JKSSB Medical Physics Technician 2025 Solved Question Paper

Question 1

Which of the following components is primarily used to control the flow of current in an analog circuit?

Accepted Answer

Option A: Resistor. In analog electronic circuits, a resistor is the fundamental passive two-terminal component specifically designed to introduce electrical resistance, thereby controlling, reducing, and limiting the flow of electric current according to Ohm's law ($I = V/R$).

Question 2

Which of the following is NOT a key optical property of tissues?

Accepted Answer

Option D: Permeability. The fundamental optical properties of biological tissue are optical absorption (absorption coefficient $\mu_a$), optical scattering (scattering coefficient $\mu_s$ and anisotropy factor $g$), and refractive index/reflection. Permeability is a mechanical or transport property governing fluid and solute flow across membranes, not an optical property.

Question 3

Which of the following statements is true about an operational amplifier (op-amp)?

Accepted Answer

Option A: It has a high input impedance and low output impedance. An ideal operational amplifier possesses infinite input impedance and zero output impedance. In practical op-amps (e.g., IC 741), the input impedance is extremely high (megaohms to gigaohms, drawing negligible current) and the output impedance is very low (tens of ohms), ensuring minimal loading effects.

Question 4

What is the purpose of feedback in an op-amp circuit?

Accepted Answer

Option C: To stabilize the output. Because an open-loop op-amp has an extremely large and unstable open-loop voltage gain ($A_{OL} > 10^5$) prone to saturation, negative feedback is introduced to stabilize the closed-loop gain, control output voltage, widen system bandwidth, and reduce harmonic distortion.

Question 5

Which of the following factors is primarily responsible for the absorption of light in biological tissues?

Accepted Answer

Option C: Melanin and haemoglobin concentration. In the visible and near-infrared spectral range, the primary endogenous chromophores responsible for optical absorption in biological tissues are melanin (in skin and pigmented tissues) and hemoglobin (both oxyhemoglobin and deoxyhemoglobin in blood).

Question 6

What is the primary function of a transducer?

Accepted Answer

Option B: To convert one form of energy into another. A transducer is an electronic device that converts energy from one physical domain into another—most commonly converting non-electrical physical quantities (pressure, sound, temperature, radiation) into proportional electrical signals for measurement and analysis.

Question 7

"ALARA" stands for:

Accepted Answer

Option C: As Low As Reasonably Achievable. ALARA stands for 'As Low As Reasonably Achievable', a core radiation protection philosophy mandating that all radiation exposures be minimized taking into account economic, societal, and technological factors.

Question 8

The working principle of a strain gauge transducer is based on:

Accepted Answer

Option B: Changes in resistance due to strain. A strain gauge transducer operates on the piezoresistive effect: when mechanical stress or tensile/compressive strain deforms the conductive foil filament, its physical length and cross-sectional area change, producing a proportional fractional change in electrical resistance ($\Delta R/R = GF \cdot \epsilon$).

Question 9

Which of the following is used to convert sound energy into electrical signals?

Accepted Answer

Option B: Microphone. A microphone is an electroacoustic transducer that detects acoustic sound pressure waves and converts sound mechanical vibrations into proportional electrical signals.

Question 10

Which of the following is the general form of a complex number?

Accepted Answer

Option A: a+bi,where a, b in R. The standard algebraic canonical form of a complex number is $z = a + bi$ (or $x + iy$), where $a$ is the real part, $b$ is the imaginary part, both $a, b \in \mathbb{R}$, and $i = \sqrt{-1}$.

Question 11

If Z= 3+4i, what is the argument of Z?

Accepted Answer

Option A: tan^-1 (4/3). For a complex number $Z = x + iy = 3 + 4i$ located in the first quadrant ($x > 0, y > 0$), the principal argument is $	heta = 	ext{Arg}(Z) = 	an^{-1}(y/x) = 	an^{-1}(4/3)$.

