2026 question paper

Radiological Equipment

28 questions

1. Q1(a). ALARA stands for: (i) Advanced Laser Radiation Application (ii) As Low As Reasonably Achievable (iii) Automatic Low Radiation Adjustment (iv) Average Level of Radiation Absorption20262m

   Unit 1: Science Behind Radiological Equipment

   ALARA stands for:

   (i) Advanced Laser Radiation Application
   (ii) As Low As Reasonably Achievable
   (iii) Automatic Low Radiation Adjustment
   (iv) Average Level of Radiation Absorption

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   Worked Solution

   Answer: (ii) As Low As Reasonably Achievable

   ALARA is the radiation protection principle: keep exposure as low as reasonably achievable using time, distance and shielding.

2. Q1(b). The SI unit of absorbed radiation dose is: (i) Sievert (Sv) (ii) Gray (Gy) (iii) Becquerel (Bq) (iv) Coulomb (C)20262m

   Unit 1: Science Behind Radiological Equipment

   The SI unit of absorbed radiation dose is:

   (i) Sievert (Sv)
   (ii) Gray (Gy)
   (iii) Becquerel (Bq)
   (iv) Coulomb (C)

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   Worked Solution

   Answer: (ii) Gray (Gy)

   Absorbed dose is energy absorbed per unit mass: 1 Gy = 1 J/kg. Sievert is the unit of equivalent/effective dose, and Becquerel is the unit of activity.

3. Q1(c). Which imaging technique uses a strong magnetic field? (i) CT (ii) X-ray (iii) MRI (iv) PET20262m

   Unit 2: Operation and Analysis of Imaging Equipment

   Which imaging technique uses a strong magnetic field?

   (i) CT
   (ii) X-ray
   (iii) MRI
   (iv) PET

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   Worked Solution

   Answer: (iii) MRI

   MRI uses a strong static magnetic field (1.5 T or 3 T), gradient coils and radiofrequency pulses. It uses no ionizing radiation.

4. Q1(d). CT scan mainly produces: (i) 2D shadow images (ii) Cross-sectional images (iii) Ultrasound waves (iv) Optical images20262m

   Unit 2: Operation and Analysis of Imaging Equipment

   CT scan mainly produces:

   (i) 2D shadow images
   (ii) Cross-sectional images
   (iii) Ultrasound waves
   (iv) Optical images

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   Worked Solution

   Answer: (ii) Cross-sectional images

   CT rotates an X-ray source and detectors around the patient; a computer reconstructs axial slices (tomograms) that can be stacked into 3D.

5. Q1(e). Deep learning commonly uses: (i) CNN (ii) GPS (iii) ECG (iv) LCD20262m

   Unit 3: Integrate AI and Robotics into Radiological Systems I

   Deep learning commonly uses:

   (i) CNN
   (ii) GPS
   (iii) ECG
   (iv) LCD

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   Worked Solution

   Answer: (i) CNN

   Convolutional Neural Networks are the standard deep learning architecture for images, used in classification, detection and segmentation of medical scans.

6. Q1(f). AI is widely used for: (i) Blood collection (ii) Tumor detection (iii) Drug manufacturing (iv) Patient registration20262m

   Unit 3: Integrate AI and Robotics into Radiological Systems I

   AI is widely used for:

   (i) Blood collection
   (ii) Tumor detection
   (iii) Drug manufacturing
   (iv) Patient registration

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   Worked Solution

   Answer: (ii) Tumor detection

   In radiology AI analyses CT, MRI and X-ray images to detect and segment tumours, nodules and fractures.

7. Q1(g). Tele-radiology enables: (i) Remote image reporting (ii) Blood testing (iii) Surgery without imaging (iv) ECG monitoring only20262m

   Unit 4: Integrate AI and Robotics into Radiological Systems II

   Tele-radiology enables:

   (i) Remote image reporting
   (ii) Blood testing
   (iii) Surgery without imaging
   (iv) ECG monitoring only

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   Worked Solution

   Answer: (i) Remote image reporting

   Tele-radiology transmits medical images (DICOM) electronically so that a radiologist at another location can read and report them.

