RADIOLOGY QUICK REVISION NOTES
GENERAL RADIOLOGY Effects of radiation
STOCHASTIC “chance” DETERMINISTIC
Mechanism of action of ionizing
No threshold Threshold exists
radiation
Probability increases with Severity increases with
1. DNA damage -- ds DNA damage (M/C)Q dose dose
2. Free radicals damage Delayed Immediate
Cancer, Genetic mutations Skin erythema (M/C),
“All or none” Cataracts, epilation.
Ionising radiation
RAYS PARTICULATE MATTER
Cosmic rays γ-rays X-rays Radiotherapy
•• a particles
•• Background •• Nuclear medicine scan •• Radiographs •• β particles
radiationQ - Scintigraphy •• Fluoroscopy •• Neutrons
- SPECT •• DSA •• Protons
•• PET •• CT
Modalities Using Ionising Radiation
NON-IONISINGQ IONISING : X-RAYS IONISING : GAMMA RAYS
- USG - Radiography - Scintigraphy
- MRI - CT scan - SPECT
- Thermography - Fluoroscopy / Contrast study - PET scan
eg; HSG/ ERCP/ IVP
- DEXA scan
Radiation Unit
Entity SI Unit Conventional unit
Radioactivity Becquerel / Disintegration per Curie
second (dps) 1 Ci = 3.7 x 1010 Bq
Exposure Coulomb/Kg Roentgen
(basically means ionization)
Absorbed dose GrayQ Rad
Air kerma 1 Gy = 100 Rad
(ABG RAD)
Equivalent Sievert (Sv) Rem
1 Sv = 100 Rem
Effective dose Sv Rem
, 10
Radiology
Maximum permissible dose according to AERB
(Atomic Energy Regulatory Board)
Occupational Exposure Public Exposure
Overall 20 mSv/year averaged over 5 consecutive years Q 1 mSv / year
- 30 mSv in any single year
Lens 150 mSv in a year 15 mSv / year
Skin, Extremities 500 mSv in a year 50 mSv / year
Pregnant female 2 mSv / yearQ 1 mSv / year
Fetus 1 mSv / year 0.5 mSv / year
Thermoluminiscent Dosimeter / TLD BADGE
•• Made up of:- CaSO4: Dysprosium (LiF can also be used)
•• 3 monthly
•• Worn below the lead apron at the level of the chest.Q
LEAD Apron
•• Minimum thickness: 0.25 mmQ
•• M/C thickness used: 0.5 mm
Basics of imaging modalities -
Modality X-ray CT MRI USG
Ionising Radiation √ √ x X
Overall Status Initial IOC: IOC: Initial / Best
investigation; - Acute - Brain/ Spine / - GB
- Air haemorrhage Nerve - Fluid/cyst
- Ortho - Foreign body
- Ca2+
,104
Cerebellum Quick Revision Notes
Thumb rules: X-ray
EMERGENCIES – AIR MSK FOREIGN BODY LINES & TUBES
- Pneumothorax - Fracture Initial - X-ray - Best – X-rayQ
- Pneumoperitoneum - Bone Tumor IOC-NCCTQ Exception:-
- Intestinal obstruction - Arthritis CI-MRIQ ET Tube → ET Co2
Thumb rules: CT
IOC → NCCT
CALCIUM BONE FOREIGN BODY ACUTE HEMORRHAGE AIR
- Intracranial Ca2+ - Fracture - IOC: Head traumaQ Lung pathology
- Renal / Ureteric except- C/I → MRI - Initial: StrokeQ
stones HRCT – IOC: ILD,
stress fracture Q
- Salivary stonesQ Bronchiectasis,
except- COVID-19Q
- Osteoid osteoma
Gall stone (USG)
Periventricular calcification: Left ureteric calculus Left intraocular Right acute EDH
Congenital CMV metalic foreign body left acute SDH
, 10
Radiology
NCCT: CECT: CT ANGIOGRAPHY:
-IOC for head, spine trauma (Q) Lung Tumors Aortic dissectionQ
-IOC for acute SAH (Q) Renal Tumors Aortic aneurysmQ
-IOC for intracranial calcification (Q) Pancreatic Carcinoma Pulmonary embolism
-IOC for renal calculi Liver Tumors Mesenteric ischemia
-IOC FOR IOFB Mediastinal Masses Sequestration
-IOC for bone cortex Acute Pancreatitis
-Initial Investigation in stroke (Q)
MRI
Sequences of MRI
•• Since bones are black, it is MRI
•• Once recognized that it is MRI, look at the CSF.
•• CSF is white, it is T2 (Water, Fluid is white on T2: WW2)
T1 T2 FLAIR
- Grey matter: Grey - Grey matter: White - CSF in the ventricles is suppressed
- White matter: White - White matter: Grey - Periventricular white matter is hyperintense
- T1 follows the anatomy - FLAIR helps to pick oedema in the
periventricular area
- Helps in demyelinating lesions as in Multiple
sclerosis (Dawson fingers)
STIR (Short Tau Inversion Sequence MRI)
•• T2 WI MRI in which fat signal is suppressed
•• IOC → Bone marrow oedema -- Osteomyelitis, Sacroiliitis, Stress fracture
GENERAL RADIOLOGY Effects of radiation
STOCHASTIC “chance” DETERMINISTIC
Mechanism of action of ionizing
No threshold Threshold exists
radiation
Probability increases with Severity increases with
1. DNA damage -- ds DNA damage (M/C)Q dose dose
2. Free radicals damage Delayed Immediate
Cancer, Genetic mutations Skin erythema (M/C),
“All or none” Cataracts, epilation.
