Editorial 1 : Understanding the science behind magnetic resonance imaging
Introduction
For those trying to look inside the human body without surgery, magnetic resonance imaging is an indispensable tool. Paul Lauterbur and Peter Mansfield refined them to pave the way for their commercial use. For these efforts, they were awarded the Nobel Prize in medicine in 2003.
Magnetic resonance imaging
- Magnetic Resonance Imaging (MRI) is used to obtain images of soft tissues within the body. Soft tissue is any tissue that hasn’t become harder through calcification.
- It is a non-invasive diagnostic procedure widely used to image the brain, the cardiovascular system, the spinal cord and joints, various muscles, the liver, arteries, etc.
- Its use is particularly important in the observation and treatment of certain cancers, including prostate and rectal cancer, and to track neurological conditions including Alzheimer’s, dementia, epilepsy, and stroke.
- Researchers have also used MRI scans of changes in blood flow to infer the way the activity of neurons is changing in the brain; in this form, the technique is called functional MRI.
- Because of the MRI technique’s use of strong magnetic fields, individuals with embedded metallic objects (like shrapnel) and metallic implants, including pacemakers, may not be able to undergo MRI scans.
The working
- An MRI procedure reveals an image of a body part using the hydrogen atoms in that part. A hydrogen atom is simply one proton with one electron around it.
- These atoms are all spinning, with axes pointing in random directions. Hydrogen atoms are abundant in fat and water, which are present almost throughout the body.
- An MRI machine has four essential components. The machine itself looks like a giant doughnut. The hole in the centre, called the bore, is where the person whose body is to be scanned is inserted.
- Inside the doughnut is a powerful superconducting magnet whose job is to produce a powerful and stable magnetic field around the body. Once the body part to be scanned is at the centre of the bore, the magnetic field is switched on.
- The machine’s third component is a device that emits a radiofrequency pulse at the part under the scanner. When the pulse is ‘on’, only the small population of ‘excess’ atoms absorbs the radiation and gets excited.
- When the pulse goes ‘off’, these atoms emit the absorbed energy and return to their original, lower energy states.
- The frequency of pulse the ‘excess’ atoms have to absorb is called the Larmor frequency. Its value depends on the strength of the magnetic field and the type of tissue in which the atoms are present.
- The fourth and final component, a detector, receives the emissions and converts them to signals, which are sent to a computer that uses them to recreate two- or three-dimensional images of that part of the body.
Pros of MRI
- MRI machine activates three magnets that produce smaller magnetic fields that are weaker than the main field by about 80-times, if not more. These fields also have a gradient, that is, they are not uniform.
- By turning the gradient magnets on and off in specific sequences, the MRI machine can thus scan portions that are just a few millimetres wide.
- In fact, because of the way the machine is built and the magnets are organised inside it, an MRI scan can practically image the body from all useful directions and, if required, in very small increments.
- When the ‘excess’ atoms emit the energy they’d absorbed to return to their lower energy states, the return happens over a duration called the T1 relaxation time.
- The hydrogen atoms in water have different values of T1 depending on the tissue in which they’re present. An MRI machine exploits this fact to show different tissues in different shades of grey.
- Clinicians may also inject an individual with a contrast agent — typically a gadolinium-based compound — that lowers the T1 time in some tissues, improving their visibility in an MRI scan.
Cons of MRI
- MRI machines are expensive: depending on the specifications, including the strength of the magnetic fields and the imaging quality, they cost from a few tens of lakh rupees to a few crores.
- These costs are compounded by the discomfort of using the machine. While it’s an advantage that an individual inside the bore doesn’t have to move for the machine to scan different parts, the individual is actually expected to lie still for tens of minutes, until the scan is complete.
- If the individual moves, the resulting image will be distorted and the scan will have to be repeated. The problem is exacerbated if the individual is claustrophobic.
- Further, the switching of such heavy currents within the machine, as the gradient coils are operated in sequence, means the machine produces loud noises when operating. This can be an additional source of discomfort for the individual.
Way forward
- Researchers have deeply investigated the effects of strong magnetic fields on the body. MRI scans don’t pose any threats; once the magnetic fields are taken away, the atoms in the scanned part don’t remain affected.