8. Q1(h). Robotic-assisted surgery primarily improves: (i) Radiation production (ii) Surgical precision (iii) MRI magnet strength (iv) X-ray wavelength20262m

   Unit 4: Integrate AI and Robotics into Radiological Systems II

   Robotic-assisted surgery primarily improves:

   (i) Radiation production
   (ii) Surgical precision
   (iii) MRI magnet strength
   (iv) X-ray wavelength

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   Worked Solution

   Answer: (ii) Surgical precision

   Robotic systems give tremor filtering, motion scaling, 3D magnified vision and dexterous instruments, so surgery is more precise and less invasive.

9. Q1(i). Calibration is performed to ensure: (i) Low electricity bill (ii) Accurate image quality (iii) Patient registration (iv) Hospital networking20262m

   Unit 5: Maintenance and Troubleshooting of Radiological Devices

   Calibration is performed to ensure:

   (i) Low electricity bill
   (ii) Accurate image quality
   (iii) Patient registration
   (iv) Hospital networking

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   Worked Solution

   Answer: (ii) Accurate image quality

   Calibration adjusts the equipment to reference standards (correct dose, CT numbers, geometry), so images and measurements are accurate and reliable.

10. Q1(j). AERB is associated with: (i) Food safety (ii) Radiation safety (iii) Internet security (iv) Biomedical waste only20262m

    Unit 1: Science Behind Radiological Equipment

    AERB is associated with:

    (i) Food safety
    (ii) Radiation safety
    (iii) Internet security
    (iv) Biomedical waste only

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    Worked Solution

    Answer: (ii) Radiation safety

    AERB (Atomic Energy Regulatory Board, India) regulates the use of ionizing radiation: licensing, safety codes and inspections.

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12. Q2(a). Describe the construction and working of an X-ray tube with a neat diagram.20267m

    Unit 1: Science Behind Radiological Equipment

    Describe the construction and working of an X-ray tube with a neat diagram.

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    Worked Solution

    X-ray Tube: Construction and Working

    An X-ray tube is a vacuum diode that converts electrical energy into X-rays (about 99% becomes heat, about 1% X-rays).

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    Main parts

    Part	Function
    Cathode (tungsten filament)	Heated to about 2200 C, emits electrons (thermionic emission)
    Focusing cup	Negatively charged; focuses the electron beam on the focal spot
    Anode (target)	Tungsten or tungsten-rhenium on copper; electrons strike it
    Rotating anode	Spreads heat over a larger track, allows higher power
    Glass/metal envelope	Maintains high vacuum
    Oil bath and housing	Cooling, insulation, lead shielding with an exit window

    Working

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    • kVp controls the energy (penetration) and mA controls the number of electrons (quantity of X-rays).
    • Bremsstrahlung (braking) radiation: electrons decelerate near nuclei and give a continuous spectrum.
    • Characteristic radiation: an incoming electron ejects an inner (K) shell electron, and the vacancy is filled with emission of a fixed-energy photon.

    Exam tip

    Draw the cathode, anode, vacuum envelope and mention the two X-ray production mechanisms.

13. Q2(b). What are ALARA and AERB? Explain their role in radiation safety.20267m

    Unit 1: Science Behind Radiological Equipment

    What are ALARA and AERB? Explain their role in radiation safety.

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    Worked Solution

    ALARA and AERB

    ALARA

    As Low As Reasonably Achievable: radiation exposure to patients and staff must be kept as low as possible, considering economic and social factors, while still obtaining the diagnostic benefit.

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    Inverse square law: $I \propto 1/d^2$.

    AERB

    Atomic Energy Regulatory Board is the Indian regulatory authority (under the Atomic Energy Act, 1962) for radiation safety.

    Role in radiation safety

    Body	Role
    ALARA	Guiding principle: justification, optimisation, dose limits
    AERB	Issues licences and registration for X-ray, CT and nuclear medicine facilities
    AERB	Sets safety codes and guides, equipment type approval and QA tests
    AERB	Inspects, enforces dose limits (public 1 mSv/yr; radiation workers 20 mSv/yr average over 5 years)
    AERB	Requires Radiological Safety Officer (RSO), personal dosimeters (TLD/OSL), safe waste handling

    Practical measures

    Lead aprons and shields, collimation, filtration, dose monitoring, DRLs (diagnostic reference levels), protective room design.

    Exam tip

    Explain ALARA through time, distance and shielding and AERB as the licensing and enforcement body.

14. Q3(a). Explain the working principle and applications of CT scan.20267m

    Unit 2: Operation and Analysis of Imaging Equipment

    Explain the working principle and applications of CT scan.

