Anatomy of the Chest
in Computed Tomography
Michael C. Ficorelli, RT
Lesson Description
To explain the various exams pertaining to the
chest and thorax using computed tomography,
incorporating cross sectional anatomy from
images
Lesson Description
• To be able to identify anatomy of the thoracic cavity.
Understand the clinical indications for exams of the
chest. To understand the methods of patient
scanning, positioning, and protocols. To understand
indications for contrast.
• Chapter 16
CT of the Chest
Bony Thorax / Visceral Thorax
Bony Thorax
• Protects and aids in the organs of respiration
– Thoracic vertebrae – ( 12 ) - Posterior boundary
– Sternum – Anterior boundary with 3 components
• Manubrium – superior articulates with clavicles and first pair
of ribs, contains jugular notch (level T2 – T3)
– Sternal Angle – where manubrium and body come
together ( T4 – T5 )
• Body – articulates with the cartilage of the 3rd through 7th
ribs
• Xiphoid – muscle attachments
– Ribs – ( 12 pair ) – head, neck, tubercle and body
• First 7 pair = True ribs
• Lower 5 pair = False ribs
– Costal Cartilage
Thoracic Apertures
• 2 openings
• Superior – Thoracic Inlet
– Formed by first thoracic vertebrae, First pair of ribs w/ costal
cartilage, and Manubrium
– Allows passage of nerves, vessels and viscera from the neck
• Inferior – Thoracic Outlet
– Much Larger than the Inlet, made up of 12th thoracic vertebrae,
12th pair of ribs and xiphoid sternal junction
Pleural Cavities
• Pleura – serous membrane in which each lung
lies which secrete fluid to provide lubrication
for the lungs while breathing
– Parietal Pleura – outer layer; continuous with
thoracic wall and diaphragm; moves with
inspiration
– Visceral pleura – inner layer; closely covers outer
surface of lung and falls into the fissures
Lungs
Lungs
• Conical shaped organs of respiration
composed of spongy like material called
parenchyma
– Apex – above level of first rib
– Bases – aka diaphragmatic surfaces – dome of the
diaphragm
– 3 borders
• Inferior
• Anterior
• Posterior
– 2 Angles
• Cardiophrenic sulcus – medial
• Costophrenic sulcus - lateral
Lungs
– Divided into lobes by fissures lined by pleura
• Right – 3 lobes
– Inferior lobe separated from middle by oblique fissure
– Middle lobe separated from superior by horizontal fissure
• Left – 2 lobes
– Lobes separated by oblique fissure
– Cardiac Notch – located on medial surface
– Lingula – tongue-like projection on infero-anterior surface
• Hilum – opening on the medial surface of each lung
which acts as a passage for main bronchi, blood vessels,
lymph and nerves entering and exiting
Bronchi
• Trachea bifurcates into right and left mainstem
bronchus at carina ( T-5 )
– Right mainstem is wider, shorter and more vertical
than the left
• Enter the lungs and divide into secondary bronchi
• Secondary divides into tertiary or segmental bronchi
which extend into each of the approximately 10
segments within the lung
• Continues to divide into smaller bronchi then into
bronchioles which continue to divide into alevoli (
functional units of the respiratory system )
Secondary Pulmonary Lobule
• Basic unit of pulmonary structure and function
• Surrounded by connective tissue and consists
of 3 – 5 acini ( which contain alveoli ) for gas
exchange
• Visualized with High-Resolution Chest CT – ILD
(Interstitial Lung Disease)
Mediastinum
• Midline region of the thoracic cavity between the two
pleural cavities of the lungs which is further divided into
2 compartments – Contains the thymus gland, trachea,
esophagus, lymph nodes, thoracic duct, heart, great
vessels and various nerves
