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The correct CHOICE is (b) Gadolinium

The best explanation: BISMUTH GERMINATE OXIDE (BGO), gadolinium oxyorthosilicate (GSO) or lutetium oxyorthosilicate detectors (LSO) are three materials that can be used to form the detectors for PET. They can record IMPULSES from the gamma rays and convert them into electrical signals which are finally processed to form images.

The correct answer is (c) T2* time

Explanation: When the gradient and RF coils are POWERED off, the magnetized elements get demagnetized and this causes the image to be formed. T1 is the time for the elements to go back to the original, demagnetized state. T2 is the time needed for the elements to go out of phase. T2* is the time needed for the SPIN to dephase. T2* is important for fMRI because oxygenated hemoglobin is diamagnetic while deoxygenated hemoglobin is PARAMAGNETIC. Thus, the T2* star time will be different for the TWO of them and the amount of OXYGEN used by the brain can be mapped.

Correct answer is (a) spatial

Easy explanation: MRI can form a 3D IMAGE of the organ which is ANATOMICAL in nature. It gives good clarity and resolution for the finer DETAILS of the image. In the same WAY, fMRI has a good temporal resolution. It maps the BRAIN with respect to time, scanning the oxygen used at the regular intervals.

Correct answer is (b) cerebral blood flow and NEURONAL activity are connected

The best I can explain: The body functions with the help of OXYGEN. The oxygen supply allows glycolysis (the breakdown of the sugar molecules), the FIRST step in generating ATP.THUS, when the brain has a good amount of oxygen supply, the neurons will work properly. The supply of oxygen may affect the activity levels of neurons. Maybe diseased neurons will show a different PATTERN of oxygen consumption.Since oxygen is provided by the blood, thus the researchers came to the conclusion that blood supply and neuronal activity are connected and thus it forms the underlying principle of fMRI.

The correct answer is (d) electron beam and detectors

Explanation: In the olden generation of CT, the beam of X – Rays and detectors used to move together to scan and TAKE the image. However, in the latest CT scanners, an electron gun fires an electron beam at the target rings, the focus of which is DECIDED by a tungsten anode. This target rings GIVE of X – Rays which are used to image the desired organ.The X-Ray produced can move along a certain diameter. This SYSTEM can take a better image of the heart.

Correct answer is (c) gamma

The explanation is: Gamma rays are energy rays or photon rays and do not have a mass. Thus, they do not destroy the cancerous cells or provide any relief in therapies. HOWEVER, since they have a GREATER penetration power, they can be used for imaging. If the body is exposed to these penetrating radiations for a long time, the body may have burn and a prolonged and continuous EXPOSURE will result in damaged DNA. INCREASING the intensity of the radiations also causes harm to the body.

The correct answer is (c) time

To elaborate: A fMRI scan MEASURES the amount of OXYGEN used by the body. In ORDER to MEASURE the oxygen used up, a continuous scan is done every few seconds, mostly within a span of 2 – 5 seconds. Thus, the images received are a function of time.

Correct choice is (a) Helium

For explanation: Helium is a noble gas which is non REACTIVE in NATURE. A good coolant has a high THERMAL CAPACITY, low viscosity, non toxic, chemically inert, all the properties that Helium possesses. Another advantage is that Helium does not have the tendency to absorb any neutrons and so it cannot become radioactive. Being a noble gas, it is non reactive and so non corrosive in nature. Thus, it is used a coolant for the MRI machine, especially the magnet.

Right answer is (a) PET

Easiest EXPLANATION: PET scan is used to look into the metabolic ACTIVITIES while the CT scan is used to look into the anatomical STRUCTURE of the organ. Thus, while a CT scan may hint the PRESENCE of a tumour, a PET scan can confirm if the tumour is benign or malignant.

Correct choice is (a) longer

Explanation: Since PET has 2 gamma rays, it USES the correlation of the images to form the final image. The process is also faster. However, with SPECT, there is only 1 gamma ray produced. The process is longer. Thus, for BETTER imaging and allowing multiple imaging with a single SHOT of dye, SPECT radioisotopes need to have a longer HALF life.

Correct choice is (b) OXYGEN

The explanation is: In an MRI, the scans are taken with the help of the Hydrogen atom but in fMRI, the blood oxygen, i.e. the oxygen CONTENT of the blood is TARGETED. It measures the oxygen used up by the various tissues in the organs and images that as the FUNCTIONAL MRI.

