complete ppt on pet scan with case scenarios and images

1. POSITRON
EMISSION
TOMOGRAPHY
(PET)
PRESENTER-DR ANIRUDH
MODERATOR-DR SHAIKH MOHAMMED ASLAM

2. OUTLINE
 INTRODUCTION
 PRINCIPLE
 INDICATIONS
 PREPARATION AND PROCEDURE
 INTERPRETATION
 UTILITY IN VARIOUS FIELDS OF MODERN MEDICINE
 PITFALLS
 RECENT ADVANCES

3. INTRODUCTION
 Noninvasive imaging is of fundamental and increasing importance in the daily management of
the patient in clinical practice.
 In our daily quest of arriving at a diagnosis or the detection of micrometastasis or even to
study the function of the normal brain,PET scans are beginning to play a major role in modern
medicine.
 Positron Emission Tomography (PET) is a nuclear medical imaging technique that produces an
image of functional processes in the body.
 Computed tomography (CT) and magnetic resonance (MR) imaging rely on anatomic changes
for diagnosis, staging, and follow-up of cancer. However, PET has the ability to demonstrate
abnormal metabolic activity (at the molecular level) in organs that as yet do not show an
abnormal appearance based on morphologic criteria

6. PRINCIPLE

7. PET CT FUSION
 PET is limited by poor anatomic detail, and correlation with some other
form of imaging, such as CT, is desirable for differentiating normal from
abnormal radiotracer uptake.
 PET-CT scanner is used in clinical imaging, in which precisely coregistered
functional and anatomic images can be obtained by performing a PET
study and a CT study on the same scanner without moving the patient.

8. INDICATIONS
 The indications for F-18 fluorodeoxyglucose (FDG) PET-CT imaging include:
 staging of cancer which potentially can be treated radically
 establish baseline staging before commencing treatment
 evaluation of an indeterminate lesion (solitary pulmonary nodule)
 assessing response to therapy
 evaluation of suspected disease recurrence, relapse and/or residual disease
(e.g. lymphoma, testicular seminoma)
 to guide a biopsy (e.g. pleural biopsy for mesothelioma)

9.  PET-CT can also be used as a problem-solving tool:
 occult primary lesion (e.g. non-metastatic manifestation of neoplastic
disease)
 evaluation of suspected recurrence in patients with equivocal conventional
imaging
 evaluation of residual disease in patients with treated differentiated thyroid
carcinoma and treated medullary thyroid carcinoma with
negative/equivocal conventional imaging
 differentiate between radiation-induced necrosis and tumour recurrence
(e.g. primary CNS malignancy)

10.  Neurology
 Refractory Epilepsy: Inter-ictal FDG-PET is recommended for lateralization
of epileptogenic foci prior to surgical intervention in patients with
medically refractory epilepsy and where inconclusive localising information
is provided by a standard assessment, including seizure pattern,
electroencephalography and MRI.
 Dementia: In the work-up of patients with dementia, FDG-PET is helpful in
identification of early Alzheimer’s disease before the onset of cerebral
atrophy, especially in younger patients with dementia and normal MRI or
CT.

11. CONTRAINDICATIONS
 Pregnancy
 Breastfeeding poses some limitations for the examination - it is advisable to stop breastfeeding for
12 hours after administration of the radiotracer, and the first lot of milk produced after the
procedure should not be given to the child
 Blood glucose level above 200 mg%
 Improper preparation of the patient for the PET-CT scan
 The scan should not be performed immediately after or during radiotherapy, chemotherapy, after
endoscopic examinations, operations, and biopsies

12.  Cardiological indications :
 Assessment of myocardial viability in patients with ischemic heart failure
and poor left ventricular function being considered for revascularization,
usually in combination with perfusion imaging with sestamibi.

13.  Pyrexia of unknown origin (PUO) :
 To identify the cause of a PUO where conventional investigations have not
revealed a source.

14. PREPARATION
 Patients are required to fast for approximately 4–6 hours prior to PET-CT to
enhance FDG uptake by tumors as well as to minimize cardiac uptake.
 They are instructed to avoid caffeinated or alcoholic beverages but can have
water during this period. Before injection of FDG, the blood glucose level is
measured; a level of less than 150 mg/dL is desirable.
 Good control of blood glucose is essential because the uptake of FDG into
cells is competitively inhibited by glucose, as they use a common transport
mechanism (glucose transporters [GLUT]) for facilitated transport into both
normal and tumor cells

15. PROCEDURE
 The typical dose of FDG is 10 mCi injected intravenously. Patient activity and speech are
limited for 20 minutes immediately following injection of the radioisotope to minimize
physiologic uptake by muscles.
 Imaging is initiated approximately 60 minutes following the injection of FDG
 They are positioned either with the arms above the head or with the arms at the side. Except
for patients being studied for head and neck cancer, arms above the head is the preferred
position to decrease beam-hardening artifact during the CT portion of the examination.
 The CT study takes approximately 60–70 seconds to complete and the PET study takes
approximately 30–45 minutes, depending on the coverage required.

