Principles and application of PET CT & PET MR
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Transcript of Principles and application of PET CT & PET MR
PRINCIPLES & PRINCIPLES & APPLICATIONS OF PET - APPLICATIONS OF PET -
CT and PET - MRCT and PET - MRPRESENTATION BY-
CHARUSMITA CHAUDHARY
Moderator: Prof. (HOD) R .K. GOGOI
INTRODUCTIONINTRODUCTIONCancer is one of leading causes of morbidity and mortality in
developed countries.
Most radiologic procedures map the anatomy and morphology of
tumors with little or no information about their metabolism
Positron emission tomography (PET) is a coalition of physics,
chemistry, physiology, and medicine united in an effort to measure
physiologic parameters noninvasively.
Positron Emission Tomography and Computed Tomography / MRI
is the combination of functional imaging as well as anatomical
imaging.
HistoryHistory
1978 the first commercial PET scanner was introduced
70s and 80s PET was mainly used for research
1990s being used in clinics regularly
First approval in 1998.
PRINCIPLE OF PETPRINCIPLE OF PET The concept of PET is to radiolabel a bio-compound, inject it into the patient, and
then measure its bio-distribution as a function of time to determine physiologic
quantities associated with the biocompound.
All PET compounds are radiolabeled with positron-emitting radionuclides.
These radionuclides have decay characteristics that enable localization in the
body.
A positron is emitted from the nucleus, travels a short distance, and annihilates
with its antiparticle (an electron), which results in two 5 I l-keV photons traveling
in opposite directions.
After both photons are detected, the activity is localized somewhere along the line
defined by the two detectors.
2-[F-18]Fluoro-2-Deoxy-D-Glucose (FDG)
OH
O
OH
HO
F
H
H
H
HH
CH2OH
511 keV photon
511 keV photon
E = mc2
180o
+ -
UCLA
producing radiotracers
Synthesizing radiopharmaceuticals from the tracers
administering the radiopharmaceutical to a patient
measuring the resulting radioactivity distribution in an organ of interest
interpreting activity distribution as a function of physiologic parameters.
A PET study consists of
PRODUCTION OF RADIONUCLIDEPRODUCTION OF RADIONUCLIDE
PET radionuclides are positron emitters.
There are 5 convenient nuclides-
HALF LIFE (min)
Rubidium- 82 1.23
Fluorine – 18 109
Oxygen- 15 2
Nitrogen- 13 10
Carbon- 11 20
Commonly produced isotopes : “F O N C”
SYNTHESIS OF F-18 &FDGSYNTHESIS OF F-18 &FDG
Over 500 PET compounds have been
synthesized since 1970.
Natural substrates such as amino acids,
analogues ,fluorinated glucose &drugs.
MC used is a glucose analogue, 2-[F18]fluoro-
2-deoxy-D-glucose (FDG).
Why is 18 F the most used positron emitter?
18F is a small atom.
its addition to a molecule does not deform it to the point
where it is not recognized by the body anymor
has a half-life of 109 minutes.
This is long enough to perform a complicated chemistry
(labelling) , and to allow transport over some distance.
It is also long enough to keep the radiation burden to patient
low
USES
Fluorodeoxyglucose
[18F]-labeled 2-deoxyglucose (FDG) is used in neurology,
cardiology and oncology to study glucose metabolism. FDG is
potentially useful in differentiating benign from malignant forms of
lesions because of the high metabolic activity of many types of
aggressive tumors.
Oxygen
[15O]-labeled water is used to evaluate myocardial oxygen
consumption and oxygen extraction fraction. It can also be used to
measure tumor necrosis.
Ammonia[13N]-labeled ammonia can be used to measure blood flow.
Leucine[11C]-labeled methionine and leucine can be used to evaluate amino acid uptake and protein synthesis, providing an indicator of tumor viability.
Fluorine IonRadiolabeled fluorine ion [18F-] was once a standard agent for clinical bone scanning.
A typical production schedule for FDG is 3hours in duration,
starting from the time the chemist walks into the laboratory
until the radiochemical is produced.
The synthesis is 50%-60% efficient, so accounting for this and
the radioactive decay, about 200 mCi (7.4 GBq) of FDG is
available at the end of the synthesis.
A patient usually receives A patient usually receives 10 mCi (370 MBq).
