IT includes everything related to fluoroscopy, radiation exposure, it,s effects, contrast agents , and it,s newer variants including gadolinium, anaphylaxis reactions and it,s management, images for epidural,intrathecal,subdural, intrarterial and intravenous contrast picture.

1. Radiation safety & contrast
agents in pain medicine
Dr Ravi Shankar Sharma
Moderator-Dr. Ajit Kumar

2. Aim:-
• Detailed understanding of:
Physics behind X-ray generation
Fluoroscopy in pain management
Radiation safety measures including ALARA
Contrast media in chronic pain.

3. Content:-
• Introduction and physics of X ray
• Fluoroscope components
• Radiation safety including measure to reduce radiation exposure.
• Radiographic contrast medium
• Adverse reaction of contrast media and their Management.

4. Contributions:

5. Introduction –X rays
• 1895 Roentgen discovered x-rays Wurzburg University in Germany.
• 1896Thomas Edison created the first fluoroscope
• No. of interventional pain procedures has ↑ past 20 years.
• Advantages of fluoroscopy  visualization of the procedure area, needle
placement, and unintentional intravascular injection
• Increase clinical efficacy and patient safety ,↓possible side effects.

6. THE PHYSICS OF X-RAYS
• X-rays Ionizing radiation (created in fluoroscope & harnessed for imaging).
• X-ray tube  contains a cathode and metal anode.
• Cathode (high-velocity electrons) collide with the metal anode kinetic
energy  Electromagnetic energy  X-rays.
• Close to light photons on the electromagnetic spectrum
• Have shorter wavelength ( than UV rays) and higher energy( 100ev to 100kev)

7. X- Ray Tube operation

8. Electromagnetic spectrum

9. When these x-rays contact matter, they interact in one of three ways:
1. They are absorbed.
2. They are deflected and scattered.
3. They pass through matter unheeded.
• X-ray interact with certain media To visualize.
• Fluoroscopy, x-rays Phosphorous in a fluorescent screen to emit visible light.
• Modern fluoroscopic  zinc-cadmium sulfide as an effective phosphor.

10. • As the density of matter increases, x-rays are absorbed or scattered to a
greater extent, giving rise to the 5 radiologic densities commonly used to
describe radiographs:
1. Air
2. Fat
3. Water (soft tissue)
4. Bone
5. Metal
Higher Density Appears darker on the displayed image
(x-rays contacting the phosphor create light)

11. Components of fluoroscope
• X-ray generator
• X-ray tube
• Collimator
• Image intensifier
• Optical coupling chain
• Viewing monitor

12. Current:
• X-ray generator ACDC x-ray tube.
• Unit- mA
• Number of x-rays produced by the x-ray tube
• Controls the density and intensity of the x-ray beam. ( blacks and whites).
• Higher number higher amount of x-rays delivered.
• Range  2 and 6 mA.

13. Voltage
• kVp
• Strength of the x-ray penetrability & the energy of the x-rays produced.
• Main component of the image contrast (shades of gray).
• Range 75–125 kVp.

14. INCREASING KvP CAUSES LIGHTER IMAGE

15. C-arm panel

16. Collimator:
• Reduces the amount of x-rays delivered to the patient
• Less scattered radiation
• Reduces glare and improves the clarity of the image.
• Two types:
1. Horizontal collimation  e.g. facet injections
2. Circular or “shutter”  e.g. tunneled approach

17. Collimation:

18. Controls for both radial (iris) and rectangular collimation on a typical C-arm
fluoroscope.

19. Units:
ROENTGEN = RAD= REM

20. RADIATION SAFETY:
• Effects of x ray proportional to time of exposure
• Exposure to x-rays free radicals damage to cell structures.
• Chemical chain reactions changes in cell membrane permeability 
resulting in cellular dysfunction.
• Damage to DNA  somatic mutations harm to subsequent generations.
• 50 mSv/y (5 rem/y) & cumulative < 10 mSv (1 rem) times the age

22. Skin Manifestation and Radiation Exposure Dose
Frazier etal. Fluoroscopy-induced chronic radiation skin injury: a disease perhaps often
overlooked. Arch Dermatol. 2007;143:637–640.

23. Annual Maximum Target Organ Permissible
Radiation Doses
Data from NCRP (National Council on Radiation Protection and Measurements)

24. ALARA
• Regulatory requirement for all radiation safety programs.
• Operator should continuously minimize radiation dosage by using all
reasonable methods.
• This principle is referred to as “ALARA (As Low As Reasonably
Achievable)”

25. Minimizing Patient Radiation Exposure
• Minimize time: Most effective way ↓ radn. exposure.
1. Review available imaging before starting
2. Anticipating the appropriate C-arm position before obtaining an image
3. Properly center the fluoroscope over the targeted structure
4. Use the fluoroscope’s laser beam, if available.
5. Multilevel procedures place needles for all levels ( before multiplanar imaging).
6. Trajectory view, the needle should be parallel to the beam

26. For this right-sided L5 transforaminal epidural steroid injection, the needle has
been inserted and is not parallel with the beam.

