Isolated Common Iliac Artery Aneurysm – Complicated by Peripheral Artery Insufficiency in the Lower Limb?

Shufang Cheng, MD; JianSong Ji, MD; Xi Zhao*, MD
Department of Radiology, Lishui Central Hospital, The No. 5 Affiliated Hospital of Wenzhou Medical College, Lishui, Zhejiang, P.R. China
*Siemens Healthineers China
|

An 80-year-old male patient, complaining of chest discomfort, shortness of breath and lower limb edema, came to the hospital for a checkup. A Dual Energy (DE) CT angiography (CTA), followed by a dynamic 4D CTA were performed for evaluation.

CTA images revealed an isolated aneurysm in the right common iliac artery (RCIA). It extended from the aortic bifurcation to the proximal right external iliac artery (REIA), with a maximum diameter of 4.1 cm. Severe stenoses in the proximal left renal artery (LRA) and the left internal iliac artery (LIIA) were seen. Extensive calcified plaques in multiple abdominal and peripheral arteries, causing mild to moderate stenoses, were also visualized. Peripheral artery insufficiency was ruled out by dynamic 4D CTA however severe stenosis in the right posterior tibial artery (RPTA), caused by calcified plaques, was confirmed. Subsequent percutaneous implantation of endovascular stent-grafts was successfully performed in the aortic bifurcation and in the proximal LRA, and the patient’s symptoms were significantly improved.

A male patient with chest discomfort and limb edema was scanned with a SOMATOM Force.
Courtesy of Lishui Central Hospital, The No. 5 Affiliated Hospital of Wenzhou Medical College.

Fig. 1:
A cinematic VRT image shows an overview of the complete scan range.

A severe stenosis could be seen on a CT scan with SOMATOM Force.
Courtesy of Lishui Central Hospital, The No. 5 Affiliated Hospital of Wenzhou Medical College.

Fig. 2:
MPR images show an aneurysm in the RCIA extending from the aortic bifurcation to the proximal REIA. A severe stenosis of the left renal artery is also seen (Fig. 2b, arrow).

After complaining about chest discomfort and limb edema, a 80-year old male patient underwent a Dual Energy CT angiography.
Courtesy of Lishui Central Hospital, The No. 5 Affiliated Hospital of Wenzhou Medical College.

Fig. 3:
Right-posterior views of pre- (Fig. 3a, cVRT; Fig. 3b, MIP) and post (Fig. 3c, MIP) stenting show an ectatic RCIA, severely stenosed LRA and LIIA, as well as stent grafts in the aortic bifurcation and in the proximal LRA (Fig. 3c, arrow).

Chest discomfort, shortness of breath, and lower limb edema were evaluated with a Dual Energy CT angiography.
Courtesy of Lishui Central Hospital, The No. 5 Affiliated Hospital of Wenzhou Medical College.

Fig. 4:
A comparison of inverted MIP images (at the same windowing) derived from mixed image (Fig. 4a), mono+50 keV image (Fig. 4b) and dynamic CTA image (Fig. 4c). The peripheral arteries in the lower limbs are best shown in the dynamic 4D CTA, confirming a severe stenosis in the RPTA (arrow).

Isolated aneurysms in the iliac arteries are uncommon and may lead to peripheral artery insufficiency in the lower limbs. Appropriate candidate selection, for endovascular or surgical therapy, greatly relies on imaging classifications. Runoff CTA is usually performed. And DE allows automatic bone removal, as well as significant enhancement of vascular details using “syngo. CT DE Monoenergetic Plus”. However, if the peripheral arteries in the lower limbs are not well shown in DE CTA images, such as in this case, a critical question can be raised – does this indicate peripheral artery insufficiency or missing the bolus? Dynamic 4D CTA is performed using Adaptive 4D Spiral scanning to acquire images at multiple time points with defined intervals. This makes wrong bolus timing highly unlikely. Peripheral arteries are clearly demonstrated using the fused temporal maximum intensity projections (tMIP), which improves diagnostic confidence and helps the physicians making an appropriate treatment plan.

Scanner

 

Scan area

Runoff

Upper femur to toes

Scan mode

Dual Source DE

Adaptive 4D Spiral

Scan length

1294 mm

796 mm

Scan direction

Cranio-caudal

Bi-directional

Scan time

3.6 s

21 s

Tube voltage

70 / Sn150 kV

80 kV

Effective mAs

136 / 47 mAs

35 mAs

Dose modulation

CARE Dose4D

CARE Dose4D

CTDIvol

2.99 mGy

6.46 mGy

DLP

399.4 mGy cm

493 mGy cm

Rotation time

0.28 s

0.25 s

Pitch

0.6

-

Slice collimation

192 x 0.6 mm

48 x 1.2 mm

Slice width

1.5 mm

1.5 mm

Reconstruction increment

1.0 mm

1.0 mm

Reconstruction kernel

Qr40 (ADMIRE 3)

Br36 (ADMIRE 3)

Heart rate

 

 

Contrast

320 mg/mL

320 mg/mL

Volume

90 mL + 40 mL saline

35 mL + 35 mL saline

Flow rate

5 mL/s

3.5 mL/s

Start delay

Bolus tracking with 100 HU at the popliteal artery + 5 s

Same as CTA trigger time