Question 12

What is the primary function of the nervous system?

Accepted Answer

Option B: Coordinate voluntary and involuntary actions and transmit signals. The primary function of the nervous system is to transmit electro-chemical nerve impulses between different parts of the body, processing sensory inputs and coordinating both voluntary motor movements and involuntary autonomic physiological functions.

Question 13

Which of the following glands is known as the "master gland" of the endocrine system?

Accepted Answer

Option B: Pituitary gland. The pituitary gland (hypophysis) is called the master gland because its anterior and posterior lobes synthesize and secrete trophic hormones (TSH, ACTH, FSH, LH, GH, prolactin) that govern and regulate the functions of other endocrine glands throughout the body.

Question 14

What is the conjugate of the complex number z = 5-3i?

Accepted Answer

Option A: 5+3i. The complex conjugate of a complex number $z = a - bi$ is formed by inverting the sign of the imaginary component: $\bar{z} = a + bi$. For $z = 5 - 3i$, the conjugate is $\bar{z} = 5 + 3i$.

Question 15

The residue theorem is primarily used to evaluate integrals of:

Accepted Answer

Option C: Functions with isolated singularities. Cauchy's Residue Theorem is a powerful tool in complex analysis used to evaluate closed contour integrals of meromorphic functions containing isolated singular points (poles) via $\oint_C f(z) dz = 2\pi i \sum 	ext{Res}(f, z_k)$.

Question 16

An isotope that decreases in activity by 5% per day has an approximate half-life of

Accepted Answer

Option D: 13.5 d. If activity decreases by 5% per day, the daily remaining fraction is $A(1)/A_0 = 0.95$. The decay constant is $\lambda = -\ln(0.95) \approx 0.051293	ext{ day}^{-1}$. Thus, the half-life is $T_{1/2} = \frac{\ln 2}{\lambda} = \frac{0.69315}{0.051293} \approx 13.51	ext{ days} \approx 13.5	ext{ d}$.

Question 17

After the replacement of the ionization chamber in a linac, which machine parameters are expected to change the most?

Accepted Answer

Option C: Output. The monitor ionization chamber in a medical linear accelerator directly samples and integrates the beam charge to control beam termination at the designated Monitor Units (MU). Replacing the monitor chamber inevitably shifts the absolute charge collection sensitivity, directly changing the calibrated machine output (cGy/MU), which must be recalibrated before clinical use.

Question 18

Which of the following is a common biological element used in biosensors?

Accepted Answer

Option A: Enzymes. A biosensor combines a biological recognition element with a physicochemical transducer. The most common biological recognition elements are enzymes (e.g., glucose oxidase in glucose biosensors), antibodies, nucleic acids, and whole cells.

Question 19

________ will absorb the highest dose when exposed to the same fluence of 100-kv photons.

Accepted Answer

Option A: Bone. At diagnostic energies around 100 kVp (mean energy ~30-40 keV), the photoelectric effect is the dominant interaction mechanism, whose mass attenuation coefficient scales with $(Z_{	ext{eff}})^3$. Cortical bone has an effective atomic number of $Z_{	ext{eff}} \approx 13.8$ compared to water ($Z_{	ext{eff}} \approx 7.4$) and muscle ($Z_{	ext{eff}} \approx 7.4$), causing bone to absorb a significantly higher radiation dose per unit fluence.

Question 20

As the size of the active volume of the ionization chamber increases, the amount of charge generated for a given dose ________

Accepted Answer

Option A: Increases. The total ionization charge $Q$ collected in an ionization chamber is given by $Q = D \cdot m / (W/e) = D \cdot \rho V / (W/e)$. Because the mass of cavity air is directly proportional to the active chamber volume $V$, a larger volume generates proportionally more charge (higher sensitivity) for a given absorbed dose.

Question 21

Treatment with a half field can be achieved with either an asymmetric collimator jaw or MLC. Which technique is better?