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    Worked Solution

    CT Scan: Principle and Applications

    Computed Tomography uses X-rays and computer reconstruction to produce cross-sectional (axial) images of the body.

    Principle

    A thin fan-shaped X-ray beam passes through the patient while the X-ray tube and detector array rotate around the patient. Different tissues attenuate the beam by different amounts: $I = I_0 e^{-\mu x}$. Detectors record many projections, and the computer reconstructs the image (filtered back projection or iterative reconstruction).

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    CT number (Hounsfield unit): $HU = 1000 \times (\mu - \mu_{water})/\mu_{water}$. Water = 0, air = -1000, bone > +400.

    Components

    Gantry (tube, detectors, slip ring), patient table, high-voltage generator, DAS, computer and console.

    Generations

    Spiral/helical CT with multi-slice detectors scans the volume quickly in one breath-hold.

    Applications

    Area	Use
    Head	Stroke, haemorrhage, tumours
    Chest	Lung nodules, pulmonary embolism
    Abdomen	Tumours, stones, trauma
    Bone	Complex fractures
    Cardiac	Coronary calcium, CT angiography
    Radiotherapy	Treatment planning, image-guided biopsy

    Limitations

    Higher radiation dose, contrast reactions, cost.

    Exam tip

    Write attenuation law, HU scale, the block diagram and four applications.

15. Q3(b). Explain the principles of ultrasound imaging and its obstetric applications.20267m

    Unit 2: Operation and Analysis of Imaging Equipment

    Explain the principles of ultrasound imaging and its obstetric applications.

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    Worked Solution

    Ultrasound Imaging: Principles and Obstetric Applications

    Ultrasound uses high-frequency sound waves (2 to 18 MHz), which are non-ionizing.

    Principle

    A piezoelectric transducer converts electrical pulses into ultrasound pulses and converts returning echoes back into electrical signals (pulse-echo principle). Echoes arise at tissue boundaries with different acoustic impedance ($Z = \rho c$). Depth is found from time of flight: $d = c\,t/2$ with $c \approx 1540$ m/s in soft tissue.

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    Display modes

    Mode	Shows
    A-mode	Amplitude vs depth
    B-mode	2D brightness image
    M-mode	Motion vs time (heart valves)
    Doppler	Blood flow velocity: $f_d = 2 f v \cos\theta / c$

    Obstetric applications

    • Confirm pregnancy and gestational age, count foetuses.
    • Measure biparietal diameter, femur length and abdominal circumference to estimate foetal growth.
    • Detect foetal heartbeat and malformations (anomaly scan).
    • Locate placenta (placenta previa) and assess amniotic fluid.
    • Doppler for foetal and umbilical blood flow; 3D/4D scans for the face and structure.
    • Guide procedures such as amniocentesis.

    Advantages

    Safe (no radiation), real-time, portable and low cost.

    Exam tip

    Write the pulse-echo principle, $d = ct/2$, the block diagram and four obstetric uses.

16. Q4(a). Explain the role of Artificial Intelligence in radiological image analysis.20267m

    Unit 3: Integrate AI and Robotics into Radiological Systems I

    Explain the role of Artificial Intelligence in radiological image analysis.

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    Worked Solution

    Role of AI in Radiological Image Analysis

    AI, mainly deep learning with CNNs, learns patterns from large sets of labelled images to support radiologists.

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    Task	Example
    Detection	Lung nodules on chest CT, fractures on X-ray, breast lesions on mammograms
    Classification	Benign vs malignant, pneumonia vs normal
    Segmentation	Tumour or organ outlines for radiotherapy planning
    Image enhancement	Noise reduction, dose reduction, faster MRI reconstruction
    Workflow	Triage of urgent cases (stroke, haemorrhage), auto-reporting
    Quantification	Tumour volume, bone density, cardiac measurements
    Prediction	Prognosis and treatment response

    Benefits

    Faster reading, fewer missed findings, consistency, reduced workload.

    Challenges

    Need for large annotated data, bias, explainability (black box), validation and regulatory approval, privacy, integration with PACS.

    AI is an assistant; the radiologist remains responsible for the final diagnosis.

    Exam tip

    Draw the pipeline and give 4 tasks with examples.

17. Q4(b). Differentiate between Machine Learning and Deep Learning with medical examples.20267m

    Unit 3: Integrate AI and Robotics into Radiological Systems I

    Differentiate between Machine Learning and Deep Learning with medical examples.

