Girraj shakyaMvsc (4999)
Vet surgery and radiology
RECENT ADVANCES IN SCINTIGRAPHY RECENT ADVANCES IN SCINTIGRAPHY AND NUCLEAR IMAGINGAND NUCLEAR IMAGING
Introduction
Principle, Equipments and Radiopharmaceutical agents
Applications in Veterinary field
Miscellaneous applications
Conclusion
Future prospects
INTRODUCTION
Nuclear medicine is a branch of medicine and medical imaging that uses radioactive isotopes (radionuclides) and process of radioactive decay in the diagnosis and treatment of disease
Diagnostic branch of nuclear medicine
Nuclear imaging :
It is a generic term that cover many imaging techniques
Common theme being that ionization radiation originating with in
the body is detected and imaged in order to determine something
about the physiology or anatomy of the subject
Scintigraphy :
Involves the production of images demonstrating the distribution of
radioactive materials within a patient following the internal
administration of a radioactive pharmaceutical
PRINCIPLE
Two basic requirements :
1. A gamma ray emitting pharmaceutical that concentrates in the area of interest
2. A gamma camera (detector) to provide information or image of the pharmaceuticals distribution
Pharmaceuticals which after entry into blood stream gets localized in a particular tissue or organ
Before the injection it is labelled with a radioisotopes, thus localization of the isotopes can be detected by using gamma camera due to emission of gamma rays from the area of interest
PROCEDURE
Radiotracer Administered
Biodistribution (Space and Time)
Gamma ray emission
Gamma camera detection
Computer Image formation
Schematic presentation for a gamma camera .
Information gathered from the patient is saved as numerical data pattern
and intensity of gamma rays
Numerical data displayed as a gray-scale map in a matrix on a monitor
Ability to post-process and image manipulation
Ability to archive and transmit images easily
ONE HEAD GAMMA CAMERA TWO HEAD GAMMA CAMERA
Radiopharmaceutical Applications
99mTechnetium-MDP Bone imaging
99mTcO4 & 131Iodine Thyroid imaging
99mTc-DTPA Renal Study (GFR)
99mTc-DMSA Kidney imaging
99mTc-HMPAO Brain imaging
99mTc-HSA Lungs imaging
99mTc- Setambi Heart imaging
99mTc-HMPAO-Leucocytes Infection imaging
99mTc-RBCs Spleen
Commonly used radioisotopes for imaging
ADVANTAGES OF TECHNITIUM
• Metastable nucleoisomer
• Isometric decay
• Lower price
• Greater availability
• Faster blood clearance
• High resolution image
THYROID SCINTIGRAPHY
Thyroid scintigraphy is one of the most common nuclear medicine applications in
veterinary medicine (Balogh et al. 1998)
Recently sodium 99mTechnetium-pertechnetate (99mTcO4-) has been used more
extensively for thyroid imaging than radioiodine because of its availability, low
cost and radiation safety.
Isotope Half-life Gamma energy
99mTcO4- 6 hours 140 keV
123I 13.3 hours 159 keV131I 8 days 356 keV
Dose : 37 and 222 MBq IV for a cat or dog
99mTcO4- localizes in the thyroid glands 20-30 min after application
Ventral and lateral aspects of the neck region are imagined
routinely
Additional ventral and lateral views of the neck and thorax should
also be acquired to rule out ectopic tissue or tumor metastasis
Images are evaluated visually and quantitative analysis can be performed
Morphological data include :
location, and size of thyroid lobes are extremely important before surgical excision
Response to therapy especially when suspected malignancy is diagnosed
Quantitative data such as:
Time-activity curves of the thyroid gland ,
Radionuclide uptake of the thyroid gland
Calculated activity ratios (thyroid / salivary glands)
reveal very useful additional information for estimating the
functional status of the thyroid glands
Thyroid scintigraphy
Time-activity curves of the thyroid gland
Activity ratios of the thyroid gland, salivary glands and background
Thyroid uptake of injected dose
( Balogh et al ., 1999)
Indications
Hyperthyroid cats
Thyroid tumors in dogs
Post operative evaluation
Detection of thyroid metastasis
Congenital thyroid dysfunction
Image: 20-30 min after 80-150 MBq/0.5-1.5mL 99mTc-pertechnetate application.
Notice the differences between radiopharmaceutical concentration in thyroid
glands.
Euthyroid Hyperthyroid Hyporthyroid
• Thyroid carcinoma causing hyperthyroidism
• Notice increased uptake in the left- sided thyroid tumor and the
complete suppression of the normal right thyroid lobe.