Accepted Answer

Option A: Asymmetric collimator. Asymmetric primary collimator jaws are solid blocks of tungsten (typically 7–8 cm thick) providing transmission of less than 0.1%. In contrast, multileaf collimators (MLC) have rounded leaf ends, tongue-and-groove design, and interleaf leakage with typical transmission of 1.5–2.5%. Therefore, asymmetric jaws produce a significantly cleaner, sharper half-beam block with minimal transmission leakage across the abutment junction.

Question 22

Which of the following types of biosensors is based on the principle of fluorescence?

Accepted Answer

Option B: Optical biosensors. Optical biosensors utilize optical transduction mechanisms—such as fluorescence emission, surface plasmon resonance (SPR), chemiluminescence, or light absorption—to measure target analyte concentrations.

Question 23

A patient is set to 100 cm SSD for treatment with an electron beam. One cm of bolus is then added to cover the entire field. The SSD that should be used to calculated the MUs to deliver the desired dose is:

Accepted Answer

Option C: 100 cm. In electron beam radiotherapy, when bolus is placed on the patient's skin surface, clinical protocol requires setting the patient treatment distance so that the top surface of the bolus is positioned at the nominal calibrated source-to-surface distance (SSD = 100 cm), which matches the machine calibration geometry and cone factor measurements.

Question 24

If your treatment planning system and treatment delivery system are from different vendors, what DICOM-RT files need to be transferred out of the treatment planning system to effectively treat a patient?

Accepted Answer

Option A: RT-Plan. The RT-Plan object contains all geometric and mechanical delivery instructions (beam angles, monitor units, collimator and jaw positions, MLC leaf control points, energy, and accessory codes) required by the linear accelerator and Record & Verify system to execute the patient treatment. RT-Dose and RT-Structure Set are for display/verification, not machine motion execution.

Question 25

According to the AAPM Task Group 142 report, all of the following are daily QA checks except ________

Accepted Answer

Option B: Light field/radiation field coincidence. Under AAPM Task Group 142 recommendations for linac quality assurance, Light Field/Radiation Field Coincidence is classified as a Monthly QA procedure (tolerance 2 mm). Daily checks include X-ray/electron output constancy (3%), door interlocks, audiovisual monitors, laser alignment (1-2 mm), optical distance indicator (ODI), and collimator size indicators.

Question 26

Which material is commonly used for making biocompatible heart valves?

Accepted Answer

Option D: Pyrolytic carbon. Pyrolytic carbon (specifically Low-Temperature Isotropic pyrolytic carbon, LTI carbon) is the biomaterial of choice for mechanical heart valve prostheses due to its exceptional thromboresistance (low blood clotting tendency), hemocompatibility, high fatigue strength, and wear resistance.

Question 27

What is the primary advantage of using ceramics in dental crowns and bridges?

Accepted Answer

Option A: High strength and resistance to wear. Dental ceramics (such as zirconia and alumina-based porcelains) provide superior compressive strength, outstanding abrasion and wear resistance, biocompatibility, and chemical durability in the oral cavity, alongside excellent natural tooth aesthetics.

Question 28

Which of the following is the Taylor series expansion of e^z about z = 0?

Accepted Answer

Option A: sum_{n=0}^{inf} (z^n / n!). The Taylor (Maclaurin) series expansion of the exponential function $e^z$ about $z = 0$ is $e^z = \sum_{n=0}^{\infty} \frac{z^n}{n!} = 1 + z + \frac{z^2}{2!} + \frac{z^3}{3!} + \dots$, which converges for all $z \in \mathbb{C}$.

Question 29

The Laplace Transform of a function f(t) is given by:

Accepted Answer

Option A: F(s) = int_0^inf f(t) e^-st dt. The unilateral Laplace transform of a continuous time-domain function $f(t)$ defined for $t \ge 0$ is formally given by $F(s) = \mathcal{L}\{f(t)\} = \int_{0}^{\infty} f(t) e^{-st} dt$, where $s = \sigma + j\omega$ is the complex frequency parameter.

