Dr ML Bera, Sr. Consultant & Coordinator Radiology, Fortis Memorial Research Institute, Gurgaon

Peripheral vascular disease (PVD) is most common in elderly age group with majority of them being asymptomatic or undiagnosed. Good patient outcome depends on prompt diagnosis and early intervention while emergencies are reversible. The choice between different imaging techniques depend on local protocols, availability of local expertise/services, and needs of the local population. Digital subtraction angiography (DSA) is considered as gold standard in the diagnosis of PVD, but it is an invasive technique and caries potential risks for iatrogenic complications.

Non-invasive imaging tools play a major role in diagnosis, treatment planning, and subsequent follow-up of PVD patients. Duplex ultrasound (DU), MR angiography (MRA), and CT angiography (CTA) are the most common non-invasive imaging tools for evaluation of PVD. All these imaging modalities are quite promising and have their merits and demerits. The DIPAD trial results suggest that both CTA and MRA are clinically more useful than duplex sonography and that CTA leads to cost savings compared with both MRA and DU in the initial imaging evaluation of peripheral arterial disease.

CT angiography has revolutionized vascular imaging in recent years. As a result of concomitant rapid evolution of MDCT technology and its easy availability, high-resolution imaging of the peripheral vasculature has become routinely possible. With the introduction of high-end multidetector computed tomography (MDCT) scanners and multi-task contrast injectors, non-invasive CTA has become a viable option and imaging the entire inflow and runoff vessels is now possible with single acquisition and single intravenous contrast medium injection. Isotropic volumetric data sets can now be acquired with MDCT angiography, allowing for 3D reconstruction of vascular tree and many more post-processing methods to enable both diagnostic interpretation and eloquent anatomical and pathological arterial display.

CT angiography is attractive due to its shorter acquisition times and thinner slices with higher spatial and temporal resolutions. This is only possible due to availability of newer generation scanners with much thinner tube collimation and better understanding with improved imaging techniques. Advanced technology has helped us scan the whole vascular tree in a shorter time period with much reduced contrast dose and reasonably lower radiation to patient. Recent studies on peripheral CTA have reported sensitivity and specificity over 98-100 percent for detecting peripheral vascular diseases.

PV-CTA is an accurate modality to assess the presence and extent of PVD, pre-treatment planning, and subsequent follow-up. PV-CTA continues to shape the comprehensive treatment of PVD with far fewer challenges. Diagnostic advantage of PV-CTA includes simultaneous visualization of vessel wall and vessel lumen along with surround soft tissue and bony structures. PV-CTA helps in accurate diagnosis, reliable treatment planning, vascular access planning with much reduced overall complication rates. It also helps as base line study in subsequent follow-up to asses disease progression, graft/stent evaluation or detection of complication.

PV-CTA has a wider range of clinical applications. The most common indication for PV-CTA is for further evaluation of PAD, whether it is acute and chronic limb-threatening ischemia or intermittent claudication. The Trans Atlantic Inter-Society Consensus guidelines recommend appropriate endovascular or surgical treatment of PAD based on lesion location, lesion number, lesion severity, lesion length, and lesion morphology. PV-CTA fulfils all of these criteria to enable appropriate treatment planning. Availability and rapid access places PV-CTA at the forefront for fast and complete arterial assessment in suspected vascular injuries, both in trauma settings and iatrogenic events. Aneurismal disease can be eloquently evaluated with PV-CTA as sac size, relation to parent vessel, thrombus load and distal run-off can all be demonstrated prior to endovascular therapy or surgical repair. Rarer indications of PV-CTA include vascular malformations, localization of blood flow and arterial compression by adjacent masses, adventitial cystic disease, and popliteal entrapment syndrome. Vascular Mapping as part of pre-treatment planning and follow-up and surveillance after surgical or percutaneous revascularization are also popular clinical indications.

Advancement in MDCT technology coupled with innovative imaging protocols, contrast delivery system, and post-processing techniques has made PV-CTA a powerful tool for non-invasive imaging and treatment planning of PAD in this millennium and established itself as most viable non-invasive alternative imaging tool to DSA for evaluation of PVD.

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