16. INTERPRETATION
 Standardized Uptake Value
 The SUV is a semiquantitative assessment of the radiotracer uptake from a
static (single point in time) PET image. The SUV of a given tissue is
calculated with the following formula:

18.  The primary data from PET has been traditionally displayed on a linear grey
scale. This is because the human eye is adept at discerning subtle
differences in contrast from white through grey to black
 "rainblow" colour scale that has low activity regions displayed in the blue-
green range and higher intensity regions in the orange-red spectrum. With
this colour scale, the liver will generally appear blue with flecks of green.
 This corresponds to an upper SUV window threshold of 8–10 and will
usually achieve an appropriate contrast

19. USE IN MODERN MEDICINE-CASE
SCENARIOS.

20. CASE 1
 The patient is a 71-year-old male who presented with asymptomatic
microhematuria on routine physical checkup. CT scan of the abdomen/pelvis
revealed an incidental lung nodule in the right middle lobe. A subsequent CT scan
of the chest revealed a 1.7 x 1.9 cm right upper lobe nodule, an 8 mm right middle
lobe nodule, and several small subcentimeter right lower lobe nodules. The patient
is a former smoker (18 pack-years). He had no dyspnea, hemoptysis, fevers, chills, or
night sweats. Based on these CT findings, a brain MRI and FDG-PET/CT were
ordered.

22.  Brain MRI revealed a mass in the sella turcica, which was biopsied and found to
be pituitary adenoma. CT-guided biopsy of the nodule posterior to the left
kidney revealed diffuse large B-cell lymphoma. Based on these results, the
patient underwent video-assisted wedge biopsy of the right upper lobe nodule
and right lower lobe nodule, which revealed large B-cell lymphoma. The patient
was seen by medical oncology, and a bone marrow biopsy showed no evidence
of lymphoma involvement. He subsequently began a course of chemotherapy.
 FDG-PET/CT played a key role in this case by helping to confirm an unusual
presentation of large B-cell lymphoma. The PET/CT detected an FDG-avid soft
tissue nodule behind the left kidney which was found to be large B-cell
lymphoma. Prior to the PET/CT scan, the working diagnosis was that of metastatic
lung cancer given the chest CT findings.

23. CASE 2
 A 27-year-old female presented with intractable complex partial seizure
disorder for a period of three years. An MRI study of the brain was
unremarkable and EEG was inconclusive. A PET FDG scan was requested for
further evaluation and was performed as an interictal study.

24. The PET scan demonstrated focal areas of hypometabolism involving the right medial and the
anterior aspect of the right temporal lobe, which is suggestive of seizure focus of interictal
status.

25.  The patient underwent depth electrode placement for seizure monitoring. This
confirmed that the seizure was from the right temporal lobe. The patient then
underwent right anterior temporal lobectomy and amygdaohippocampectomy
and was seizure-free after the surgery. The patient was still seizure free at a
follow-up exam three months after surgery.
 PET helped to identify seizure focus and guided depth electrode placement. PET
proved beneficial in pre-surgical evaluation and planning.

26. CASE 3
 The patient in this case is a 39-year-old male who had a melanoma in the left anterior
chest wall and metastasis to the left axilla. He then underwent melanoma resection and
axillary node dissection. His initial staging was Stage III. The patient is at high risk for
local regional and systemic recurrence. One-and-a-half months after surgical treatment,
the patient was seen by a radiation oncologist for possible postoperative adjuvant
radiation therapy. A PET scan was ordered for staging the patient.

27. The FDG-PET scan demonstrated a focus of intense uptake in the left anterior chest wall near the axilla which
is likely a rib lesion. There are also multiple foci of uptake in the right lower ribs and one left posterior rib. A
focus of hypermetabolism is noted in the upper thoracic spine. Increased uptake is also noted in both humeri.
There are two foci of uptake seen in the left iliac crest. These findings are consistent with osseous metastasis.

28.  PET in this case helped to detect unknown osseous metastasis and thus
changed the stage of the disease. Before the PET, the patient was thought
to be Stage III (Clark’s Level 4, T4b, N1b, M0). After the PET, the patient
was upgraded to Stage VI. The findings of the PET study may have also
impacted the planned adjuvant radiation treatment.

