Tetralogy of Fallot (TOF)

Benefits or pitfalls of dual-energy CT

13-year-old male presented for imaging 13 years after surgery for Tetralogy of Fallot. Physical examination showed pulmonary stenosis six months ago.

The use of spectral low virtual monoenergetic, iodine density, and virtual non-contrast reconstructions allowed for a more detailed evaluation of cardiac anatomy and post-surgical changes after surgery for Tetralogy of Fallot.

Key images

Findings

Axial images, curved planar reformation (CPR)

The conventional image demonstrates enlargement of all cardiac chambers, but the boundaries between the cavities and abnormal cardiac structures are not clear. Spectral virtual monoenergetic 50 keV image and iodine density map allow for improved identification of pulmonary stenosis and overriding aorta, while VNC image clearly shows postoperative changes after ventricular septal defect repair.

Discussion

Due to the low contrast agent dose and altered hemodynamics after surgical correction of Tetralogy of Fallot, there is poor opacification of cardiac chambers, which limits identification of relevant cardiac structures. Spectral CT enabled retrospective identification of all necessary information, which is especially helpful in patients with congenital heart disease.

50 keV Image

Conventional image: Coronary and pulmonary arteries cannot be identified clearly.

Spectral virtual monoenergetic 50 keV image: Coronary and pulmonary arteries can be delineated clearly.

Conventional Image

Monoenergetic 50 keV Image

Conventional axial image: The boundaries of the heart chambers are not clear. The CT value of the LV cavity is 158.8 HU.

Spectral virtual monoenergetic 50 keV axial image: Clearly shows the boundaries of all cardiac chambers. The CT value of the LV cavity is boosted to 438.8 HU.

Conventional Image

Monoenergetic 40 keV Image

Conventional image: Aorta and pulmonary artery have poor enhancement and poor contrast.

Monoenergetic 40 keV image: Aorta and pulmonary artery have good contrast, which can display the pulmonary stenosis clearly (arrow).

Conventional image MPR: Left and right ventricle are poorly enhanced. The lesion with high density (arrow) was suspected as partial ventricular septal defect with aorta overriding left and right ventricles.

Virtual monoenergetic 50 keV image: Left and right ventricles now show good enhancement. The boundary of the membranous septum is clear. The CT value of the lesion (arrow) remains unchanged, which means that this lesion is not a structure that contains contrast agent.

Iodine density

Iodine density image MPR: The lesion (arrow) has no iodine uptake, and thus it was considered as postoperative changes.

History

Benefits or pitfalls of dual-energy CT

Key images

Findings