Non-contrast Brain Computed Tomography - Report Example

CT Protocol

Summary

A computed tomography or CT scan of the brain is a detailed X-ray image obtained from different angles of the same tissue which are processed in a computerised manner to come up with cross-sectional images of the tissue (Trattner et al., 2014). When studying the brain and conditions that may be associated with the brain, brain CT scans can be obtained from the cerebral hemispheres, cerebellum as well as from the brain stem for assessment. Typically, physicians inquire about a previous history of heart diseases, kidney disease, asthma or even thyroid disease before exposing the patient to a brain CT scan. On the other hand, a multiphasic chest, abdominal and pelvis scan is indicated if the doctor anything wrong on the chest area or in the abdominal region. It may take approximately 10 to 30 minutes to complete a multiphasic chest, abdominal and pelvic scan. It is recommended that all patients explain any dye allergies they may have before being exposed to the scanning protocol. The scans illustrate specific cross-sections of the associated regions of the body. Specialized radiology technicians receive the images in a specialised computer and can interpret the outcomes for clinical diagnosis. The indications and contraindications, technical parameters and radiology safety techniques, as well as the image quality factors of both of these CT techniques, are discussed hereunder.

Part A: Non-contrast Brain Computed Tomography

Indications

A CT scan of the brain is majorly obtained to analyse sections of the brain for any traces of pathology including tumerous cell collections such as abscesses and ischemic conditions like stroke (Sharif-Alhoseini, Khodadadi, Chardoli, and Rahimi-Movaghar, 2011). Furthermore, such a scan would be essential when studying the presence or absence of haemorrhages, trauma as well as fractures associated with the skull, and to diagnose hydrocephalus. Even though not often needed, the brain CT scan can be done with contrast or without contrast, a choice which is left for the physician to make. When a non-contrast brain CT is required, usually there are no preparations required by the involved physicians.

A brain CT scan can be indicated in cases where minor head injuries are suspected since the method has been found crucial in the investigation to diagnose intracranial lesions although with certain disagreements on its use. Scan scans are majorly performed in the hospital emergency departments where such injuries are common. The use of such brain scan protocols in the emergency department, however, can be contraindicated depending on the possible radiation complications, cost and time. The CT scan has also been indicated for persons with symptoms such as loss of consciousness (amnesia), contusions, physical evidence of trauma above the clavicles, headaches, vomiting, racoon signs, seizures associated with trauma and coagulopathy. Furthermore, persons aged above 60 years may also be indicated to undergo a non-contrast brain CT scan. The presence of these predisposing factors of minor head injuries in a brain scan is a recipe for an abnormal brain CT scan as found out by Sharif-Alhoseini et al. (2011). In some cases, the indications for a non-contrast brain CT scan may include sudden unexplained changes in the mental status, psychiatric disorders, signs of dizziness as well as a suspected vascular occlusive disease and evaluation of an aneurysm.

Contraindications

Most of the contraindications for Ct scans emanate from the Nuclear Law Act of 29th November 2000 as well as from the regulations given by the Minister of Health on 18th February 2011 regarding the safe administration of ion-based radiations in all medical exposures. Like many other CT scans, the non-contrast brain CT has no absolute contraindication as observed in many other attempts to obtain information from the brain (Trattner et al., 2014). However, it is important to avoid such CT scans when dealing with pregnant women in their first trimester to avoid fetal abnormalities. In such cases, a risk to benefit evaluation is conducted by the physician in consultation with the patient to make an informed decision on whether to proceed with the diagnosis under prevailing circumstances. Evidently, it should be understood that repeatedly exposing patients to X-rays may put them at a risk of suffering from cancer; hence, the need for prior discussions with the patient on such risks before undergoing the procedure. Nevertheless, undergoing a single scan within a lifetime poses minimal risk to the patient with the benefit of obtaining an accurate diagnosis for proper treatment plans, a benefit that may significantly outweigh the risk. A consideration of the adverse effects should be made before administering a contrast medication in patients even though most patients exhibit little to no reactions at all to such contrast substances. For nursing mothers, it is advised that they should wait for about a day before they resume breastfeeding their newborn babies. The use of contrast brain scanning protocols may be contraindicated in cases where the patients are found to have iodine allergies, toxic goitre and expected radioiodine therapy for thyroid cancer, among children below two years of age as well as among people with 60 years and above. Since the current research reviews the contraindications for non-contrast brain scanning protocols, however, there are limited contraindications considering that most of such contraindications occur when a contrast substance is administered to the patient before the diagnostic procedure begins.

Technical Parameters and Post Scan Techniques

The brain CT scans can be obtained through the performance of different techniques including a sequential single-slice technique, a multi-slice helical or spiral procedure or even via a multi-detector multi-slice algorithm. It should be noted; however, the thickness of the typical slice in the brain scanning protocols should not at any time be larger than 5mm (Goldman, 2007). The technician should try as much as possible to use soft tissue and body window algorithms when assessing for abnormalities in the brain. When found to be appropriate, the physician should ensure that the window settings are performed manually to ensure accurate results.