Correct choice is (d) Bone Marrow

To EXPLAIN I would say: Bone marrow is a soft tissue as compared to the encasing bone STRUCTURE. Also, it had water WHOSE Hydrogen is used by the MRI to form an image. The other parts of the bone do contain hydrogen but the hydrogen is placed in a crystal structure, making it difficult to move or be magnetized. Thus, it is difficult to image any other parts of the bone with MRI except for the bone marrow.

Right CHOICE is (a) True

To explain I would say: A CAT scan is basically an X-ray of soft tissues. It will not necessarily NEED a dye or a contrast MEDIUM. A contrast is used when some portion needs to be enhanced or better details of the organ need to be SEEN.

Right choice is (d) HU

Explanation: HU stands for Hounsfield Unit. It represents the opacity to the X – rays. HIGHER the opacity, the brighter the image is formed on the screen. A NORMAL X-Ray has the bones and tissues blocking its PATH so the opacity is really low but with CT Scan, with its 3D imaging technique, the opacity for the tissue is INCREASED and the image is taken better. The CT is able to negate out the resistance provided by the bone and other tissues.

Correct OPTION is (C) x-ray of soft tissues

Explanation: The X – rays pass through the body completely. The bones are ABLE to provide resistance to them to a limit by absorbing them. This resistance causes the image to appear. However, for soft tissues, the single shot of X- Rays cannot give an image as they do not pose any obstruction to them. To image soft tissues, multiple X – Rays of high energy need to be passed. Since it can NEGATE out the effect of the BONE and image in slices, CT is good for imaging soft tissues.

Correct ANSWER is (b) has white matter which more than normal

To elaborate: A person suffering from SCHIZOPHRENIA suffers from problems like hallucinations, listening to non existent SOUNDS etc. The persistent problem can be ANALYZED by looking at the brain scan which shows that the white matter in a particular part of the brain has become more than normal. Since white matter is responsible for sending impulses, a bigger area of white matter will mean faster travelling of impulses and therefore such thoughts. However, since the CT shows the negatives of the original, the white matter will LOOK gray and gray matter will look white. Thus, in a scan, if there is a large gray area and the person suffers from symptoms like hallucinations or anxiety etc, then it’s a high possibility that they have schizophrenia.

Correct option is (B) SHRINKING brain

Easiest explanation: Frontotemporal Dementia (FTD) is the most common kind of dementia found in the population. In this, the neural cells of the brain go for apoptosis (cell death) causing an atrophy (SHRINKAGE) of the brain. This causes the PERSON to have memory disorders.

The correct answer is (c) Tc

The BEST I can explain: Tc – 99m is ACTIVATED Technetium which can be produced from Molybdenum. Tc – 99m has a HALF life of AROUND 6HRS, is relatively easy to produce and can be flushed out of the body without causing much harm. It is also relatively stable and thus makes a good choice for SPECT scanning.

Correct option is (a) with no gyri and sulci

The explanation is: Lissencephaly is a neuronal defect that is present right from BIRTH. It may or may not be detected in the fetal stage. In this DISORDER, the BRAIN in smooth without the presence of any gyri and sulci. A child born with lissencephaly often has a normal head structure so it is often difficult to detect the presence of this defect TILL a LATER age.

Correct option is (b) voxel

Explanation: Voxel stands for the volumetric pixel. MRI is UNIQUE in a way that it can IMAGE segments of the organ from different ANGLES with various slice SELECTIONS. These slice selections HELP choose which layer of the organ will be imaged and the smallest unit of this image is called a voxel. Since MRI can produce 3D scans, the image is volumetric in nature and thus, volumetric pixel or voxel is used.

The correct option is (b) CT = 2.304HU, ΔX-RAY= 2.304

Easy EXPLANATION: To solve the above,

For CT

 ΔCT = l1 – l2

= 63 – 35

= 28

HU for CT = (l1 – l2)X 1000/(l1 + l2)/2

= (63 – 35)X 1000/(63 + 35)/2

= 571.4285HU

For X – Ray

ΔX-Ray = Σl1 – Σl2

= 1738 – 1734

= 4

HU for X – Ray= (Σl1 – Σl2)X1000/(Σl1 + Σl2)/2

= (1738 – 1734)X1000/(1738 + 1734)/2

= 2.304HU.

The correct option is (b) – 30.212

The explanation is: Gyrometric ratio is the ratio of the magnetic moment to the angular moment of the ELEMENT. LAMAR frequency, also called as Lamar precision is the frequency by which the element will undergo a change in ORIENTATION when placed in a strong EXTERNAL magnetic field. Lamar frequency is given by the formula:f = γn x B0/2Π

Here γn/2Π is the gyrometric ratio. Thus,

 f=-4.316*7 = -30.212.

