Magnetic Resonance and Ultrasound Imaging - Medical Imaging Systems - Biomedical Engineering Previous Year Questions

1

2020 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2020

The MRI scanner parameter of long \(T_{Rep}\) or short \(T_{Echo}\) will generate a _____ contrast image

A

Proton Density -weighted

B

T2- weighted

C

T1- weighted

D

T2*- weighted

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2

2020 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2020

A 5 MHz ultrasound pulse is used to image a tumor at a depth of 2 cm in a soft tissue. It takes time \(t\) for the reflected echo from the tumor to come back to the receiver. Instead, if a 2.5 MHz wave is used, how long will it take for the echo from the same tumor to arrive at the receiver?

A

\(t / 2\)

B

\(t\)

C

\(2 t\)

D

\(4 t\)

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3

2020 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2020

A patient is initially imaged in a 1 Tesla MRI scanner and induced voltage is found to be equal to \(V_1\). The expression for the magnitude of the received voltage in RF coil is given below. \(|V| = 2\pi\gamma_0 V_s M_0 (\sin\alpha) \beta''\) \(V_s\): MR slice volume, \(M_0\): Magnitude of resultant magnetic vector at equilibrium, \(\gamma_0\): Larmor frequency, \(\alpha\): tip angle, \(\beta''\): Magnetic field sensitivity of receive coil. When the patient is shifted to a 3 Tesla MRI scanner that uses the same RF coil and the slice thickness is halved, the magnitude of the induced voltage was found to be equal to \(V_2\). The ratio \(V_2/V_1\) is

A

1.5

B

3.0

C

4.5

D

6.0

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4

2020 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2020

A 3 MHz ultrasound transducer transmits a 3-cycle long pulse into a soft tissue at normal incidence to fat and liver interface. The axial resolution (mm) and the amplitude reflection coefficient at fat-liver interface, respectively, are Use \(C_{tissue} = 1500\) m/s, \(C_{fat} = 1450\) m/s, \(C_{liver} = 1570\) m/s, \(\rho_{fat} = 920\) kg/m³, \(\rho_{liver} = 1060\) kg/m³

A

0.5, 0.22

B

0.75, 0.22

C

0.5, 0.11

D

0.75, 0.11

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5

2021 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2021

An RF pulse is applied to acquire an axial MR image at the isocenter of a 1.5T MRI scanner with slice thickness of 2.5 mm. Assuming a gradient field strength of 2 Gauss/cm is applied and Gyromagnetic ratio of protons is 42.58 MHz/T, the RF pulse bandwidth required for slice selection is ______ kHz.

A

1.06

B

2.13

C

6.66

D

13.31

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6

2021 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2021

A longitudinal pressure wave travelling inside a muscle tissue is incident at an angle of 60° at the interface between the muscle and kidney. Let the wave impedance be \(Z_{muscle} = 1.70 \times 10^5 \text{ g cm}^{-2} \text{ s}^{-1}\), \(Z_{kidney} = 1.62 \times 10^5 \text{ g cm}^{-2} \text{ s}^{-1}\) and wave velocities in muscle and kidney tissues be 1590 and 1560 m/s respectively. The transducer centre frequency is 1.5 MHz. The pressure wave propagation angle in the kidney tissue and intensity transmission coefficient at the tissue interface are ________ degrees (rounded off to the nearest integer) and ________ (rounded off to two decimal places), respectively.

A

58, 0.24

B

30, 0.68

C

58, 0.94

D

30, 0.99

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7

2021 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2021

A PZT crystal of thickness 1 mm and wave velocity 4000 m/s is emitting a longitudinal pressure wave, which is incident on a blood vessel at an angle of 30°. The doppler shift in the ultrasound wave for a blood flow of 10 cm/s and wave velocity in the soft tissue of 1540 m/s is ________ Hz.

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8

2022 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2022

In the process of obtaining a Magnetic Resonance Image (MRI), the terms T1 and T2 time constants of the material are very crucial to decide on getting suitable weighted images. Choose the correct explanation relating to these two constants from the following options.

A

T1 is the spin-lattice or longitudinal relaxation time, and T2 is the spin-spin or transverse relaxation time

B

T1 and T2 indicate the durations that Free Induction Decay (FID) signal to be recorded in x and y axes directions, respectively

C

T1 and T2 refer to the durations of flipping pulses used to tilt the resultant magnetic vector into x-y plane and inverse z-direction, respectively

D

T1 is the spin-spin or transverse relaxation time, and T2 is the spin-lattice or longitudinal relaxation time

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9

2022 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2022

The thickness of piezoelectric crystal (PZT5A) used in ultrasound applications will determine the resonant frequency of the transducer. To work at a resonance frequency of 5 MHz, the thickness of a PZT5A transducer must be ______ mm (rounded off to three decimal places).
Given: The velocity of sound in PZT5A is 4350 m.s^-1.

