Wednesday, April 24, 2019

Think before you order a test: High resolution CT scan (HRCT)

Hello, 

Let's talk about HRCT today!

HRCT is the use of thin-section CT images (0.625-mm to 1.5-mm slice thickness) with a high spatial frequency reconstruction algorithm, to detect and characterize diseases that affect the pulmonary parenchyma and small airways.

HRCT cuts THIN slices.

Awesome, isn't it? Why not use an HD camera for every photograph?

Because it comes with a price!


1. Substantially increased radiation dose to the patient in comparison to the usual CT scan.

Even with reduced radiation dose scanning technique, the radiation dose of HRCT can exceed the radiation dose of a chest radiography by 100 times!!!

2. HRCT images spaced at 10-mm to 20-mm intervals throughout the lungs.

This means that you for every 1 mm you image, you miss 10-20mm in between - essentially missing out on 90% of the lung!!!

That is why, HRCT should be restricted to carefully selected indications such as investigation of suspected interstitial lung disease, airspace diseases and in immunocompromised patients with acute parenchymal abnormalities, where differential diagnosis or a specific diagnosis can be made.

Thank you, Dr. M, for teaching me this!

Source:
Radiation exposure from Chest CT: Issues and Strategies
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2822293/

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