Needs-Specification-Document PDF

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Prof. Michael Walsh...

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Needs Specification Document. Introduction This need specification document was developed in relation to addressing medical issues associated with the processes by which blood supply is reverifiable and temporarily stopped in target tissues for the purposes of patients undergoing interventional radiology procedures. "Interventional Radiology" (IR) refers to a range of techniques which rely on the use radiological image guidance (X-ray fluoroscopy, ultrasound, computed tomography [CT] or magnetic resonance imaging [MRI]) to precisely target therapy’’.

Needs Statement The need statement developed during the course of this project is as follows: 

‘’A way to stop blood supply to target tissues in patients undergoing interventional radiology procedures that is reversible and reduces complications’’.

The Problem This section examines the problem at hand, a need and demand for a more efficient, safer and less invasive way of restricting blood flow to target tissues for the purpose of interventional radiology procedures. ‘’Interventional Radiology (IR) is a subspecialty of radiology encompassing procedures performed using imaging guidance such as fluoroscopy, CT, ultrasound and MRI to diagnose and treat a wide variety of conditions’’.[ CITATION Hos17 \l 6153 ], Interventional radiology possesses a broad scope of procedures including, Angiography, Angioplasty, Endogenous Laser Treatment (EVLT), Stent, Aortic endograft and stent-grafts, Aortic aneurysm endograft stent, Chemoembolization, Embolization, Needle biopsy, Thrombolysis and UFE (Uterine Fibroid Embolization). Cutting off blood supply to a specific area of the body (Embolization), can be an important form of care when treating tumours (or other abnormal growths), internal bleeding, defects in blood vessels, or other conditions. Interventional radiologists can inject special materials that form a blockage (embolize) arteries and other areas to close off (occlude) them for this purpose. Catheter embolization places medications or synthetic materials called embolic agents through a catheter into a blood vessel to block blood flow to an area of the body. It may be used to control or prevent abnormal bleeding, close off vessels supplying blood to a tumour, eliminate abnormal connections between arteries and veins, or to treat aneurysms. Embolization is a highly effective way to control bleeding and is much less invasive than open surgery.

Often, existing means of methods of embolization of target tissues can lead to complications which threaten patient health.

Anatomy Interventional Radiology can be applied to many areas of the human body and can used during many different procedures. For the purpose of this project, the group has chosen the heart as the specific area to investigate. The average human heart is around 120x80x60 mm in size. The heart is a very muscular organ and requires very thick walls on the left side as it needs to build up huge pressure to pump the blood around the body. The pressure on the left ventricle is around 120 mmHg for the average adult. The average adult heart pumps between 6000-7500 litres of blood daily.

Disease Mechanism While there are numerous diseases associated with the heart, a thoracic aortic aneurysm has been chosen. A thoracic aortic aneurysm, or TAA, is a bulging, weakened area in the wall of the aorta.(Stanford Health Care, 2017)i. A TAA will result in a widening of the aortic wall and may result in rupture due to weakening of the wall. A TAA can occur in the ascending, descending or aortic arch. Symptoms: Most patients do not experience any symptoms, however, those who do might experience some of the most common symptoms; 

Chest or back pain

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Difficulty breathing or swallowing

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Shortness of breath

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Coughing

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Hoarseness

(WebMD, 2005-2017)ii TAA can be caused by a number of factors such as; high blood pressure, infection, plaque build-up, high cholesterol and in some cases sudden traumatic injury. A thoracic aortic aneurysm can be detected through screening methods such as X-Ray, echocardiogram, CT scan or an ultrasound.

Existing Methods Currently, there are various methods by which Interventional radiologists occlude blood flow to the target areas, these methods also vary primarily due to the area of interest in terms size of the blood vessel or malformation and whether the treatment is intended to be permanent or temporary. A list of existing methods is as follows: 

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Coils: various sized metallic coils made of stainless steel or platinum are used to block or occlude large arteries. They can be positioned very precisely to stop bleeding from an injured artery or halt arterial blood flow into an aneurysm. Particles: particulate agents, including Polyvinyl alcohol (PVA) and gelatine-impregnated acrylic polymer spheres, which are suspended in liquid and injected into the bloodstream to block small vessels. These agents are used to block or occlude vessels permanently, including the treatment of uterine fibroid tumours. Foam: a gelatine sponge material, which is cut into small pieces that are injected into an artery and float downstream until they can go no further. After a period ranging from a few days to two weeks, the material dissolves. Liquid glue: When injected into the target channel that needs to be closed off, it hardens quickly. liquid sclerosing agents: such as alcohols, which are used to destroy blood vessels and vessel malformations. Filling a vessel or a vascular malformation with this liquid agent causes blood clots to form, closing up the abnormal vascular channels.

