The Effects of a Computed Tomography (ct) Scanner on The Human Body

A Computed Tomography (CT) Scanner consists of 3 major elements; a scanning gantry, a data handling unit and a storage. A patient is surrounded by a gantry which consist of several components. The scanning gantry has 4 major components :X-Ray Tubes, Collimator, Anti-scatter grids and Detectors.

A large voltage will be applied between two electrodes in vacuum. The filament, which is the cathode, is the source of electrodes whereas the tungsten target, which is the anode, is the area of target for the electrons. The filament is heated to produce electrons and they are accelerated towards the anode. At the tungsten target, the kinetic energy of the of the electrons are converted into X-rays.

A collimator is used to allow all the X-ray beams to transverse in the same direction. Their main purpose is to provide good quality images. They are placed in between the X-ray source and the patient. Large amount of X-rays might undergo scattering before reaching the detector. To allow maximum amount of X-ray beam to reach the detector, an anti-scatter grid is placed in between the patient and the X-ray detector, enabling the unscattered photons to pass through the grids without attenuation. The grid is made of high-Z material, such as tungsten, to prevent scattering when the X-ray passes through.

There are various detectors such as multiple detector arrays, xenon detector and solid state detectors. CT scan is operated using different components namely a specific scanner, an x-ray system, a patient table, and a computer workstation. The CT scanner comes in two structures - a large square-shaped or annular with a hole in the center. X-rays are produced from the X-ray tubes in the form of a beam revolves around the patient to get a 3D image. During a CT scan, the patient table is passed through the center hole for the x-ray beam to traverse through the patient's body. The x rays are converted into a series of binary coloured images - black and white, where each of which represents a "slice" of the anatomy.

After one complete round of the x-ray source around the patient,, the CT computer uses advanced mathematical techniques to establish a 2D image slice of the patient. The depth of the tissue depicted in each image slice can differ subjected to the CT machine that is used. However, the thickness generally ranges from 1-10 millimeters. When a full slice is completed, the image is stored and the motorized bed is moved forward incrementally into the gantry. To accumulate the desired number of slices, the scanning process is repeated several times to provide more layered images. CT scans can be used to detect diseases or injury located in the different parts of the body. CT scans are commonly used in clinical applications. CT scans are crucial to determine potential cranium fractures or an underlying injury to the cerebrum in head traumatic patients. Apart from cerebral scans, CT scans are necessary in pulmonary diseases. This is due to the severe difficulty in imaging organs in the pulmonary circuit, such as the lungs, using MRI and ultrasound.

In this category of application, it is able to detect many diseases related to the pulmonary circuit such as cystic fibrosis, pulmonary fibrosis, emphysema and etc. Other than that, CT scans are used in abdominal imaging. CT scans are able to visualize images in a 3-dimensional platform, where it is used to detect compound fractures in organs, such as those in the pelvic region, that typically happen to elderly patients. In addition, CT scans are utilized in identifying tumors in the abdomen and ulcerations in the liver.

An electrosurgical unit consist of 3 compartments; generator, inactive patient plate and active electrode to allow the current to flow. Electrosurgical generator provides electron flow and voltage. Active Electrode are known as electrosurgical pencil which are either controlled by hand or foot. Electrical current is delivered back to the generator via the inactive patient plate that is set on the patient. Electrical current is delivered back to the generator via the inactive patient plate that is set on the patient. In a Monopolar ESU, electrical current flows from the generator to the active electrode and passes through the patient to the dispersive cauter pad, completing the circuit. Monopolar modes are usually used to cut, coagulate, desiccation, fulguration or blend and involves the use of two electrodes. The first electrode, known as the active electrode, with the aid of a pencil instrument, is fixed onto an entry site. This allows tissue to be lacerated and blood to clot as the active electrode has a comparatively small contact area which results in a very high current density attained at the surface. A second electrode, which is a large-area patient plate, or also known as neutral or return electrode, is placed on a proper position on the patient’s skin. A high frequency current is then emitted, resulting in a surgical slit or congelation at the active electrode which heats the tissue that is contact with the patient plate.

