THE TARE PRE-TREATMENT WORKUP:
MAPPING ANGIOGRAM AND MAA SCAN
Before Y-90 radioembolization can proceed, a mandatory planning session โ the mapping angiogram and MAA scan โ is performed to characterise hepatic anatomy, quantify lung shunting risk, and determine whether treatment is safe. This guide explains every step.
analyticsAt a Glance
- check_circleThe mapping angiogram identifies the hepatic arterial supply to the tumour and detects any vessels that could carry microspheres to non-target organs
- check_circleThe Tc-99m MAA (macroaggregated albumin) scan simulates microsphere distribution and quantifies lung shunting fraction
- check_circleA lung shunt fraction above 20% typically contraindicates TARE โ preventing radiation pneumonitis
- check_circleMapping and MAA scan are performed in the same session, typically 1โ2 weeks before Y-90 treatment
Why the Pre-Treatment Workup Is Mandatory for Every Patient
Unlike most medical treatments, TARE cannot be offered to a patient on the basis of imaging and blood tests alone. A dedicated pre-treatment planning procedure โ the mapping angiogram and MAA scan โ must be performed before any treatment decision can be finalised. The reasons are safety-critical: microspheres injected into the wrong vessel can cause radiation pneumonitis (from lung shunting), gastric or bowel ulceration (from gastrointestinal vessel communication), or cholecystitis (from cystic artery access).
โThe mapping session is not a formality โ it is the procedure that determines whether TARE is physically safe for this patient's anatomy.โ
Hepatopulmonary Shunting โ The Key Safety Question
Some patients have abnormal vascular connections between the hepatic arteries and the pulmonary circulation. If Y-90 microspheres shunt to the lungs in significant quantities, the result is radiation pneumonitis โ a potentially severe and irreversible lung injury. The MAA scan quantifies the lung shunt fraction before treatment to prevent this.
Gastrointestinal Vessel Identification
Aberrant or parasitic hepatic artery branches can arise that supply adjacent GI organs โ stomach, duodenum, colon, gallbladder. Microspheres entering these vessels cause radiation-induced ulceration and necrosis. The mapping angiogram identifies and coils off (embolizes) these vessels before treatment.
The Mapping Angiogram and MAA Scan โ Step by Step
The entire pre-treatment workup is performed in a single session in the angiography suite, typically lasting 1โ2 hours. Here is a detailed walkthrough of what happens.
- 1
Arterial Access โ Femoral or Radial
Using local anaesthesia and conscious sedation, a vascular sheath is inserted into the femoral artery (groin) or radial artery (wrist). A guide catheter is advanced under X-ray fluoroscopy guidance through the aorta to the coeliac trunk and superior mesenteric artery.
- 2
Hepatic Arteriogram
Contrast medium is injected into the hepatic arteries while X-ray images are acquired โ mapping the entire hepatic arterial anatomy: proper hepatic artery, right and left hepatic artery branches, and any accessory or replaced hepatic arteries arising from the superior mesenteric artery.
- 3
Identification and Coiling of Aberrant GI Vessels
If any gastric, duodenal, cystic, or colonic arteries arising from the hepatic circulation are identified, the interventionalist places small metallic coils into these vessels to permanently occlude them โ preventing microspheres from reaching non-target GI organs during the actual treatment.
- 4
Tc-99m MAA Injection
After angiographic mapping, technetium-99m macroaggregated albumin (Tc-99m MAA) particles โ which behave similarly to microspheres in vascular flow โ are injected through the catheter at the intended treatment injection position. MAA particles are temporary and clear from the body within hours.
- 5
Nuclear Medicine SPECT/CT Scan
The patient is transferred to the nuclear medicine department (same day) for a SPECT/CT scan. This imaging shows where the MAA particles distributed โ mapping the expected microsphere distribution across the liver and any extrahepatic organs, particularly the lungs.
- 6
Lung Shunt Fraction Calculation
The SPECT/CT results are used to calculate the lung shunt fraction (LSF) โ the percentage of injected MAA activity that distributed to the lungs. LSF is the primary safety gating parameter for TARE eligibility.
- 7
Treatment Decision โ Proceed, Modify, or Decline
If LSF <10%: standard TARE proceeding. LSF 10โ20%: proceed with activity reduction to limit lung dose. LSF >20%: TARE is typically contraindicated โ risk of radiation pneumonitis is unacceptable. This decision is made by the interventional oncology team within a few days of the mapping session.
