CT Scan - Assignment (PDF)

CT SCANS
Student’s Name
INTRODUCTION
There has been new technology coming
up to reduce the CT Scan dose in recent
light of the result outcomes to exposing
kids to more radiation. The cells in
children mutate different and thus their
radiation needs are different from those
of adults. Therefore, there is need for
more optimization to reduce risks to
children from the dosages. There has
been acknowledgement that the scans
are in high dosages than necessary.
The radiation dose is measured in units
if the dose that the body absorbs per unit
mass. (Gray1J/Kg). some of the body
tissues are more sensitive than others
and thus an effective dose needs to be
determined with consideration of risks
from the radiation, measured in (SV)
sieverts. The determination of effective
dose is measured from the amount
absorbed by critical organs of the body.
The Es can be compared between
different types of parameters (Sarabjeet
Singh, 2009).
The CT dose is determined using the
CTDI (CT dose index) in volume.
LITERATURE REVIEW
Factors affecting dose reduction
Pitch
The ratio of gantry rotation to beam width
over some distance is inversely proportional to
the dose.
Exposure length
The distance of patient anatomy in the Z
direction when exposed to the X ray should be
limited to specific organ.
Scan Phases.
The number of times a body is radiated in a
multi-liver study needs to be maintained to
specific organs as opposed to multiphase
scans.
Helical Over-Ranging
There should be an important tissue for
pediatric parings need to have shorter
acquisition distances when compared to adults
(Racadio, 2014).
Course:
Approved by the Human Research
Committee (HRC) in compliance with the
Health Insurance Portability and
Accountability Act guidelines, gradual
incremental stepwise reduction method
was used for kids. This involved analysis
the noisier images associated with lower
radiation doses. Each CT scan was divided
into 6 color zones with pink for rule out,
green for follow-up, red for bone
evaluation, yellow for kidney stone, blue
for small lesions and gray for vascular
assessments. The radiation optimization
was then centered around four phases that
fell between different weight ranges. By
studying the CT scans on adults and then
kids, the result showed that lower nose
index could be used for children who
weighed less than 27.2 kgs. From the
studies, the image noise was graded from 1
to where 1 was minimal noise and 65 was
unacceptable noise. Compared to the
noncompliant examinations used in CT
scan, the color noise examination showed
use of lesser radiation doses for chest
sections ad abdominal sections as well.
.
RISKS
As the age increases, so does the risk of cancer
induction as well.
The risk with radiation scans comes in from the
population of patients involved.
The risk versus benefit assessment for ach CTY
study and lastly,
Diseases that are independent of radiation can
develop from weakening body immunity.
CONCLUSION.
•Based on the cylinder tests and color tests for
reduction of dose in CT scan its velar that using
physical measured data, the use of the
parameters stated above will enable reduction of
dosages while the CNR is preserved.
METHODOLOGY
Rational Approaches to Dose Reduction
There has been attempts made to reduce the dosages through determining
dependent size technique factors from computed tomography (CT), using
physically measured objective data. Experiments using cylinders have been
made by passing them through CT and studying the noise reflected from
them. Similarly, diluted iodine and tissue contracts were determined from
computer calculation. The doses, noise reflected and contrast offered by
iodine were used to optimize the radiation for pediatric CT, especially for
abdominal and head examinations (Boone, 2003).
There has been successful research that has shown that aorta, renal, hepatic
and superior mesenteric arteries to showing noise reduction technologies
while maintaining the standard references in ensuring pairwise ration doses
and image quality comparison. The image noise showed at interference
point intervention using air kerma, there was reduction in dosages. This
technique is referred to as image localization.
More strategies include the fixed tube strategy that considered children’s
weight to reduce the peak voltage of the CT in order to reduce the radiation
dose. Exposure techniques including current modulation have also been
employed where the size of the child is directly linked to the radiation dose
offered. This is done while maintaining desired images quality and the tests
have been successfully carried out among volunteering patients for kidney
stone evaluations, bone indicators and follow-up head scans for conditions
such as hydrocephalus and chest conditions like cystic fibrosis. Other
conditions successfully conducted considering size of the child in CT scans
include bronchiectasis, and pulmonary nodules follow-ups (Boone, 2003).
Dose Reduction Techniques
Coronary CT angiography is reliable as it’s a non-invasive imaging
modality for evaluating heart diseases using the right clinical settings. With
the increase of the condition among many people, the issue of the radiation
dosing has come to light. Therefore, advances have been made to achieve
lowest angiography protocols that consist of low radiation and highly
defined 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 appropriate
for CT angiography (Nelson, 2014).
DEMERITS.
The method tends to have a lot of image noise which makes the quality of
the image poor.
The method when using current-time depends on the body mass index
(BMI). The radiation dose is reduced through reducing current and peak
voltage as well as table speed and gantry rotation. This method has been
known to have high noise levels for images and also causes poor image
quality. ACTM (Automatic tube current modulation) in the CT helps in
achieving good image quality using the noise index (NI). The higher the
NI, the lower the radiation (Nelson, 2014).
Image noise can also be reduced using advanced reconstruction algorithms
which include ASIR or MBIR (newer model-based iterative
reconstruction). Filtered back projection (FBP) help reduce noise though
maintaining spatial resolution and image quality.
Another effective method is image reconstruction. The initial image quality
is edited through reducing quantum noise and artifacts which improves the
quality of CT image quality.
Image quality is computed using combined adaptive statistical iterative
reconstruction (ASIR). An image is set under different ASIR ranges from
0-80% ASIR and the image assessed for image noise, image artifacts and
visibility. Through recording of ED (Effective dose) from the image noise
to the signal to noise ration (SNR), ASIR can be increased or reduced to
optimum 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 CT
angiography voltage modulation work by reducing image noise.
•MBIR uses image analysis to determine the image quality with 1 as
excellent and 4 as severe reduction in image quality.