If two scanners are available so that a patient can receive an injection If two scanners are available so that a patient can receive an injection
every half hour, every half hour, one production run will allow scanning about run will allow scanning about six
patients per day. .
Principle of metabolic imaging with FDG
Glucose 18 FDG Blood vessel
Cell
Glucose 6 Phosphate 18FDG 6 Phosphate
Fructose 6 Phosphate
Pyruvate
Anaerobic resp Citric acid cycle
G LUT
SCANNER DESIGNSCANNER DESIGN
A positron emission tomography (PET) scanner is a large machine with a round, doughnut shaped hole in the middle
Within this machine are multiple rings of detectors that record the emission of energy from the radiotracer in your body.
A nearby computer aids in creating the images from the data obtained by the camera or scanner.
SCANNER DESIGN….SCANNER DESIGN….
Detectors are 18-40 rings of crystals forming a cylindrical field of view about 15cm long that can acquire many slices of coincidence data
PET scanners use crystals with higher density & higher Z numbers due to sensitivity
Group of crystals is put together into a block Four PMT’s to each block of crystalUse “electronic collimation” to detect location of
annihilation event
SCANNER DESIGN….SCANNER DESIGN….
Localizing the site of impact is achieved by measuring the light detected in each PMT
Signal is then amplified System must be able to determine which signals
come from paired 511keV photons and record the time of detection (timing discriminator)
Coincidence circuit then examines signals to confirm it if it occurred with in the time window
CRYSTALS USED IN PETCRYSTALS USED IN PET
BaFBaF22 – Barium
Flouride(0.8ns)BGO BGO – Bismuth Germinate
Oxide(300ns)LSOLSO – Lutetium
Orthosilicate(40ns)GSOGSO – Gadolineum
Orthosilicate(60ns) YLSO YLSO – Yttrium Lutetium
Orthosilicate(40ns)
COINCIDENCE DETECTIONCOINCIDENCE DETECTION
Photons should arrive with in a certain time of one another
A coincidence timing window allows detection of the PMT electrical signal from photon pair (4-12ns)
If it falls within timing window it is registered as a true event
When two different annihilation events are detected with in the timing window is known as “random event”
DATA ACQUSITIONDATA ACQUSITIONThe detection of photon pairs by opposing crystals
create one event (LOR)Millions of these event will be stored with in
sinograms and used to reconstruct the image Spatial resolution is determined by the size of
crystal and their separation and is typically 3-5mmPET is 50-100 times more sensitive and produces
higher quality than a SPECTReconstruction is similar to SPECT
RECONSTRUCTIONRECONSTRUCTIONPET reconstruction can be performed with a
variety of algorithms
o Filtered back projection
o Iterative reconstruction(ordered subset reconstruction )
ATTENUATION CORRECTIONATTENUATION CORRECTION
Mathematical attenuation correction techniques may be used if tissue attenuation is the same at all areas within a transaxial slice .
Measured attenuation may be performed by two methods:– Transmission scan using a radioactive source rotating it
around the patient – CT scan to measure tissue density
The ability to correct for attenuation improves quality and permits absolute quantification of radioactivity in the body
Resolution in PET is determined by three factors:
distance the positron travels before it annihilates with an electron,
variation in angle between the two annihilation photons, and
physical size of the detectors.
A positron will travel between 0.5 and 2 mm in tissue before annihilation, depending on its energy.
Typical detector sizes are 1 -3 mm.
The best possible resolution of a PET scanner is 1-2mm. Typical clinical scanners have a resolution of approximately 4-7 mm.
PET vs. CT & MRIPET vs. CT & MRIPET CT and MRI
Shows extent of diseaseDetects changes in body structure
Can help in monitoring treatment and shows it’s effectiveness
Simply confirms the presence of a mass
Reveals disease earlier, can diagnose faster
Can detect whether a mass is benign of malignant
Can detect abnomalities before there is an anatomical change
SAFETY ASPECTS OF PETSAFETY ASPECTS OF PET PET has 511Kev gamma rays energy, that is 3 times of
140Kev gamma ray energy of Technitium99m Due to their high energy 16 times more lead is required to
obtain the same stopping effect for 511Kev photons as compared to 140Kev photons
SAFETY ASPECTS OF PETSAFETY ASPECTS OF PET
So Tungsten shielding is used for Positron emitting radionuclide. It provides 1.4 times the shielding capability for the same thickness of Lead
CONTRA INDICATIONSCONTRA INDICATIONS
Pregnancy Use of caffeine, tobacco, or alcohol in past 24hours before scanUsing sedativesUsing medicines that change metabolism ex: INSULIN.
