LabCT scan

Murad Kharabsheh Yaman Alali

Some rules to read The CT Scan :1. Remember that it’s a transverse section across the body and we are looking at the inferior part of the section (not the superior), so what is your right will be actually the left side on the scan and vice versa.2. when you find the Ascending Aorta , you must see the SVC and Pulmonary trunk with it. 3. Don’t forget the relations between the atria and ventricles (more coronal than sagittal).4. We use a special dye in order to see the vessels.

Section At level of the Aortic Arch Branches

We should see this picture to understand the relation of the aortic arch branches

This Picture Contains the level of section (behind the upper half of manubrium sterni in superior mediastinum).

The CT scans

Right Lung (i.e. right side)

Left Lung (i.e. left side)

Notes : 1. In this section we see the left Brachiocephalic vein crossing the branches of the aortic arch to meet the right Brachiocephalic vein .

2 . We see the branches of the aortic arch from right to left, respectively: Brachiocephalic trunk , left common carotid artery and the left subclavian artery.

3. most posterior ; we see the trachea but the esophagus is hardly seen because it collapsed .

4.This section is behind the upper half of manubrium sterni in superior mediastinum.

Section at the level of the Aortic Arch

Level of the section (lower half of manubrium sterni in the superior mediastinum).

The CT scans

Notes 1. In these sections we see four structures : The Aortic Arch, SVC, the trachea and the azygos vein .

2. Trachea appears in the CT scan as tube with black lumen.

3. This section is behind the lower half of manubrium sterni in the superior mediastinum.

Section At the level of Aorticopulmonary window

Level of section

The CT Scans

This Pic is more acurrate

Note :1. In this picture we see the empty area below the aortic arch which is called Aorticpulmonary window .

2. The pulmonary Trunk emerges from this window.

3. We see the Aortic Arch beginning and its end but we don’t call it “ascending / descending” ; the reason behind this is the ascending aorta is the name that we use only when the pulmonary trunk emerges (i.e. only when we see the pulmonary trunk with the aorta we call it the “ascending aorta” and always when we see the ascending aorta we see the descending aorta).

4. The trachea is preparing to divide (tracheal bifurcation).

5. The azygos drains into SVC .

Extra notes

1 .The sections are following this arrow .

2. The left pulmonary artery is slightly higher than Right Pulmonary artery when they divide (but not always), but we may see both of them in one section and that depends on

position of the body .

Section at the level of left pulmonary origin

The CT Scans

Notes :1. The origin of Left Pulmonary artery .

2. We see the Ascending aorta, SVC and the Pulmonary trunk. 3. When the Ascending Aorta appears, the descending aorta also appears in the posterior mediastinum with the esophagus .

4. We see the right bronchus .

Section at the level of origin of Right pulmonary artery :

The CT Scans

6 is left pulmonary artery

Notes : 1. It shows the Right Pulmonary artery origin.

2. It shows the Ascending Aorta, Descending Aorta and SVC.

3. It shows the left pulmonary (variations due to the body positions).

4. It shows the left bronchus.

CT Scan at the level of the heart:

Notes : 1. we must know that the interatrial and interventricular septum is more to coronal than sagittal.

2. Aortic vestibule is posterior to the infundibulum .

3. Descending aorta (DA) is shown .

RA

LA

RV

LV

DA

Where to find the pulse?We must feel the pulse gently.- Pulse of Radial artery: just lateral to flexor carpi radialis .- Pulse of brachial artery: just medial to biceps tendon .- Pulse of femoral artery: at midinguinal point (mid point between Anterior superior iliac spine and symphysis pubis) and not the mid point of the inguinal ligament.- Pulse of popliteal artery : we have to compress on it a bit because it’s a deep structure.- Pulse of Anterior tibial artery (Dorsalis pedis) : we feel the dorsalis pedis artery (absent in 10% of people, therefore if we don’t find a pulse we must check the pulse of the posterior tibial artery before giving any conclusions) just lateral to the tendon of extensor hallucis longus (we feel it proximal part of the foot because its distal part will go down and supply the sole of the foot). - Pulse of posterior tibial artery : behind the medial malleolus .

Symptoms of occluded vessel :1. Pain : accumulation of metabolites (mainly lactic acid) downstream of block irritates the sensory nerves. 2. Pallor due to decreased perfusion of blood.3. Paresthesia and paralysis : the nerves (sensory and motor respectively) are sensitive to hypoxia . 4. Polar : coldness

Causes of vessel occlusion

Emboli :1.cardiac : Atrial fibrillation stagnation of the blood (stasis) thrombus part of it systemic circulation .MI (subendocardial most area for infarction) rough wall helps making a mural thrombus detach systemic circulation.2. Arterial : Atherosclerosis plaque detaches systemic circulation.

Aneurysms : predispose to thrombus detaches systemic circulation. Most site for aneurysms is abdominal aorta below the renal artery and above its bifurcation point. Most site for aneurysms that leads to emboli in lower limb is popliteal , because of “Jazmat “.

3. veins ( rarely ) - we call it DVT (deep venous thrombosis)- may lead to Pulmonary embolsim or systemic emboli (if there is ASD , VSD …)