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CT & Ultrasound Intervention

Doctor Operating CT Scanner

Angiography & Intervention involves cross-modality training and dual-imaging with angiography and computed tomography (CT), or angiography and ultrasound (U/S), or all three! Interventional radiographers can be trained in operating angiography systems (which also have cone-beam CT capabilities), CT scanners for intervention, and ultrasound machines as well. Some radiographers have foundation knowledge and skills in CT before upskilling into angiography, as well as operating theatre skills which are also valuable. Ultrasound skills are typically leant on the job, gaining more experience with different types of procedures and different anatomical areas being scanned.

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CT Intervention

What procedures can this involve?

What patient preparation is required?

CT Scan Machine

 PREPARATION

Patient preparation is important before starting any procedure.

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  • Have pathology and bloods been collected?

  • Is the patient on any blood thinning medication (anti-coagulants)?

  • Check for International Nationalised Ratio (INR) results? Should be <1.5 for any interventional procedure.

  • Any allergies or previous iodinated contrast media reactions?

  • ​Monitoring for patients under sedation or general anaesthesia.

  • Prepare the contrast injector if needed.

  • Some interventions can benefit from using both ultrasound and CT guidance. The patient is scanned prior to the procedure using the appropriate probe (linear for superficial and vascular access, and curved array for deep organs/tissue).

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PATIENT POSITIONING

  • Speak to the interventional radiologist to ensure that the correct patient position is used.

  • Check the request form and review previous imaging, especially cross-sectional imaging such as CT, MRI, and SPECT.

  • Always check and consider patient comfort and mobility. Additional staff support? PAT slide?

  • Any intervention that is head and neck (e.g. cervical injections) or lumbar region/prone should be head-first.

  • Any intervention that is supine chest and/or abdomen should be feet-first.

  • Patients can be supine, prone, or even decubitus.

  • Use of pillows, sponges, and support straps to stabilize and minimize patient movement during the scan and procedure.

SCANNING

  • Check and review the previous imaging to see the region of interest (ROI).

  • Is contrast media required for this biopsy to avoid surrounding vasculature? Or is it needed to highlight the tumour or mass?

  • Determine the contrast injection rates (fill up the syringe to max. 100-150ml). Check the size of the cannula. Is it arterial (~20-30 sec), portal venous (70 sec), or delayed?

  • Always check patient comfort and positioning of any lines, tubing, and monitoring.

  • Place and secure a marking grid over ROI.

  • Perform scout views and appropriate slice thicknesses for the ROI (e.g. 2.5 or 5 mm). Adjust mAs depending on patient size.

  • Scan the patient with clear instructions on respiration, contrast injection etc.

IMAGE INTERPRETATION

  • Interpret the CT scans acquired for the given patient, with the marking grid in profile along the axial volume.

  • Change window settings as required (e.g. lung window for chest lesions, soft tissue for para-aortic or abdominal masses, and bone window for facet joint injections).

  • Correlate CT intervention scans with previous scans done to determine size and location, and any changes since the last imaging.

  • Note that there may be differences due to patient positioning and respiration timing.

  • The interventional radiographer can mark the patient under the correct slice number and grid coordinates.

  • The intervention (biopsy, injection, ablation, or other treatment) can proceed with "step and shoot" technique to acquire sequential axial images to check and guide intervention and positioning.

What about Ultrasound Intervention?

It takes 10,000 hours of deliberate practice to become an expert.

- Malcolm Gladwell

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