Medical imagery ranges from existing technologies like MRI, CT, ultrasound or sonograms to recent developments like augmented reality and robotic controlled surgery.
Magnetic resonance imaging (MRI)
Figure 1: Example MRI scan image (Wikipedia)
MRI scans produce detailed images of the inside of the body by using strong magnetic fields and radio waves. The strong magnetic field aligns the protons of the hydrogen atoms in the human body and short bursts of radio waves then bring the protons out of alignment. As protons realign they create another radio signal, which can be measured by receivers. As protons in different types of tissues realign at different speeds, these data can be used to create an image of the inside of the body. 
According to Radiologyinfo.org, MRI scans are often used to diagnose:
- tumors of the chest, abdomen or pelvis.
- diseases of the liver, such as cirrhosis, and abnormalities of the bile ducts and pancreas.
- heart problems, such as congenital heart disease.
- malformations of the blood vessels and inflammation of the vessels (vasculitis).
- a fetus in the womb of a pregnant woman.
Pros & Cons
- non-invasive as it doesn’t involve ionizing radiation
- images of soft tissues like the heart, liver and other organs are often more detailed than other imaging methods
- enables discovery of abnormalities close to bones that might not have been visible with other imaging methods
- patients with implanted medical devices such as pacemakers might not be able to undertake MRI scans due to the strong magnetic field
- contrast injections might pose an allergic risk
- imaging takes relatively long
- high cost
Computed tomography scan (CT scan)
Figure 2: CT scan 3D bone reconstruction (By Zgyorfi via Wikipedia)
CT scans work by using x-rays and producing multiple images that are then combined.
Pros & Cons
- Fast enough to reveal internal injuries and bleeding during emergency situations
- Scans soft tissue, blood vessels and bones at the same time
- Unlike conventional x-ray, it provides detailed images of different types of tissue
- More cost-effective than MRI
- Patients with implanted medical devices are not affected
- Less sensitive to movement
- No immediate side effects
- Small doses of radiation, which might affect certain people, e.g. pregnant women
- risk of allergic reactions to contrast materials
Figure 3: Ultrasound image of fetus at 12 weeks (By Wolfgang Moroder via Wikimedia Commons)
Ultrasound makes use of high frequency sound waves to produce images of the inside of the human body. The transducer (probe) of the scanner emits short sound waves and receives and processes the sound waves that are reflected from the internal tissue. Different areas in the tissue reflect the sound waves at different intensities and take different times for it depending on the composition and depth of the area. The visual image produced is called a sonogram.
Some common applications include:
- examination of baby during pregnancy
- diagnose cause of symptoms like pain, infection or swelling
- assess damage after heart attack
- diagnose heart conditions
Pros & Cons:
- Non-invasive (except for special cases)
- Not painful
- Wide availability
- Relatively low cost
- Clear picture of soft tissue
- Real-time imaging
- Not as detailed as other imaging methods
Ultrasound 3D imaging
Figure 4: 3D ultrasound image at 12 weeks (By Rizome via Wikimedia Commons)
3D ultrasound works similarly to traditional ultrasound, but sound waves are sent out at different angles. Computers can then construct a 3D image from the resulting echoes. 4D ultrasound allows to see the object over time, so that time is considered the fourth dimension.
3D ultrasound is mostly used for pregnant women to detect or confirm fetal anomalies. However, this is restricted to external features and often such anomalies can be detected through conventional ultrasound as well. For this reason and the high cost of the technology, most clinics keep using 2D ultrasound. Often 3D ultrasound is also carried out for mothers to see their baby.
The idea of augmented reality is to add computer-generated information to the view on the physical real world. In the context of medicine, the additional information available can prove a significant advantage in fields such as diagnosis and surgery. Some of the possible future uses of AR in medicine include:
- medical education: provide deeper and more available insight into human anatomy, virtual access to surgeries, OCR to suplement visual help to textbooks
- video support in telemedicine
- nurse support: finding veins for injections (AccuVein)
- vision support: helping visually impaired that have some vision left to recognize shapes by making them more recognizable, e.g. giving object a clearer outline (VA-ST)
- allowing surgeons to show patients planned surgeries (SNAP)
- augmented reality-assisted surgery/ augmented reality surgical navigation
Research is being conducted on augmented reality-assisted surgery, where AR supports surgeons during surgeries. Often, surgeons will need to use external sensory sources such as CT scans or endoscopic cameras, to guide the operation. AR could assist the process by overlaying such imagery in real-time, which can allow for more precise surgeries.
- TUM “A Look into the Body – Augmented Reality in Computer Aided Surgery” 
- Philips Media “Philips announces new augmented-reality surgical navigation technology designed for image-guided spine, cranial and trauma surgery” 
Robotic controlled surgery
- Wired “Surgical Robots Operate With Precision” 
- All About Robotic Surgery “Surgical Robots” 
- NYU School of Medicine “What is Robotic Surgery?” 
- Engadget “Surgical robot makes highly precise eye injection possible” 
Robotic controlled surgeries make use of robotic systems to aid surgical procedures, often to enhance the capabilities of the surgeon and allow minimally invasive surgeries. Such robotic systems are usually not autonomous yet, but are controlled by a surgeon, who can be in the same location or even at distance in the case of telesurgery. The controls usually take form of a so called telemanipulator which allows the surgeon to perform the normal movements of a surgery. Robotic systems can also be used to enhance precision of the surgeon, e.g. in an open surgery.
Pros & Cons
- smaller, less invasive & more precise interventions
- better work environment, specially for long procedures, where the surgeon often gets fatigued. Robotic system stay steady and smooth all time
- possibility of telesurgery with all its benefits, e.g. specialists at distance
- might reduce costs in the future by making surgeries more accessible and reducing trauma & healing time
- might reduce amount of personall required in the operating room
- usually high initial cost (some above $1 million) & maintainance cost
- extensive training is required
- very few manufacturers lead to little competition allowing high prices
- latencies need to be very low
- programming errors would be critical
Examples of robotic systems
The most promising uses of robotic systems are full surgical systems such as da Vinci or Zeus, which allow the operation to be fully undertaken by the robotic arms and tools controlled by the surgeon. These robots have tools to grasp, hold, move, cut and sewing so that they can perform a surgery.
A recent example use of the accuracy and precision of such systems is an eye surgery carried out by researchers from KU Leuven, where a drug is injected into the around 0.1 millimeter wide retinal vein for around 10 minutes. 8 Such an operation is too hard to be performed manually, showing the power of robotic surgery.
Other systems can help to autonomously take blood samples or provide improved images during operations, e.g. through a laparoscopic camera which allows very small cuts and minimally invasive surgeries.
Possible future uses of robotic systems include robots that would be ingested by the patient and operate from within the patients body. This could provide meaningful diagnosis and an even less invasive way of surgery. An example of such experimental systems is the ARES robot.
Another possible future use of such systems is to make them autonomous through some form of artifical intelligence. This would be another step towards more accessible and affordable surgery (although the costs are still too high) and could also be useful for applications in rural areas, battlefields or space, where specialist surgeons are not available.
 NHS “MRI scan”