27. LIMITING EXPOSURE TIME-Machine
• Use pulse-mode of exposure rather than continuous exposure.
• Use Low Dose Mode whenever possible.
• Use Last Image Hold.

28. PROPER C-ARM OPERATION: MAXIMIZING DISTANCE FROM
SOURCE
• Inverse square law -As the distance from the source increases, radiation
intensity decreases exponentially.
Position the x-ray tube
as far from the patient
as possible.

29. Position the Image intensifier as close
to the patient as possible.

30. A smaller air gap reduces radiation
dose to the patient and staff and improves
image quality.

31. Employ Collimation

32. MINIMIZING PRACTITIONER EXPOSURE
• Practitioner Position-stand as far as possible from the x-ray tube

33. X-Ray tube beneath the patient
tube
tube

34. Beware of the scattering during angulation of
c-arm ( oblique view)

35. Other measures:
• Reducing the exposure time
• Using an intravenous extension tube

36. Employ Proper Shielding
• X- rays can be attenuated by using lead shields equivalent to 0.5 mm
of lead

37. RADIATION PROTECTION
• Regular technical checks of Device – to avoid tube housing leakages.
• Radiation shielding – lead aprons, thyroid shields, lead gloves, eyeglasses.
• Avoid direct exposure of practitioners hands within the x-ray field.
• Do not fold or throw the lead aprons randomly. Yearly checks of aprons for
cracks or breaks.
• Dosimeter

39. Optimizing image quality
• Automatic Brightness Control automatically adjusts mA and kVp to optimize image.
• Increasing kVp high energy x ray brighter image.
• Vignetting: less sharpness at the periphery of the image due to a fall off in brightness
and spatial resolution.
• Pincushion distortion: occurs toward the periphery of the image because the x-rays
emanate from a spherical surface and are detected on a flat surface.
• Flat plate detectors can eliminate both.
• Collimation

40. Radiographic contrast medium

41. Radiographic contrast agents
• Aids in the localization of anatomic structures during placement of needles.
• Exclude accidental i.v. placement & identification of the epidural & I/T space.
MOA:-
• x-ray passes body  Attenuated by the various anatomic structures
• Iodine atoms (triiodinated benzoate anion), of contrast agents provide greater
attenuation & ↓amount of radiation reaching the I. intensifier.

42. Ionic monomers
• DIatrozoate (Urografin),
• Iothalarnate (Conray),
• Metrizoate (Isopaque)
Non-ionic monomers
• Iodixanol (Visipaque)
• Iohexol (Omnipaque)
• Iopamidol (Isoview)
• ioversol (Optiray)
These agents have an osmolality of near physiologic levels of 300 mOsm/kg, in
contrast to older agents, which were hyperosmolar and highly ionically charged.
Pharmacology of radio contrast medium

44. • Toxicity of contrast agents ↓ as their osmolality ~serum.
• Developing nonionizing compounds & combine 2 monomers dimer.
• Representative osmolality : Serum: 290 mOsm/kg of H2O
 Nonionic monomer: iohexol 240 (Omnipaque): 518 mOsm/kg of H2O
Nonionic monomer: iohexol 300 (Omnipaque): 672 mOsm/kg of H2O;
Nonionic dimer: iodixanol 320 (Visipaque): 290 mOsm/kg of H2O.
Maximum daily dose is 3g/day.

45. The toxicity of contrast agents can also be ↓ by doing the following:
 Adding calcium ions, which reduces cardiac toxicity.
Establishing a neutral pH, which predisposes to vasodilatation
 Altering the number and distribution of oh- ions, which ↓ neural toxicity.
• Cleared almost completely  Glomerular filtration.
• Patients with ↓ renal function, excretion  bile and through the bowel.
• Circulatory half-life is approximately 1 to 2 hours( normal renal function)

46. Adverse Reactions
• A/t ACR--adverse reactions to contrast agents into 3 categories:
 Mild : signs and symptoms are self-limited and without progression
Moderate: reactions that require Rx but are not life-threatening.
Severe: life-threatening, immediate Rx and usually requiring hospitalization.

