Congress:
EuroSafe Imaging 2018
Keywords:
Aneurysms, Radiation safety, Diagnostic procedure, Audit and standards, CT-Angiography, Vascular, Radioprotection / Radiation dose, Interventional vascular, Action 2 - Clinical diagnostic reference levels (DRLs), Action 3 - Optimisation, diagnostic reference levels, image quality, Dosimetric comparison
Authors:
M. A. Fink, A. Steuwe, M. Cattelaens, L. Born, W. Stiller, H. U. Kauczor, F. Rengier
DOI:
10.1594/esi2018/ESI-0037
Background/introduction
Endovascular aortic repair (EVAR) has become an accepted and to date widely used minimally invasive alternative for the treatment of thoracic and abdominal aortic pathologies including aortic aneurysms,
penetrating aortic ulcers and aortic dissections [1,2].
Imaging plays a crucial role both for preinterventional planning and for postinterventional follow-up.
In the postinterventional setting,
imaging aims at confirming treatment success and detecting potential complications.
Complications of EVAR include endoleaks,
endograft migration,
endograft collapse,
stent thrombosis and perigraft fistula formation [3].
Endoleaks represent the most common complication after EVAR with a rate of up to 42% and are defined as persistent periprosthetic flow.
Importantly,
endoleaks constitute the major risk factor for late aneurysm rupture and the main indication for conversion to open repair [4,5].
Therefore,
it is crucial to identify endoleaks that require secondary interventions to ensure treatment success and to prevent late rupture after aneurysm repair.
In order to obtain this objective and ensure effective patient monitoring,
a life-long surveillance strategy with a regular follow-up examination is required,
usually performed with a single-energy based triphasic CT angiography (CTA).
However,
this procedure is inevitably accompanied by substantial patient radiation exposure which has been linked to an increase in the lifelong risk of developing fatal cancers [6-8].
The risk of developing cancer is cumulative and increases with any further follow-up examination.
As a result,
considerable research is being performed to develop and optimise CT acquisition protocols according to the ALARA principle ("as low as reasonably achievable") in an effort to avoid high cumulative radiation doses while retaining diagnostic accuracy [3].
Dual-source dual-energy CT (DECT) offers an interesting approach to save radiation dose.
This technique is based on material differentiation at different kVp settings using the photoelectric effect in materials with large atomic numbers,
like iodine and calcium,
and thus allows selective image postprocessing.
It offers the capability to subtract iodine from contrast-enhanced images,
thereby creating virtual noncontrast images (VNC images),
which could potentially replace true noncontrast images.
Similarly,
it is possible to selectively color code materials such as iodine and calcium (iodine overlay,
hard plaque imaging) [9,10] and to create weighted average datasets from the DECT raw data which both may enhance the sensitivity of endoleak detection.
Nonetheless,
there is still controversy regarding the optimal imaging strategy in patients after EVAR [6,11].
According to the principles of the EuroSafe Imaging Stars Network,
we here illustrate one possible approach based on DECT to reduce radiation dose in daily clinical routine,
particular regarding the follow-up examinations of patients who underwent EVAR.