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    Worked Solution

    Machine Learning vs Deep Learning

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    Deep learning is a subset of machine learning, which is a subset of AI.

    Point	Machine learning	Deep learning
    Features	Hand-crafted by experts (texture, shape, intensity)	Learned automatically from raw images
    Models	SVM, random forest, k-NN, logistic regression	Multi-layer neural networks: CNN, U-Net, transformers
    Data needed	Small to medium	Very large
    Computing	CPU is enough	GPU required
    Training time	Short	Long
    Interpretability	Easier	Black box
    Accuracy on images	Good	Usually higher

    Medical examples

    • Machine learning: radiomics features extracted from a tumour CT, then a random forest or SVM classifies benign vs malignant; predicting disease risk from lab and patient data.
    • Deep learning: a CNN detects pneumonia on chest X-ray; U-Net segments brain tumours on MRI; deep networks find diabetic retinopathy on retinal images; AI reconstructs low-dose CT.

    Exam tip

    Draw the nested diagram and write the feature-extraction difference first.

18. Q5(a). Explain robotic-assisted surgery and its advantages in healthcare.20267m

    Unit 4: Integrate AI and Robotics into Radiological Systems II

    Explain robotic-assisted surgery and its advantages in healthcare.

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    Worked Solution

    Robotic-assisted Surgery

    In robotic-assisted surgery the surgeon controls robotic arms with surgical instruments and a 3D camera from a console. The robot does not act on its own; it follows the surgeon's hand movements. Example: da Vinci system.

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    Components

    Part	Function
    Surgeon console	3D view, hand and foot controls
    Patient-side cart	Arms holding wristed instruments and camera
    Vision cart	Image processing, display
    Image guidance	Pre-operative CT/MRI registration and navigation

    Advantages

    • Higher precision with motion scaling and tremor filtering.
    • 3D magnified high-definition view.
    • Greater dexterity (wristed instruments with 7 degrees of freedom).
    • Minimally invasive: smaller cuts, less blood loss, less pain, quicker recovery, shorter hospital stay, lower infection risk.
    • Surgeon comfort (ergonomic) and possibility of tele-surgery.

    Limitations

    High cost, training need, no force feedback in many systems, longer set-up time.

    Applications

    Urology (prostatectomy), gynaecology, cardiac, orthopaedic (knee/hip), general and head-neck surgery.

    Exam tip

    Draw the console - control - arms flow and list 5 advantages.

19. Q5(b). Explain the concept of tele-radiology and remote diagnostics.20267m

    Unit 4: Integrate AI and Robotics into Radiological Systems II

    Explain the concept of tele-radiology and remote diagnostics.

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    Worked Solution

    Tele-radiology and Remote Diagnostics

    Tele-radiology is the electronic transmission of radiological images (X-ray, CT, MRI, ultrasound) from one location to another for interpretation and consultation by a radiologist.

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    Key technologies

    Element	Role
    DICOM	Standard format and communication protocol for medical images
    PACS	Picture Archiving and Communication System: stores and distributes images
    RIS / HIS	Radiology and hospital information systems
    Network	Broadband, VPN, encryption (HIPAA-style privacy)
    Compression	Lossless or controlled lossy to speed up transfer
    Viewer	Diagnostic-quality monitors and 3D tools

    Remote diagnostics

    Expert diagnosis, second opinion and even equipment monitoring are done at a distance, for example reading a rural hospital's CT in a city centre, or a vendor engineer diagnosing a machine fault remotely.

    Advantages

    • Specialist access for rural and remote areas.
    • 24x7 emergency reporting (night-time coverage), faster turnaround.
    • Second opinions and teaching; reduced patient travel and cost.

    Challenges

    Data security and privacy, bandwidth, legal responsibility, image quality, integration and standards.

    Exam tip

    Draw the DICOM - PACS - remote reader flow and list 3 benefits and 3 challenges.

20. Q6(a). Explain preventive maintenance strategies for radiological equipment.20267m

    Unit 5: Maintenance and Troubleshooting of Radiological Devices

    Explain preventive maintenance strategies for radiological equipment.

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    Worked Solution

    Preventive Maintenance of Radiological Equipment

    Preventive maintenance (PM) is scheduled work done before failure to keep equipment safe, accurate and available.