• Thyroid scan performed on normal dog,
• Notice the 2 symmetrical thyroid lobes that are
approximately as "bright" as the dog's salivary tissue
Thyroid carcinoma with pulmonary metastasis
Unilateral thyroid adenoma Bilateral thyroid adenomaSimilar uptake
Hyperthyroid cat with a single ectopic (and intrathoracic) thyroid adenoma
HEPATIC SCINTIGRAPHY
There are 3 main forms of hepatic scintigraphy
(Wolff et al. 1988; Koblik et al. 1990)
Reticuloendithelial scintigraphy Tc labelled colloids : sulphur colloid, serum albumin microaggregates The uptake mechanism is based on phagocytic activity of the RES-cells (in the liver – Kupffer’s
cells)
Indications: Evaluating hepatic and splenic morphology (size and shape) Hepatic or Splenic masses of unknown origin (Cyst, haematoma, abscess, tumor)
Hepatobiliary scintigraphy
99m Tc IDAs (Derivatives of iminodiacetic acids )
The radiopharmaceutical is in normal cases in the liver parenchyma within 2
min, in the gall bladder between 2 and 20 min and thereafter it is excreted into
the small intestines
Indications:
Hepatobiliary scintigraphy holds for morphological and functional information
Bile excretion function of hepatocytes, biliary tract patency,
Extrahepatic biliary obstructive lesions, acute or chronic cholecystitis
• Dynamic pictures of hepatobiliary scintigraphy in a dog.
• After 80 MBq/1mL 99mTc BrIDA injection the radiopharmaceutical distributes
in the whole body, concentrates in the liver parenchyma and is excreted through
the gall bladder into the intestines
Portosystemic scintigraphy
Agents:
99m Tc –pertechnetate, 201 Thallium or 99mTc serum albumin macroaggregate
In parallel with the administration 3-4 seconds frame are acquired until 3-5 min
while the radiopharmaceutical is passing through the v.portae into the liver and
after capillarization into the heart
Indications :
Portosystemic shunt scintigraphy is a very sensitive, non-invasive screening test
for the presence of an pathological connection between portal and systemic veins
.
Schematic drawing of the normal portal circulation of
a rectally administered material. Notice that the
material is initially transported to the liver.
Normal study: Composite image of a normal dog
showing the uptake of radioactivity into the portal
vein and liver
Portosytemic Shunt: Composite image showing
uptake of the radioisotope from the rectum into the
portal vein
Notice that the dye bypasses the liver and appears in
the heart and lungs first
Reticuloendothelial : 60 min - whole liver visualized Static imaging
Hepatobiliary : Dyanamic or static frame imaging (2,10,15, 20, 25, 30, 45 and 60 min)
Portosystemic: Always rapid dynamic study . Image taken until 3-5 min (Wolf et al., 1998 and Koblik et al ., 1990)
Imaging Protocol
Renal scintigraphy
One of the earliest nuclear medicine applications in both veterinary and
human fields is renal morphologic imaging.
(Twardock et al.1991; Nemeth et al. 1998)
Radiopharmaceuticals used for this method are numerous;
99mTechnecium labelled diethylene triamine penta aceticacid (99mTc DTPA)
Glucoheptonate (99mTc GH), or
More frequently dimercaptosuccinic acid (99mTc DMSA)
Doses : range 37-185 MBq/0.5-1mL
Renal scintigraphy
Two types:
Quantitative renal imaging (morphology)
99m Tc -DTPA, 99m Tc -GH and 99m Tc -DMSA
DMSA in used in humans for detection of cortical disorders pyelonephritis
Functional renal scintigraphy 99m Tc MAG 3 10% filtered and 80% excreted by PCT
99m Tc DTPA Determination of GFR
GFR = 0.194 X (% Dose uptake Rt. & Lt. kidney) – 0.37
Nementh et al.,1998
Contd ...
Dose : 37-185 MBq IV ( avg dose 90)
Imaging varies with agent used :
99m Tc DTPA ( Few minutes)
99m Tc DMSA (Hours)
Renal morphologic study : Static images
Functional renal scintigraphy – Dynamic images are taken.
In the first minute to examine arterial blood flow of kidneys and thereafter until 20 min to evaluate renogram
Indications
Evaluate renal blood flow and function.
Evaluate for urinary tract obstruction (transit time)
Evaluate for renovascular hypertension.