The correct choice is (d) MRI images soft tissues so it does not image the CRANIUM properly. Thus, the cranial ring is more PROMINENT in CT than in MRI

Easiest explanation: The cranium is MADE of flat bones with spongy bones in between was shock absorbers. They are flat and thin and thus do not have bone marrow. Thus, the HYDROGEN content in these bones is less than those in long bones. Also, MRI mostly targets Hydrogen in water to GET magnetized while the hydrogen in bones is arranged on another structure which restricts its mobility as well. Thus, bones normally don’t show up in an MRI but the bones with bone marrow can be imaged.

Correct answer is (a) Brain

For explanation I would say: fMRI is in a way an exclusive way to scan for the brain. One of the main reasons is that fMRI does not REQUIRE any DYES, even when doing a deep scan. THUS, it is a safer process for doing brain scan as compared to other scanning methodologies. Also, the brain is the most complex organ so using fMRI to get BETTER details about the brain helps in a better study.

The correct answer is (b) CT Angiography

Explanation: Angiography is a process in which the blood vessels are visualized USUALLY with the HELP of a contrast. ANGIOPLASTY is a process in which a catheter is inserted to remove or open a blocked blood vessel. CT Angiography has an advantage of being 3D as compared to normal fluoroscopic angiography. Thus, the image FORMED is more detailed.

Right choice is (a) 1.5 – 3 Tesla

To explain: MRI’s have three major PORTIONS which work TOGETHER to form an image. The largest portion is TAKEN up by the magnet. This magnet is ALWAYS on and produces a Magnetic Field of the strength of 1.5 – 3 Tesla. Commercially, 1.5 – 2 T was used but now even with 3T have been introduced.For research purposes, MRI of 7T has also been CONSTRUCTED.

Right answer is (b) To enhance a particular tissue

Easiest explanation: The contrasts are usually of iodine BASED and get absorbed by the body. They weaken the radiation passing through the area of interest making white PATCHES turn up. These white PATCHED actually represent a tumour that was not seen previously or a patch of diseased cells.Basically, they enhance the image by weakening the AMOUNT of radiation passing through.

Correct answer is (c) Z plane

For explanation I would say: An MRI can give a 3D image of an object and we can choose the FORM which direction and from which angle we would like to view the image. The image is always perpendicular to the GRID that has been selected. As it is given that our grid is XY, then slice selection can be done only in Z plane and so, THEREFORE, the image is also in Z plane.

Right choice is (a) Gamma Camera

The best explanation: A gamma camera had detectors made of PMTs to help form an image. Since PET produces 2 photons/gamma rays, correlation of the image formed at the two ends is USED to form a PROPER image. However, SPECT produces only 1 photon so if they need to be collected properly to form an image. Thus, a gamma camera, a camera SPECIALIZING in CAPTURING IMAGES by taking the impulses from the photons in used in SPECT.

Right answer is (b) Gastrointestinal TRACT

The explanation: When we swallow something, it always GOES to the Gastrointestinal Tract. Radioactive barium in trace amounts is SWALLOWED and the projected X-Ray beams photograph/record/project the whole process. The GI tract lights up and the examiner can see inside the track.

Right answer is (c) They SHOW the metabolic functions

The explanation is: The dyes used in PET and SPECT are such that they become a part of the metabolic pathways and the transmitted radiations can help visualize the metabolic pathways. The machine that does the same work as PET and SPECT, i.e. visualizing the metabolic pathways is FMRI. HOWEVER, SINCE it does not use any dyes, it does not fall under nuclear imaging.

Correct choice is (a) Cranium

To explain: BONES are natural impedance providers to ultrasound and so if any organ is covered or surrounded by bones, it is not possible or very difficult to take their ultrasound. For an infant, their bones are soft and do not provide so MUCH of a RESISTANCE to the passage of the ultrasound WAVES. THUS, it is possible to take an ultrasound of the brain at an infant stage but not at an adult stage.

Correct answer is (c) Phase Array Probe

Best explanation: This type of probe has 128 elements and each segment is used to transmit and receive data. Since EVERY ELEMENT can function individually, the user can change the SHAPE and FOCAL point of the ultrasonic beam. Their angle of inclination can also be changed. This ALLOWS the probe to image through the space of ribs and images the heart.

The correct option is (a) ULTRASOUND of the heart

For explanation I WOULD SAY: The ultrasound of the heart is called the echocardiography. It provides a REAL time imaging of the heart with the help of the ultrasound. The VARIOUS modes for imaging of the heart help detect various problems.