PRINCIPLE OF PET-CTPRINCIPLE OF PET-CT
PET-CT FUSIONPET-CT FUSION
FDG PET is a strictly functional modality and lacks anatomic landmarks.
Unless anatomic correlation is available to delineate normal structures,
pathologic sites of FDG accumulation can easily be confused with normal
physiologic uptake, leading to false-positive or false-negative findings.
Coregistration of PET scans with CT using a combined PET-CT scanner
improves the overall sensitivity and specificity of information provided by
PET or CT alone .
advantage is ability to correlate findings at two complementary imaging
modalities in a comprehensive examination. Hence, PET-CT provides more
precise anatomic definition for both the physiologic and pathologic
uptake seen at FDG PET
Max coverage during combined study
Distance betwn pet and ct scanner
SCANNING TECHNIQUESCANNING TECHNIQUE
Nil orally for approximately 4–6 hours avoid caffeinated or alcoholic beverages but can have water during this period.blood glucose level of less than 150 mg/dL is desirable. Avoid strenuous activity to avoid physiologic muscle uptake of FDG water-soluble iodinated contrast media orally for bowel opacification except for head and neck study. 10 mCi injected intravenously Patient activity and speech are limited for 20 minutes immediately following injection Pet study is started 60 mins after injection.
CT TECHNIQUE
Contrast material–enhanced helical CT is performed following injection of
125 mL of a contrast medium at a rate of 4 mL/sec by using a power
injector .
Whole-body PET-CT study scanning begins at the level of the skull base
and extends caudally to the level of the symphysis pubis.
PET TECHNIQUE
The PET scanner is located behind the CT scanner and housed in the same
extended-length gantry. PET is performed following the CT study without
moving the patient in the caudocranial direction, starting at the thighs to
limit artifacts from the FDG metabolite excretion into the urinary system
Typical scout image obtained during an FDG PET-CT study. The blue-purple rectangle
represents CT coverage during the study, and each overlapping green rectangle
represents PET coverage.
INTERPRETATION OF IMAGESINTERPRETATION OF IMAGES
PET provides images of quantitative uptake of the
radionuclide injected that can give the concentration of
radiotracer activity in kilobecquerels per milliliter .
Methods for assessment of radiotracer uptake –
• visual inspection
• standardized uptake value (SUV)
• glucose metabolic rate
LIMITATIONS AND ARTIFACTS OF PET-CTLIMITATIONS AND ARTIFACTS OF PET-CT 1.Patient motion may cause confusion as to the correct position of the
origin of the detected photon.
Patient motion is minimized by – carefully instructing patients not to move during the study; placing them in a comfortable position before the start of the
study; ensuring that they are not taking diuretics, which may otherwise
require them to evacuate the bladder during the study; having patients empty their bladder before the start of the study
or catheterizing the bladder.
2.Attenuation (transmission) correction artifacts highly attenuating objects in the path of the CT beam, such as hip prostheses, pacemakers, dental devices, and contrast-enhanced vessels
ADVANTAGES OF PET-CTADVANTAGES OF PET-CT1. helpful in accurate localization of small areas of increased radiotracer
activity that would have been difficult or not possible to localize on
PET images alone .
2. helps in distinguishing structures that normally show high metabolic
activity from those with abnormally increased activity.
3. PET-CT combines the advantages of the excellent functional
information provided by PET and the superb spatial and contrast
resolution of CT
4. Finally, attenuation correction for quantitative or semi quantitative
assessment of data is possible by using the CT data,
Whole-body PET/MRIWhole-body PET/MRI::The Future in Oncological The Future in Oncological
ImagingImaging
PET/MRIPET/MRI: TECHNICAL EVOLUTION: TECHNICAL EVOLUTION
The idea to combine PET and MRI arose as early as the mid 1990s, even before PET/CT was introduced.
The PET/MRI combination requires 3 risky technologic steps that modify state-of-the-art PET and MRI. 1. First, the photomultiplier technology must be replaced with magnetic
field–insensitive photodiodes .