– Bounded by the sternum anteriorly and posteriorly by the
thoracic vertebrae
– Superior compartment – contains thymus gland and acts as a
conduit for entrance and exits of structures
– Inferior compartment – subdivides
• Anterior - anterior to pericardial sac and posterior to sternum
• Middle – contains pericardial sac, heart and root of great vessels
• Posterior – posterior to pericardium and anterior to the inferior 8
thoracic vertebrae
Mediastinum
Thymus Gland and Lymph Nodes of
Chest
• Thymus = Triangular shaped bilobed gland
located in superior mediastinum
– Responsible for immunity, produces thymosin
(maturation of lymphocites)
• Lymph nodes in mediastinum are clustered
around the great vessels
– Difficult to see in scan unless abnormal
• Thoracic Duct – main vessel of lymph system
– Begins inferior to diaphragm
Lymph Chain of Chest
Heart
• Four chambered muscular organ lying obliquely
in the chest with 2/3 of its mass situated on the
left
– Base – Posterior aspect
– Apex – formed by left ventricle
– Sternocostal – Anterior surface formed by right atrium
and ventricle with small portion of left ventricle
– Diaphragmatic – rests on diaphragm and formed by
both ventricles and right atrium
– Pulmonary – left surface; left ventricle and rests in the
cardiac notch of the lung
Pericardium
Pericardium
• Sac which encloses the heart and proximal
portions of the great vessels
• Fibrous pericardium – attached to central tendon
of diaphragm through which the IVC emerges
– Serous pericardium – double layered inner surface of
the fibrous pericardium
• Parietal layer – Inner surface of fibrous pericardium
• Visceral layer – covers outer surface of the heart and roots
of the great vessels
• Pericardial cavity – between the two layers and contains
serous fluid for lubrication
Heart Wall
• 3 layers
– Epicardium – thin outer
layer
– Myocardium – thick
middle layer made of
cardiac muscle
– Endocardium – thin
inner lining which also
lines the heart valves
and inner lining of the
vessels
Heart Chambers
• 4 chambers – Right / Left Atrium and Right / Left
Ventricles
– Atrium – Superior chambers
• Right Atrium – receives de-oxygenated blood from the Vena
Cava (Inf. and Sup.), coronary sinus and cardiac veins
• Left Atrium – Posterior to right, receives oxygenated blood
from lungs from the pulmonary veins (4 total)
– Ventricles – Inferior chambers
• Right Ventricle – Lies on diaphragm, receives de-oxygenated
blood from the atrium and displaces it to the pulmonary
architecture in the lungs
• Left Ventricle – Receives oxygenated blood from the left
atrium and pumps it into the Aorta
Cardiac Valves
• 4 valves of the heart
– Atrioventricular (2)
• Entrances to ventricles
– Tricuspid – right
– Bicuspid (Mitral) – left
– Semilunar (2)
• Ventricles to Great Vessels
– Pulmonary semilunar –
right
– Aortic semilunar - left
Blood Path in Heart
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
SVC
Rt. Atria
Tricuspid Valve
Rt. Ventricle
Pulmonary Valve
Pulmonary Artery
Lungs
Pulmonary Veins
Lt. Atrium
Mitral Valve
Left Ventricle
Aortic Valve
Ascending Aorta
Great Vessels
• Aorta – Largest artery of the body divided into
ascending, aortic arch and descending
– Ascending - begins at base of left ventricle
• Aortic root divides into 3 sinuses for coronary flow
– Aortic Arch – ( T-3 ) superior, posterior curve of
the ascending aorta located over the right
pulmonary artery and the left mainstem bronchus
– Descending – passes slightly anterior and to the
left of the vertebrae and continues through both
the thoracic and abdominal cavities
Aorta
Great Vessels
• Branches of Aortic Arch – 3 main branches
