A Smoking can harm and tighten blood vessels,

A
54-year-old African-Caribbean man who is 5’7 and weighs 198lbs, BMI of 31.01
which is classified as being overweight. He’s a heavy smoker, has a high-fat
diet and high blood pressure. He has excessive amount of alcohol and
sedentary lifestyle which are all risk influences that escalate
likehoods of atherosclerosis. Smoking can harm and tighten blood
vessels, contributes to high cholesterol levels and blood pressure.
It doesn’t allow acceptable amounts of oxygen to reach the body’s tissues
as patients experienced shortness of breath. Alcohol is risk factor due to
damaging the heart muscle. He went to the GP complaining with the following
symptoms such as sweating, fatigue, dizziness, light-headedness, nausea
and numbness on the shoulder. He also distressed tightening and squeezing pain
in the chest.

The
doctor reviewed patients’ medical history and asked if he had any previous
family history of heart disease, stroke or other circulatory problems. The
doctor then carried out physical inspection to measure the blood pressure and
heart rate. Doctor checked for a weakened pulse, an aneurysm which
checks for abnormal inflammation or widening of arteries that can be
because of faintness of artery walls. The doctor also identified any slow wound
healing which is signal that blood flow is restricted. Blood
tests showed high levels of certain fats, cholesterol levels.

The
patient then would be referred to a Cardiologist to carry out further
investigation, due to the results of the above tests Coronary Artery
Atherosclerosis would be suspected. The most suitable imaging technique to make
diagnosis would by using CT Angiography (CTA). CTA is an examination that
uses a dye and special x-rays to identify the insides of arteries and can show
whether plaque is blocking the arteries and severity of the plaque (Nair
and Devaraj, 2017). A thin, stretchy tube named catheter is put into the
blood vessel in the arm. A iodine rick contrast material dye is inserted into
the patients’ bloodstream to enhance the area of interest which may be the
artery or tissue. The medicine sow down or steadies the patients heart rate to
advance the imaging results. Patient lies in CT scanner for about 10 minutes
and must embrace breath between 10-30 seconds throughout imaging (Mendes,
2014). The advantage of CT angiography it has a higher temporal and spatial
resolution, which allows the specialist to see small structures without
motion artefact. The more slices (between 128 and 320 slices)
are essential to the short scan time (1-2s). It improved
actualisation and visualisation in 3D of the vessels of the heart, nearby
vessels and coronary structure. This has meant the visualisation of anatomy can
be done in several planes (Scottsdale Medical Imaging, 2017). The advantages of
high resolution technology are essential to better image quality with the equal
radiation dose or same image quality with a reduced radiation dose.
The advantages of higher temporal resolution are essential to a reduced use of
drug administration. CT angiography can capture vessels from a limitless number
of angles, from both inside and outside the vessel wall. It detects
arrowing and obstruction of blood vessels which permits for suitable therapy to
be carried out. Its precise anatomical detail compared to MRI mostly in
small blood vessels. With variability of visualise techniques such as
multiplanar reconstructions, volume rendered (VR) images, and maximum intensity
projections (MIP) and vessels walls can be assessed (Larner, 2017).
Multiplanar reformation (MPR) is technique that presents plane in 3D image
volume. This plane can be at 90 degree angle to the axial slice of the image
volume. Luminal narrowing of located plaques can be evaluated by assessing
plaques in planes longitudinal and ninety degree to the vessel midpoint (Voros,
2009).
                                                                                                                                              A
maximum-intensity projection (MIP) each pixel in the image a ray is cast
through the 3D image volume and only the highest-attenuation voxels are kept.
MIP shows coronary arteries plus their side branches in a sole image and can
image smaller branches with less attempt contrast with other 3D techniques. MIP
technique used in complete image volume and the coronary arteries will overlap
with the contrast-medium cardiac hollows, high-attenuation pericardial metal
clips and bones of the ribcage can cover these structures (Crownover and Bepko,
2017). Additionally, if surgery is required, it can be carried out more
accurately. CT angiography is quick, non-invasive and have less complications.
To perform a CT it can last up to 20 minutes compared to an MRI scan can last
up to 1.5 hrs. CT angiography is lower cost examination compared to 2/3
investigations required to make a diagnosis which can help in earlier detection
of disease. There is also potentially less discomfort because contrast material
is injected. Minimising Radiation Exposure Special care is taken during x-ray
investigations to use the lowest radiation dose possible while creating the
greatest images for assessment. Modern x-ray systems take controlled x-ray
beams and dose control methods to reduce stay (scatter) radiation. This
safeguards those parts of a patient’s body not being imaged receive
minimal radiation exposure, including tailoring the scan parameters
specifically to their body type and weight (RSNA, 2017). On the other hand, the
disadvantages are the awareness of the vitalness that there is a radiation
dose. But the lifetime attributable risk of cancer from an effective
radiation dose of 10 mSv is small, in the order of 1 in 2000, but varies with
age and gender. MRI does not use radiation to acquire images,
but MRI imaging is extensive procedure and is an expensive diagnostic
scanning tool (Voros, 2009). 