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    Strategy	Description	Example
    Scheduled (time-based) PM	Fixed intervals set by manufacturer	Quarterly X-ray tube and collimator check
    Predictive / condition-based	Uses monitoring data to predict failure	Tube-heat units, helium level, log analysis, remote monitoring
    Corrective	Repair after failure	Replace faulty detector
    Calibration and QA	Accuracy and performance tests	CT number, kVp, mA, timer, light-field alignment
    Safety checks	Radiation leakage, interlocks, earthing	Lead apron integrity

    Typical PM tasks

    1. Visual inspection and cleaning of filters, cables, connectors.
    2. Check cooling (oil, water, helium), vacuum and high-voltage cables.
    3. Check mechanical parts, brakes, table movement.
    4. Software, firmware updates and backups.
    5. Dosimetry and image-quality phantom tests.
    6. Keep a maintenance logbook and service history.

    Benefits

    Longer life, fewer breakdowns and downtime, lower cost, consistent image quality, patient and staff safety.

    Exam tip

    Classify strategies and list 5 PM tasks with a logbook.

21. Q6(b). Describe the roles of IEC, AERB and FDA standards in radiological device maintenance.20267m

    Unit 5: Maintenance and Troubleshooting of Radiological Devices

    Describe the roles of IEC, AERB and FDA standards in radiological device maintenance.

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    Worked Solution

    IEC, AERB and FDA Standards in Maintenance

    Body	Full form	Region / scope	Role in maintenance
    IEC	International Electrotechnical Commission	International standards	Safety and performance standards for medical electrical equipment (IEC 60601 series, e.g. 60601-1 general safety, 60601-2-44 CT, 60601-2-54 X-ray) and acceptance/constancy test methods (IEC 61223)
    AERB	Atomic Energy Regulatory Board	India	Licenses radiation facilities; sets QA tests and periodic inspections; requires RSO, dosimetry and records; approves equipment type
    FDA	Food and Drug Administration	USA	Regulates device approval (510(k), PMA), performance standards for X-ray equipment (21 CFR 1020), service and recall rules; requires maintenance records and reporting of faults

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    How they guide maintenance

    1. Define acceptable limits for kVp, mA, timer, dose output, leakage and image quality.
    2. Specify test frequency (acceptance, annual and constancy tests).
    3. Require documentation, traceable calibration and trained personnel.
    4. Require safety interlocks, labelling and electrical safety (earth leakage).
    5. Enforcement through audits, licence renewal and penalties.

    Exam tip

    Write a 3-row table (IEC standards, AERB regulator, FDA regulator) with one line on maintenance duties each.

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23. Q7(a). Explain 3D and 4D medical imaging technologies with applications.20267m

    Unit 6: Advancements in Radiological Technology

    Explain 3D and 4D medical imaging technologies with applications.

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    Worked Solution

    3D and 4D Medical Imaging

    3D imaging

    A volume of data (stack of 2D slices from CT, MRI, ultrasound or PET) is processed by a computer to display the anatomy in three dimensions.

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    Rendering methods: MPR (multi-planar reformat), MIP (maximum intensity projection), surface rendering, volume rendering.

    4D imaging

    4D = 3D + time. The volume is captured continuously, so motion such as breathing, heartbeat or foetal movement is seen.

    Point	3D imaging	4D imaging
    Dimensions	x, y, z	x, y, z + time
    Output	Static volume	Moving volume (cine)
    Examples	CT angiography, 3D reconstruction of skull	4D CT for lungs, 4D ultrasound of foetus, cardiac MRI
    Data size	Large	Very large

    Applications

    • Surgical planning and 3D-printed anatomical models.
    • Radiotherapy: 4D CT accounts for tumour motion with respiration.
    • Cardiology: heart wall motion, valves, 4D flow MRI.
    • Obstetrics: 3D/4D foetal face and movement.
    • Orthopaedics, dental implant planning, vascular imaging.

    Exam tip

    Define 4D as 3D plus time and give three applications for each.

24. Q7(b). Compare PET, PET-MRI, SPECT and Dual-Energy CT.20267m

    Unit 6: Advancements in Radiological Technology

    Compare PET, PET-MRI, SPECT and Dual-Energy CT.

