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Multiple coronary stents – in-stent restenosis?

Le Qin, MD, PhD1; Haipeng Dong, MD1; Fuhua Yan, MD, PhD1,2; Xi Zhao, MD3; Wenjie Yang, MD, PhD1
1 Department of Radiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, P. R. China
2 College of Health Science and Technology, Shanghai Jiao Tong University School of Medicine, Shanghai, P. R. China
3 Siemens Healthineers, China

2025-01-29
A 71-year-old male patient with a history of coronary stenting came to the hospital for a regular follow-up. Four stents had been implanted, namely in the left main (LM), proximal and middle left anterior descending (LAD) and the circumflex (Cx) coronary arteries. A coronary CT angiography (CCTA) was performed on a dual source photon-counting detector (PCD) CT scanner, NAEOTOM Alpha®, using an ultra-high resolution (UHR) scan mode (Quantum HD Cardiac), to assess the coronary stent patency and plaque burden.
UHR CCTA images showed three interconnected stents – one in the LM and proximal LAD (4 mm), two in the middle LAD (3 mm and 2.75 mm) – all were patent without any evidence of in-stent restenosis (ISR). Another single stent in the proximal Cx (3.5 mm) was seen with signs of intimal hyperplasia in the mid portion, causing a less than 50% narrowing of the lumen. Multiple calcified plaques in the proximal and distal Cx, the second obtuse marginal branch and the right coronary artery (RCA), as well as two mixed plaques in the mid RCA were seen, causing mild stenosis. CT findings were classified as CAD-RADS 2/S. Coronary ISR was ruled out and, as the patient was asymptomatic, no further invasive work-up was considered necessary.
An axial UHR image acquired with PCD-CT and a coronal MPR image show the mass of tophaceous gout in contact with the malleus and the tympanic segment of the facial nerve. The incus is not affected.
Courtesy of Department of Radiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, P. R. China

Fig. 1: A curved MPR image (Fig. 1a) shows three interconnected stents in the LM and LAD without evidence of ISR. The stent struts and the components of calcified and mixed plaques outside the stents are visually well distinguished. A single stent in the proximal Cx (Fig. 1b) is seen with signs of intimal hyperplasia in the mid portion (arrow), causing a less than 50% narrowing of the lumen. Multiple calcified plaques in the proximal and distal Cx and the RCA (Fig. 1c), as well as two mixed plaques (dotted arrows) in the mid RCA are present, causing mild stenosis.

An axial UHR image acquired with EID-CT shows a millimetric calcified mass anteriorly in the middle ear, suggesting a residual or recurrent gout tophus. In a paracoronal image, a gap between the stapes head and the incus interponate is seen, suggesting a suboptimal contact between the remodelled incus and the stapes.
Courtesy of Department of Radiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, P. R. China

Fig. 2: Curved MPR images, reconstructed with standard images (Fig. 2a) and UHR images (Fig. 2b), show an imaging comparison of the stent in the proximal Cx. In standard image, the intimal hyperplasia in the mid portion of the stent appears to cause an ISR, while in UHR image, a less than 50% narrowing of the lumen is clearly shown, ruling out an ISR.

Oblique MPR images and cVRT images show a dislocated medial part of the TORP in the retrotympanon and a revised TORP centered on the oval window. UHR images are acquired with PCD-CT.
Courtesy of Department of Radiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, P. R. China

Fig. 3: A cinematic VRT image rendered with UHR images shows a three-dimensional view of the coronary tree with the stents and the calcified plaques highlighted in blue.

Coronary ISR is defined as a higher than 50% re-narrowing of the previously stented arterial lumen, requiring revascularization. It is frequently encountered, due to stent-related, procedure-related and biological factors. Intracoronary imaging, such as angiography, intravascular ultrasound (IVUS) and optical coherence tomography (OCT) have been performed to identify and characterize the underlying mechanisms and substrate of ISR and to guide clinical management. [1] CCTA assessment for the patency of coronary stents, using conventional energy-integrating detector (EID) CT, has been limited to a borderline of 3 mm stent diameter in the American Heart Association guidelines, due to the challenge of blooming artifacts caused by stent struts. [2] Potential improvement has been shown with the introduction of a UHR scan mode provided by a dual source PCD-CT, NAEOTOM Alpha. In the PCD, an electric field, instead of physical separation as in an EID, is applied to define smaller detector sub-pixels which are read out separately to increase the spatial resolution while retaining geometrical dose efficiency. In the dual source PCD-CT, UHR data acquisition is achieved at a temporal resolution of 66 ms. A recent study using this mode achieved a 100% negative predictive value for coronary stent patency evaluation against invasive angiography as the reference standard. [3] 

In this case, an ISR is ruled out in the UHR images (0.2 mm, kernel Bv72), as the hypodense intimal hyperplasia causing a less than 50% narrowing of the lumen, is clearly visualized. However, when images are reconstructed at 0.6 mm with a kernel of Bv48, simulating a standard image reconstruction in CCTA with an EID-CT, an ISR could have been diagnosed leading to the necessity of further invasive work-up. The combination of high spatial and temporal resolution provided by PCD-CT effectively improves the visualization of coronary stents, minimizing the blooming interference caused by calcified plaques and stent struts.[4] This helps the physicians to make a confident assessment of the stent patency and the appropriate decision on patient management.

Scanner

Scan area

Heart

Scan mode

UHR mode (Quantum HD Cardiac), Retrospectively ECG gated spiral scan

Scan length

148 mm

Scan direction

Cranio-caudal

Scan time

8.1 s

Tube voltage

120 kV

Effective mAs

40 mAs

IQ level

64

Dose modulation

CARE Dose4D

CTDIvol

20.5 mGy

DLP

332 mGy*cm

Rotation time

0.25 s

Pitch

0.19

Slice collimation

120 x 0.2 mm

Slice width

0.2 mm

Reconstruction increment

0.2 mm

Reconstruction matrix

768 x 768

Reconstruction kernel

Bv72, QIR 4

Heart rate

59 bpm

Contrast

400 mg/mL

Volume

75 mL + 43 mL saline

Flow rate

4.3 mL/s

Start delay

Bolus tracking triggered at 80 HU in the ascending aorta + 7 s

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