Lung Shunt Fraction โ Decision Framework
The lung shunt fraction (LSF) calculated from the MAA SPECT/CT scan is the primary safety gate for TARE eligibility. This table summarises the clinical decision framework used by most centres.
| LSF Range | Clinical Decision | Activity Adjustment | Rationale |
|---|---|---|---|
| < 10% | TARE proceeds as planned | Standard eligibility โ lung dose well within safe limits | |
| 10โ15% | TARE proceeds with monitoring | Activity modification considered | Lung dose approaches but does not exceed threshold |
| 15โ20% | TARE may proceed with activity reduction | Activity reduced to limit lung dose to <30 Gy | Borderline โ requires dose planning review by dosimetrist |
| > 20% | TARE typically contraindicated | N/A | Unacceptable risk of radiation pneumonitis at any safe therapeutic dose |
Preparing for Your Mapping Session โ Do and Don't
Practical guidance for patients and families preparing for the TARE pre-treatment workup.
Do
- Fast from midnight the night beforeAngiography with conscious sedation requires fasting โ no food after midnight, clear fluids may be permitted until 2โ4 hours before as directed by the team.
- Bring your imaging to the sessionBring recent CT or MRI images (on CD/USB) and the reports โ the interventional radiologist will review them immediately before the procedure to plan the angiographic approach.
- Disclose all current medications โ especially anticoagulants and antiplatelet agentsAspirin, clopidogrel, warfarin, and NOACs must be adjusted or held before arterial access โ specific timing depends on the agent and should be confirmed with the team in advance.
- Arrange someone to drive you homeConscious sedation means you will not be able to drive for 24 hours after the procedure โ ensure a companion is available for the return journey.
Don't
- Don't take metformin before the procedure without checkingMetformin should typically be held before contrast-enhanced procedures โ confirm with the treating team based on your renal function.
- Don't underestimate the procedure durationThe mapping session typically takes 2โ4 hours from admission to discharge โ including preparation, the procedure, recovery, and transfer to nuclear medicine for MAA imaging. Plan accordingly.
- Don't resume anticoagulants without confirmation from the teamAfter femoral arterial access, anticoagulants should not be restarted until the site has been cleared by the team โ typically 4โ12 hours post-procedure depending on haemostasis.
TARE Pre-Treatment Workup โ Key Numbers
Reference figures from the workup process that determine eligibility and safety.
- >20%Lung shunt fraction threshold for TARE contraindicationThe safety cut-off above which risk of radiation pneumonitis from unmodified TARE is unacceptable โ applies to both TheraSphere and SIR-Spheres.
- ~5โ10%Proportion of TARE candidates excluded at mapping due to high LSFThe majority of patients referred for TARE proceed after mapping โ high LSF disqualification is uncommon but must be screened for.
- 1โ2 wksInterval between mapping session and actual Y-90 treatmentSufficient time for coil embolization sites to thrombose fully, LSF results to be reviewed, and activity calculation to be completed.
More from the TARE / Y-90 Resource Library
Continue your Y-90 journey โ from physics and platform comparisons to dosimetry and the complete treatment guide.
Frequently Asked Questions About the TARE Mapping Session
Is the mapping session painful?
The procedure is performed under conscious sedation โ a combination of sedative and analgesic medication that keeps you comfortable and relaxed, but not fully unconscious. Most patients report feeling drowsy and relaxed, with minimal awareness of discomfort. The arterial puncture site (femoral or radial artery) is anaesthetised with local anaesthetic before the catheter is inserted. Some patients describe mild pressure or warmth in the abdomen when contrast dye is injected โ but significant pain is not expected. Post-procedure, mild groin or wrist discomfort at the puncture site is common and usually resolves within 24โ48 hours.
What happens if the MAA scan shows high lung shunting?
If lung shunt fraction is above 20%, TARE is generally considered too risky at a therapeutic dose โ there is no safe way to deliver enough Y-90 to the liver without exceeding the lung radiation dose limit. In this situation, the interventional oncology team will discuss alternative locoregional treatments (TACE, ablation, systemic therapy), whether any measures to reduce shunting (such as portal vein embolization or interim treatments) might change eligibility, or whether a lower-activity 'radiation-reduced' TARE is clinically meaningful for your tumour volume. CancerFax advises on alternative options when TARE is excluded at mapping.
Do I need to be admitted to hospital for the mapping session?
The mapping session is typically performed as a day procedure โ hospital admission in the morning, procedure in the angiography suite, recovery, transfer to nuclear medicine for SPECT/CT imaging, and discharge in the afternoon or evening. Overnight admission is not routinely required unless the patient has significant comorbidities, complex anatomy requiring prolonged intervention, or develops a post-procedural complication. Most patients are discharged with a small pressure bandage at the puncture site and return home the same day.
How CancerFax Helps
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Scheduled for a TARE Planning Session? CancerFax Can Help You Prepare.
CancerFax reviews your liver tumour imaging and liver function results before your pre-treatment workup โ and advises on what to expect at the mapping session and how results will determine your treatment plan.
This content is for informational purposes only and does not constitute medical advice. Always consult a qualified interventional radiologist before making treatment decisions.