2. Second, compact PET detectors must be constructed so that it shouldn't interfere with the field gradients or MR radiofrequency.
3. Finally, the MRI scanner must be adapted to accommodate the PET detectors and to allow simultaneous data acquisition without mutual interference.
Based on the technologic challenges to combine PET and MRI into a single gantry, Philips and Siemens proposed 2 fundamentally different prototype PET/MRI designs.
In the Siemens prototypes include 4 dedicated brain PET scanners that fit into a standard 3-T clinical MRI scanner.
The PET/MRI system, together with a dedicated radiofrequency head coil, allows simultaneous PET/MRI data acquisition of the human
brain or body extremities. Philips developed a PET/MRI design in which the gantries are
approximately 2.5 m apart but share a common patient handling system. This implementation does not allow for simultaneous data acquisition and, therefore, results in longer examination times.
Scanner DesignScanner Design
CLINICAL POTENTIAL OF PET/MRICLINICAL POTENTIAL OF PET/MRI It is reasonable to expect that brain PET/MRI will provide new
insights in the field of neuroscience and neurologic disorders, such as neuro degeneration, brain ischemia, neuro oncologyor seizures .
It is feasible with current prototypes and future-generation systems to simultaneously study brain function, metabolism, oxygen consumption, and perfusion.
In oncology, an accurate spatial match between PET and MRI data is mandatory for both radiation therapy planning and biopsy guidance.
Combining PET with cardiac MRI may enable detection and differentiation of vulnerable plaques and diseased myocardium.
Advantage of PET/MRI over PET/CT
1. is not associated with significant radiation exposure
2. has a much higher soft tissue contrast.
3. MRI allows for additional techniques - such as angiography, functional MRI ,diffusion ,spectroscopy and perfusion techniques within one single examination.
PHYSIOLOGIC VERSES PATHOLOGIC FDG UPTAKE PHYSIOLOGIC VERSES PATHOLOGIC FDG UPTAKE of FDGof FDG
There are several sites of normal physiologic accumulation of FDG. FDG
accumulation is most intense in the cerebral cortex, basal ganglia,
thalamus, and cerebellum. The myocardium expresses insulin-sensitive
glucose transporters, which facilitate the transport of glucose into muscle. A
recent meal often causes intense myocardial FDG uptake because of the
associated elevated serum insulin levels
Because FDG appears in the glomerular filtrate and, unlike glucose, is not
reabsorbed in the tubules, intense FDG activity is seen in the intrarenal
collecting systems, ureters, and bladder
The most common areas of normal distribution of FDG
include the brain, myocardium, and genitourinary tract.
SEMI QUANTITATIVE VALUE- CALCULATION OF INTENSITY OF FDG UPTAKE IN REGION OF INTERST.
SUV-5 Indicates five times the average uptake.
RISUV - new index, Retention Index SUV after 3 hours.
STANDARDISED UPTAKE VALUE
Physiologic FDG uptake
The distribution of FDGwithin a normal individual (MIP).
Chest
•Moderate to high FDG uptake is noted in patients with thymic
rebound and should not be confused with asymmetric uptake due
to lymphoma in this location .
•In pediatric patients, anatomic correlation is necessary following
chemotherapy to differentiate the enlarged thymus from residual or
recurrent disease at this location, especially with focal thymic
uptake .
Physiologic thymic uptake in a 23-year-old woman with a
history of Hodgkin disease of the chest who was referred for
posttherapy evaluation.
Low to moderate FDG uptake is noted in the distal esophagus,
particularly in patients with gastroesophageal reflux secondary to
inflammatory changes.
However, high-grade uptake in the same location may be caused
by malignant processes (ie, carcinoma of the distal esophagus,
usually associated with morphologic esophageal changes)
Nonneoplastic esophageal uptake in a 21-year-old woman with a
history of non-Hodgkin lymphoma
Esophageal adenocarcinoma in a 52-year-old man who was
referred for presurgical evaluation.
THE ROLE OF PET/CT IN LUNG CANCER
Assessment of the solitary pulmonary nodule (SPN)
Staging of non-small cell lung cancer (NSCLC)
Assessment of mediastinal lymphadenopathy
Identification of distant metastatic disease
Detection of recurrent disease
Solitary pulmonary noduleSolitary pulmonary nodule
? Benign or malignant
No activity. Diagnosis: benign bronchocoele
Top TipApproximately 85% of metabolically active pulmonarynodules are malignant. If an FDG positive pulmonarynodule is found, it should be assumed to be malignant untilproved otherwise.
