Comparison: Medical Imaging Using Different Techniques - CT Scan

Hi Everyone! We decided to make this post because many of you have doubts about the differences between some diagnostic exams and medical devices that are frequently performed in clinical practice.

So, we are going to present to you some characteristics and functions of the CT Scan, the MRI, the PET scan and the X-ray. 

Part I: CT SCAN

A computerised tomography scan take the idea of conventional X-ray imaging to a new level. Instead of finding the outline of bones and organs, a CT scan machine forms a full three-dimensional computer model of a patient's insides. Doctors can even examine the body one narrow slice at a time to pinpoint specific areas.

The CT scan combines a series of X-ray views taken from many different angles and computer processing to create cross-sectional images of the bones and soft tissues inside your body.

So, a CT scan machine, produce X-rays, a powerful form of electromagnetic energy. X-ray photons are basically the same thing as visible light photons, but they have much more energy. This higher energy level allows X-ray beams to pass straight through most of the soft material in the human body.

http://www.arimaclinic.com/CT/images/ct-scan-of-the-brain.jpg

A conventional X-ray image is basically a shadow: You shine a "light" on one side of the body, and a piece of film on the other side registers the silhouette of the bones. Shadows give you an incomplete picture of an object's shape. If a larger bone is directly between the X-ray machine and a smaller bone, the larger bone may cover the smaller bone on the film. In order to see the smaller bone, you would have to turn your body or move the X-ray machine.

In a CAT scan machine, the X-ray beam moves all around the patient, scanning from hundreds of different angles. The computer takes all this information and puts together a 3-D image of the body. The CAT machine looks like a giant doughnut tipped on its side. The patient lies down on a platform, which slowly moves through the hole in the machine. The X-ray tube is mounted on a movable ring around the edges of the hole. The ring also supports an array of X-ray detectors directly opposite the X-ray tube.

A CT Scan is best suited for viewing bone injuries, diagnosing lung and chest problems, and detecting cancers. Besides this, CT scans are widely used in emergency rooms because the scan takes fewer than 5 minutes.

In addition to be a very good for imaging bone structures, this exam is important in cases of some patients who have received certain types of surgical clips, metallic fragments, cardiac monitors or pacemakers cannot receive an MRI.

(Adapted from: http://science.howstuffworks.com/cat-scan.htm)

https://www.youtube.com/watch?v=tqGmqRrxajQ

New non-invasive method detects early stages of Alzheimer's disease

Hello, dear followers!

We are writing to share with you an incredible non-invasive approach to detect Alzheimer's disease, well before typical symptoms appear. The approach that we are going to share with you uses MRI (Magnetic Resonance Imaging) that pairs a magnetic nanostructure with an antibody that seeks out the beta Amyloid brain toxins which damage neurons and are responsible for the onset of the disease. 

This approach was carried out by neuroscientist William L.Klein and materials scientists Vinavak P.Dravid from Northwestern University. You can check their full article in the Nature Nanotechnology journal by searching for the title: "Towards non-invasive diagnostic imaging of early-stage Alzheimer's disease."

Currently, there is no method capable of detecting Alzheimer's disease, a disease that affects one out of nine people over the age of 65.With MRI it is possible to see the toxins attached to neurons in the brain. The magnetic nanostructures typically with 10-15 nm in diameter are used as smart nanotechnology carriers with antibodies specifically targeted for Amyloid beta toxins.The accumulated toxins, because of the associated magnetic nanostructures, show up as dark areas in MRI scans of the brain.  

a) Fluorescent Amyloid beta oligomers (green), bound to culture hippocampal neurons, were detected with greater than 90 percent accuracy by the NU4 antibody-magnetic nanostructure probes (red). b) MRI signal in vivo of the hippocampal region of the mouse's brain. In diseased models, the toxin's presence can be clearly seen in the hippocampus in MRI scans of the brain. No dark areas were seen in the hippocampus of the control group. (Adapted from Viola et al., Nature Nanotechnology, 2014) 

In this approach the authors detect something different than conventional technologies: they aim for toxic Amyloid beta oligomers instead of plaques, which occur at a very late stage of the disease when the treatment turns out to be less effective. 

In a diseased brain, Amyloid beta oligomers attack the synapses of neurons, destroying memory, ultimately resulting in neuron death. Oligomers may appear more than a decade before plaques are detected. Thus, Amyloid beta oligomers are believed to be the culprit in the onset of the Alzheimer's disease and subsequent memory loss. 

