Embolic coils are a familiar device for interventional radiologists. The author describes personal experience of the development of medical devices especially detachable coils and the importance of cross-disciplinary collaboration between scientists and the medical industry.

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Endovascular aneurysm repair (EVAR) using stent and stent-graft has advanced markedly in recent years. Recently, hemodynamic modification by means of flow diversion is increasingly used for treating aneurysms. For this treatment, the stent is placed in the parent vessel and then the aneurysm embolization is completed by thrombus formation as a result of the stagnant flow in the aneurysm.
These endovascular devices must have a high biocompatibility to prevent damage to vascularized tissue such as vessel dissection and rupture. To minimize these complications, various stents and stent-grafts have been developed by biomechanical and physiological approaches. However, some clinical problems such as endoleak and in-stent thrombosis are still reported for treated aneurysms. Therefore, highly biocompatible stents and stent-grafts that have mechanical flexibility and haemocomaptibility are required for aneurysm stenting.
In this article, we briefly reviewed the developmental history of stents and stent-grafts for aneurysm treatment. Moreover, we proposed our original development methodology based on our research and discussed medical-engineering collaborations for progressive stent and stent-graft technologies in the future.

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Over 15 years has passed since aneurysm coil embolization using detachable coils was approved in Japan. Since then, the surgical indications for this procedure have increased and clinical outcome has improved, mainly through technological advances. In this article, we describe the indication, surgical equipment used (microcatheter, microguidewire, and coils), and technical considerations (including adjunctive techniques) for aneurysm embolization.

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Recent progress of neuro-interventional radiology (neuro-IVR) for cerebral aneurysm is remarkable. Adjunctive techniques such as double catheter technique, balloon-assisted technique, and stent-assisted technique have been developed and their clinical usefulness has been shown in formidable lesions with simple technique using platinum coils. New devices including covered stent, flow diverting stent, or liquid embolic material have been introduced already in most Asian countries. Japan has been for several years behind foreign countries in neuro-IVR due to so-called "device-lag". However, a recent acceleration of government approval for new devices has led to the introduction of Enterprise VRD, closed cell stent for cerebral aneurysm, to Japan in July 2010. Initial treatment results are being accumulated and tips / pitfalls of this device have recently been elucidated. Current status of stent-assisted coil embolization for cerebral aneurysm in Japan is reported in this article including illustrative case presentations of the author.

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Aneurysms of the thoracic aorta are life-threatening. While open aortic repair has been a standard procedure, thoracic endovascular aortic repair (TEVAR) has gained acceptance as an alternative for high-risk patients. The recent release of the PMDA-approved stent-grafts for thoracic aortic aneurysms has led to the widespread use of TEVAR in Japan because of its lower mortality and morbidity based on its lower invasiveness. We describe here not only the basic consensus or indications about TEVAR but also mention the features of each available device at the time of writing in Japan. Furthermore, we discuss the particular issues regarding TEVAR such as type II or type III endoleaks in the follow-up period. The hybrid TEVAR for aortic arch aneurysms or thoracoabdominal aortic aneurysms widens the treatment choices for patients with complicated aortic aneurysms. Advanced techniques such as the chimney technique or the in-situ fenestration technique can also provide other treatment options for patients who are not suitable for thoracotomy or aortic side clamps.

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Conventional management of abdominal aortic aneurysm (AAA) has been open surgical repair. However, recently endovascular aneurysm repair (EVAR) has been alternative treatment for AAA, and so far over 12000 cases have been treated with stent graft in Japan. For successful EVAR, it is very important to learn device specific characteristics and how to troubleshoot in diffficult cases. Basically the indication of EVAR is limited to patients at high surgical risk having suitable anatomy. However, the indications are expanded to anatomically EVAR unfit cases (so-called "outside IFU"). There are unsuitable conditions, for example, short proximal neck, tortuous aorta, and small diameter iliac artery. Even in such cases, we can conduct a successful EVAR procedure by analyzing correctly the anatomical information, considering device specific characteristics, and understanding technical pitfalls. Besides, I refer to additional procedures of internal iliac artery embolization, safe method for tortuous access site, and avoiding coverage of renal arteries. We should continue to learn device specific managements and make efforts to obtain new device information.

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Visceral artery aneurysms are uncommon, but can cause life-threatening hemorrhage. Endovascular treatment for visceral artery aneurysms as well as other aneurysms is a minimally invasive and well-established therapy. For safe and effective treatment, we have to take into consideration the anatomical features of aneurysms, relationships between aneurysms and parent arteries, blood flow into corresponding organs, and patient background features. In addition, knowledge of various devices is important. In this article, we summarize the endovascular treatment for both visceral artery and other aneurysms, and also describe our experience with embolization of aneurysms.

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Polyarteritis nodosa (PN) is a necrotizing vasculitis that may affect multiple organ systems. We report a case of man with spontaneous perirenal hematoma due to the rupture of microaneurysms of the left kidney. Left renal arteriography showed many bleeding sites arising from ruptured microaneurysms; this finding along with the other clinical symptoms led to the final diagnosis. The ruptured lesions were embolized by coiling successfully, and oral corticosteroid resulted in the alleviation of the clinical symptoms. Left acute pyelonephritis developed due to ureteral calculi, leading to a non-functioning kidney; therefore, surgical resection was carried out 8 months after the initiation of corticosteroid therapy. Pathologic examination of the surgical specimen showed segmental interruption of the arterial elastic laminae and microaneurysms, suggesting healed stage of PN, although it failed to reveal features of fibrinoid vasculitis.

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