- There is no long-term harm associated with scans. However, a scan’s effects on pregnant women aren’t as well-studied, therefore more research has to be done on this.
Editorial 2 : What is carbon farming?
Introduction
Carbon is found in all living organisms and many minerals. It is fundamental to life on earth and plays a crucial role in various processes, including photosynthesis, respiration, and the carbon cycle. Carbon farming combines two concepts by implementing regenerative agricultural practices that restore ecosystem health while improving agricultural productivity and soil health, and mitigating climate change by enhancing carbon storage in agricultural landscapes and reducing greenhouse gas emissions.
The importance of carbon farming
- A simple implementation of carbon farming is rotational grazing. Others include agroforestry, conservation agriculture, integrated nutrient management, agro-ecology, livestock management, and land restoration.
- Agroforestry practices — including silvopasture and alley cropping — can further diversify farm income by sequestering carbon in trees and shrubs.
- Conservation agriculture techniques such as zero tillage, crop rotation, cover cropping, and crop residue management can help minimise soil disturbance and enhance organic content, particularly in places with other intense agricultural activities.
- Integrated nutrient management practices promote soil fertility and reduce emissions by using organic fertilizers and compost.
- Agro-ecological approaches such as crop diversification and intercropping have benefits for ecosystem resilience.
- Livestock management strategies including rotational grazing, optimising feed quality, and managing animal waste can reduce methane emissions and increase the amount of carbon stored away in pasture lands.
The challenges
- While carbon farming does offer numerous benefits, its effectiveness varies depending on multiple factors — geographical location, soil type, crop selection, water availability, biodiversity, and farm size and scale.
- Its usefulness also depends on land management practices, sufficient policy support, and community engagement.
- Regions with long growing seasons, sufficient rainfall, and substantial irrigation are best suited to practise carbon farming because they provide the best conditions in which to sequester carbon, through vegetation growth.
- On the other hand, carbon farming can be challenging in hot and dry areas where the availability of water is limited, and prioritised for drinking and washing needs.
- Limited water availability can hinder the growth of plants, thus restricting the potential for sequestration through photosynthesis.
- Moreover, selecting which plants to grow also becomes crucial because not all species trap and store carbon in the same amounts or in an equally effectively manner.
- Fast-growing trees and deep-rooted perennial grasses tend to be better at this task — but on the flip side, these types of plants may not be well-suited to arid environments.
- Further, the adoption of carbon farming practices may require financial assistance for farmers to overcome the costs of implementing them.
- In the context of developing countries like India, small-scale farmers may lack the resources to invest in sustainable land management practices and environmental services.
Carbon farming schemes worldwide
- Initiatives like the Chicago Climate Exchange and the Carbon Farming Initiative in Australia demonstrate efforts to incentivise carbon mitigation activities in agriculture.
- The processes range from no-till farming (growing crops without disturbing the soil) to reforestation and pollution reduction.
- Initiatives like Kenya’s Agricultural Carbon Project, which has the World Bank’s support, also highlight the potential for carbon farming to address climate mitigation and adaptation and food security challenges in economically developing countries.
- The launch of the ‘4 per 1000’ initiative during the COP21 climate talks in 2015 in Paris highlights the particular role of sinks in mitigating greenhouse-gas emissions.
Opportunities in India
- As climate change intensifies, climate-resilient and emission-reducing agricultural practices can benefit from adaptation strategies. Agriculture is crucial in this endeavour.
- Grassroots initiatives and pioneering agrarian research in India are demonstrating the viability of organic farming to sequester carbon.
- Regions with extensive agricultural land, such as the Indo-Gangetic plains and the Deccan Plateau, are well suited to adopt carbon farming whereas the mountainous terrain of the Himalayan region is less so.
- Coastal areas are prone to salinisation and have limited access to resources, thus limited the adoption of traditional farming practices.
- Further, carbon credit systems can incentivise farmers by providing additional income through environmental services.
- Studies have shown agricultural soils can absorb 3-8 billion tonnes of CO2-equivalent every year over 20-30 years. This capacity can bridge the gap between feasible emissions reductions and the indispensable stabilisation of the climate
Conclusion
- Promoting carbon farming is in India’s interests — to mitigate climate change while improving soil health, enhancing biodiversity, and creating economic opportunities for its adopters.