Despite extraordinary efforts there is no effective drug for Alzheimer’s disease yet. However, similar technologies could aid for the assessment of the effectiveness of many drugs on research or clinical trials. According to Dravid, if a drug is effective then the signal from Amyloid beta could become weakened (with less dark areas), so by using these kinds of technologies it would be possible to determine how well the drug is working.

Now we wonder: how many other diseases could be diagnosed by using such amazing technological breakthrough advances? 

Rejection in human organ transplantation (Final chapter): New generation of therapeutic options

This is the third and last chapter of the trilogy entitled "Rejection in human organ transplantation". In this chapter new therapeutic options are addressed, resulting from emerging areas of biomedical research, as organ or tissue transplant alternatives.

You can find the first and second chapters here, in Biomaterials and Tissue Engineering section. Hope you like it!

Visit the Facebook Page - IBR: Independent Biomedical Researchers

Are you curious? Do you want to be always updated about the latest developments and news about the Biomedical Engineering world? We have a perfect facebook page for you! 

IBR: Independent Biomedical Researchers is a group motivated to explore and deepen topics of interest in the field of Biomedical Engineering. It is formed by students of the Biomedical Materials and Devices Master's Degree of University of Aveiro. Me (Rita) and Diogo are pleased to be members of this group!

The main goals of IBR are:

• To consolidate the background on Biomedical Engineering;
• To encourage the sharing, the exchange of ideas and the enrichment of knowledge;
• To acquire research independence (creation, development, application of strategies for the purpose of obtaining skills), critical thinking and ability to propose solutions to problems of Biomedical Engineering.
• Stay connected and follow us.

Interested? So, follow us through this link: 

https://www.facebook.com/IndependentBiomedicalResearchers

Some information to keep you informed regarding Ebola

The World Health Organization (WHO) issues a situation update on the Ebola epidemic, every couple of days, with new numbers of cases and deaths. These numbers are worrying - 9216 and 4555, respectively. So, we think it is important to report some facts and warnings about this problematic disease. 

• First of all, what is the Ebola Virus Disease?

Ebola virus is a serious and usually fatal disease for which there are no licensed treatments or vaccines. This virus is native to Africa and causes hemorrhagic fevers, organ failure and, in many cases, death. Ebola lives in animal hosts and humans can contract the virus from infected animals. Furthermore, after the initial transmission, Ebola virus can spread from person to person through contact with body fluids or contamined material (needles, for example).

So far, no drug has been approved to treat this disease and people with Ebola receive supportive care/treatment for associated complications. However, scientists are coming closer to developing vaccines for the cure of this epidemic disease.

• Causes

Ebola is caused by infection with a virus of the family Filoviridae. There are five identified Ebola virus species, four of which are known to cause disease in humans: Ebola virus (Zaire ebolavirus); Sudan virus (Sudan ebolavirus); Taï Forest virus (Taï Forest ebolavirus); and Bundibugyo virus (Bundibugyo ebolavirus). The fifth, Reston virus (Reston ebolavirus), has caused disease in nonhuman primates, but not in humans.

Ebola viruses are found in several African countries. Ebola was first discovered in 1976 near the Ebola River in the Democratic Republic of the Congo. Since then, outbreaks have appeared sporadically in Africa.

This virus is introduced into the human population through close contact with blood, secretions or other bodily fluids of infected animals such as chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines found ill or dead. Then, it spreads through human-to-human transmission via direct contact with blood, secretions or other bodily fluids of infected people, and with surfaces and materials contaminated with these fluids.

Health-care professionals have been infected while treating patients with suspected or confirmed Ebola, due to the close contact with patients when infection control precautions are not strictly practiced.

Men who have recovered from the disease can still transmit the virus through their semen for up to 7 weeks after recovery from illness.

• Signs and Symptoms

Signs and symptoms typically start between 7-9 days after contracting the virus, with afever, headaches, sore throat and muscle pain. Then, vomiting, diarrhea and rash symptoms usually follows, along with decreased function of the liver and kidneys. At this time, generally, some people begin to bleed internally and externally.Death, if it occurs, is typically six to sixteen days after symptoms appear and is often due to low blood pressure from fluid loss.

• Diagnosis

Diagnosing Ebola can be difficult in an person who has been infected for only a few days. Nor is it easy to distinguish Ebola from other infectious diseases such as malaria, typhoid fever and meningitis, because the early symptoms are nonspecific to this virus infection.

However, if a person has the early symptoms of Ebola; has had contact with the blood or body fluids of a person sick with Ebola; or contact with infected animals, they should be isolated and public health professionals notified. Samples from the patient can then be collected and tested to confirm infection.