Evaluate renal transplant for complications (Susan et al., 1999)
Calculate ERPF and GFR
Research purpose (anaesthetic monitiring) (Mitchell et al., 1998)
No effect of hypoproteinemia over binding
Constraints
Effect of anaesthesia
Ageing effects
Effect of drugs
Dynamic images - uptake of radionuclide by normal kidneys
Dilated right ureter Normal kidneys
Barthez et al., 2000
Poorly functional right kidney within a large perirenal cyst
Brain Scintigraphy
Planar brain scintigraphy : Functional integrity of BBB rather than morphology
Less common in human (CT and MRI)
Passive diffusion immediately after injection (95% sensitivity )
Presence after renal clearance indicates damage to BBB
Brain accumulation
6 conditions
Increased vascularity
Abnormal capillary permeability
Uninhibited pinocytosis
Adjacent capillary oedema
Increase in extracellular space of tumor
Ability of tumor cells to bind with molecules intracellularly
Brain Scintigraphy
Dorsal, lateral and caudal images taken 1-4 hrs after injection
Agents :
99m Tc DTPA
99m Tc O4ˉ
99m Tc HM-PAO
99m Tc ECD Costly, passes BBB
Dose : 370-1110 MBq (T.D)
(Dykes et al ., 1994)
Cardiac Scintigraphy Two types:
Mycardial imaging : 99m Tc MIBI, 123I MIBG or 201 Thallium
(Fujimoto et al., 2004)
Functional scintigraphy : 99m Tc autologous RBCs
Dose : 74-370 MBq/ dog or cat
Left lateral, ventral and left ventral oblique palnnar images - 20-60 min
Functional examination : Radionuclide ventriculography
First pass radionuclide angiogram
Indications
Myocardial ischemia or infraction
Ventricular function ( ejection fraction, ejection rate)
Effect of drugs (digoxin)
Congenital cardiac diseases
Fusion images from myocardial perfusion scintigraphy (MPS) and computed tomography (CT) constructed before (A) and
after (B) the coronary artery bypass grafting (CABG)
• Images of MPS with Thallium-201 showed the improvement in myocardial ischemia
of the anterior wall (black arrow head). • The grafts, the left internal thoracic artery (LITA) to the left anterior descending
artery
(LAD) and the radial artery (RA) to the diagonal branch (Dx), were shown to be
patent with CT. RCA, right coronary artery; LCX, left circumflex artery; and SVG,
saphenous vein graft.
To visualise the irrigation capacities of the heart muscle during an exercise.
The living areas of the muscle are coloured red whereas the dead zones are coloured blue or green
All red or orange areas are normal, whereas the yellow or blue areas do not
have enough blood.
Note that some areas of the heart appear yellow, whereas they were red during
rest.
Pulmonary scintigraphyTwo types
Ventilation: 133, 127 Xenon, 81 m Krypton or 99m Tc DTPA
Perfusion : 99m Tc labelled macroaggregate serum ablumin (99m Tc MAA)
Dose : 20-150 MBq/dog or cat
555-740 MBq/horse
Static images are taken of ventral , dorsal and lateral thorax after 2-5 min
Indications:
Ventillation study : Research purpose
Perfusion study : PTE, COPD , heart worm or EIPH(Harnagle et al ., 1987)
Pleural effusion
Pleural effusionPleural effusion along with hyperthyroidism
Broome , 1993
Other applications of pulmonary scintigraphy
Study of the regional lung function (Votion et al., 1999)
Imaging of pulmonary infection and/or inflammation
Chronic and diffuse inflammation (67Ga) and acute inflammatory lesion (labelled WBCs) (Chianelli et al., 1997)
Inflammatory cell involvement in lung diseases
To determine the role of specific inflammatory cells in the pathogenesis of respiratory disorders and for investigating the effect of anti-inflammatory drugs on inflammatory cell recruitment into the lung s (Ussov et al., 1999)
Alveolar-capillary barrier integrity Imaging of lung cancers (Chiti et al., 1999)
Aerosol deposition studies (Wilson, 1998)
Gastro intestinal scintigraphy
Radionuclide studies of gastric emptying and motility are the most physiologic studies available for studying gastric motor function
The study is noninvasive, uses a physiologic meal (solids with/without liquids)
Scintigraphic assessment of gastric emptying in a healthy dog Fifteen minutes after feeding of a radioactively-labeled meal, radioactivity can only be observed in the stomach As time passes, the radioactively-labeled food moves into the small intestine and after 6 hours, there is only a small amount of radioactivity detectable in the stomach
scintigraphy is performed in patients suspected of active gastrointestinal bleeding
using Tc-99m labeled red blood cells (RBCs)
Bleeding site in right colon
(Terdiman et al., 1997
Dynamic anterior abdominal images are acquired at a frame rate of 10–60 sec / frame over a 60 to 90 min period
GIT bleeding
BONE SCINTIGRAPHY
Bone scintigraphy seems to be the most frequently performed veterinary nuclear
medicine procedure (Lamb 1991; Chambers 1996)
99mTc methylene diphosphonate (99mTc MDP) most commonly used one
Dose ranges10-20 Megabecquerel(MBq) / Bwt in kg
The skeletal scintigraphic examination can be divided into three imaging phases
(3-phase bone scintigraphy)
Vascular phase or blood flow phase or nuclear angiogram (phase I),
Extracellular or soft tissue phase (phase II),
Bone phase (phase III)
phase I
The first phase imaging is showing larger blood vessels (both arteries and veins)
Phase I imaging is a sensitive test for loss of vascularity
(e.g.: ischemic injury, vascular infarction),
Acute inflammatory processes where significant local capillary recruitment has
occurred (e.g. in acute localized cellulitis).