Thinner
slices improve the quality of the 3-dimensional image; on the downside it
also increase the image noise and radiation dose because of the larger
overlap and lower pitch, which increases achievement time and potentially
limit the diagnostic accuracy of the CTA of the examination. The CTA
images are usually reconstructed with a medium smooth reconstruction
kernel. The reform  kernel, also known as filter which is most vital
parameters affecting the image quality. There is weigh up between the spatial
resolution and noise for each kernel. Smooth kernels produce images with little
noise, resulting in lower spatial resolution. However sharp kernel,
produces images with high spatial resolution but have amplified noise
levels (Wong and Keng,
2011).                                                                                                                               
                      A person who
is very large may not fit into the opening of a CT scanner or may be over the
weight limit usually 450lbs for the moving table. Tube current can be modified
according to the patient body mass index (BMI). Higher tube current increases
the amount of photons per exposure time, reducing the image noise, but at
the same time increasing the radiation does. Patients with higher BMI need
higher tube current to reduce the noise level, generated by
the higher amount of tissue penetrated (Dewey, 2009). The tube current
should only be increased to a level necessary for acquiring adequate diagnostic
images. Increasing tube voltage will lead to higher energy X-ray beams with
higher tissue penetration, and substantially increased radiation dose.
Generally, 100 to 120 KeV tube voltages are sufficient for cardiac imaging.
Only in large patients, 140 KeV could be used. Reducing tibe voltage will
reduce radiation dose in proportion to the square of changes in tube
voltage (Roberts et al, 2008). CTA contra-indications are if patients who are
at risk for kidney failure and who already have borderline kidney
function, administering iodinated contrast material may potentially further
damage kidney function. Large quantity of x-ray contrast material outflows from
the vein being inserted and spreads beneath the skin where the intravenous is
located, it may harm the skin, blood vessels and nerves (Robert et al, 2008).
CT angiography should be avoided in patients with a previous severe reaction to
contrast material, advanced kidney disease or severe diabetes, because x-ray
iodine-rich contrast material may be harmful. Medical history of allergy to
x-ray contrast material, the specialist may instruct them to take special
preventive medicine such as a steroid, for upto 24 hours before of scan to
reduce the risk of allergic reaction. Women always should notify their
specialist if there is any likelihood that they are pregnant.
Contrast-medium manufactures direct mothers must not breastfeed their
babies after contrast-medium is given for about 24-48hrs (Khan et al,
2010).                                                                                                
                                                       A non-compliant
patient, leads to movement artefact. CTA is unsuitable when there is
large amount of existing coronary artery calcification.
Arrhythmias (irregular heartbeat) and unusually high heart rates. Artefact
(degrade image quality) due to pounding from blood flow in vessels and the chambers
of the heart, respiratory artefact, beam-hardening effects caused by
implant/metal artefacts or air bubbles in the pulmonary artery.
Patient inability to hold a breath for at least 15-20sec (Dewey, 2011).  

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