The patient will hardly notice any heat given off from the high frequency current. However, in the case of poor contact or a little contact area between patient plate and skin, burns may occur. Less energy is required in a bipolar electrosurgical unit as they run under lower voltage. However, they are limited to cut and coagulate larger bleeding areas only. The current is in the patient is confined between the forceps electrodes giving more appropriate control over the area that has to be treated, minimising the any tissue damage. It doesn’t require a patient plate. Bipolar electrosurgery prevents patient from burns. Although bipolar has more safety, it can’t be used for many application compared to monopolar.

Electrosurgical Unit has a wide range of application during surgeries. They are used to perform surgical cut easily with minimum bleeding using a blunt electrode, prevent bleeding at large areas, devitalization and shrinkage of tissue. There are few surgical techniques using an ESU. The most constantly used method is cutting and homeostasis. Bipolar forceps and clamps are used on large blood vessels in tissues to be sealed. Devitalization and shrinkage tend to tumors, lesions and hyperplastic tissue. Tissues are able to be eradicated with a snare electrode.

Computed Tomography (CT) emits ionizing radiation which causes cancer in human. A CT Scanner utilizes x-rays which are form of ionizing radiation in the electromagnetic spectrum. When these ionizing radiation traversing through human body, two main risk may occur; deterministic or stochastic effects. Deterministic effects cause damages to the cells. Examples of this effect are skin reddening, swelling or burns, hematologic depression, sterility and cataracts.

Stochastic effects leads to the development of cancers in human body. Usually, CT emits higher amount of radiation compared to a typical x-ray procedures although the risk of cancer minior. Children are more prone to developing cancer as they have longer life spend than adults since the cancer have enough time to grow. Adding on, at a growing stage, children are sensitive to ionizing radiation as the cells are dividing at a faster rate. Fair amount of dose have to be given to different people with different sizes. Dose can be adjusted according to the width of the human body parts such as chest, hips, thigh or waist.

CT scans should only be carried out if its obligatory. The necessity of a scan will be discussed by the doctors and radiologist. Lower-resolution scans will be able to make diagnosis. They use least amount of radiation. Hence, use lesser scan lines as possible. Burns or fires may occur due to apparatus failure in a connection between an expected electrosurgical unit activation and its electrode, also known as inadvertent activation. Nowadays, ESUs have detectable activation tone that is able to be adjusted. These detectable activation tone is able to inhibit injuries and helps to reduce the seriousness of burns. Even though a handful of surgeons are against using of such activation tones, it is still considered a crucial safety aspect because it is disturbing to the patients. When the tone is disabled, the odds of unforeseen electrosurgical burns and related negligence allegedly increases. Radio-frequency (RF) leakage current can pass through the patient via the electrodes. There are two possibilities of why this happens. Firstly, the electrodes may be insufficiently isolated at a frequency of 300 kHz higher than normally used for electrosurgery. Secondly, with capacitive coupling, high-frequency currents produced is able to flow from the electrode to ground.

Although in the case where the line is disconnected from the power, the coupling may still be large enough that it causes leakage to the ground. The small surface contact area of the electrodes provide an adequate amount of radio-frequency (RF) leakage current that causes high current density. This leakage causes burns on the tissue on contact with the electrodes. Replace all ESUs that do not have audible activation tones. If needed, contact the manufacturer and enquire whether the minimum volume setting could modified to ensure that it remains at an audible level.

Surgeons are to explain the activation tone to their patients so as to lessen their worries. By allowing patients to wear headphones to mask disturbing noises, including audible activation tones would help as well. When electrodes are not in use, they are to be kept in well-insulated safety holsters. To stop the possibility of any burns or fire, the active electrode line should be decoupled from the unit itself when not in use. Needle electrodes of the ESU could be replaced with adhesive electrodes as it has enough contact area to limit the RF leakage current and avoid burns. During an ESU surgery, the power output has to be set to its minimal that provides the necessary surgical execution.