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Page 10 of 13 Misra et al. Vessel Plus 2022;6:32 https://dx.doi.org/10.20517/2574-1209.2021.104

Aortic root dilation:
Aortic root dilation that has been well-established and reported in patients with repaired TOF can be
accurately assessed. Inadequate presentation suspicious for dissection CT scan may be an imaging modality
of choice due to the rapidity with which it can be obtained and the spatial resolution it provides.

Advantages
Widely available, very quickly performed, noninvasive, excellent spatial resolution such that anatomical
abnormalities/smaller structures such as coronary arteries can be easily resolved (high contrast-to-noise
ratio), can be performed in patients with contraindications for CMR such as pacemakers and defibrillators,
and allows successful imaging in those patients with significant metallic artifacts on CMR . Shorter scan
[33]
duration makes it attractive for those with claustrophobia, anxiety and in less co-operative patients such as
children. RV volumetric and functional data can be obtained with offline processing.

Limitations
CT scan Involves ionizing radiation that increases the risk for carcinogenesis, particularly with the need for
[34]
recurrent scanning and electrocardiographically gated scans . For this reason, pregnancy would be a
relative contraindication. Temporal resolution is somewhat lower than CMR and echocardiography. There
is a need for a robust kidney function for the use of contrast, and risks/complications related to contrast can
be of importance, particularly in those with compromised renal function. To improve image quality,
minimize cardiac motion, and prolong the diastolic window in order to image coronary arteries accurately,
beta-blockade (oral or intravenous) can be used. Another limitation may be the unavailability of advanced
scanner/scanning capabilities in many institutions. Finally, the inability to obtain hemodynamic
information such as velocity of flow/rate may make this less attractive of an option in general except for
those situations when there is a contraindication for CMR.

Images

NUCLEAR SCAN IMAGING FOR EVALUATION OF REPAIRED TOF
Diagnostic role
There is a clear role for nuclear scintigraphy in those situations when a CMR cannot be performed, and
[35]
there is a need for quantification of differential pulmonary artery blood flow . The quantification of
differential flow to each lung assumes an important role in patients with branch pulmonary artery stenosis,
particularly before and after intervention in the form of angioplasty/stent placement. Inherent to the
technique, a quantitative assessment of ventilation-perfusion ratio can be obtained. Other occasional
instances where nuclear imaging can be utilized include ventricular function evaluation, myocardial
[36]
perfusion evaluation, and assessment of viability .
Advantages
Nuclear scintigraphy is a reliable technique to measure differential blood flow, ventricular function, and
viability. It can be performed in those with contraindications for CMR, such as incompatible metallic
implants/pacemakers/ICD.

Limitations
Nuclear scanning leads to exposure to ionizing radiation, which increases with the repeated examination. It
is not a perfect technique for the assessment of RV function/viability.