– Brachiocephalic (Innominate) Artery – First major
vessel arising from arch which divides into the right
common carotid and right subclavian arteries
• Right Common Carotid – extends superiorly until C-4 where
it divides into right external and internal carotids
• Right subclavian – becomes right axillary artery
– Left Common Carotid – Second vessel on arch extends
superiorly until C-4 where it divides into left external
and internal carotids
– Left Subclavian Artery - becomes left axillary artery
Aorta / Arterial Network of Neck
Great Vessels
• Pulmonary Trunk (Artery) – main pulmonary
artery lying within the pericardial sac
– Arises from the right ventricle and ascends in front of
the aorta until T-4 where it bifurcates into the right
and left pulmonary arteries
• Right pulmonary artery – enters hilum of right lung and
divides into 2 branches; upper feeds superior lobe, lower
feeds middle and inferior lobes
• Left pulmonary artery – shorter and most superior
pulmonary vessel; enters hilum of left lung
– Both arteries descend and divide into lobar and
segmental arteries and continue to branch out into
smaller divisions of the pulmonary tree
Great Vessels
• Pulmonary Veins – (4)
– 2 superior and 2 inferior
– Start as capillary network along alveoli and continue to merge until
they form a single trunk for each lobe eventually combining until
both pairs extend into the left atrium from the lungs
Great Vessels
• Vena Cava – Largest Vein in the body
– Superior Vena Cava – formed by junction of
brachiocephalic veins and carries blood from
thorax, upper limbs, head and neck
• Found posterior and lateral to ascending aorta before
entering the right atrium
– Inferior Vena Cava – formed by junction of
common iliac veins in pelvis, ascends through the
abdomen to the right of the abdominal aorta
Vena Cava
Chest Imaging
• May be performed to assess the chest and its
organs for tumors and other lesions, injuries,
intra-thoracic bleeding, infections, unexplained
chest pain, obstructions, or other conditions,
particularly when another type of examination,
such as X-rays or physical examination, is not
conclusive
–
–
–
–
Lung Infiltrates
Surveys for metastatic disease
Parenchyma disease
Pleural disease
Preparation
•
•
•
•
•
Patient is in the supine position and either feet or head first
Arms over the head
Scout from the thoracic inlet to adrenal glands on inspiration
Assess patient to see if they and hold breath for need time
Contrast indications
– Pumonary emboli
– Mediastinal and hilar masses
– Lung infiltrates ( differentiating infiltrate from lung
cancer )
– Lung nodules
• High resolution scans can be done supine and prone
Chest Protocol
Parameters
Single Slice
4 SLICE
• Lung nodules
APEX TO ADRENAL GLANDS
SAME
SCANNING AREA
• Cancer
100ML AT 2ML/SEC @ 45
SAME
CONTRAST
• Vascular disease
SECOND DELAY
NA
4X1MM OR 1.25MM
DETECTOR COLLI
• Effusion and infiltration
DEPENDS ON PATIENT
SAME
DFOV
• Trauma
5 MM
SAME
SLICE THICKNESS
• Pulmonary Parenchymal diseases
NONE
SAME
ANGLE
• Hilar Masses
6MM
VARIES
TABLE FEED/ROT
PATIENT
HEAD or FEET FIRST. SUPINE
SAME
16 SLICE
SAME
SAME
SAME
16X0.75 OR 16X1.25
SAME
SAME
SAME
VARIES
PITCH
1 OR 1.5
VARIES
VARIES
ROT TIME
1 SEC
0.5 SEC
0.5 SEC
RECON
STANDARD/LUNG
SAME
SAME
WINDOW
450W/30L—1600W/600L
SAME
SAME
Chest CT (Lower
Neck)
1
2
1 – Trachea
2 – Jugular Vein
3 – Common Carotid
4 – Esophagus
3
4
Apex of
Chest
1
2
3
4
1 – Right Subclavian
2 – Right Common
Carotid
3 – Left Common
Carotid
4 – Clavicle
5 - Scapula
5
Main Takeoffs of
Heart
2
1
3
4
1 – SVC
2 – Rt. Innominate
3 – Lt. Common
Carotid
4 – Lt. Subclavian
5 – Lt.
