Nuclear imaging assesses how organs function, whereas other imaging methods assess anatomy. It involves injecting radiopharmaceuticals labeled with radioactive tracers, which accumulate in organs of interest and emit gamma rays that are detected by gamma cameras. There are several types of nuclear imaging including planar scintigraphy, SPECT and PET. SPECT provides 3D tomographic images by detecting gamma photons from multiple angles, while PET involves detecting pairs of gamma rays emitted by positron-emitting radiotracers to construct 3D functional images. Nuclear imaging is used clinically to investigate organ function and detect diseases.

1. Nuclear Imaging

2. Contents
-Introduction
-Nuclear Imaging vs X-ray Imaging
-Working principle
-Scintigraphy
-SPECT, PET
-Hybrid Imaging
-Applied Aspects

4. Nuclear imaging assesses how organs function,
whereas other imaging methods assess anatomy,
or how the organs look.

6. Atom

7. Electromagnetic Spectrum

8. Ionising radiation
• Alpha radiation – 2N+2P
• Beta radiation – electron emitted
• X-Rays
• Gamma rays EM RADIATION

9. Types of Ionizing Radiation
Alpha Particles
Stopped by a sheet of paper
Beta Particles
Stopped by a layer of clothing
or less than an inch of a substance
(e.g. plastic)
Gamma Rays
Stopped by inches to feet of concrete
or less than an inch of lead
Radiation
Source

10. When atoms decay by emitting a or b particles to form a
new atom, the nuclei of the new atom formed may still
have too much energy to be completely stable.
This excess energy is emitted as gamma rays

11. RADIOISOTOPES
Elements containing atoms with same
atomic number and different number of
neutrons.
A radionuclide is a radioactive form of an
isotope that behaves chemically in a
similar manner to the non radioactive
counter part.
The nuclear BE is not capable of holding
the nucleus together and undergoes
disintegration releasing particulate or
ionizing radiation.

12. Particulate radiation is utilized for internal
therapy (thyroid disease, malignancies)
Detection of electro magnetic radiation
forms the basis for radionuclide imaging

13. Radioactive transformation
• Isobaric Transitions
• Beta Emission
• Positron Emission
• Electron Capture
• Isomeric transitions
• Gamma Emission
• Internal Conversion
• Excited state transitions
• Metastable state transitions
• Alpha transition

14. Gamma Emission
• In most isomeric transitions, a nucleus will emit its
excess energy in the form of a gamma photon.
• A gamma photon is a small unit of energy that travels
with the speed of light and has no mass; its most
significant characteristic is its energy.
• The photon energies useful
for diagnostic procedures
are generally in the range
of 100 keV to 500 keV.

15. Positron Emission
• A positron is a particle similar to electron except
that it has a positive electric charge.
• p+ n + β + + ѵ + energy.
• The behaviour of positron in the tissue is very
similar to β particles with one important
difference – once the positron has been slowed
down by the atomic collisions , it is annihilated
by the interaction with an electron from a nearby
atom.
• The combined mass of the proton & electron is
converted into two annihilation photons – each
with energy 511 KeV .
• The two photons are emitted at 180° to each
other – this property is exploited by PET.

18. • We need a short-lived radio nuclide which has to be
combined to a pharmaceutical of interest and
injected iv and this radio pharmaceutical goes and
attaches to the organ of interest and we can catch
the gamma rays emitted by it with help of gamma
cameras and pictures are reconstructed in
computer

19. 1. RADIONUCLIDE
2. PHARMACEUTICAL
3. GAMMA CAMERA
SPECT

20. Ideal Radionuclide
• Emits gamma radiation at suitable energy for
detection with a gamma camera (60 - 400 kev, ideal
150 kev)
• Should not emit alpha or beta radiation
• Half life similar to length of test
• Cheap
• Readily available

21. Technetium
• This is the most common radio
nuclide used in Nuclear Medicine.
• Taking its name from the Greek
work technetos meaning artificial ,
it was the first element to be
produced artificially.

22. Technetium (99mTc) : The most commonly used isotope for the
following reasons:
• Gamma emission : Single 141 KeV gamma emissions which are ideal for
imaging purposes.
• Short half - life : A short half life of 6 ½ hours that ensures a minimal
radiation dose.
• Readily attached to different substances : It can be readily attached to a
variety of different substances that get concentrated in different organs . Egs.
99m Tc + MPD ( Methylene diphosponate ) in bone , 99m Tc + RBC in blood ,
99mTc + sulphur colloid in the liver and spleen.
• Ionic form : It can be used on its own in its ionic form (pertecnetate 99m Tc
O+) , since the thyroid and salivary glands take this up selectively.

23. TECHNETIUM PRODUCTION
• FROM MOLYBDENUM by radioactive decay

24. Radiopharmaceuticals
Substances which tend to localize in the tissue
of interest is tagged with gamma ray emitting
radionuclide.

