9. Nonvascular interventional radiology Flashcards
What are the advantages of US guidance in interventional radiology?
- availability
- continuous and real-time scanning
- any imaging plane
- feasible for bedside
What are the disadvantages of US guidance in interventional radiology?
- depth resolution is limited
- certain structures (bone, air) produce acoustic shadowing
- operator-dependent
- needs practice
What are the advantages of fluoroscopy guidance in interventional radiology?
- real-time guidance
- high spatial resolution
What are the disadvantages of fluoroscopy guidance in interventional radiology?
- radiation exposure (ionizing)
- soft tissue contrast is poor
- 2D display
What are different planes for US guidance?
in-plane needle visualization: needle is parallel to US beam
out-of-plane needle visualization: needle is perpendicular to the US beam
What is fluoroscopy guidance used for?
vascular, lymphatic, bile duct, genitourinary, gastrointestinal and musculoskeletal interventions
What are the advantages of CT guidance in interventional radiology?
- approach deeper areas that aren’t visible on US
- 3D display
- good spatial resolution
What are the disadvantages of CT guidance in interventional radiology?
- radiation exposure (ionizing)
- time-consuming
What are the advantages of MR guidance in interventional radiology?
- approach deeper areas than US
- 3D display
- non-ionizing
- great soft tissue contrast
What are the disadvantages of MR guidance in interventional radiology?
- availability
- cost
- MRI compatible instruments
What are the advantages of fusion imaging guidance in interventional radiology?
identifying lesions that are barely visible on US
What are the disadvantages of fusion imaging guidance in interventional radiology?
- time consuming
- special instruments
- need for softwares
How to choose the imaging modality for biopsy?
- use the imaging that demonstrates the lesion most clearly (if possible)
- if there is more than one that provides good visualization then choose the simpler/available one
Overview of FNAB
- 21-23G needle
- local anesthesia is not required
- used for both solid and cystic lesions
- SAFE: simple, accurate, fast and economic
- major disadvantage: relatively small sample and cannot differentiate b/w in situ cc. or invasive cc. (cytological only)
Overview of core biopsy
- 14-20G needle
- local anesthesia and small incision is required
- used for solid lesions only
- vacuum-assisted core biopsy for breast microcalcifications
What are the drainage methods?
- trocar technique: usually US guided, and there is a trocar used for direct punture to place tubes and drains
- Seldinger technique: two step process
What are the ablation techniques?
- thermal ablation: uses heat or cold (cryoablation) to destroy tissue
- nonthermal ablation: chemical ablation by processes such as irreversible electroporation
What is radiofrequency ablation?
- an electric circuit is formed within the patient’s body for concentrated heat generation that can destroy tissue
- “heat sink” effect is when the effectiveness is limited because a large vessel is near the target and the flow of blood produces a cooling effect
What is microwave thermoablation?
- rotating, frictional movement of water molecules generates heat
- radiofrequency/microwave ablation can be used in combination with other therapies, in case of tumors smaller than 3cm
What is cryoablation?
- application of extreme cold by liquid nitrogen (or He-Ar) to destroy tissue
- usually for kidney, breast and prostate tumors
- important for renal tumor ablation when the patient has comorbidities that contraindicate surgery, or when the patient requests minimally invasive treatment
What is laser ablation?
- optical fibers are used through a needle to transmit a laser light that destroys tissue
- less traumatic ablation method, and has least risk of bleeding
Overview of percutaneous chemical ablation
- direct puncture and injection of chemical compounds to coagulate or dehydrate cells
- 96% ethanol is most often used
Overview of irreversible electroporation
- micro-millisecond electric pulses that increase cell membrane permeability and thus lead to cell death
- no “heat-sink” effect
What are the indications for biliary interventions?
- biliary obstruction
- bile leakage
- biliary stone removal
