Related Experiment Video
Updated: Oct 7, 2026
Echocardiographic Evaluation of Atrial Communications before Transcatheter Closure
Published on: February 8, 2022
Embolic distribution through patent foramen ovale demonstrated by (99m)Tc-MAA brain SPECT after Valsalva radionuclide
K Hayashida1, K Fukuchi, M Inubushi
1Department of Radiology, National Cardiovascular Center, Suita, Osaka, Japan.
Unlabelled:
Cryptogenic stroke might relate to paradoxical embolism stemming from right-to-left shunt caused by patent foramen ovale (PFO). We performed radionuclide venography using the Valsalva maneuver, followed by (99m)Tc-macroaggregated albumin (MAA) brain SPECT to investigate the fate of emboli originating from the lower extremities.
Methods:
Ten patients (9 men, 1 woman; mean age, 61 +/- 17 y) with PFO underwent radionuclide venography with and without the Valsalva maneuver on the whole-body image, followed by brain SPECT with (99m)Tc-MAA to determine the cortical uptake that would detect right-to-left shunt. After counts in each region of interest (ROI) were normalized by comparison with the averaged count, the distribution of MAA was compared with that of (99m)Tc-hexamethyl-propyleneamine oxime (HMPAO) brain SPECT by drawing ROIs on frontal, temporoparietal (anterior circulation territory), occipital, and cerebellar areas (posterior circulation territory).
Results:
The thyroid on the whole-body scan was visualized after the Valsalva maneuver in 2 of the 10 patients. In 7 of 10 patients, 56 ROIs in the visualized cortical uptake showed that the distribution of MAA correlated well with that of HMPAO according to the equation: HMPAO = -71.21 + 1.71 x MAA, (r = 0.575, P < 0.01). The excess difference in the relative counts in the posterior over anterior circulation territory was 5.6% and 16.1% of the HMPAO and MAA values, respectively.
Conclusion:
Brain SPECT with (99m)Tc-MAA was more sensitive than thyroid visualization in detecting right-to-left shunt. The excess flow in the posterior cerebral circulation indicated an increased likelihood of cerebral emboli originating from the lower extremities and indicated that the flow difference between HMPAO and MAA probably resulted from poor linearization of HMPAO in the high-flow area.
Insights
Patent foramen ovale (PFO) can cause cryptogenic stroke via paradoxical embolism. Technetium-99m-MAA brain SPECT effectively detects right-to-left shunts, indicating potential lower extremity emboli in PFO patients.
Area of Science:
- Nuclear Medicine
- Radiology
- Neurology
Background:
- Cryptogenic stroke may result from paradoxical embolism due to patent foramen ovale (PFO) and right-to-left shunts.
- Investigating the origin of emboli in PFO patients is crucial for stroke prevention.
Purpose of the Study:
- To evaluate the efficacy of radionuclide venography with Valsalva maneuver and (99m)Tc-macroaggregated albumin ((99m)Tc-MAA) brain SPECT in detecting right-to-left shunts.
- To assess the origin of potential emboli from lower extremities in patients with PFO.
Main Methods:
- Ten patients with PFO underwent radionuclide venography with and without the Valsalva maneuver.
- Brain SPECT using (99m)Tc-MAA was performed to quantify cortical uptake, indicating shunt presence.
- Regions of interest (ROIs) were analyzed and compared with (99m)Tc-hexamethyl-propyleneamine oxime (HMPAO) SPECT.
Main Results:
- Thyroid visualization occurred in 2 of 10 patients post-Valsalva maneuver.
- (99m)Tc-MAA distribution correlated well with (99m)Tc-HMPAO SPECT in 70% of patients (r = 0.575, P < 0.01).
- A significant excess relative count was observed in posterior circulation territories using (99m)Tc-MAA compared to (99m)Tc-HMPAO.
Conclusions:
- Brain SPECT with (99m)Tc-MAA is more sensitive than thyroid visualization for detecting right-to-left shunts.
- Increased posterior cerebral circulation uptake suggests a higher likelihood of emboli originating from the lower extremities.
- (99m)Tc-MAA demonstrated superior sensitivity in identifying shunt-related cerebral blood flow alterations.
Related Concept Videos
01:20Imaging Studies for Cardiovascular System II:Types of Echocardiography
Types of Echocardiography
Transthoracic Echocardiography (TTE)
TTE is the most common type of echocardiogram which involves placing a transducer on the patient's chest, emitting sound waves to create heart images. TTE is invaluable for evaluating the heart's size, structure, and motion, making it particularly useful for diagnosing...
01:13Radiological Investigation III: Pulmonary Angiogram and PET Scan
Pulmonary Angiogram
A Pulmonary Angiogram is an invasive procedure involving injecting a contrast medium through a catheter threaded into the pulmonary artery or the right side of the heart to visualize the pulmonary vasculature. Computed Tomography (CT) scans have mainly replaced this...
01:30Radiological Investigation II: MRI and Ventilation Perfusion Scan
Magnetic Resonance Imaging (MRI) and Ventilation Perfusion Scans are two radiological investigations that offer detailed diagnostic images of the body, particularly lung structures.
MRI
MRI uses magnetic fields and radiofrequency signals to distinguish between normal and abnormal tissues. This technology provides a more detailed diagnostic image than CT scans, enabling it to characterize pulmonary nodules, stage bronchogenic carcinoma, and evaluate inflammatory activity in...
01:24Magnetic Resonance Imaging