25. 99mTc
Excited Nucleus
Gamma ray
99Tc
Stable Nucleus
Photon Decay

27. Ideal radiopharmaceutical
• Cheap and readily available
• Radionuclide easily incorporated without altering
biological behavior
• Radiopharmaceutical easy to prepare
• Localizes only in organ of interest
• t1/2 of elimination from body similar to duration of
test

28. • Thyroid scintigraphy
• Salivary gland studu
99mTc pertechnetate
• Cerebral metabolism PET
• Tumor imaging
18 FDG
Fludeoxyglucose
• Parathyroid scintigraphy
99mTc MIBI
Tc bound to six
methoxyisobutylisonitrile ligand

29. • Bone scintigraphy
99mTc
polyphosphate
• Cardiac ventriculography
• GI bleed study
99mTc red
blood cells
• V/Q scan ventilation-perfusion
scan
99mTc albumin

30. • Esophageal transit and
reflux
• GI bleed study
99mTc sulphur
colloid
• White cell scintigraphy99mTc leucocytes
• Hepatobiliary study
99mTc
iminodiacetic
acid derivatives

31. Radiopharmaceutical administration:
The radiopharmaceutical should be administered by the intravenous
route.
Image acquisition:
Between 2 and 5 hours after injection.
Later (6-24 hour) delayed images (higher target-to-background ratio and may
permit better evaluation)

32. Gamma Camera
A gamma camera consists of three main parts:
Electronic systems
Detector
Collimator

34. Gamma Imaging

35. This is a device made of a highly
absorbing material such as lead, which
selects gamma rays along a particular
direction.
They serve to suppress scatter and select
a ray orientation.
The simplest collimators contain parallel
holes.

36. DETECTOR / SCINTILLATOR
• Made up of sodium iodide crystals.
• It produces multi-photon flashes of light when an
impinging gamma ray, X-ray or charged particle interacts
with the single sodium iodide crystal of which it is
comprised.

37. • The scintillation counter not only detects the presence and type of
particle or radiation, but can also measure their energy.

38. Photomultiplier tube (PMT)
• This is an extremely sensitive photocell used to convert light
signals of a few hundred photons into a usable current pulse

39. PULSE HEIGHT ANALYZER (PHA):
• It lets through only those pulses which lay within the window of
±10 % of the photopeak energy.
• The pulses so selected – ‘Counts’.
• The X Y Z pulses are next applied directly to a monitor for visual
interpretation as in older machines or in newer systems via
analogue-digital converters into a computer.
• This enables dynamic & gated studies to be undertaken as well
as range of image processing.

41. Pharmaceuticals that are labeled
with radionuclides
Accumulate in organs of interest
Emit gamma radiation
Detection system sensitive to this
obtain images

42. Nuclear Imaging
Scintigraphy
SPECT PET

43. Planar Scintigraphy :
Planar imaging produces a 2D
image with no depth information
and structures at different depths
are superimposed.
The result is loss of contrast in the
plane of interest.

44. Single Photon Emission Computed Tomography (SPECT)
• SPECT was developed as an enhancement of
planar imaging.
• It detects the emitted gamma photons (one at
a time) in multiple directions.
• Uses one or more rotating cameras to obtain
projection data from multiple angles.
• SPECT displays traces of radioactivity in only
the selected plane.
• Axial, coronal and sagittal.

45. • SPECT is a method of acquiring tomographic slices through a
patient.
• Most gamma camera have SPECT capability.
• In this technique either a single or multiple ( single , dual or triple
headed system ) gamma camera is rotated 360° about the patient
• Image acquisition takes about 30 -45 minutes.
• The acquired data are processed by filtered back projection & most
recently iterative reconstruction algorithms to form a number of
contiguous axial slices similar to CT by X – ray.

46. • After every 6° camera halts for 20 – 30 seconds & acquires the view
of the patient .
• 60 views are taken from different directions .
• These data can then be used to construct multiplanar images of the
study area.
• SPECT studies can be presented either as a series of slices or 3 D
displays.
• By changing contrast & localization , SPECT imaging increases
sensitivity & specificity of disease detection.
• Tomography enhances contrast & removes superimposed activity.
• SPECT images have been fused recently with CT images to improve
identifying of the location of the radionuclide.

47. SPECT bone scintigrams show increased uptake in the right
mandible (arrows) in the region of a sequestrum.

48. Positron Emission Tomography (PET)
• Positron emission tomography (PET) is a nuclear
medicine imaging technique which produces a three-
dimensional image or picture of functional processes in
the body.
• The system detects pairs of gamma rays emitted
indirectly by a positron-emitting radionuclide (tracer).