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    Worked Solution

    Comparison: PET, PET-MRI, SPECT and Dual-Energy CT

    Feature	PET	PET-MRI	SPECT	Dual-Energy CT
    Type	Nuclear (functional)	Hybrid functional plus soft-tissue anatomy	Nuclear (functional)	Anatomical plus material information
    Source	Positron emitter (F-18 FDG), annihilation gives two 511 keV gamma rays	Same as PET plus magnetic field and RF	Gamma emitters (Tc-99m, I-123)	X-ray tube at two energies (e.g. 80 and 140 kVp)
    Detection	Ring of detectors, coincidence detection	PET detectors (SiPM) inside MRI	Gamma camera rotating, collimator	Dual-source, fast kVp switching or dual-layer detector
    Resolution	About 4 to 6 mm	PET about 4 mm, MRI sub-mm	About 8 to 12 mm	Sub-mm
    Sensitivity	High	High	Lower	High
    Radiation dose	Moderate	Lower than PET-CT (no CT dose)	Moderate	Similar to CT, can be reduced
    Time	About 20 to 30 min	Long (60 min)	30 to 60 min	Seconds
    Main use	Cancer staging, brain, heart metabolism	Brain, prostate, paediatric oncology, soft tissue	Bone scan, myocardial perfusion, thyroid	Material separation: kidney stones, gout, iodine maps, metal artefact reduction
    Cost	High	Very high	Moderate	Moderate to high

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    Exam tip

    Tabulate source, detection, resolution and uses; mention PET-MRI avoids CT radiation.

25. Q8(a). Explain how AI is enabling personalized medicine in modern radiological imaging.20267m

    Unit 6: Advancements in Radiological Technology

    Explain how AI is enabling personalized medicine in modern radiological imaging.

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    Worked Solution

    AI and Personalized Medicine in Radiological Imaging

    Personalized (precision) medicine tailors diagnosis and treatment to each patient's characteristics. AI extracts information from images that humans cannot easily see and combines it with clinical and genetic data.

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    Area	AI contribution
    Radiomics	Thousands of quantitative features from a tumour linked to its biology
    Radiogenomics	Predict gene mutations (e.g. EGFR, MGMT) from images, avoiding some biopsies
    Treatment selection	Predict response to chemo, radio or immunotherapy
    Radiotherapy planning	Auto-contouring and dose optimisation for each patient
    Risk prediction	Personal risk of cancer or cardiac events (e.g. coronary calcium, breast density)
    Dose personalisation	Adjust scan protocol and contrast to body size, lower radiation
    Prognosis and follow-up	Track tumour change over time

    Benefits

    Better outcomes, fewer side effects, avoids unnecessary procedures, early detection.

    Challenges

    Data privacy, bias in training data, validation, cost, integration with clinical workflow.

    Exam tip

    Explain radiomics and radiogenomics with the multi-source data flow.

26. Q8(b). Explain calibration of imaging equipment and quality assurance procedures.20267m

    Unit 5: Maintenance and Troubleshooting of Radiological Devices

    Explain calibration of imaging equipment and quality assurance procedures.

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    Worked Solution

    Calibration and Quality Assurance of Imaging Equipment

    Calibration

    Calibration compares the equipment's output against a known reference and adjusts it so the measurements fall within tolerance.

    Equipment	Parameters calibrated
    X-ray	kVp accuracy, mA/mAs linearity, exposure timer, HVL, output (dose) reproducibility, focal spot size
    CT	CT number of water (0 HU), uniformity, noise, spatial resolution, slice thickness, CTDI dose
    MRI	Magnetic field homogeneity, RF coil, gradient accuracy, SNR
    Ultrasound	Depth and distance accuracy, dead zone, uniformity, resolution
    Display and film	Monitor luminance, DICOM grayscale (GSDF)

    Quality assurance (QA) programme

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    1. Acceptance testing confirms the new unit meets specifications.
    2. Commissioning/baseline records reference values.
    3. Constancy tests at daily, weekly, monthly and annual intervals using phantoms.
    4. Corrective action if limits are exceeded.
    5. Documentation of every test; audits.
    6. Reject analysis and dose monitoring (DRLs) for patients.

    Tools: phantoms (CT water phantom, ACR MRI phantom), dosimeters and ion chambers, kVp meters, test patterns.

    Exam tip

    Write the QA cycle, 3 tests for X-ray and CT, and mention phantoms.