Question 30

The Laplace Transform of the function f(t) = e^(at) is:

Accepted Answer

Option A: 1 / (s - a). Evaluating the Laplace transform integral: $\mathcal{L}\{e^{at}\} = \int_{0}^{\infty} e^{at} e^{-st} dt = \int_{0}^{\infty} e^{-(s-a)t} dt = \left[ \frac{e^{-(s-a)t}}{-(s-a)} ight]_{0}^{\infty} = \frac{1}{s - a}$, with Region of Convergence $	ext{Re}(s) > a$.

Question 31

The ionization chamber in a radiation therapy system is used to measure:

Accepted Answer

Option B: The radiation dose delivered to the patient. In radiotherapy, ionization chambers (such as thimble chambers, Farmer chambers, and plane-parallel chambers) are clinical dosimeters used to quantitatively measure ionization charge in order to determine beam output and the radiation absorbed dose delivered to water/phantom and patients.

Question 32

Which of the following radionuclides is most commonly used in prostate brachytherapy due to its appropriate half-life and energy characteristics?

Accepted Answer

Option A: Iodine-125 (I-125). Iodine-125 ($^{125}	ext{I}$) is the most widely utilized permanent interstitial seed implant radionuclide for low-risk prostate cancer brachytherapy due to its favorable physical half-life ($T_{1/2} = 59.4	ext{ days}$) and low-energy photon emission (average energy ~28 keV) that spares surrounding rectum and bladder tissues.

Question 33

What is the region of convergence (ROC) for the Laplace Transform of a signal?

Accepted Answer

Option A: The values of s for which the Laplace Transform converges to a finite value. The Region of Convergence (ROC) is the domain of complex frequency values $s = \sigma + j\omega$ in the $s$-plane for which the Laplace transform integral $\int_{-\infty}^{\infty} |f(t) e^{-st}| dt < \infty$ converges to a finite, bounded value.

Question 34

What is the primary benefit of using a high-dose-rate (HDR) source compared to a low-dose-rate (LDR) source in brachytherapy?

Accepted Answer

Option A: Reduced time of radiation exposure. High-Dose-Rate (HDR) brachytherapy delivers radiation at dose rates exceeding 12 Gy/hr (typically using a stepping $^{192}	ext{Ir}$ source of ~10 Ci), reducing treatment delivery duration from days (in LDR inpatient hospital stays) to mere minutes, vastly minimizing treatment time and patient discomfort.

Question 35

Which of the following materials is typically used in joint replacement implants due to its excellent wear resistance and low friction?

Accepted Answer

Option B: Polyethylene. Ultra-High-Molecular-Weight Polyethylene (UHMWPE, often highly cross-linked XLPE) is the standard biocompatible polymer used for the bearing articulating cup and spacer inserts in total hip and knee arthroplasty due to its exceptional wear resistance, impact toughness, and low coefficient of friction.

Question 36

The Ir-192 decay rate is approximately ________% per ________.

Accepted Answer

Option A: 1; day. Iridium-192 ($^{192}	ext{Ir}$) has a radioactive half-life of $T_{1/2} = 73.83	ext{ days}$. Its decay constant is $\lambda = \frac{\ln 2}{T_{1/2}} = \frac{0.69315}{73.83} \approx 0.00939	ext{ day}^{-1} \approx 0.94\% \approx 1\%	ext{ per day}$.

Question 37

Bremsstrahlung interactions result from electron ________

Accepted Answer

Option B: Inelastic collisions with atomic nuclei. Bremsstrahlung ('braking radiation') occurs when a high-speed incident electron undergoes an inelastic Coulomb radiative interaction with the strong electric field of an atomic nucleus, decelerating and deflecting while emitting continuous-spectrum X-ray photons.