49. Positron Emission
• In this, a proton in the nucleus is transformed into a
neutron & a positron.
• Positron emission is favored in low atomic number
elements.

50. Positron Annihilation:
• The positron has short life in solids & liquids.
Interactions with atomic electrons
Rapidly loses kinetic energy
Reaches the thermal energy of the
electron
Combines with the electron
Undergoes annihilation

51. • Their mass converts into energy in the form of gamma rays.
• The energy released in annihilation is 1022 KeV.
• To simultaneously conserve both momentum & energy,
annihilation produces 2 gamma rays with 511 keV of energy that
are emitted 180 degree to each other.
• The detection of the two 511 keV gamma rays forms the basis for
imaging with PET.

53. Coincidence detection
• Coincidence detection- simultaneous detection of the 2
gamma rays on opposite sides of the body.
• If both gamma rays can subsequently be detected, the
line along which annihilation must have occurred can be
defined.

54. • By having a ring of detectors surrounding the
patient, it is possible to build a map of the
distribution of the positron emitting isotope in
the body.
• PET employs electronic collimation.
• 3 types of coincidence detection .

55. • Radionuclides used in PET scanning are typically isotopes
with short half lives:
• Carbon-11 (~20 min),
• Nitrogen-13 (~10 min),
• Oxygen-15 (~2 min), and
• Fluorine-18 (~110 min).
• These radionuclides are incorporated either into
compounds normally used by the body such as glucose (or
glucose analogues), water or ammonia, or into molecules
that bind to receptors or other sites of drug action.

56. Glucose
FDG

57. Hot/cold spots
• Hot spots- Radiotracer uptake
• Cold spots- Radiotracer uptake

58. Advantages
• Target tissue function is investigated
• All similar target tissues can be examined-whole body.
Disadvantages
• Image resolution is poor
• Radiation to whole body could be high
• Images are not disease specific
• Time consuming
• Poor grainy images difficulty to differentiate inflamm ps, neoplasia
and metastasis with perio/endo/other problems

59. Types of Scintigraphy• SPECT- Single photon emission Computed tomography
• Rotates 3600 about the patient
• Normal scan shows uniform, bilateral symmetrical distribution of
tracer
• PET-Positron emission tomography
• 100times more sensitive than that of gamma camera
• After Inj. of RN, the isotope in the body tissues emits
positron.
• This positron than interacts with a free electron and results
in production of photons.

60. Hybrid scanning techniques
• PET scans are increasingly read alongside CT or magnetic resonance imaging (MRI) scans, the
combination ("co-registration") giving both anatomic and metabolic information.
• Clinically it has been used in the management of patients with epilepsy, cerebrovascular disease
and cardiovascular disease, dementia and malignant tumors including identification of recurrent
head and neck cancers.

61. Indications
• Investigation of salivary gland functions
• Tumor staging-assessment of sites & extent of bone
metastasis
• Inflammation-detection of osteomyelitis
• Trauma-to detect recent fractures
• To assess the bone graft
• TMJ changes
• Infective foci of TB
• Investigation of thyroid

62. 62
Salivary Gland Imaging
99MTc pertechnetate administered intravenously in
dose range 0.5 to 10 mCi.

63. 63
Primary glandular malignancies as well as metastatic tumor of
the gland ,abscess cyst fails to accumulate pertechnetate and
appears as region devoid of radionuclide. This focus is called
“cold focus”.
COLD FOCUS

64. 64
Hot focus
Benign neoplasm like warthins
tumor actively accumulate
radionuclide to a greater depth
than surrounding normal
glandular tissue due to the ductal
inclusion from which the tumor is
thought to arise retaining their
ability to concentrate
pertechnetate.

65. 65
Warm focus
Mixed tumor like
pleomorphic adenoma
accumulates radionuclide
nearly equal to surrounding
normal gland

66. Regions of interest
on dynamic
scintigraphy. RP,
right parotid; LP, left
parotid; RSm, right
submandibular
gland; LSm, left
submandibular
gland; B, background

67. Salivary Gland Imaging
SALIVARY GLAND SCINTIGRAPHY WITH 99mTc-PERTECHNETATE
IN NORMAL SUBJECTS

68. Schall et al.(1971) evaluated the normal and abnormal pattern of pertechnetate uptake
and excretion
Class 1. Normal results, with rapid uptake of 99mTc-pertechnetate by the salivary glands
within the first 10 minutes, progressive increase in concentration, and prompt excretion
into the oral cavity by 20 to 30 minutes. At the end of the study (at 60 to 80 minutes), the
oral activity is higher than activity in the glands.
Class 2. Mild to moderate dysfunction, with relatively normal salivary dynamics, but
reduced absolute level of concentration; or with normal uptake, but a delay in the entire
time sequence. Oral activity is less than normal and approximately equals glandular uptake
at the end of the study.
Class 3. Severe dysfunction, with markedly delayed and diminished concentration and
excretion of 99niTc-pertechnetate. Oral activity may not be obvious even at the end of the
study.
Class 4. Very severe dysfunction, with complete absence of active concentration. Glandular
activity is no more than background, and the oral cavity may even appear as a negative
defect.

