Week 8: Ct Thorax Flashcards
1
Q
CT Thorax Indications
A
- pulmonary embolism
- pulmonary nodules/mass
- infection
- trauma
- bronchiectasis
- inhalation injury
- interstitial disease
- emphysema
- coronary artery disease
2
Q
CT Thorax Routine Patient Position
A
- supine (most often but some protocols require prone)
- arms up
- short scan time to minimize breathing and cardiac/vessel motion artifacts
- scouts AP and Lat (site specific)
- single breath hold, inspiration mostly
- routine chest is scanned from apices to below costophrenic angles
- CTA for pulmonary embolism can be scanned inferior to superior
3
Q
A
4
Q
Non Contrast CT Thorax
A
- screening
- detection or exclusion of pulmonary nodules or primary lung disease (emphysema, fibrosis, etc)
5
Q
Contrast Enhanced CT Thorax
A
- differentiate vascular from. non-vascular
- primary lymph nodes
- cardiovascular structures
- lesions
- esophageal studies
6
Q
Windowing CT Thorax
A
- soft tissue: ww:350, wl: 50
- lung: ww:1500, wl:-700
7
Q
CT Airways/Bronchography
A
- commonly used to look for narrowing of airways
- thin slices (1.25 mm or less)
- single breath hold, fast acquisition, both inspiration and expiration
- no IV or oral contrast unless tumour in airway suspected
- virtual bronchoscopy offers internal rendering of bronchial tree, walls and lumen
8
Q
High Resolution CT (HRCT)
A
- evaluates lung parenchyma or diffuse lung disease
- thin slices, ≤ 1.5 mm (thicker used on larger patients to decrease mottle, 2.0-2.5 mm used)
- fast single breath hold, expiration and prone options as well
- edge enhancing algorithm used to optimize spacial resolution
- can be incremental or volumetric
- no contrast
- may be three scan series: supine inspiration, supine expiration and then prone inspiration
- reformats at 1.25 intervals
9
Q
Why are prone images taken?
A
to help differentiate actual pathology from effects of gravity that may mimic pathology
10
Q
Incremental HRCT
A
scans only 10% of lung, reducing dose but disease may be missed
11
Q
Volumetric HRCT
A
- helical
- complete lung and airways assessment
- MIP and MinIP reformats
- increased radiation dose but mA can be reduced to compensate
12
Q
What is used for early diagnosis of interstitial lung disease (ILD)?
A
- ILD is main cause of death in systemic sclerosis
- gold standard is HRCT but regular screening faces increased radiation dose
- 9 slice low dose HRCT is a great alternative for the detection of ILD in patients with systemic sclerosis
13
Q
CTA in the Diagnosis of Pulmonary Embolism
A
- scanned inferior to superior/caudal to cranial to minimize respiratory artifact and streaking artefacts from CM
- 30% death rate if PE left untreated
- CTA must be careful considered for young or pregnant women due to the high radiation dose (tech must identify and bring attention to rad)
- dose, rate and timing of CM is critical to CTA exams, spine flush recommend
- MDCT is the mainstay if PE diagnosis
- CT pulmonary angiography studies better than traditional angiography
14
Q
Disadvantages of MDCT in PE Diagnosis
A
- cases with sub optimal vessel opacification or variations
- breathing artifacts
- overt patient motion
- require CM (patients with contraindications can’t get)
- radiation dose high (risk vs benefit)
- learning curve, requires knowledgeable and experienced techs
15
Q
Advantages of MDCT in PE Diagnosis
A
- thinner slices = improves spatial resolution
- MPRs, reconstructions further improve spacial resolution
- rapid imaging for patients who are SOB
- fast, allowing for pan contrast fill of arteries
- establish alternative diagnosis if no PE present
- cost effective