To achieve acceptable brain scans that are within the recommended range, the scan time should never exceed two seconds per slice or image production with a slice thickness of not more than 2mm as earlier mentioned. Furthermore, the technologists should strive to ensure that the inter-scan delay does not go beyond four seconds unless an intravascular contrast media is not used in the diagnostic protocol. The limiting spatial resolution should be adjusted to concur with the unit manufacturer's specifications. Notably, such spatial resolution should be more than 10lp/cm if the display field of view appears to be less than 24cm. Furthermore, the physician and technologist should ensure that the table pitch does not go beyond 2:1, an average ratio applicable in most CT scans (Trattner et al., 2014). If an advanced application such as an angiogram is required to study perfusion in the head, a cine-capable scanner would be preferred with a tube rotation of one or less than one second alongside a continuous cine imaging of one minute or slightly more. For best practices, it is advisable for the physicians to obtain CT scans for the specific appropriate indications to provide critical answers to clinical questions when no other imaging techniques are available. As such, the clinicians, physicians and technologists need to familiarise themselves with more than one imaging diagnostic protocols.

Attempts should be made to revisit the imaging protocols and radiation doses on a regular basis in addition to installing a radiation control and quality control programme within the institution. Counselling sessions need to be organised for pregnant women and patients at risk of developing allergic reactions when exposed to CT scanning procedures. Patients with diabetes and using metformin need to be advised to stop the medication for a while after exposure to the brain CT scanning procedure (Alhoseini et al., 2011). When this procedure is performed under the existing guidelines, it is expected to be fast, painless, accurate and noninvasive. The radiology results are beneficial in that they can aid in reducing the probability of having to carry out an unnecessary explorative surgery or biopsy.

Radiation Safety

Exposing oneself to ionising radiation beyond the permissible limits can cause adverse biological damages to the brain cells. As the ionising radiations go through the brain cells and any other cells along the locale, the may cause rupturing of the molecular bonds resulting in molecular alterations that may cause cellular injuries. Apart from destroying the ability of some cells to undergo normal cell division, such molecular changes may be responsible for mutations in which the dividing cells appear phenotypically different from the parent cells. Small exposures with smaller radiation doses are apparently safe, but after several years of repeated exposure, the impact is as potentially detrimental as a single large exposure. Penetrating radiations are characterised by a latent period that exists between the period of exposure and before the actual signs of the effects. Shorter latent periods are experienced with an increasing dosage of the ionising radiations. The basic safety factors when using radiations rays include time, distance and shielding. Reducing the exposure time is the best safety mechanism against ionising radiations even when other protective mechanisms are adopted. In fact, reducing the exposure time halfway may also reduce the radiation dose by half. When working in an inadequately shielded environment, it is advisable to minimise the distance between yourself and the source of radiation. Shielding is achieved through aluminium for beta particles or lead for gamma particles.

Image Quality Factors

The image quality factors include resolution, noise and contrast. The resolution provides information on the maximum distance that can be maintained before images can be considered to be two distinct ones. Noise degrades the quality of the image by lowering the contrast resolution which introduces uncertainties in the Hounsfield units of the images. The sources of noise include quantum noise, electronic and reconstruction processes (Alhoseini et al., 2011). The factors that influence contrast include the described noise, tube current, inherent tissue properties, the beam kilovoltage as well as the use of contrast media which may not have an impact in the current research which considers only non-contrast brain CT scans (Goldman, 2007).

Part two: Multiphasic Chest Abdomen and Pelvis CT Scan Protocol

Indications

The CT of the abdomen and pelvis is indicated to evaluate the abdominal flank or pelvic pain, suspected appendicitis or even urinary calculi (Raman, Mahesh, Blasko, and Fishman, 2013). Any abdominal trauma can also be evaluated by this scan in addition to assessing, gynaecological masses, renal and adrenal masses of the urinary tract problems in a tailor-made scan referred to as a CT urography. Lesion characterisation, their staging as well as treatment can also be achieved through this type of CT scanning. Other conditions that can be monitored via the chest, abdomen and pelvis CT scanning protocols include tumour recurrence, abdominal surgical complications, cirrhosis, steatosis, and ion deposition disease (Kalra et al., 2005). Further, the scan method can be used to monitor diseases such as and infectious, inflammatory bowel diseases through CT enterography. Venography can be indicated in cases of suspected pelvic abnormalities in addition to suspected colonic polyps and cancers where a CT colonography can be carried out. If a physician wants to drain an abscess, he or she may also require the chest, abdomen and pelvis protocol in addition to indicating it to perfume perfusion studies.