47. Adverse Reactions to Contrast Agents by Category
APA Gevirtz, Clifford MD, MPH Contrast Agents in Pain Practice,
Topics in Pain Management: July 2014 - Volume 29 - Issue 12 - p 1-7

48. Delayed Contrast Reaction
• Delayed contrast reactions 3 hours to 7 days after the contrast inj.
• Includes cutaneous exanthem, pruritis without urticaria, nausea,
vomiting, drowsiness, and headache.Rarely S.J syndrome
• Common in h/o previous contrast reaction and in those Rx with IL-2
• Exact mechanism of delayed reactions is unknown, T-cell mediated

49. Anaphylaxis to contrast media
• Allergen + IgE  induce mast cells chemical mediators(Histamine)
Skinvasodilatation produces urticaria and erythema.
Mucosa vasodilatation produces nasal congestion and laryngeal edema.
 Respiratory tract smooth-muscle contraction produces bronchospasm.
 Peripheral vesselsvasodilatation produces hypotension and shock.
GIT nausea, vomiting, diarrhea, and cramps.

50. Anaphylaxis Vs Anaphylactoid reaction
• Anaphylactoid rkn can occur even if the 1st time contrast is administered.
• Severity of anaphylactoid reaction is not dose related; test dose -no value
• Occurrence of a contrast reaction--does not necessarily mean that it will
occur again (although risk is greater)
• Although the circulating contrast is systemic, the nature of the response is
variable such that more than one type of reaction may occur simultaneously.

51. Steps for managing anaphylactoid & anaphylactic reactions :
1. Stop the injection. If a patient is having a sudden reaction, stop the injection and
withdraw the needle.
2. Check the airway , Administer 100% oxygen, Intubate
3. Start I.V. fluid with a goal of 25 to 50 mL/kg of RL/NS/colloid.
4. Administer epinephrine 0.1 mg IV and then start an infusion of 1 to 4 mcg/min
titrated to restore BP to the normal range.
5. If hemodynamic stability cannot be restored, start the ACLS protocol.
(Clinical pearl: 1 mg of epinephrine in 250 mL results in a concentration of 4 mcg/mL,
so running this IV solution at 60 mL/hr should support the blood pressure.)

52. Pretreatment Protocol in Patients With Previous Allergic Reaction to a Contrast
Agent:

53. MRI Contrast Agents:
• Gadolinium-based, non-nephrotoxic and are safe and effective for IPP
• Ability to attenuate x-rays , in place of iodinated contrast media for
angiography and spinal injections.
• 3 contrast agents are:
 Gadobenate dimeglumine (MultiHance)
Gadoxetate (Eovist),
 Gadodiamide (Omniscan).

54. Pharmacokinetics:
• Do not cross the intact BBB and do not accumulate in normal brain or in
lesions that do not have an abnormal BBB (eg, cysts or P/o scars).
• Disruption BBB or abnormal vascularity accumulation (neoplasms,
abscesses, and subacute infarcts.)
• Does not bind to human serum proteins in vitro.
• Eliminated primarily in the urine
• No detectable biotransformation or decomposition

55. Nephrogenic systemic fibrosis (NSF)
• NSF was first described in 1997.
• Irreversible fibrotic systemic disorder  causing disabling limitation of
movement, swallowing problems, and breathing difficulties.
• Estimated risk ~ 4%.
• Risk of patients with normal or slightly impaired renal function is minimal.
• No effective treatment for NSF.

56. High Risk For NSF-criteria from both section 1 and section 2
1. Does the patient meet any of the following criteria?
A. Kidney or liver transplant ,GFR < 60
B. Intrinsic renal disease with an estimated GFR< 30
C. Acute renal failure
2. Does the patient have a recent (1-month) history of any of the following?
A. Major infection.
B. Vascular ischemia of the extremities
C. Venous or arterial thrombosis
D. Major surgery or vascular procedures
E. Multiorgan system failure

57. Epidural contrast injection
DOUBLE-LINE OR RAIL-ROAD TRACK appearance of contrast in
anterior and posterior epidural space

58. Subdural spread

59. Intrathecal spread

60. Intravenous contrast injection

61. Intra-arterial contrast injection

62. References:-
1. APA Gevirtz, Clifford MD, MPH Contrast Agents in Pain Practice, Topics in Pain Management: July 2014 -
Volume 29 - Issue 12 - p 1-7
2. Safriel Y, Ang R, Ali M. Gadolinium use in spine pain management procedures for patients with contrast
allergies: results in 527 procedures [retracted in: Cardiovasc Intervent Radiol. 2009 Jul;32(4):847]. Cardiovasc
Intervent Radiol. 2008;31(2):325-331. doi:10.1007/s00270-007-9192-5
3. Kothari K, Sahu DK. Ultrasonography versus fluoroscopy in modern pain management. Indian J Pain
2016;30:71-6
4. Manchikanti L, Cash KA, Moss TL, Pampati V. Radiation exposure to the physician in interventional pain
management [published correction appears in Pain Physician. 2003 Jan;6(1):141]. Pain Physician.
2002;5(4):385-393.
5. Wang D. Image Guidance Technologies for Interventional Pain Procedures: Ultrasound, Fluoroscopy, and
CT. Curr Pain Headache Rep. 2018;22(1):6. Published 2018 Jan 26.