CT Scan - Assignment (PDF)

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CT SCANSCT SCANSStudent’s NameINTRODUCTIONThere has been new technology comingup to reduce the CT Scan dose in recentlight of the result outcomes to exposingkids to more radiation. The cells inchildren mutate different and thus theirradiation needs are different from thoseof adults. Therefore, there is need formore optimization to reduce risks tochildren from the dosages. There hasbeen acknowledgement that the scansare in high dosages than necessary.The radiation dose is measured in unitsif the dose that the body absorbs per unitmass. (Gray1J/Kg). some of the bodytissues are more sensitive than othersand thus an effective dose needs to bedetermined with consideration of risksfrom the radiation, measured in (SV)sieverts. The determination of effectivedose is measured from the amountabsorbed by critical organs of the body.The Es can be compared betweendifferent types of parameters (SarabjeetSingh, 2009).The CT dose is determined using theCTDI (CT dose index) in volume.LITERATURE REVIEWFactors affecting dose reductionPitchThe ratio of gantry rotation to beam widthover some distance is inversely proportional tothe dose.Exposure lengthThe distance of patient anatomy in the Zdirection when exposed to the X ray should belimited to specific organ.Scan Phases.The number of times a body is radiated in amulti-liver study needs to be maintained tospecific organs as opposed to multiphasescans.Helical Over-RangingThere should be an important tissue forpediatric parings need to have shorteracquisition distances when compared to adults(Racadio, 2014).Course:Approved by the Human ResearchCommittee (HRC) in compliance with theHealth Insurance Portability andAccountability Act guidelines, gradualincremental stepwise reduction methodwas used for kids. This involved analysisthe noisier images associated with lowerradiation doses. Each CT scan was dividedinto 6 color zones with pink for rule out,green for follow-up, red for boneevaluation, yellow for kidney stone, bluefor small lesions and gray for vascularassessments. The radiation optimizationwas then centered around four phases thatfell between different weight ranges. Bystudying the CT scans on adults and thenkids, the result showed that lower noseindex could be used for children whoweighed less than 27.2 kgs. From thestudies, the image noise was graded from 1to where 1 was minimal noise and 65 wasunacceptable noise. Compared to thenoncompliant examinations used in CTscan, the color noise examination showeduse of lesser radiation doses for chestsections ad abdominal sections as well..RISKSAs the age increases, so does the risk of cancerinduction as well.The risk with radiation scans comes in from thepopulation of patients involved.The risk versus benefit assessment for ach CTYstudy and lastly,Diseases that are independent of radiation candevelop from weakening body immunity.CONCLUSION.Based on the cylinder tests and color tests forreduction of dose in CT scan its velar that usingphysical measured data, the use of theparameters stated above will enable reduction ofdosages while the CNR is preserved.METHODOLOGYRational Approaches to Dose ReductionThere has been attempts made to reduce the dosages through determiningdependent size technique factors from computed tomography (CT), usingphysically measured objective data. Experiments using cylinders have beenmade by passing them through CT and studying the noise reflected fromthem. Similarly, diluted iodine and tissue contracts were determined fromcomputer calculation. The doses, noise reflected and contrast offered byiodine were used to optimize the radiation for pediatric CT, especially forabdominal and head examinations (Boone, 2003).There has been successful research that has shown that aorta, renal, hepaticand superior mesenteric arteries to showing noise reduction technologieswhile maintaining the standard references in ensuring pairwise ration dosesand image quality comparison. The image noise showed at interferencepoint intervention using air kerma, there was reduction in dosages. Thistechnique is referred to as image localization.More strategies include the fixed tube strategy that considered children’sweight to reduce the peak voltage of the CT in order to reduce the radiationdose. Exposure techniques including current modulation have also beenemployed where the size of the child is directly linked to the radiation doseoffered. This is done while maintaining desired images quality and the testshave been successfully carried out among volunteering patients for kidneystone evaluations, bone indicators and follow-up head scans for conditionssuch as hydrocephalus and chest conditions like cystic fibrosis. Otherconditions successfully conducted considering size of the child in CT scansinclude bronchiectasis, and pulmonary nodules follow-ups (Boone, 2003).Dose Reduction TechniquesCoronary CT angiography is reliable as it’s a non-invasive imagingmodality for evaluating heart diseases using the right clinical settings. Withthe increase of the condition among many people, the issue of the radiationdosing has come to light. Therefore, advances have been made to achievelowest angiography protocols that consist of low radiation and highlydefined images. This has been achieved through tube potential modulation,where lower volts are used and thus radiation exposure is reduced as well.Iodine induced contrast is enhanced which makes the method appropriatefor CT angiography (Nelson, 2014).DEMERITS.The method tends to have a lot of image noise which makes the quality ofthe image poor.The method when using current-time depends on the body mass index(BMI). The radiation dose is reduced through reducing current and peakvoltage as well as table speed and gantry rotation. This method has beenknown to have high noise levels for images and also causes poor imagequality. ACTM (Automatic tube current modulation) in the CT helps inachieving good image quality using the noise index (NI). The higher theNI, the lower the radiation (Nelson, 2014).Image noise can also be reduced using advanced reconstruction algorithmswhich include ASIR or MBIR (newer model-based iterativereconstruction). Filtered back projection (FBP) help reduce noise thoughmaintaining spatial resolution and image quality.Another effective method is image reconstruction. The initial image qualityis edited through reducing quantum noise and artifacts which improves thequality of CT image quality.Image quality is computed using combined adaptive statistical iterativereconstruction (ASIR). An image is set under different ASIR ranges from0-80% ASIR and the image assessed for image noise, image artifacts andvisibility. Through recording of ED (Effective dose) from the image noiseto the signal to noise ration (SNR), ASIR can be increased or reduced tooptimum levels. Different ASIR levels are suitable for different scans. E.g.50% ASIR is recommended for CT protocol (Nelson, 2014).COMPARISON.ASIR, ATCM and FBP work through image reconstruction while CTangiography voltage modulation work by reducing image noise.MBIR uses image analysis to determine the image quality with 1 asexcellent and 4 as severe reduction in image quality.
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