HDS Tutorials 2022 Imaging Biomarkers Strand

Hello, dear friend, you can consult us at any time if you have any questions, add WeChat: daixieit

HDS Tutorials 2022 Imaging Biomarkers Strand

Example Exam Questions

Question 1

Briefly explain the difference between an imaging biomarker that is an intensive        variable and an imaging biomarker that is an extensive variable.  For each give, with justification, a suitable example of an imaging biomarker.

[6 marks]

Question 2

Some researchers have developed a novel MRI technique called Gluco-CEST that    can image glucose delivery, uptake and metabolism in cancer.  Non-radioactive         glucose is delivered intravenously using a carefully controlled infusion protocol.         Chemical Exchange Saturation Transfer (CEST) MR imaging is then used to acquire an image. This is a new, emerging type of MRI that enables the detection of low-      concentration marker molecules and can be used to track metabolite dynamics.  In    Gluco-CEST, CEST-MRI is used to image the glucose molecule. The researchers    hope that this technique will provide an imaging biomarker that can be used to detect and measure metabolic activity within tumours in lung cancer patients.  They hope    that this will be an alternative to [18 F]FDG-PET imaging in lung cancer for tumour      detection, staging and identifying metastases.

a)  Describe, with justification, an advantage that Gluco-CEST has compared to FDG-PET imaging for this application.

[2 marks]

b)  Describe an activity that could be conducted to give evidence of the technical validity of Gluco-CEST for this application.

[4 marks]

c)  Describe a study that could be performed to provide evidence of the biological validity of the new imaging biomarker, classifying the type of evidence             provided according to the Bradford-Hill criteria.


Example Answers

Question 1

An extensive imaging biomarker measures an extent or number i.e. "how big" or        "how many", whereas an intensive imaging biomarker measures how much signal     there is i.e. "how hot". An example of an extensive imaging biomarker is tumour         volume measured with CT, which is an extensive imaging biomarker as it measures  how big the tumour is. An example of an intensive imaging biomarker would be DCE- MRI, where the amount of signal measures the uptake of a contrast agent into           tissues within the body.

 

Question 2

a)  In contrast to FDG-PET, which depends on the injection of glucose molecules tagged with a radioactive tracer, Gluco-CEST uses non-radioactive glucose as a contrast agent.  This removes the risks associated with the delivery of an     ionizing radiation dose to the patient.

 

b)  A study could be done in which images are acquired from lung cancer patients on more than one occasion.  The imaging biomarker could be calculated from each imaging procedure and the results compared to measure the differences between the multiple images, which would measure the random error on the   biomarker.  If this were done at the same site on the same scanner, it would    measure the repeatability of the biomarker.  Conversely, if it were done across multiple sites and on different scanners, it would measure the reproducibility    of the biomarker.

 

c)  A study could be done in which FDG-PET and Gluco-CEST images are          obtained from the same lung cancer patients.  The number and size of           tumours with increased metabolic activity, tumour staging and identification of metastases could be estimated from each and the correlation between the     two biomarkers calculated. This would be an example of coherence with       known science.











2022-08-02