Bilateral pulmonary nodules. Diagnosis: metabolicallyactive pulmonary sarcoidosis.
False positive SPN False negative SPN
1.Granulomas BAC
2.Sarcoidosis Scar adenoca
3.Infection carcinoids
4.Adenomas
5.Hamartomas
6.Neurofibromas
Top TipWithout the aid of PET/CT it can be difficult to distinguishactive tumor from collapsed lung or necrotic tissue.
Identification of distant metastatic disease
Top TipEvidence suggests that the removal of a solitary adrenaldeposit at the time of resection of the lung primary results in an increased life expectancy.Liver, adrenal, brain and bony deposits are common withlung cancer but many of the lesions are undetected inthe course of conventional staging
PET/CT IN RADIOTHERAPY PLANNING
Patient for radiotherapy. Where does the tumor end and thecollapsed lung begin ?
The Role of PET/CT in Lymphoma Assess response to therapy/residual disease Identify recurrent disease Initial diagnosis and staging Identify suitable sites for biopsy Disease surveillance Radiotherapy planning
An example of stage 4disease. NHL with disease in the mediastinum,neck, and abdomen
ASSESSMENT OF TREATMENT RESPONSE
Pretherapy and post therapystudies showing a complete metabolicresponse to therapy.
Top Tip
Brown fat activation can cause confusion and care mustbe taken to ensure that each area of uptake corresponds to fat. Activated brown fat is seen more commonly in thin individuals during the winter months, but there is also an increased incidence in women and in patients suffering from lymphoma
Intense marrow activationfollowing granulocyte stimulating factor.
Head and Neck
Moderate to high FDG uptake is noticeable in the muscles,
including the ocular muscles.
may be a potential source of false-positive findings in patients
with malignant head and neck tumors.
Contraction-induced FDG uptake in cervical muscles in tense
patients can be confused with lymph node metastasis which
constitutes a serious problem in patients with
asymmetric muscle uptake due to prior neck
dissection.
FDG accumulates in the striated laryngeal muscles in
proportion to contractile activity during speech.
This phenomenon is a major concern and may lead to false
readings in patients with head and neck cancers .
Rigorous approach to preventing physiologic FDG uptake in
the laryngeal muscles should be adopted to avoid false-positive
findings.
Physiologic laryngeal uptake in a 52-year-old woman
with squamous cell carcinoma of the floor of the mouth.
Primary tumor of the larynx in a 45-year-old man with epiglottic
carcinoma who was referred for presurgical evaluation.
NEUROLOGY INDICATIONSNEUROLOGY INDICATIONS
NEURO-ONCOLOGYTumor recurrence versus radiation necrosisDiagnosisGrading
Monitoring response to therapy Radiotherapy planning Biopsy planningSEIZURE FOCUS IDENTIFICATIONSTROKEDEMENTIAS OTHER APPLICATIONS
Brain injury- vascular, traumaPsychiatry- depression, schizophrenia,anxietyMovement disorders with 18F-dopaMiscellaneous- infection, substance abuse,eating disorders
rerelymphoma
Residual glioma
rt parietal gbm
LOSS OF VISION BOWEL & BLADDER INCONTINENCESINCE I MONTH
BUTTERFLY GLIOMA
High precision Radiation therapy Planning
PETPET
CTCT
PET/CTPET/CT
Biopsy Planning
Localizing
the most
viable tissue
in the lesion
Comparison of MRI time-to-peak (TTP) and PET O2 extraction fraction (OEF) images
Extensive hypo metabolism of entire brain parenchyma, except thalami & basal ganglia
METABOLIC ENCEPHALOPATHY
PET in NeurologyPET in Neurology
The Active Human BrainThe Active Human Brain
PET in Brain DisordersPET in Brain Disorders
Simultaneous PET/MRI study in Alzheimer disease
Hypo metabolism in left temporal lobe secondary to epilepsy
Abdomen and Pelvis
Moderate to high FDG uptake is visible in the muscles that contribute to breathing in patients with chronic obstructive pulmonary disease.
due to difficulty in breathing and use of accessory muscles to facilitate
breathing. In addition, due to an imbalance between oxygen supply and increased demand,
the decrease in oxygen delivery causes a switch to anaerobic metabolism. Hence, the increased uptake seen in the diaphragmatic cruces may be the result
of accentuated abdominal breathing effort and the anaerobic metabolism that leads to increased FDG uptake similar to the physiologic alterations in cancer cells.