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Bead Block Microspheres: are made from an acrylic polymer matrix impregnated and embedded with porcine gelatin. The particles are packaged in a 20-mL syringe prefilled with 2 mL of normal saline. A hydrophilic surface and uniformly spherical shape prevents aggregation.

Outcomes and Complications Embolization is a highly effective way of controlling bleeding, especially in an emergency situation. However, there are still complications which may arise such as:  

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allergic reaction if contrast material is injected. Any procedure that involves placement of a catheter inside a blood vessel carries certain risks. These risks include damage to the blood vessel, bruising or bleeding at the puncture site, and infection. However, precaution is taken to mitigate these risks. embolic agent can lodge in the wrong place and deprive normal tissue of its oxygen supply. there is a risk of infection after embolization, even if an antibiotic has been given. However, the physician takes ample care to minimize this risk. A small percent of women has uterine injury from embolization of fibroid tumours — see the Uterine Fibroid Embolization page — and this may make it necessary to remove the uterus. In a few cases in women over age 45, menopause has begun within one year of embolization of fibroids. The effect of fibroid embolization on fertility is not clearly understood. There is also a risk of kidney damage due to the contrast material, particularly in patients with diabetes or other pre-existing kidney disease.

The Market According to a new study conducted by Grand View Research Inc, the global transcatheter embolization and occlusion devices market is expected to reach over USD 4.75 billion by the year 2022. (Grand View Research, 2016). The main reasons for such an increase in the demand for transcatheter embolization and occlusion devices are the increase in popularity of minimally invasive surgical techniques, the increase in cancer patients and the increase in patients suffering from heart disease. According to the national cancer institute, in 2017 alone, there will be an estimated 1,688,780 new cases of people being diagnosed with cancer in the US and approximately 600,920 will die from the disease. (American Cancer Society, 2012). This combined “with the global burden of new cancer cases expected to grow to 21.7 million by 2030” is a clear indication that there is an extensive market for treating such cases.( IARC,2012 ). As well as being used for embolization of tumours, “the growth of the use of embolization techniques as a treatment for conditions other than cancer such as vascular malformations and fibrosis is fuelling the demand for TEO devices globally”. (Grand View Research, 2016). Minimally invasive surgeries are becoming increasingly popular due to reduced trauma experienced by the patient, decreased risk of infection, lower cost and faster recovery times, which are all factors that increase the market for TEO devices worldwide.

Need Criteria “The need criteria are the major elements that any proposed solution must demonstrate in order to deal with the specific need. These elements are governed by the specific needs or requirements of the relevant stakeholders, which in this particular case are the interventional radiologists who perform the transcatheter embolization and occlusion procedures and, to a lesser degree, the patients who undergo such surgeries.”(University of Limerick, 2017)

Regarding Surgeon Uptake 

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Procedural times must not exceed the current duration for such procedures. As transcatheter procedural durations can range from 30 mins to several hours it clearly depends on the specific procedure that the interventional radiologist is undertaking. The device must be cheaper than predicate devices, however if it is a more expensive device it must be considerably more effective at treating such diseases than its predicate devices. The procedure used by the interventional radiologists must be repeatable across all hospitals and clinics to ensure that patients receive consistent high-level care. The proposed device’s recovery time must not exceed current recovery times.

i Stanford Health Care, 2017. [ONLINE] Available at: https://stanfordhealthcare.org/medical-conditions/blood-heartcirculation/thoracic-aortic-aneurysm.html

ii WebMD, 2005-2017. [ONLINE] Available at: http://www.webmd.com/heart-disease/heart-disease-aorticaneurysm#1 Grand View Research, 2016. [ONLINE] Available at: http://www.grandviewresearch.com/press-release/globaltranscatheter-embolization-occlusion-market American Cancer Society, 2017 [ONLINE] Available at: https://www.cancer.org/content/dam/cancerorg/research/cancer-facts-and-statistics/annual-cancer-facts-and-figures/2017/cancer-facts-and-figures-2017.pdf IARC, 2012. [ONLINE] Available at: https://www.cancer.org/research/cancer-facts-statistics/global.html Walsh, M.(2017) “Needs Specification Document”; ME4427: Medical Device Design and Placement, 15 th Sept, University of Limerick, unpublished....