Contraindications

Research has found no specific contraindications for the use of chest, abdomen and pelvic CT scan disease diagnosis. However, it is necessary to perform a cost-benefit analysis before a decision is made to use this CT scanning protocol for any patient. The risks of using this technique should be analysed before its use is indicated, whether with or without the administration of an iodinated contrast material. Like in many other CT scan procedures, the technologist should try to minimise the risk of exposure while using preventive guidelines in the administration of iodinated contrast materials to patients (Kalra et al., 2005). Proper assessments should be performed for the pregnant and potentially pregnant women to weigh the option of undergoing the procedure or looking for other alternatives considering that such rays may interfere with the growth of the foetus (Raman et al., 2013). Patients with any electrically, magnetically or mechanically activated implants such as insulin pump biostimulators among others may not be subjected to the chest, abdomen and pelvic CT scan protocols. Furthermore, this diagnostic technique is contraindicated in persons with intracranial aneurysm clips, ferromagnetic surgical clips or metal shrapnel and bullets.

Radiation Safety

This CT scan technique should consider reducing the radiation dose while maintaining quality through centring the patient in the gantry, ensuring that the patient's arms are above their abdomen and removing any unnecessary densely radiopaque items from the patient. When imaging younger patients with ages below 40 years or when collecting minor details, and when evaluating nephrolithiasis, the accompanying physician should make arrangements to use low dose CT techniques. It is the responsibility of all persons involved in the diagnosis of diseases using CT scans of this nature to ensure the safety of all staff and the environment at large through proper disposal mechanisms. As low as reasonably achievable (ALARA) doses should always be advocated for when using the chest, abdomen and pelvic CT scans. To achieve ALARA, it is important for all members of staff engaging themselves in the use of radiations for diagnosis to familiarise themselves with the essential principles of occupational and public radiation protection as well as the principles of properly managing radiation doses among patients. To prevent unwarranted exposure to radiations, the technologists should strive to use the most appropriate imaging protocols among different patients. The facilities should also meet the expected requirements according to existing policies and protocols for varying ionising radiation exams such as fluoroscopy, interventional radiology and radiography. Such protocols ensure that the patient's body habitus is taken into account including his or her dimensions, weight and body mass index, a procedure that helps to minimise the radiation dose while maximising the quality of images produced. When appropriate, the automated dose reduction techniques should be applied to most of the imaging devices failure to which the manual dose reduction procedures should be applied.

Scan Parameters and Posts Scan Techniques

The parameters involved in chest, abdomen and pelvic CT scan protocols include kVP, Exposure time, collimation or reconstructed slice thickness, the filter or reconstruction algorithm, table speed also referred to as the helical pitch, detector efficiency, and the helical interpolation algorithm. Most of these parameters have been used t reduce the radiation doses administered to patients, especially among children and young adults. To achieve such small radiation doses with these parameters, it is recommended to reduce the tube current (mA) while increasing the pitch. Furthermore, it is recommended that the radiologist should come up with mA settings depending on the weight (diameter) of the patient or their body region (Raman et al., 2013). A reduction in the number of multiple scans is also recommended alongside the elimination of inappropriate referrals for CT scans. Notably, most of these parameters have an impact on the quality of the image while reducing multiple scans and avoiding unnecessary referrals for scans may not have such impacts.

Image Quality Factors

The image quality in this CT protocol is influenced by the technical parameters considering that only a clinically acceptable quality of the image is of concern in an environment that requires the reduction of the radiation dose. The image quality factors of the essence here include noise, and slice thickness also referred to as the Z-axis resolution, low contrast resolution as well as high contrast resolution. How these image quality factors are affected by the various CT scan parameters is also important in understanding the diagnostic procedure (Kalra et al., 2005). Image noise is the measured standard deviation of voxel values in a homogeneous phantom and especially water. All the above-described parameters affect the quality of the image. A good example is that a reduction in the mAs increases the noise by a certain factor. The factors affecting the Z-axis resolution include X-ray beam collimation in single slice CT scanners, the width of the detectors majorly in multidetector CT scanning devices, table speed and the helical interpolation algorithm. However, some multidetector scanning devices may not depend on the table speed considering the interpolation algorithm used. Objects with high signal to noise ratios can be used to determine the spatial resolution of any system used to obtain chest, abdomen and pelvic scans. In this way, the ability of the system to obtain a resolution of high contrast objects with increasingly small sizes. The factors that influence high contrast spatial resolution include focal spot size, the pixel size and mathematical reconstruction filter among others. Using reconstruction filters that enhance the higher spatial frequencies also suggests an increase in the noise produced in the image. Low contrast resolution, on the other hand, may be obtained via the use of objects with relatively small differences from the background. Noise becomes an important factor in the system considering that the signal is significantly small.