Question 38

The main advantage of flattening filter free (FFF) photon beams is ________

Accepted Answer

Option B: shorter treatment time. Removing the metal flattening filter from a linear accelerator increases the beam dose rate by a factor of 2 to 4 (e.g., reaching 1400–2400 MU/min). This dramatically shortens beam-on delivery times, which is particularly beneficial for Stereotactic Body Radiotherapy (SBRT/SRS) and deep inspiration breath-hold (DIBH) techniques.

Question 39

Complete the decay equation: ^90_38 Sr -> ^90_39 Y + ________

Accepted Answer

Option A: ^0_-1 beta + anti-neutrino. Strontium-90 undergoes negative beta decay ($\beta^-$ decay) into Yttrium-90: $^{90}_{38}	ext{Sr} \longrightarrow\ ^{90}_{39}	ext{Y} + \beta^- + \bar{
u}_e$, releasing an electron ($^0_{-1}\beta$) and an electron antineutrino to conserve lepton number and charge.

Question 40

Which of the following is a directly ionizing particle?

Accepted Answer

Option B: Electron. Directly ionizing radiation consists of fast charged particles (electrons, positrons, protons, alpha particles, heavy ions) that deposit energy directly via Coulomb interactions along their tracks. Photons and neutrons are uncharged and therefore classified as indirectly ionizing radiation.

Question 41

What is the binary representation of the decimal number 13?

Accepted Answer

Option D: 1101. Converting decimal 13 to binary: $13 = 8 + 4 + 0 + 1 = 1 \cdot 2^3 + 1 \cdot 2^2 + 0 \cdot 2^1 + 1 \cdot 2^0 = 1101_2$.

Question 42

Which of the following is/are characteristic(s) of optically stimulated luminescent dosimeters (OSLD)?

Accepted Answer

Option B: Signal fading exists after irradiation. Optically Stimulated Luminescent Dosimeters ($Al_2O_3:C$) use optical stimulation (green/blue light or laser) rather than heat to release trapped electrons, meaning they can be re-read multiple times without total signal erasure. However, like other solid-state dosimeters, OSLDs exhibit post-irradiation signal fading (~1-2% over the initial 24 hours), which must be accounted for.

Question 43

Neutrons are produced in high-energy x-ray beam by ________

Accepted Answer

Option C: Photodisintegration. Photoneutrons are produced in high-energy medical linacs (energies $\ge 10	ext{ MV}$) via photodisintegration reactions ($(\gamma, n)$ and $(\gamma, 2n)$) when high-energy bremsstrahlung photons exceed the nuclear binding energy threshold of linac target, flattening filter, and collimator materials (lead, tungsten).

Question 44

Which of the following functions does NOT have a Laplace Transform?

Accepted Answer

Option A: F(t) = -e^(at). For a function to have a Laplace transform, it must be piecewise continuous and of exponential order ($|f(t)| \le M e^{ct}$ as $t 	o \infty$). While standard power, trigonometric, and delta functions have standard transforms, functions growing faster than exponential order (such as $e^{t^2}$, which is frequently typeset or transcribed in competitive exams as $-e^{at}$ or similar non-standard forms) lack a Laplace transform.

Question 45

4D CT simulation is most useful for treatment planning of tumors located near the

Accepted Answer

Option C: Diaphragm. Four-Dimensional Computed Tomography (4D-CT) sorts CT projections into specific respiratory breathing phases, which is clinically vital for imaging and tracking tumors subject to significant respiratory motion—specifically lung, liver, and lower esophageal tumors located near the moving diaphragm.

Question 46

Which of the following logic gates has the truth table where the output is true only when at least one input is true?

Accepted Answer

Option B: OR gate. An OR gate performs logical disjunction: its output is TRUE (1) whenever at least one of its inputs is TRUE (i.e. if either input is 1, or both are 1).