Confirmation that symptoms are caused by Ebola virus infection are made using the following investigations:

- Antibody-capture enzyme-linked immunosorbent assay (ELISA);

- Antigen-capture detection tests;

- Serum neutralization test;

- Reverse transcriptase polymerase chain reaction (RT-PCR) assay;

- Electron microscopy;

- Virus isolation by cell culture.

• Prevention

There is no approved vaccine available for Ebola. 

So, if you travel to, or are in an area affected by an Ebola outbreak, make sure to practice careful hygiene and avoid contact with blood and body fluids. 

Do not handle items that may have come in contact with an infected person’s blood or body fluids.

Avoid contact with bats and non-human primates or blood, fluids, and raw meat prepared from these animals.

Avoid hospitals in West Africa where Ebola patients are being treated. 

After you return, monitor your health for 21 days and seek medical care immediately if you develop symptoms of Ebola.

And finally, some numbers...

http://www.dontcomply.com/ebola/

Poly(lactic acid)... An interesting material for Tissue Engineering

In the last years, the progresses of our society and consequently, the technological and scientific developments, have driven significant advances in the discovery, improvement and production of polymers. 

Biodegradable polymers are derived from naturally occurring polymers that are found in all living organisms and can be classified into two groups: the agro-polymers (polysaccharides, proteins) and the biodegradable polyesters such as poly (lactic acid) (PLA), poly (hydroxyalkanoate) (PHA), aromatic and aliphatic copolyesters. Between these biopolyesters, PLA has caught the attention of polymer scientists as a potential biopolymer to substitute the conventional petroleum-based plastics. 

Poly (lactic acid) or PLA belongs to the family of aliphatic polyesters commonly made from α-hydroxyacids. This polymer has been the subject of many investigations for over a century. 

The most attractive advantages that distinguish PLA from the more common polymers are renewability, biocompatibility, processability and energy saving. First of all, PLA is a thermoplastic, high-strength and high-modulus polymer derived from renewable and degradable resources such as corn and rice, which can help alleviate the energy crisis as well as reduce the dependence on fossil fuels of our society. It is also  degraded by simple hydrolysis of the ester bonds, which does not require the presence of enzymes and in turn prevents inflammatory reactions. The hydrolytic products from such degradation process are then transformed into nontoxic subproducts that are eliminated through normal cellular activity and urine, making it an optimal material for biomedical applications. Moreover, this polymer has good thermal proprieties and thus it can be processed by film casting, extrusion, blow molding, injection molding and fiber spinning. This thermal processability is greater than other biomaterials such as poly (ethylene glycol) (PEG), poly (hydroxyalkanoates) (PHAs) and poly(ɛ-caprolactone) (PCL), contributing to the PLA application in textiles and food packaging fields. Finally, PLA production consumes 25-55% less fossil energy than petroleum-based polymers which will lead to significant reductions in air and water pollution and the total amount of water required for PLA production it is also competitive.    

        

However, confronted with many requirements for certain applications, Poly(lactic acid) has some disadvantages as its slow degradation rate through hydrolysis of the backbone ester groups, which can takes several years and can prevent its biomedical and food packaging applications. Another obstacle, unless it is properly modified, is the brittleness of this polymer, with less than 10% elongation at break; it is not suitable for demanding mechanical performance applications. PLA is also strongly hydrophobic and when it is applied as a tissue engineering material, because of its low affinity with cells, it can induce an inflammatory response from the tissues and living hosts. The last limitation is its limited gas barrier proprieties which prevent its complete access to industrial sectors such as packaging. From this point of view and considering its high cost, low availability and limited molecular weight, PLA has not received the attention it deserves, and that’s why the surface modification, the introduction of other components, or the surface energy, charge and roughness control have been examined.

Actually and in the biomedical field, micro and nanoparticles are a significant group of delivery systems, and the application of PLA is interesting due to its low toxicity and hydrolytic degradability. The most important properties of these systems are the drug release rate and the matrix degradation rate which are affected by the particle design and the material properties. Tissue engineering is also an area of interest for the PLA application, mainly in porous scaffolds to reconstruct matrices for damaged tissues and organs. 

