Q-51. Investigation of choice for a lesion of temporal bone–
a) CT
b) MRI
c) USG
d) Plain x-ray
Answer: CT
Explanation:
Bony structures are better demonstrated on CT.
MRI cannot distinguish between dense bone and air spaces.
MRI is better for evaluating the otic capsule contents, brain, cranial nerves and blood vessels.
Q-52. Radiation exposure is the least in the following procedure –
a) Micturating cytourethrogram
b) IVP
c) Bilateral nephrostomogram
d) Spiral CT for stones
Answer: Micturating cytourethrogram
Explanation:
Procedure——————–Radiation dose mSv
X-ray abdomen AP———0.7
Intra-venous urogram—-2.5
Cystography—————–1.8
Lithotripsy——————-1.3
Nephrostomy—————3.4
PCNL—————————4.5
Ureteric stenting———–4.7
CT Abdomen—————–10
Renal angiogram———–2 to 30
Micturating cytourethrogram-1.2
Q-53. Most sensitive test to diagnose ductal carcinoma in situ –
a) Mammography
b) MRI
c) PET
d) USG
Answer: MRI
Explanation:
MRI has higher sensitivity than mammography and ultra-sonography for detection of DCIS and greater accuracy for depicting the extent of disease.
Q-54. Patient with 6th cranial nerve palsy, T2 weighed MRI showing hyper-intense shadow which shows contrast enhancement in the cavernous sinus, diagnosis is –
a) Schwannoma
b) Meningioma
c) Cavernous sinus hemangioma
d) Astrocytoma
Answer: Schwannoma
Explanation:
Schwannoma:
Mostly hypo-intense on T1 and Hyper-tense on T2
Smaller tumors show homogenous density and strong homogenous enhancement.
Cavernous sinus hemangioma is very rare tumor in cavernous sinus.
Q-55. Frontal sinus can be best visualized by –
a) Caldwell’s view
b) Water’s view
c) Towne’s view
d) Schuller’s view
Answer: Caldwell’s view
Explanation:
Frontal sinus can be best visualized in Caldwell’s view or occipito-frontal view.
Maxillary sinus can be best visualized in Water’s or occipito-mental view.
Q-56. Which one of the following is not a CT feature of adrenal adenoma?
a) Low attenuation
b) Homogenous density and well defined borders
c) Enhances rapidly, contrast stays in it for relatively longer time and washes out late
d) Calcification is rare
Answer: Enhances rapidly, contrast stays in it for relatively longer time and washes out late
Explanation:
Q-57. Radiation induced necrosis can be diagnosed by
a) PET
b) CT
c) MRI
d) Biopsy
Answer: PET
Explanation:
PET and SPECT have ancillary roles in the imaging of the brain tumors, primarily in distinguishing tumor recurrence from tissue necrosis that can occur after radiation.
Biopsy is frequently required to establish the correct diagnosis.
Q-58. Which of the following elements is obsolete in radio-therapy?
a) Radium 226
b) Cobalt 60
c) Iridium 192
d) Cesium 137
Answer: Radium 226
Explanation:
Radioactive isotopes used for brachytherapy:
These include radium-226, cesium-137, cobalt-60, iridium192, iodine-125, gold-198 and palladium-103. Radium has a longer half-life compared to some of the other radioactive isotopes.
In the past radium was the primary isotope used in brachytherapy, but recently radium has been largely replaced by cesium, gold and iridium, which have relatively shorter half-life and lower energies and because of this the radiation from these isotopes can be easily shielded.
Q-59. A child presents with respiratory distress. A vascular ring is suspected. Investigation of choice is
a) PET
b) CT
c) MRI
d) Angiography
Answer: MRI
Explanation:
Initially diagnosis of vascular ring is made by a high index of suspicion and the barium swallow is the first investigation.
Echocardiography can document an abnormal head and neck vessel branching pattern excluding intra-cardiac abnormalities.
MRI provides complete anatomic details.
Q-60. CT or Hounsfield numbers depend upon:
a) Mass density
b) Electron density
c) Atomic number
d) Atomic mass
Answer: Mass density
Explanation:
The Hounsfield unit (HU) scale is a linear transformation of the original linear attenuation coefficient measurement into one in which the radio-density of distilled water at standard pressure and temperature (STP) is defined as zero Hounsfield units (HU), while the radio-density of air at STP is defined as -1000 HU.
It is the definition for CT scanners that are calibrated with reference to water.
Water is the reference material for CT numbers: value of zero. Attenuation (density) > water: positive CT numbers. Density < water: negative CT numbers. X-ray attenuation and CT number depends on the density.