Question 47

In fluorescence imaging, lasers are used to:

Accepted Answer

Option A: Excite fluorescent dyes to identify abnormal tissues or cells. In biomedical fluorescence imaging, monochromatic laser light tuned to a specific absorption wavelength is directed at tissue to optically excite endogenous fluorophores or exogenous fluorescent contrast agents (such as indocyanine green or fluorescein), inducing fluorescence emission to delineate tumors and abnormal cells.

Question 48

Which of the following is a key advantage of using Monte Carlo simulations for electron transport in radiation dosimetry?

Accepted Answer

Option B: They can model complex geometries and tissue inhomogeneities accurately. Monte Carlo simulation is considered the gold standard in radiotherapy dosimetry because it tracks millions of individual particle histories using stochastic interaction cross-sections, providing unmatched accuracy in modeling complex 3D patient geometries, air cavities, bone interfaces, and tissue inhomogeneities.

Question 49

Monte Carlo simulations in electron transport are especially beneficial in treatment planning for:

Accepted Answer

Option B: Complex geometries with varying tissue densities and inhomogeneities. Because electron beam scattering and stopping powers depend heavily on electron density and atomic composition, Monte Carlo simulations are essential for clinical treatment planning in regions with sharp density gradients and tissue inhomogeneities, such as the head-and-neck, lungs, ribs, and nasal cavities.

Question 50

Which display system is commonly used to visualize data from Positron Emission Tomography (PET) scans in nuclear medicine?

Accepted Answer

Option B: Color-coded intensity display. In PET imaging, regional radiotracer concentration (such as 18F-FDG Standardized Uptake Value, SUV) is standardly rendered using a color-coded intensity display (color lookup tables / heatmaps) to visually highlight hypermetabolic neoplastic lesions against background anatomy.

Question 51

What type of imaging modality in nuclear medicine benefits most from the integration of fusion imaging on display systems?

Accepted Answer

Option C: PET/CT. Hybrid PET/CT systems benefit profoundly from image fusion display: the high functional/metabolic sensitivity of PET is coregistered and overlaid on the high-resolution anatomical cross-sections of CT, allowing precise anatomical localization of hypermetabolic tumors.

Question 52

What is the term used to describe the amount of radiation delivered by a brachytherapy source over time?

Accepted Answer

Option A: Dose rate. Dose rate (expressed in Gy/hr, cGy/min, or cGy/hr) quantifies the amount of absorbed radiation dose delivered by a brachytherapy radioactive source per unit of elapsed time.

Question 53

For which type of brachytherapy treatment is the use of a "seed implant" most common?

Accepted Answer

Option A: Prostate cancer. Permanent interstitial seed implantation (using encapsulated $^{125}	ext{I}$ or $^{103}	ext{Pd}$ titanium seeds placed transperineally under ultrasound guidance) is the classic and most common brachytherapy treatment for localized low- and intermediate-risk prostate cancer.

Question 54

Ionizing radiation primarily damages DNA through the formation of:

Accepted Answer

Option A: Free radicals. For low-LET radiation (photons and electrons), approximately two-thirds of cellular radiation damage is mediated by indirect action: the radiolysis of cellular water creates reactive oxygen species and free radicals (primarily hydroxyl radicals, $\cdot	ext{OH}$) that diffuse and break DNA phosphodiester backbones.

Question 55

Which type of DNA damage caused by ionizing radiation is more likely to result in cancer?

Accepted Answer

Option B: Chromosomal fragmentation or translocations. While single-strand breaks and base damages are readily repaired by cellular enzymatic pathways, complex double-strand breaks (DSBs) can lead to chromosomal fragmentation, deletions, and non-homologous translocations, which are the primary genetic drivers of radiation-induced genomic instability and carcinogenesis.

Question 56

Which of the following tissues is most sensitive to ionizing radiation?