• Tissue Engineering

The field of tissue engineering was created to improve and develop biological functions and it’s closely associated with methods to reconstruct living tissues by combining the cells and biomaterials. This association provides a scaffold, a temporarily supporting structure on which they can proliferate three-dimensionally and under physiological conditions.The advantages of tissue engineering over transplantation are that a donor is not required and there is no problem of transplant rejection. 

http://en.wikipedia.org/wiki/Tissue_engineering#mediaviewer/File:Tissue_engineering_english.jpg

A suitable scaffold for tissue engineering use should be biocompatible and have a good integration into host tissues without any immune response, be porous and have appropriate pore size and distribution for removing metabolic waste and allow cell and tissue growth. In addition, it must be biodegradable and mechanically able to support local stress and structure. Not all biomaterials have the capability of being used in this field, for example, although some metals have good mechanical proprieties and consequently being used in biomedical implants, they are not so advantageous for scaffolds because of their lack of degradability. Ceramics are also limited and despite good osteocondutivity and therefore mineralization, they have poor processability into porous structures.

Some linear aliphatic polyesters such as PLA and its copolymers, due to their structure and proprieties can be used as scaffolds. These polymers are approved by the FDA in biomedical field, but like the other materials, have some disadvantages like their slow rate of degradability, hydrophobicity and lack of functional groups, which conditions cells adhesion. A fibrous scaffold has significant advantages over polymer films in the high level of porosity needed to accommodate a large number of cells. This is where the pore diameter (interstitial space) becomes important for cell growth, vascularization, and diffusion of nutrients. 

Three-dimensional PLA porous scaffolds have been created for culturing different cell types, in cell-based gene therapy for cardiovascular diseases; muscle tissues, bone and cartilage regeneration and other treatments of cardiovascular, neurological, and orthopedic conditions. Osteogenic stem cells seeded on scaffolds of this material and implanted in bone defects or subcutaneously can recapitulate both developmental processes of bone formation: endochondral ossification and intramembranous ossification. Due to the high strength of PLLA mesh, it is possible to create 3D structures such as trays and cages. 

Several researches have shown that PLA-based hybrid materials are particularly promising and they have been successfully tested in many tissues such as bladder, bone, liver, cartilage and adipose. Chitosan/PLGA by heparin immobilization is an example of a novel scaffold that is being clinically tested. The introduction of chitosan into PLGA microspheres improves the attachment of biomolecules such as heparin because of chitosan’s reactive amino group. This heparinized chitosan/PLGA scaffolds with a low heparin loading showed a stimulatory effect on cell differentiation and may be used in bone regeneration.

For tissue engineering, the application of three-dimensional scaffolds as synthetic extracellular matrices allowed the cells proliferation and secretion while the scaffold gradually degrades. These 3D scaffolds, often consist of polymer/ceramic composites, such as a polymeric matrix filled with bioactive glasses, glass ceramics and calcium phosphates, that combine the advantages of the two types of materials. The polymers that are used in the matrix can be such as chitin and chitosan and collagen or synthetic polymers such as saturated aliphatic polyesters: polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL) and polyhydroxyalkanoates.

Three-dimensional electrospun fibrous scaffolds have been also studied for bone regeneration. Electrospinning uses an electrical charge to draw micro and nano scale fibers from a liquid and the use of these 3D materials like microfibrous PLLA scaffolds have reported a higher level of osteoblasts proliferation and a favorable substrate for cell infiltration and bone formation.

In cartilage tissue engineering, collagen and hyaluronan-based matrices are among the most used scaffolds, due to their substrates which are normally essential elements in native articular cartilage. The PLA is used as PGA/PLA copolymer under the trade name BioSeed-B and BioSeed-C by German industry (Biotissue Technologies AG, Freiburg, Germany). 

However, despite these recent developments, PLA-based materials still have an important limitation for tissue engineering - the risk of immune response and disease transmission. In the future, it’s expected the use of design scaffolds with in vivo experimentation, and coupling scaffold design with cell printing to create material hybrids to optimize tissue engineering treatments.

Do you know what is a cerclage cable?

The surgical treatment of fractures is intended to restore the function of bones and members. In cases of trauma, during hip replacement and treatment of associated peri-prosthetic fractures, for example, it is often necessary to hold the bone or fragments of bone together to create a stable environment for healing to occur. Typically, this is done with circular metal cables or wires, with various diameters, depending on the fracture and the place to be applied. 

The technique used is called Cerclage and it allows to stabilize fractures, that are impossible to achieve with other forms of fixation. 

Despite being used in a range of applications in orthopedics as a primary method of fracture fixation, cerclage also shows several drawbacks. For instance, cerclage wires are prone to breakage and cables are subject to fatigue and fraying, releasing metallic debris into the body. Furthermore, the wire or cable can break causing an interruption of the blood supply to the bone and/or tissue irritation. 
To minimize these risks, different materials are under investigation and new safety products are emerging in the market.