Correct ANSWER is (c) M – MODE

To explain: The M – Mode depicts the incoming image in a wave like a manner. This wave is generated by the moving parts of the body.Thus, the moving HEART valve can be depicted in a wave like a manner and so any blockages or abnormalities can be detected with the irregular wave PATTERN.

The correct choice is (b) Silver HALIDE

The explanation: The PLATE coated with Silver Halide, mostly silver bromide is USED to image the X – Rays. Silver halides when EXPOSED to X – Rays END up becoming black and so the images of the X – Rays are formed.

Right ANSWER is (c) < 30keV

Easy explanation: Mammography is the X-Ray done for the breasts to detect breast stones or early stages of cancer. It is also called as mammography. SINCE the breast CONSISTS of soft tissue, the exposed radiation is of a lesser intensity and should not EXCEED 30keV.

The correct choice is (a) bombardment of cathode RAYS on a radioactive material

The best explanation: Cathode Rays are high speed ELECTRON beams that when fall on the radioactive MATERIALS causes the emission of electrons and ENERGY. This energy is X-Ray. The X – Rays are emitted DUE to various types of collisions happening in the radioactive element with the emitted electron beams.

The correct choice is (a) Pressure wave ULTRASOUND

The EXPLANATION: A piezoelectric crystal is a special transducer which converts mechanical energy into electrical energy and vice-versa. THUS, when the electrical impulses are given to the transducer, it is converted into mechanical energy. The transducer starts vibrating CAUSING a pressure difference and the ultrasound waves are produced.

Right choice is (a) Reflection and Refraction

For explanation: The ultrasound works on the PRINCIPLE of reflection and refraction. While it is necessary that sound waves NEED a MEDIUM to travel, so we can say propagation is important but it is only because the sound wave gets refracted when the medium CHANGES and are reflected back that the image is FORMED. Thus, the principle for ultrasound is reflection and refraction.

Correct option is (b) SPECT

Explanation: SPECT uses Tc – 99m in its dyes. Bone Scintigraphy is a process in which the DYE is injected and the bones are imaged. It can help look for CANCER, inflammation, FRACTURES etc. Since it can image with RESPECT to TIME, it can also help plot out the metabolism of the bone.

The correct CHOICE is (b) Photon

The best explanation: SPECT STANDS for Single Emission Photon Tomography. In this process, the radioactive dyes give out photons which are detected by the detector and forms an image. The photon detector USUALLY has Photo Multiplier Tubes (PMTs) that can AMPLIFY the received impulses from the photon and FORM an image.

Correct choice is (c) C – Arm

Easy explanation: C – Arm is used for DIAGNOSIS and minimally invasive PROCEDURES. The two plates at the end of the two arms have receiving and transmitting ends for X – Rays. The C – Arm can also rotate and MOVE at various degrees thus PROVIDING access and VISUALS from many directions and angles.

Right answer is (a) True

The BEST I can explain: Fluoroscopy is a process that DEPENDS upon the radioactivity of the dye to show the IMAGE. When the dye is injected or INGESTED, it emits radioactive waves which are captured/recorded using devices. Thus, for fluoroscopy, dye is a NECESSITY.

The correct option is (b) Stress Echocardiography

The best explanation: To check for a CORONARY HEART DISEASE, the person may get subjected to some sort of stress in the form of a physical exercise. The doctor will take an echocardiogram before the test and ONE after the test. For continuous monitoring, an ECG may be TAKEN. Through this method, the strength of the heart muscles can be monitored.

The correct option is (b) transabdominal imaging

For explanation I would say: The CURVE of the curvilinear probe increases the footprint i.e. the DEPTH and surface area for imaging along with low frequency. Thus, it is used for taking the images of the abdomen. To take an image of the superficial structures and vessels, a linear probe is used as it can produce high frequency waves. PHASE array probes are used for cardiac ULTRASOUND as it can image between the ribs and endocavity probes are used for transrectal and transvaginal imaging.

Correct choice is (a) γ INCREASES, penetration of sound increases, resolution decreases

The best I can explain: When the frequency (γ) of the sound waves increases, it gains more ENERGY to overcome the impedance barrier and so is ABLE to PENETRATE deeper. However, the penetration may not be uniform in all places and reflection may be UNEVEN thus it affects the resolution of the image.

Right choice is (a) glucose

To explain: For any growing or recovering part of the body, the most important content is carbohydrate which is PROVIDED by glucose. Thus, to test for a suspected malignant tumour, a glucose based radioligand is used. This radioligand is absorbed by a tumour and it collects and BECOMES part of the normal FUNCTIONING of the body. The more the collection of the radioligand at one place, greater is the SIZE or the ACTIVITY of a tumour.