Phase II
The images represent the radiopharmaceutical bio-distribution in the ECF space of
all body tissues after delivery via the vascular system
Phase II imaging is useful in detecting and evaluating inflammatory diseases in
soft tissues surrounding the skeleton
(e.g. in tendon or ligament injuries, synovitis, myositis)
Phase III
The radiopharmaceutical localizes in bone on the surface of the exposed hydroxy-
apatite crystals while the remaining radiopharmaceutical is excreted via the urinary
tract
Phase III imaging detects and evaluates acute or chronic bone disease
(e.g. in complete or incomplete fractures,
osteoarthritis,
osteomyelitis,
periosteal reactions,
Primary or metastatic malignancies
Advantage :
scintigraphy is able to detect abnormalities at a very early stage: a few hours after
injury incomplete bone fractures can be detected scintigraphically
Whole-body imaging of a dog having osteosarcoma. Notice the very clear radiopharmaceutical uptake in the left knee. No metastases are seen anywhere else in the body
The dog was injected 370 MBq/0.5mL 99mTc MDP two hours before investigation.
Oncological scintigraphy
Detecting malignancies : 99mTc MIBI, 99m Tc DMSA and 99m Tc MoAbs
(Balogh et al., 1997 )
Extent of invasios (Infln. foci) : 99m Tc HM-PAO,111 Indium oxine & 99m Tc IgG
(Tucker et al., 1989)
Dose : 100-740 MBq/dog
Static imaging or whole body examinations are performed 2, 4,6 hours or later Dorsal, ventral and left lateral image taken
Multiple delayed images with diffuse metastatic disease
Intestinal lesions
AVMI, 1999
Malignancy detection
Cervical LN metastasis
Additional diagnostic value of fused SPECT and CT images in assessing possible bone
metastases.
A. Transverse SPECT image show bilateral foci of increased tracer uptake in thorasic vertebra
B. Transverse CT image shows no apparent bone lesion.
C. Transverse fused image shows precise localization of abnormal tracer uptake in articular
facets of head of rib (arrows)
A. Coronal SPECT image show increased tracer uptake in the lumbar vertebral bodyB. Coronal reformatted CT image shows compression fracture in third lumbar vertebral bodyC. Coronal fused image shows precise localization of abnormal tracer uptake in end plate of 3rd lumbar vertebral body
Splenic sequestration scintigraphy (Berry 1996)
Lymphoscintigraphy (Daniel andBailey
1996)
Gastrointestinal motility (Voges et al. 1996)
Mucociliary transport (Whaley et al. 1987)
Sperm motility (Balogh et al. 1995)
Bleeding detection (Metcalf 1987)
Miscellaneous applications
Disadvantages of Scintigraphy High cost of radiopharmaceutical agent
Strict safety precaution required
Non-specificity to the etiology
Poor intrinsic anatomical resolution
Complementing with other diagnostics is challenging
Difficult interpretation and prognosis
Dosages need to be standardized for different species
Trained staff needed
Conclusions
Reliable technique
Most sensitive (????)
In naive phase in our country
Cost limit its application in animals
Radioactive hazards are comparable
What has to be achieved in future?
Useful in diagnosis where conventional methods fails
Making technique available at affordable rates
Collaboration with medical science
Employment generation