Any disease process involving the celiac or perigastric lymph nodes (eg, lymphoma, nodal metastatic disease) can be difficult to interpret in patients with diaphragmatic uptake, especially in the posttherapy setting.
Physiologic diaphragmatic uptake in a 49-year-old woman with a
history of abdominal lymphoma and severe COPD who was
referred for posttherapy follow-up.
Low to moderate uptake is usually observed in
the stomach.
Focal and irregular uptake in the stomach is
usually due to a malignant process;
nevertheless, local gastritis cannot be excluded
with certainty without the help of CT.
Physiologic gastric uptake in a 52-year-old man with colorectal
cancer who had undergone surgical tumor resection.
Gastric cancer in a 59-year-old woman
The importance of FDG PET in the evaluation of colorectal cancer is well
established.
Both small and large bowel may demonstrate varying degrees of FDG
uptake, usually with a diffuse and linear pattern.
However, focal physiologic uptake is not an uncommon finding in short
segments of the bowel.
Unless CT correlation is available, the configuration of uptake in these cases
may be indistinguishable from malignant processes .
Adenocarcinoma of the cecum in a 77-year-old man.
Gallbladder uptake of FDG is not a common finding.
When activity is observed in this anatomic location,
choleductal cancer, adenocarcinoma of the gallbladder,
and primary or metastatic disease of the liver should be
considered in the differential diagnosis.
CT correlation is most helpful in delineating anatomic
landmarks and distinguishing a benign gallbladder
variant from malignant lesions.
Chronic cholecystitis in a patient with papillary thyroid
cancer who underwent thyroidectomy
Liver metastasis in a 55-year-old man with rectal adenocarcinoma.
Unlike glucose, FDG is not reabsorbed by the renal tubules
after filtration.
Thus, significant FDG accumulation is seen in the intrarenal
collecting system and renal pelvis.
This accumulation may interfere with the identification of
renal parenchymal or pelvic urothelial tumors.
However, anatomic information provided by CT allows proper
assessment and characterization of renal masses
Renal cell carcinoma in a 60-year-old woman
Focal FDG accumulation in the ureters is a
common finding due to the pooling of radiotracer
in the recumbent patient.
although the intensity and location of uptake
usually allow accurate identification of the ureters
in patients with abdominal malignancies, this
finding can be misdiagnosed as pelvic lymph
node metastasis or nodal lymphoma.
Physiologic uptake in the renal pelvis in a 66-year-old man
with a history of colorectal cancer .
There is usually no FDG accumulation in the uterus, although focal
FDG uptake in the uterus during menstruation has been described.
can be attributed to heavy bleeding or to necrotic endometrial
epithelium due to sudden reduction of estrogen and progesterone
levels at the end of the secretory phase of the menstrual cycle.
It may not be possible to differentiate this uptake pattern from uterine
carcinoma, even with the help of PET-CT .
However, FDG uptake is usually more irregular, diffuse, and
extensive in uterine cancer .
Physiologic uterine uptake in a 40-year-old woman with a
history of lymphoma who was referred for posttherapy
evaluation.
Endometrial cancer in a 66-year-old woman.
Cardiac PET and Cardiac PET and Myocardial perfusion ImagingMyocardial perfusion Imaging
Rb Distributed in the myocardium depending on the regional blood flow
Rb delivery limited to ischemic or underperfused areas
These areas will appear as defect on initial images
On delayed images(2-4hrs) post inj
Defects resolves due to redistribution which reflects not only eventual accumulation of Rb in viable ischemic zones but release & washout from
normally perfused area
(Areas of myocardial infarction or fibrosis present as permanent defects due to lack of perfusion)
CARDIAC PET and PET CT IMAGING
The stress images show a severe perfusion defectthroughout the anterolateral wall that is completely reversible at rest
The first heart has a mycardial infarction. The arrows point to damaged areas (‘dead’ tissue).Therefore it is assumed that the patient will not benefit from heart surgery.