Brachiocephalic Vein
5
Mag View of Takeoffs and Cava
7
2
1
1- SVC
3
2- Brachiolcephalic
Artery
3- Lt. Common
Carotid Artery
4
4- Lt. Subclavian
Artery
5- Esophagus
5
6
6- Trachea
7- Lt.Brachiolcephaic
Vein
Aortic Arch
2
1
1 – SVC
2 – Aortic Arch
3 – Trachea
4 - Espohagus
3
4
Chest Pulmonary
Trunk
1
1 – SVC
3
2
2 – Ascending Aorta
3 – Main Pulmonary
Trunk
4 – Right Pulmonary
Artery
5 – Carina
6 – Descending Aorta
6
4
5
7
7 – Left Pulmonary
Artery
Chest MidHeart
1-Rt.Ventricle
3
1
2- Rt.Atrium
2
3- Aortic Root
6
4-Lt. Atrium
5- Pulmonary
Vein
6-Lt.Ventricle
4
5
Chest Heart
1
2
3
1 – Rt. Atrium / SVC
2 – Aortic Root
3 – Lt. Ventricle
4 – Rt. Pulmonary Vein
5 – Lt. Atrium
4
5
Chest Heart
2
3
1
4
1 – Right Atrium
2 – Aortic Root
3 –Right Ventricle
4 – Left Ventricle
5 – Right Pulmonary Vein
6 – Left Atrium
5
6
Chest Heart
1
2
3
1 – Right Ventricle
2 – Septum
3 – Left Ventricle
4 – Left Atrium
Chest Inferior
2
1
1 – Liver
2 – Stomach
3 – Descending Aorta
4 – Spleen
5
5 – Splenic Flexure
4
4
3
Lung Windows
1 – Posterior segmental
bronchus of right upper
lobe
2 – Anterior segmental
bronchus of right upper
lobe
3 – Rt. Mainstem bronchus
4 – Lt. Main Bronchus
5 – Superior lobe Lt. Lung
6 – Inferior Lobe Lt. Lung
From Google…
Lung Windows
Nodule
Pulmonary Embolism Protocols
• Pulmonary Embolism
(PE) – sudden blockage
in a lung artery,
normally from a blood
clot traveling to the
lungs from the legs
(DVT)
– Can be fatal as low
oxygen levels in the
blood could be a byproduct of a large clot
Pulmonary Embolism Protocols
• Considered CTA of Chest (Pulmonary Arteries)
– Results are best when MDCT is utilized for exam
– Approximately 50 – 150 cc of contrast injected
through a large bore IV cannula (generally 18 gauge
however 20 gauge can be used) at a rate up to 8 cc per
second…(practically 3.5 – 5)
– When utilizing bolus tracking, scan is started when
intensity of contrast is optimized in a region of interest
taken in the main pulmonary artery**
• **Localized at level of carina
– Generally slices between 0.5 mm to 3 mm are utilized
with thinner slices being preferred
• Reformats especially in coronal plane
Pulmonary Embolism Protocols
High Resolution Chest CT
• HRCT is utilized for the diagnosis and assessment
of Interstitial Lung Disease (ILD)
– Ex. Asbestosis, Sarcoidosis, Lupus, Pulmonary Fibrosis
• Utilizes narrow slice widths (1 – 2 mm) in sections
approximately 10 – 40 mm apart in a axial
(conventional) acquisition in a high pass
algorithm (Bone/Detail)
– Soft tissues generally present a great amount of noise
due to the algorithm so it is not utilized for routine
diagnosis
Parameters
PATIENT
Single Slice
HEAD or FEET FIRST. SUPINE
PRONE FOR ASBESTOSIS
4SLICE
SAME
• Lung nodules
APEX TO ADRENAL GLANDS
SAME
SCANNING AREA
• Cancer
NONE
SAME
CONTRAST
• Vascular
disease
NA
2X0.5MM OR .625MM
DETECTOR
COLLI
SKINinfiltration
TO SKIN
SAME
DFOV
• Effusion and
1 MM
SAME
SLICE THICKNESS
• Trauma
NONE
SAME
ANGLE
• Pulmonary10Parenchymal
diseases
MM
SAME
TABLE FEED/ROT
1NA
VARIES
• Hilar Masses
PITCH
16 SLICE
SAME
SAME
SAME
1MM
SAME
SAME
SAME
SAME
VARIES
ROT TIME
1 SEC
0.5 SEC
0.5 SEC
RECON
HIGH RESOLUTION/LUNG
SAME
SAME
WINDOW
1600W/600L
SAME
SAME
High Resolution Chest CT
Chest
Chest (cont’d)
Chest (cont’d)
Chest (cont’d)
Chest (cont’d)
Chest (cont’d)
Chest (cont’d)
Chest (cont’d)
Chest (cont’d)
Chest (cont’d)
Case Presentation
1. Pulmonary Embolus Protocol
2. Hi-Resolution Chest
3. “Low Dose” Chest