69. Sjogren’s syndrome
Sialosis

71. 71
Clinical uses of radionuclide in salivary gland imaging
Abnormality Scintigraphic Appearance
Warthins tumor Hot Focus
Oxyphilic adenoma Hot focus or cold focus
Mixed tumors Cold or warm focus
Malignant tumors Cold focus
Cysts Cold focus
Abscesses Cold focus

72. 72
Sialadenitis
Acute Increased uptake
Chronic Decreased uptake

73. 73
Bone scanning is used to detect
• Metastatic neoplasia when the primary tumor originated in
lungs,prostate,breast, head&neck
• Pagets disease
• Hyperparathyroidism
• Ameloblastoma
• Fibrous dysplasia.

74. BONE SCINTIGRAPHY
• A bone scan or bone scintigraphy is a nuclear scanning test to
find certain abnormalities in bone which are triggering the
bone's attempts to heal.
• Bone scintigraphy is an highly sensitive method for
demonstrating disease in bone, often providing earlier
diagnosis or demonstrating more lesions than are found by
conventional radiological methods.
Technique:
• The patient is injected with a small amount
of radioactive material such as 600 MBq
of technetium-99m-MDP .

75. • Methylene Diphosphonate (MDP) has affinity for calcium rich
hydroxyapatite crystals of bone. The technetium (Tc) 99m-
MDP undergoes ‘chemisorption’ and gets bound to bone
matrix.
Reduced radioactivity can result from:
• Replacement of bone by destructive lesion (lytic lesion)
- primary or metastatic.
• Disruption of normal blood flow consequent to radiation.
• Reduced radioactivity is visualized as 'cold spot' or
photopenic bone lesion.

76. The oncological indications are:
• Primary tumors (e.g. Ewing’s sarcoma,
osteosarcoma).
• Staging, evaluation of response to therapy
and follow-up of primary bone tumors
• Secondary tumours (metastases)
Non neoplastic diseases such as:
• Osteomyelitis
• Avascular necrosis
• Metabolic disorders (Paget, osteoporosis)
• Assessment of continued growth in condylar
hyperplasia
• Arthropathies
• Fibrous Dysplasia
• Stress fractures, bone grafts
• Infected joint prosthesis

77. Interpretation
• Symmetry of right and left sides of the skeleton
and homogeneity of tracer uptake within bone
structures - normal features.
• Both increase and decrease of tracer uptake have
to be assessed; abnormalities can be either focal or
diffuse.
• Increased tracer activity - indicates increased
osteoblastic activity.
• Compared to previous study:
Increase in intensity of tracer uptake and in the
number of abnormalities
Progression of disease

78. • Focal decrease in radioactivity:
• Benign conditions
• Attenuation
• Artefact
• Absence of bone e.g. surgical resection.
• When compared to previous study:
Decrease in intensity of tracer uptake and in
number of abnormalities
Improvement or may be secondary to focal
therapy (e.g. radiation therapy).

80. Bone scintigraphy in a patient with bisphosphonate-related
ONJ
Bone scintigram shows
uptake in the right mandible
Bone scintigram obtained
approximately 17 months
later shows progression of
the uptake

81. 81
METASTATIC CARCINOMA OF PROSTATE 99mTcscintigram

82. 82
Tumor detection

83. Plasma Cell
Transport Phosphorylation Glycolysis
Glucose
18F-FDG 18F-FDG-6-P
Glucose-6-P
Glycolysis
Glucose
18F-FDG
FDG
Malignant cells show an increased rate of
glucose metabolism ,probably due to
presence on cell surfaces of an
abnormally large number of glucose
transporters, along with increased
hexokinase-mediated glycolysis and a
reduced level of dephosphorylating by
glucose -6-phosphate.

86. Ca of mandible showing increase uptake

87. Hodgkins Lymphoma

96. Overview of the imaging modalities

97. 97
References
• Radionuclide diagnosis-Laskin vol 1
• Goaz & White radiology
• Aspects of salivary gland scintigraphy with Tc.Pertechnetate- Dr. S.K. Thoden
• Anger, H. O. Scintillation camera with multichannel collimators. J Nucl Med,
5;(1964). , 515-531.
• Jonasson, T. Revival of a Gamma Camera, Master of Science Thesis (2003).
Nuclear Physics Group, Physics Department, Royal Institute of Technology,
Stockholm, TRITA-FYS 2003:40, 0028-0316X., 0280-316

98. Thank You 