Ionising radiation
RAYS PARTICULATE MATTER
Cosmic rays γ-rays X-rays Radiotherapy
•• a particles
•• Background •• Nuclear medicine scan •• Radiographs •• β particles
radiationQ - Scintigraphy •• Fluoroscopy •• Neutrons
- SPECT •• DSA •• Protons
•• PET •• CT
Modalities Using Ionising Radiation
NON-IONISINGQ IONISING : X-RAYS IONISING : GAMMA RAYS
- USG - Radiography - Scintigraphy
- MRI - CT scan - SPECT
- Thermography - Fluoroscopy / Contrast study - PET scan
eg; HSG/ ERCP/ IVP
- DEXA scan
Radiation Unit
Entity SI Unit Conventional unit
Radioactivity Becquerel / Disintegration per Curie
second (dps) 1 Ci = 3.7 x 1010 Bq
Exposure Coulomb/Kg Roentgen
(basically means ionization)
Absorbed dose GrayQ Rad
Air kerma 1 Gy = 100 Rad
(ABG RAD)
Equivalent Sievert (Sv) Rem
1 Sv = 100 Rem
Effective dose Sv Rem
, 10
Radiology
Maximum permissible dose according to AERB
(Atomic Energy Regulatory Board)
Occupational Exposure Public Exposure
Overall 20 mSv/year averaged over 5 consecutive years Q 1 mSv / year
- 30 mSv in any single year
Lens 150 mSv in a year 15 mSv / year
Skin, Extremities 500 mSv in a year 50 mSv / year
Pregnant female 2 mSv / yearQ 1 mSv / year
Fetus 1 mSv / year 0.5 mSv / year
Thermoluminiscent Dosimeter / TLD BADGE
•• Made up of:- CaSO4: Dysprosium (LiF can also be used)
•• 3 monthly
•• Worn below the lead apron at the level of the chest.Q
LEAD Apron
•• Minimum thickness: 0.25 mmQ
•• M/C thickness used: 0.5 mm
Basics of imaging modalities -
Modality X-ray CT MRI USG
Ionising Radiation √ √ x X
Overall Status Initial IOC: IOC: Initial / Best
investigation; - Acute - Brain/ Spine / - GB
- Air haemorrhage Nerve - Fluid/cyst
- Ortho - Foreign body
- Ca2+
,104
Cerebellum Quick Revision Notes
Thumb rules: X-ray
EMERGENCIES – AIR MSK FOREIGN BODY LINES & TUBES
- Pneumothorax - Fracture Initial - X-ray - Best – X-rayQ
- Pneumoperitoneum - Bone Tumor IOC-NCCTQ Exception:-
- Intestinal obstruction - Arthritis CI-MRIQ ET Tube → ET Co2
Thumb rules: CT
IOC → NCCT
CALCIUM BONE FOREIGN BODY ACUTE HEMORRHAGE AIR
- Intracranial Ca2+ - Fracture - IOC: Head traumaQ Lung pathology
- Renal / Ureteric except- C/I → MRI - Initial: StrokeQ
stones HRCT – IOC: ILD,
stress fracture Q
- Salivary stonesQ Bronchiectasis,
except- COVID-19Q
- Osteoid osteoma
Gall stone (USG)
Periventricular calcification: Left ureteric calculus Left intraocular Right acute EDH
Congenital CMV metalic foreign body left acute SDH
, 10
Radiology
NCCT: CECT: CT ANGIOGRAPHY:
-IOC for head, spine trauma (Q) Lung Tumors Aortic dissectionQ
-IOC for acute SAH (Q) Renal Tumors Aortic aneurysmQ
-IOC for intracranial calcification (Q) Pancreatic Carcinoma Pulmonary embolism
-IOC for renal calculi Liver Tumors Mesenteric ischemia
-IOC FOR IOFB Mediastinal Masses Sequestration
-IOC for bone cortex Acute Pancreatitis
-Initial Investigation in stroke (Q)
MRI
Sequences of MRI
•• Since bones are black, it is MRI
•• Once recognized that it is MRI, look at the CSF.
•• CSF is white, it is T2 (Water, Fluid is white on T2: WW2)
T1 T2 FLAIR
- Grey matter: Grey - Grey matter: White - CSF in the ventricles is suppressed
- White matter: White - White matter: Grey - Periventricular white matter is hyperintense
- T1 follows the anatomy - FLAIR helps to pick oedema in the
periventricular area
- Helps in demyelinating lesions as in Multiple
sclerosis (Dawson fingers)
STIR (Short Tau Inversion Sequence MRI)
•• T2 WI MRI in which fat signal is suppressed
•• IOC → Bone marrow oedema -- Osteomyelitis, Sacroiliitis, Stress fracture