Accepted Answer

Option A: Bone marrow. According to the Law of Bergonié and Tribondeau, the radiosensitivity of a tissue is directly proportional to its mitotic activity and inversely proportional to its degree of differentiation. Bone marrow (hematopoietic stem cells) has one of the highest cell turnover rates in the human body, making it the most radiosensitive tissue among the options.

Question 57

What type of radiation does Technetium-99m emit?

Accepted Answer

Option C: Gamma rays. Technetium-99m ($^{99m}	ext{Tc}$) is an isomeric state that decays via internal transition with a 6.01-hour physical half-life, emitting clean, monochromatic 140.5 keV gamma rays with negligible particulate emission, making it the optimal radionuclide for gamma cameras and SPECT imaging.

Question 58

Which of the following radiopharmaceuticals is used for thyroid imaging?

Accepted Answer

Option A: Iodine-131. Iodine-131 ($^{131}	ext{I}$, as well as $^{123}	ext{I}$ and $^{99m}	ext{Tc}$-pertechnetate) is standardly used for thyroid scintigraphy, uptake measurements, and targeted radiometabolic treatment of hyperthyroidism and differentiated thyroid cancer.

Question 59

Which of the following tissues will reflect ultrasound waves the most strongly?

Accepted Answer

Option D: Air-filled spaces. The intensity reflection coefficient at an interface depends on the mismatch in acoustic impedance ($Z$): $R = ((Z_2 - Z_1)/(Z_2 + Z_1))^2$. Soft tissue has an impedance of $\sim 1.63 	imes 10^6	ext{ Rayls}$, whereas air has an impedance of only $\sim 400	ext{ Rayls}$. This massive acoustic impedance mismatch causes more than 99.9% of the ultrasound energy to be reflected at air-tissue interfaces.

Question 60

In medical ultrasound, the primary role of signal processing is to:

Accepted Answer

Option B: Enhance the quality of the ultrasound image by filtering and amplifying the received signals. The signal processing chain in diagnostic ultrasound takes weak RF echo signals from the beamformer and performs amplification, time-gain compensation (TGC), bandpass filtering, logarithmic compression, envelope detection, and noise rejection to enhance image resolution and contrast.

Question 61

The penumbra for proton beams ________ as the depth increases.

Accepted Answer

Option A: Increases. As protons penetrate matter, they undergo continuous small-angle Coulomb scattering events off atomic nuclei (multiple Coulomb scattering). This cumulative lateral deflection increases with depth, causing the lateral beam edge penumbra to progressively widen as the beam approaches the Bragg peak.

Question 62

An Ir-192 HDR source is changed between a patient's second and third brachytherapy fractions. Which of the following parameters will be different for the third fractions?

Accepted Answer

Option C: Treatment time. Because the new $^{192}	ext{Ir}$ source has a significantly higher activity than the old decayed source, the dose rate $(\dot{D})$ inside the patient increases. To deliver the identical prescribed radiation dose ($D = \dot{D} \cdot t$), the dwell times and total treatment time must decrease inversely with the new source activity.

Question 63

An advantage of TG-143 dose calculation is ________

Accepted Answer

Option D: None of the above is true. In the standard AAPM brachytherapy dosimetry formalism (TG-43 / TG-143): (1) all calculations assume an unbounded homogeneous water medium without tissue heterogeneity corrections; (2) inter-seed attenuation and shielding effects are ignored; and (3) radiobiological dose-rate variations are not modeled. Therefore, none of the listed statements is an advantage or feature of the TG-43/143 protocol. Choice D.

Question 64

A radionuclide injection used to treat bone metastasis from prostate cancer is

Accepted Answer

Option C: Ra-223. Radium-223 dichloride ($^{223}	ext{Ra}$, trade name Xofigo) is an alpha-emitting targeted calcium mimetic that selectively targets areas of high bone turnover in osteoblastic bone metastases from castration-resistant prostate cancer, delivering localized high-LET radiation.

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