still” Is what a radiographer would say to Mrs. Watt before exiting the room to take an exposure of a left PA hand. The .3 seconds that takes to capture the image on the IR is just one of the nine steps to produce a quality diagnostic image. The energy needed to heat the tungsten filament is traced back to lower granite dam in Washington where the energy is stored in Bonneville power and bought by Avista. The power then streams across the snake river to Sacajawea hall into a wall outlet. The x-ray tube housing unit is plugged into the wall outlet and inside the x-ray tube, the rotor produces the x-rays which expose the anatomic part onto the IR. The nine steps that are required to produce an acceptable and high-quality diagnostic image, starts at lower granite dam and ends with a manifest image that helps radiologists determine the outcome of the patient.

This is due to the fact that the time resolution of the plastic scintillator detectors (5~ns) is

CBCT provides more precise 3-dimensional (3D) images than conventional 2D periapical radiographs with a reasonable radiation dose. In addition, its noninvasive in vivo application allows expanding the number of samples than previous microscopic analysis by using extracted teeth (19, 20). Differences in gender and the bilateral prevalence of anatomic variations can be compared easily on in vivo CBCT images because of their certain identification of tooth position and study subjects (18, 19,

Whether a patient is opting for cosmetic dentistry or is experiencing some sort of discomfort, X-rays are often the first step to any dental procedure. In addition to showing cavities and other surface issues, X-rays can also give dentists a picture of what’s going on beneath

My imaging modality is on Bone Densitometry. Before I go into great detail about this modality I would first like to talk about what exactly is Bone Densitometry and explain the history of it and how it became about so that we can understand how we use it today. Bone Densitometry is a noninvasive procedure that allows us to measure bone mineral density. This modality and procedure plays a crucial part in being able to diagnose Osteoporosis. It can provide us with vital information that can diagnose this pathology in its early stages as well as improving our overall health by being able to monitor therapy and predict the risk of fractures. The development of Bone Densitometry started over hundreds of years but only in the past couple decades have we seen major advancements in the use and technology. Early developments believe it or not started in dentistry with plain radiographs of the mandible over hundreds of years ago. The problem with that though is that plain radiographs had limited ability in the determination of bone density. According to our text book. “A bone loss of at least forty percent must occur before it can be visualized by the unaided eye.” (Adler, A., Carlton, R., & Carlton.,. (2012). Principles of radiographic imaging.. Delmar Publishers.) In the 1930’s efforts to define bone loss were enhanced with radiographic absorptiometry(RA). A step wedge of known densities were imaged with extremities to be able to more accurately determine bone mass. As years passed

The use of MSCT scanners has resulted in increased speed of data acquisition with nearly isometric voxels, allowing the performance of CT

Computed Tomography is a combination of x-ray technology and computer. It is a scanner that moves around the patient and mathematically assembles an image. The color produced depends on upon the amount of radiation absorbed. CT is helpful in the evaluation of bones and soft-tissues.

Dentistry has been enhanced since dental radiograph has been used as an important tool to identify and treat diseases that affect the teeth and the structures that support them. Dental radiograph allows the dental professional to detect many conditions that are not possible to see with bare eyes. For examples periodontal disease, dental caries, missing or extra teeth, impacted teeth, cysts and tumor, just to name a few. In many cases these conditions produce no symptoms or clinical signs and if they do, is at a very advanced stage in where a good prognosis is not guarantee. Similarly, the dentist depend on dental radiographs when performing a root canal, examining the status of teeth and bone during growth and development, extraction of

appearance on X-ray sheets is related to the increased or decreased levels of radio density..

This issue can be mitigated by using dual­energy CT scanners, which enable imaging of patients’ tissues at two different voltages, facilitating comparison of results from two separate detectors. These scanners also enable tissue evaluation at varied energy levels, and further improve the accuracy of determination of stone composition(3,75).

Bone, muscle and fat absorb x-rays at different levels, so the screen lets see different structures of the body because the different levels of exposure are in different shades of gray. The main component of an x-ray machine is a vacuum tube with a cathode or filaments and an anode, which is usually made of tungsten, a hard-steel gray metal used to make electric light filaments. Electric current passes through the filament, raising its temperature. Once it reaches a certain level of energy, the filament starts emitting negatively charged electrons. These electrons are attracted with great force from the positively tungsten anode, taking them through the vacuum tube at very high speed. In one of the atom’s lower orbital an electron gets knocked away when the anode collides with electrons. An electron from the higher orbital takes place of the removed electron, releasing energy as an X-ray photon. (HowStuffWorks-X-Rays) Called ‘bremsstrahlung’, the reaction contains x-rays of varying wavelengths. The X-ray

According to the developers, the key is in the coherent beam. The beam is reduced to a micro-sized point source instead of the systems that we have today, which are large points. These micro-sized point sources, which emit a beam of electrons individually, “pass through a micro structured plate that emits a beam of x-ray”, aka image receptor. In layman teams they are redeveloping the cathode component of an x-ray machine, to be able operate to with an “optimized cathode chip”. With the prototype that the two research teams have invented so far, they have been “able to capture high-resolution absorption images of samples where fine soft tissue structures are clearly visible”. This may sound like a great “change the world technology” but it is not without its pros and cons.

Cone-beam computed tomography (CBCT) is a valuable tool used in dentistry. It can offer various advantages as mentioned by Delamare (2016): its smaller size and lower cost compared to the conventional computed tomography (CT), fast acquisition, submillimeter resolution, a patient radiation dose that is relatively low (approximately 0.08 mSv average) and user friendly interactive analysis features. Clinicians can use CBCT to determine the location of impacted teeth or the inferior alveolar nerve, treatment planning for implant placement, endodontic evaluations or TMJ assessments and lastly aid in locating the full extent of odontogenic pathology.

The projection sub-systems of CT scanners has experienced changes in 3 aspects including parallel, fan, and cone beam systems \cite{sidky2008image} - \cite{vo2014reliable}. Sidky and Pan \cite{sidky2008image} proposed a theoretical framework to show how accurate circular cone-beam CT image reconstruction can be done from reduced data sampling. In data acquisition phase, they assumed that the estimated projection data is within a specified tolerance of the available data and the values of voxels are non-negative. To observe these constraints, a projection onto convex sets was considered, and the total variation (TV) gets minimized by steepest descent with an adaptive step-size. They argued that the TV algorithm can resolve low-contrast structures in the presence of high-contrast objects even when the projection data sets are limited in angular range or view number, and when the low-contrast object is not at the mid-plane of the circular x-ray trajectory. Qi and Chen \cite{zhihua2008direct} considered image reconstruction in fan-beam based CT in which the derived formula applies to the real domain. First, inverse Fourier transform was applied to use the multiplication instead of convolution in Fourier space. Afterward, the range of calculation was extended to cover redundancy. This method is subject to observing full circle scan in data acquisition mode.