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10

2023 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2023

A 5 MHz ultrasound transducer is being used to measure the velocity of blood. When the transducer is placed at an angle of 45° to the direction of blood flow, a frequency shift of 200 Hz is observed in the echo. Assume that the velocity of sound is 1500 m/s. What is the velocity (in cm/s) of the blood flow? (Round off the answer to one decimal place.)

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11

2023 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2023

The free induction decay (FID) in the MRI of an object can be approximated as \[ s(t) = \iint m(x,y)e^{-j2\pi(K_x(t)x+K_y(t)y)} \, dxdy, \] where \[ K_x(t) = \int_0^t G_x(\tau)d\tau \] and \[ K_y(t) = \int_0^t G_y(\tau)d\tau \]. Here \( G_x \) and \( G_y \) are pulses of identical period and are in-phase. By changing the amplitude of the pulses, one can obtain the two dimensional Fourier transform of the object ______________.

A

over radial lines in \((K_x, K_y) \) space

B

over a parabolic contour in \((K_x, K_y) \) space

C

along \(K_y \) only

D

along \(K_x \) only

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12

2023 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2023

An ultrasound plane wave of amplitude \( P_0 \) hits the semi-infinite boundary of two media having acoustic impedances \( Z_1 \) and \( Z_2 \). The sum of the amplitudes of the reflected and the incident waves at the boundary is equal to ______________.

A

\(\frac{2P_0 Z_2}{(Z_1 + Z_2)} \)

B

\(\frac{P_0 (Z_2 - Z_1)}{(Z_1 + Z_2)} \)

C

\(\frac{P_0 Z_2}{Z_1} \)

D

\(\frac{P_0 Z_1}{(Z_1 + Z_2)} \)

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13

2024 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2024

The Larmor frequency of a Na nucleus when placed in a magnetic field strength of 3 T is ________. (The gyromagnetic ratio of Na is given as \(\gamma = 11.26\) MHz/T.) Give your answer in MHz rounded off to the nearest integer.

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14

2024 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2024

A Doppler ultrasound transducer operating at 5 MHz gave maximum output frequency shift of 3 kHz. The velocity of sound in blood is 1500 m/s. If the probe was held at an angle of 45° to the direction of blood flow, the maximum velocity of blood flow through the artery is ________ m/s. (Give your answer rounded off to two decimal places.)

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15

2024 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2024

The wavelength of the peak emission from a human body at a temperature of 37°C due to black-body radiation is ________ μm. The value of Wien’s displacement constant is \(2.898 \times 10^{-3}\) m K. (Give your answer rounded off to 2 decimal places.)

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16

2024 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2024

In magnetic resonance imaging (MRI), pulse repetition time (\(TR\)), time to echo (\(TE\)), \(T_1\) relaxation time, \(T_2\) relaxation time are some of the important pulse sequence design parameters. Which one of the following specifications is used for proton density weighted imaging?

A

\(TR \gg T_1, TE \ll T_2\)

B

\(TR \gg T_1, TE \gg T_2\)

C

\(TR \ll T_1, TE \ll T_2\)

D

\(TR \ll T_1, TE \gg T_2\)

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17

2024 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2024

If a circular ultrasound transducer of radius \(a = 8\) mm operating at a central frequency of 1 MHz has a pressure beam pattern in a medium as given below: \[ P(r, 0) \propto \sin\left(\frac{ka^2}{4r}\right) \] Here, \(k\) is the wave number, \(r\) is the axial distance from the center of aperture. The speed of sound in the medium is 1600 ms\(^{-1}\). The reduction in intensity between \(r = 8\) cm and \(r = 16\) cm is ______ dB. Give your answer as a positive quantity rounded off to two decimal places.

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18

2025 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2025

Given the following statements, which one of the options is correct?
Statement (i): Structural Magnetic Resonance Imaging (sMRI) has better spatial resolution than Electroencephalogram (EEG)
Statement (ii): EEG has better temporal resolution than sMRI

A

Both the statements are correct

B

Both the statements are incorrect

C

Statement (i) is correct; statement (ii) is incorrect

D

Statement (i) is incorrect; statement (ii) is correct

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19

2025 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2025

Which of the following statement(s) about ultrasound waves is/are true?

A

Acoustic impedance of biological tissues is directly proportional to its density

B

The reflection coefficient depends on the impedance mismatch at the interface of two biological tissues

C

The transmission coefficient is independent of the impedance of biological tissues

D

Biological tissues do not reflect ultrasound waves

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20

2025 · Biomedical Engineering · Medical Imaging Systems · Magnetic Resonance and Ultrasound Imaging

Biomedical Engineering (BM) 2025

If the gyromagnetic ratio of proton is 42.58 MHz per Tesla, the resonance frequency for protons in a magnetic field of 1.5 Tesla is ______ MHz. (rounded off to two decimal places)

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