27. Q9(a). Write a short note on: ALARA Principle20267m

    Unit 1: Science Behind Radiological Equipment

    Write a short note on: ALARA Principle

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    Worked Solution

    Short Note: ALARA Principle

    ALARA = As Low As Reasonably Achievable. It is the basic principle of radiation protection: all exposure must be kept as low as possible while obtaining the required diagnostic or therapeutic benefit, with economic and social factors considered.

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    • Time: dose is proportional to exposure time.
    • Distance: doubling the distance cuts intensity to one quarter.
    • Shielding: lead (0.25 to 0.5 mm Pb equivalent) attenuates X-rays.
    • Related measures: justification of every exam, optimisation (collimation, filtration, low-dose protocols), dose limits, personal dosimeters.
    • Regulated in India by AERB; limits: public 1 mSv/year; radiation workers 20 mSv/year average over 5 years.

    Exam tip

    Write the expansion, the three pillars and the inverse square law.

28. Q9(b). Write a short note on: Magnetic Resonance Imaging20267m

    Unit 2: Operation and Analysis of Imaging Equipment

    Write a short note on: Magnetic Resonance Imaging

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    Worked Solution

    Short Note: Magnetic Resonance Imaging (MRI)

    MRI produces detailed images of soft tissue without ionizing radiation, using a strong magnetic field and radio waves.

    Principle

    1. Hydrogen nuclei (protons) in the body have a magnetic moment; in a strong field $B_0$ (1.5 T or 3 T) they align and precess at the Larmor frequency $f = \gamma B_0/2\pi$ (about 63.9 MHz at 1.5 T).
    2. An RF pulse at this frequency tilts the magnetisation.
    3. When the pulse stops, protons relax and emit a signal, detected by receiver coils.
    4. Gradient coils add position-dependent field changes for slice selection and spatial encoding; a Fourier transform builds the image.
    5. Contrast depends on relaxation times T1, T2 and proton density.

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    Main parts

    Superconducting magnet (cooled with liquid helium), gradient coils, RF coils, shim coils, computer and console, RF shielded room.

    Applications

    Brain and spine, joints and soft tissue, heart, tumours, MR angiography, functional MRI.

    Advantages and cautions

    No radiation and excellent soft-tissue contrast; long scan time, high cost, contraindicated with pacemakers and metal implants, noisy, claustrophobia.

    Exam tip

    Write the Larmor frequency, T1/T2 contrast and the block diagram.

29. Q9(c). Write a short note on: Machine Learning in Radiology20267m

    Unit 3: Integrate AI and Robotics into Radiological Systems I

    Write a short note on: Machine Learning in Radiology

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    Worked Solution

    Short Note: Machine Learning in Radiology

    Machine learning (ML) lets computers learn patterns from data and make predictions without being explicitly programmed.

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    Type	Use in radiology
    Supervised	Classify tumour benign vs malignant, detect fracture (labelled data)
    Unsupervised	Cluster patients or tissue types without labels
    Reinforcement	Treatment planning and robotics (emerging)
    Deep learning (CNN)	Automatic feature learning for detection and segmentation

    Common algorithms: SVM, random forest, k-NN, logistic regression, neural networks.

    Applications

    Lung nodule and breast cancer detection, bone age estimation, brain tumour segmentation, image quality improvement, workflow prioritisation and radiomics.

    Challenges

    Need for good labelled data, overfitting, bias, explainability, privacy and regulatory approval.

    Exam tip

    Draw the train-validate-predict pipeline and name 3 ML types with examples.

30. Q9(d). Write a short note on: Calibration of Imaging Equipment20267m

    Unit 5: Maintenance and Troubleshooting of Radiological Devices

    Write a short note on: Calibration of Imaging Equipment

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    Short Note: Calibration of Imaging Equipment

    Calibration is the process of comparing an instrument's reading with a traceable reference standard and adjusting it to keep errors within tolerance. It ensures accurate images, correct patient dose and reliable measurements.

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    • X-ray: kVp, mA, exposure time, HVL, dose output with kVp meter and ion chamber.
    • CT: water HU = 0, noise and uniformity using a water phantom; CTDI.
    • MRI: field homogeneity, gradient and RF with a phantom.
    • Ultrasound: depth, distance and uniformity with a tissue-mimicking phantom.
    • Done at installation, after repairs or tube replacement, and periodically (annual), with records kept as required by AERB.

    Exam tip

    Define calibration, give the flow loop and mention phantoms and tolerances.