Figure 1: Bypass Graft in Volume Rendering.

In 1998, the patient underwent another angioplasty with stent in segment II of the saphenous-RCA graft.
In December 2004, the patient was examined by Cardiac CT. The exam was performed on the LightSpeed VCT and revealed a stenosis of the saphenous graft segment I, which was revascularized by another stent in April 2006 recurrent angina.
In September 2006, a new Coronary CTA exam was requested in order to assess the patency of the bypass grafts and the stents as part of routine follow-up (Figure 1).

This new exam was performed with LightSpeed VCT XT and SnapShot Pulse™ feature.

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Scan parameters :

• 64-slice detector
• Slice thickness: 0.625 mm
• Rotation time: 0.35 second
• 700 mA, 120 kVp
• Coverage: 279 mm
• Heart rate: 60 bpm
• Total X-Ray exposure time: 3.8 seconds

Injection protocol :

Three phase injection using a dual injector

• 80 ml of iodine contrast @ 4.5 cc/sec
• 30 ml of contrast media @ 2cc/sec + 30 ml of isotonic solution @ 2cc/sec
• 20 ml of saline flush @ 2.5 cc/sec Iodine concentration: 350 mg/ml

Dose

• DLP: 600 mGy.cm
• Dose: 10.2 mSv*

Scan parameters were optimized considering the morphology, the age of the patient and the indication of the exam. The exam was performed on LightSpeed VCT XT®evaluation system and the Snapshot Pulse™ feature. The radiation dose delivered during the examination was only 10.2 mSv* and the total X-Ray exposure time was 3.8 seconds.

Obtained by EUR-16262 EN using chest factor of 0.017*DLP

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Conorary artery assessment

LIMA-LAD graft

The CT exam shows no change in the LIMA-LAD graft since December 2004. The graft is still patent with a normal distal anastomosis and an excellent enhancement of the lumen (Figures 2 & 3).

Saphenous-RCA graft

The examination of the saphenous-RCA graft (Ao-RCA) demonstrates an in-stent restenosis with intimal hyperplasia in the middle part of the stent in segment I (Figures 4 & 5).

Figure 4: L-section and X-section views of the stent demonstrating the in-stent restenosis with an intimal hyperplasia.

Figure 5: Lumen and X-section views of the Ao-RCA graft.

Figure 6: Curved and X-section views of the Ao-RCA graft

As in December 2004, the whole graft is infiltrated, displaying an irregular lumen and a discrete parietal thrombus before the second stent (Figure 6). The second stent, placed in 1998 is still patent without any sign of restenosis or occlusion. In addition, the proximal segment of the PDA demonstrates a moderate stenosis (< 40%), that has not evolved since December 2004. (Figure 6).

Figure 7: Curved view of the RCA

The examination of the native coronary arteries displays, as it was in December 2004, the RCA occlusion starting at segment I (Figure 7).

Figure 8: Curved view of the LAD

On the left side, the Left Main Trunk is infiltrated but of normal size. The occlusion of the proximal LAD is demonstrated as it was in December 2004 (Figure 8)

Figure 9: Curved view of the intermediate branch

A large intermediate branch giving two other branches is visualized. The stent on the proximal segment is patent without any sign of restenosis or occlusion (Figure 9).

Figure 10: Curved view of the LCx.

Figure 11: Curved view of one LMB.

Finally, the Left Circumflex (LCx) artery and the Left Marginal Branches (LMBs) are still normal (Figures 10 & 11).

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The second exam was performed with LightSpeed VCT XT® evaluation system and the Snapshot Pulse™ feature in order to reduce the patient radiation dose, whereas the first exam was performed with the LightSpeed VCT using the helical mode, retrospective gating and ECG modulation.
With this new scanning technology, the diagnosis was achieved with an excellent image quality and a dose of only 10.2 mSv*. The total X-Ray exposure time was only 3.8 second while covering 279 mm.
GE exclusive LightSpeed VCT XT® evaluation system and the Snapshot Pulse™ feature has the potential to completely redefine the role of CT for bypass and stent follow-up, by enabling the bypass study and the native coronary arteries within a short X-Ray exposure time.