The second heart is normal
Example: Myocardial Viability
PET IN INFLAMMATORY CONDITIONS
Hepatic and splenic uptake of FDG are generally low grade and diffuse
In the setting of infection, splenic uptake can be intense.
Acquired Immuno-deficiency Syndrome.
Till now, gallium imaging radionuclide imaging - study of choice in evaluating opportunistic infections in AIDS patients.
FDG – PET – helpful in many CNS conditions in AIDS patients.
Lymphoma and toxoplasmosis are frequent CNS complications – not always distinguishable at CT and MRI.
CNS LYMPHOMA- Highly metabolically active.
TOXOPLASMOSIS- metabolically inactive.
FDG PET of Infection and Inflammation1
Toxoplasmosis in an AIDS patient
Acquired Immuno-deficiency Syndrome
CNS lymphoma in a different AIDS patientCNS lymphoma in a different AIDS patient
Acquired Immuno-deficiency Syndrome
2. Fever of unknown origin.
FDG PET- LT PL EFF: HYPERMETABOLIC FOCUS SUB PLEURAL AREA.
CTPA- LEFT LOWER LOBE PULMONARY EMBOLI, WEDGE SHAPED PULMONARY INFARCT.
FINAL DIAGNOSIS- PULMONARY EMBOLISM C INFARCTION.
3.OSTEOMYELITIS
Increased metabolic activity in inflammation results in increased FDG uptake.
Also occur ina. inflammatory arthritisb. acute fractures,c. normally healing bone after surgery.
Differentiation between inflammatory and malignant lesions.
Traditionally, a single time point SUV of 2.0–3.0 has been proposed as the optimal threshold for separating malignant from benign lesions.
With the exception of granulomatous lesions- malignant lesions shows increased SUV values on delayed images i.e., increased RI SUV ( RETENTION INDEX SUV ).
DUAL TIME FDG PET imaging at two intervals appears promising now. Lesions with decreased SUV s over time are likely to have a benign etiology. Malignant lesions tend to have increase in SUV over time.
PET vs. SPECTPET vs. SPECT
PET have superior sensitivity and resolution
Greater flexibility of incorporating positron labels into biomolecules
PET is more expensive and requires the presence of an onsite cyclotron
PEM PEM Positron Emission Mammography PEM is a specialized & improved
form of PET for imaging breasts and other small body parts.
Camera and detectors are closer to the area affected with cancer which produces a very sharp detailed image of tumors and cancerous tissue.
Can see cancers as small as 1.5 – 2mm about the width of a grain of rice.
Also allows for the earlier detection of elusive cancers such as DCIS (ductal carcinoma in situ).
PEMPEM
Breast PET MRI Breast PET MRI
Schematic diag of pet insert and mri coil
Understand the differences between whole-body PET and PEM
Spatial Resolution
better spatial resolution (1-2 mm vs. 5-10 mm). This comes at the cost of field-of-view
Photon-Detection Sensitivity •Closer proximity of PEM detectors increases geometric
sensitivity Allows lower dose/faster imaging/longer uptake time
differences between mammography and PEM Transmission vs. Emission Imaging Anatomical vs. Functional Imaging Planar vs. Tomosynthesis (or Tomographic) •Planar is single projection view with considerable tissue
overlap •Tomosynth./tomographic is 3-dimensional volumetric image Utilities, cost, dose
CONCLUSIONCONCLUSIONDetection of coincidence photons emitted during positron annihilation is the key to
PET imaging, whereas accurate coregistration of this quantitative/functional
information with the CT data is the key to successful PET-CT imaging.
Specific attention to patient preparation, data acquisition, data reconstruction, and
image interpretation is crucial to obtaining high-quality PET-CT images.
Fusion of the anatomic and functional images by using a dedicated PET-CT /Pet
mri scanner is exploited for optimal results required in the management of complex
clinical scenarios faced by our clinical colleagues. Having witnessed an impressive
technologic development of PET detector technology, first PET/MRI prototype
systems, and MRI-based PET attenuation correction, as well as encouraging clinical
and specifically preclinical PET/MRI results, we now seek opportunities to translate
these technologic advances into clinical benefits
CT/PET/MRI-Anatomical + Functional imaging.
18F-FDG-Increase glucose utilisation in malignancies.
Oncology,Neurology ,CardiologyDiagnosis.Staging.Restaging.Monitoring response to therapy.Guided biopsy.Radiotherapy planning
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