CT thorax protocol Flashcards
CT chest post contrast indications
Mass in mediastinum or lungs Malignancy staging scans Lymphoma Pneumonia Trauma Infection Long term smoker Intrathoracic bleeding Unexplained chest pain
CT chest post contrast protocol
Scout will be either AP or dual
Cover from above apices to top of kidneys
Scan supine feet first hands above head on inspiration
Scan on suspended inspiration
Mediastinal recon (ww 400, wl 40) and lung recons (ww 1500, wl -600)
Reformats 3 plane 2-5mm
Usually the technique employed with PET
CT post contrast, contrast requirements
20g cannula proximal to wrist preferably in R arm
Timing for contrast approx. 20 sec.
Use bolus tracking. Be careful of tracker placement. Some sites will use pulmonary artery others descending aorta. Thresholds used will be higher on pulmonary trackers than aortic.
Contrast volumes will vary from 40-75ml injected at 2.5-3.5 ml/sec
Pathologies for CT post contrast
SCC NSCC Lung mets Pneumonia Lung abcess Pericardial effusion Pleural effusion
Protocol alterations for CT trauma thorax
- Trauma patient: lots of staff, quick scan, organised room ready to scan
- Trauma or unconscious patient place equipment away from area to be scanned as much as possible and turn off auto instructions
- Contrast volume dependent on patient size
- Fast non-con scan to prevent patient movement and risk of repeating
Protocol alterations for CT paediatric thorax
-Paediatric patient: parent in the room, sedations/ GA, secure head, organised and quick scan, simple explanation
Dose reduction techniques
If patient hard on hearing turn auto instructions up as you need to remove hearing aids
- Contrast volume dependent on patient size
- Fast non-con scan to prevent patient movement and risk of repeating
Protocol alterations for CT thorax in an uncooperative patient
-Uncooperative: immobilisation devices, alter parameters for a fast scan, staff to help
If patient hard on hearing turn auto instructions up as you need to remove hearing aids
Trauma or unconscious patient place equipment away from area to be scanned as much as possible and turn off auto instructions
- Contrast volume dependent on patient size
- Fast non-con scan to prevent patient movement and risk of repeating
Protocol alterations for CT thorax in geriatric patients
- Geriatrics: secure head, explain simply, organised and quick scan
If patient hard on hearing turn auto instructions up as you need to remove hearing aids
- Contrast volume dependent on patient size
- Fast non-con scan to prevent patient movement and risk of repeating
Indications for CTPA
?PE
Protocol for CTPA
Now seen as gold standard in detection of PE’s
Scan supine feet first on inspiration. Important for pt not to Valsalva
Recon standard algorithm (WW 600 WL 60, wider to dull contrast and reduce artefact) and lung algorithm.
Reformat 3 planes average 2-3mm and slab MIPS 8-10mm
Contrast requirements for CTPA
Cannula 18g R arm large vein
50-75ml contrast @ 4-5ml sec
Some sites use duel inj saline push
Tracker must be placed over pulmonary artery
(pulmonary trunk)
possible pathologies for CTPA examination
PE
Indications for CTA thoracic aorta
? aneurysm
? dissection
Surgical planning
CT thoracic aorta protocol
Scan supine feet first on inspiration. Important for pt not to Valsalva
Scan on inspiration from above arch to base of lungs. Some sites will include abdo aorta to iliac bifurcation
Standard algorithm, lung recon at some sites but not all
Window level and width should be individualised to demonstrate difference between contrast and calcium in the vessels. (WW 800 WL 300 approx start)
Reformats 3 planes averaged 2-3mm, MIP 8-10mm, 3D Volume rendered 3D MIP
Contrast requirements for CT thoracic aorta
Cannula 18g R arm large vein
Contrast 75-100ml @ 4-5mls/sec. duel injection saline push at some sites
Tracker placed over descending Aorta
Possible pathologies seen on CT thoracic aorta
dissection
aneurysm
Describe instructions to patient
- Procedure explanation: hold breath
- Remove metal from chest area. (piercings, jewellery)
- Consider MAR for permanent metal
- If patient hard on hearing turn auto instructions up as you need to remove hearing aids
-Trauma or unconscious patient place equipment away from area to be scanned as much as possible and turn off auto instructions
Dose considerations (12)
Pitch closer to 1 to decrease scan time (critical cases)
Making the non con scan a fast scan: reducing dose and reducing risk of having to repeat scan
Change contrast volume (dependent on patient size)
Change technical factors dependent on patient size: reduce kV, mAs
Change tube rotation time (slow down to gain appropriate exposure)
Reduce scan range to reduce radiation exposure and maximise resolution
SFOV is appropriate: tight to maximise spatial resolution
Automatic exposure control: Automatically adjusts exposure (mA) for attenuation differences of tissue types and thicknesses.
Tight collimation: Accurate pre-patient collimation reduces dose post-patient collimation picks up unhelpful scatter and improves image quality
Bowtie filter: shape’s and hardens the beam increasing uniformity, removes low energy x-rays and increases average energy beam; lower absorbed dose to patient
Centre patient in isocentre correctly
Lead shielding if needed
If a patient presents with the following, what protocol would you do and what pathology could be present?
- 22 yr old BIBA
- Stabbed in Lt chest by knife
- Haemo unstable
- HR 110
- CXR ?Pnx ?Haemo
- UWSD in place
-CTA thoracic aorta to assess where the patient is bleeding: aortic or venous
- Pneumothorax
- Haemothorax
- Sources of blood
- See path of knife; injured heart/surrounding organs
If a patient presents with the following, what protocol would you do and what pathology could be present? - 71 yr old female Abdo pain - HR 136 irregular - BP 70/35 - Temp 36.6C RR 32 - O2 sats 92% on RA
CTA thoracic aorta: find cause of abdo pain/bleeding
Potential ruptured AAA
- Abdo pain
- Irregular heart rate (compensate for lost blood somewhere)
- Low BP (good indication there is a bleed)
- RR (becoming distressed)
