ARRT Vascular-Interventional Radiography cheat sheet

DSA subtraction requires a mask image acquired before contrast arrival; patient motion between mask and contrast frames produces misregistration artifact appearing as dark or light halos at vessel edges.

Pixel shift (remasking) is the post-processing correction for misregistration; it realigns the mask to the contrast image without re-exposing the patient.

Spatial resolution of a digital angiographic system is limited by pixel size at the image intensifier or flat-panel detector; larger field of view (FOV) spreads the same matrix over more area and reduces spatial resolution.

Contrast resolution is governed by bit depth: a 10-bit image displays 1024 gray levels, a 12-bit image 4096 gray levels.

Frame rate selection trades temporal resolution against dose: 30 frames/sec gives smoother motion depiction than 3 frames/sec but delivers proportionally more exposure per second.

Roadmapping overlays a previously acquired contrast-filled vessel image on live fluoroscopy to guide catheter and wire navigation.

Magnification modes improve spatial resolution by using a smaller input area of the detector but increase patient dose because the same output brightness requires higher exposure.

Quantum mottle appears as grainy noise when too few photons reach the detector; it is reduced by increasing exposure (mAs) or increasing detector dose, not by window/level adjustment.

Vessel stenosis quantification by DSA is performed by comparing the diameter of the narrowed segment with the adjacent normal reference diameter, expressed as a percentage reduction.

Informed consent for angiography must document the procedure, its benefits, material risks (bleeding, infection, contrast reaction, vessel injury, radiation risk), and alternatives.

Contrast-induced nephropathy risk is increased by pre-existing renal insufficiency, diabetes mellitus, dehydration, and large contrast volume; pre-procedure serum creatinine and eGFR are the standard screening labs.

Patients with a documented prior anaphylactoid reaction to iodinated contrast require premedication with a corticosteroid (e.g., prednisone) plus an antihistamine, typically beginning 13 hours before contrast.

Metformin is commonly withheld after iodinated contrast in patients with renal impairment because of lactic acidosis risk; reinstitution follows renal function reassessment per institutional protocol.

Post-angiography access-site care includes bed rest, pressure dressing, and monitoring the puncture site for hematoma, bruit, or expanding mass; a new pulsatile mass suggests pseudoaneurysm.

Pulse checks (distal pulses, capillary refill, temperature, color, sensation) are documented before and after the procedure on the accessed extremity.

Renal protective measures include hydration with isotonic saline and using the lowest contrast volume consistent with diagnostic and therapeutic needs.

Patient education before the procedure includes fasting instructions, expected sensations (warmth or flushing with contrast injection), and the need to remain still during image acquisition.

Seldinger technique: needle puncture, guide wire insertion, needle removal, catheter introduction over the wire; the wire must be secured at all times to prevent loss into the vessel.

Diagnostic catheter shapes are selected by vessel anatomy: a cobra or visceral curve for selective abdominal branches, a Simmons or reverse curve for vessels arising at sharp downward angles.

Angioplasty balloon diameter should match the diameter of the adjacent normal vessel; underexpansion leaves residual stenosis and oversizing risks dissection or rupture.

Stent placement requires adequate proximal and distal landing zones in relatively normal vessel; stents are deployed over a guide wire and typically post-dilated to ensure full expansion.

Embolization agents include coils (precise, permanent, proximal occlusion), gelatin sponge (temporary, intermediate vessel), and liquid agents such as NBCA or ethylene vinyl alcohol copolymer (distal penetration).

Thrombolysis for arterial occlusion delivers a fibrinolytic agent directly into the thrombus via a multi-side-hole infusion catheter, with fibrinogen and hemoglobin monitored during infusion.

IVC filter indications include contraindication to or failure of anticoagulation in a patient with documented deep vein thrombosis or pulmonary embolism.

Transjugular intrahepatic portosystemic shunt (TIPS) creates a channel between the hepatic vein and portal vein to decompress portal hypertension; it is used for variceal bleeding or refractory ascites.

Percutaneous nephrostomy access is obtained through a posterior calyx, typically at the 12th rib margin, to avoid pleural and vascular injury.

The inverse square law states that dose rate decreases with the square of the distance from the source; doubling the distance from the patient to the tube reduces dose to one quarter.

Fluoroscopic dose rate is proportional to the square of the tube potential (kVp); reducing kVp lowers dose but also lowers penetration and contrast.

Pulsed fluoroscopy reduces patient dose in proportion to the pulse rate: 15 pulses/sec delivers roughly half the dose of 30 pulses/sec for the same exposure per pulse.

Last-image-hold freezes the final fluoroscopic frame and eliminates additional exposure during review; it is a primary dose-reduction practice.

The image intensifier or flat-panel detector should be positioned as close to the patient as possible, and the x-ray tube as far from the patient as possible, to reduce skin dose.

Magnification modes increase dose because a smaller detector area is used, requiring higher exposure to maintain brightness; they should be used only when resolution is required.

Collimation to the region of interest reduces patient dose and improves image contrast by limiting scattered radiation reaching the detector.

Occupational protection: lead apron (0.5 mm Pb equivalent), thyroid shield, and dosimeter worn at collar level outside the apron; personnel should maximize distance and use shielding.

Air kerma (mGy) and kerma-area product (Gy·cm²) are the standard dose metrics displayed on modern interventional systems for dose tracking.