29. CASE 4
 A 54-year old man presented with persistent fever and weight loss of 5–6 kg over 1 month.
There was no demonstrable abnormality on clinical examination. Complete blood counts,
liver and renal function tests, and blood culture for common pathogens as well as
Mycobacteria were unremarkable. Chest radiography and ultrasonography of abdomen and
pelvis were normal. Erythrocyte sedimentation rate was raised (35 mm/h) and C-reactive
protein was normal. In view of persistent generalized symptoms, the absence of localizing
symptoms, with no obvious anatomical and biochemical abnormality, he was referred for
whole body F-18 FDG PET-CECT, to detect an occult pathology

30.  It was performed as standard guidelines from head to mid-thigh . There was focal intense
FDG uptake seen in the right lobe of prostate gland (standardized uptake value [SUVmax]
20.7. Overall scan findings raised possibilities of suspicious prostate infection or neoplasm

31.  Regional MRI pelvis revealed T2 hypointensity in peripheral zone of the right half of
prostrate with contrast enhancement, without any extracapsular extension, and crossing
midline, favoring neoplastic etiology. On digital rectal examination, the prostate was
found to be hard and nodular. Serum total prostate-specific antigen (PSA) level was
within normal range (2.4 ng/ml). Urine sample was negative for acid fast bacilli.
Transrectal ultrasound-guided biopsy (TRUS)-guided biopsy was performed with
sampling from base, mid zone, and apex of the right lobe of prostate. Histopathology
revealed multiple caseous epithelioid granulomas containing giant cells and central
amorphous, eosinophilic necrotic material

32.  The diagnosis was prostatic TB. Anti-tubercular therapy (ATT) was started
 18F-FDG PET-CT pointed out the probable active pathology of extremely
rare solitary prostate involvement as a part of GUTB, guided biopsy, and
directed the diagnosis of CNS involvement. Prostate tuberculosis is one of
the differentials of high-grade FDG-avidity.

33. CASE 5
 This case involves an 82-year-old female who presented with massive
rectal bleeding. A mass was found in her right transverse colon by
colonoscopy. Pre-op CT revealed a soft tissue mass in the presacral area
(arrow, CT Figure 1). The liver was reported as unremarkable on CT scan
(CT Figures 2 and 3). The patient underwent colectomy and eight out of
nine nodes were positive for metastases. A whole-body PET-FDG scan was
requested for further evaluation.

34. FDG-PET demonstrated a focus of intense uptake
corresponding to the presacral mass seen on CT (PET
Figure 1). This is likely related to metastasis. In addition,
there are at least two foci of intense uptake seen in the
liver, consistent with metastases (PET Figures 2 and 3). In
retrospect, and in light of the PET, there were subtle low
attenuation lesions that were not easily seen on CT
(arrows, CT Figures 2 and 3).

35.  Positron emission tomography is more sensitive than computed
tomography (CT) for the detection of metastatic or recurrent colorectal
cancer and may improve clinical management in one-quarter of cases1.
The sensitivity of PET in detecting hepatic metastasis is higher than for CT.
The sensitivity of PET in detecting extrahepatic metastases exclusive of
locoregional recurrence is higher than the sensitivity of computed
tomography and other conventional diagnostic studies

36. PITFALLS
 Patient motion in PET-CT imaging can produce significant artifacts on the
fused images and may cause confusion as to the correct position of the
origin of the detected photon. Patients are instructed not to move for the
entire study, that is, between the initial CT examination and the later PET
examination
 Lesions smaller than 5–7 mm may be missed by PET, especially if they are
located in a high uptake background.
 As the normal brain metabolizes glucose almost exclusively as a fuel, FDG
uptake will be high. Thus,tumors with glucose metabolism lower than or
even equal to that in normal cortex (e.g., low-grade astrocytomas)may not
be detected on FDG PET

37.  False-positive findings may occur due to increased glucose metabolism
and FDG uptake within brown adipose tissue, a normal variant,in various
granulomatous diseases such as sarcoidosis, in some benign tumors (e.g.,
paragangliomas, benign bone lesions such as eosinophilic granuloma,
nonossifying fibroma, Paget's disease),at sites of infection, or in non
specific inflammation

38. RECENT ADVANCES
 Hybrid PET/MR Machines
 While FDG remains the standard for PET tracers, specialized compounds
like amino acid tracers for brain tumor imaging and receptor-specific
peptides have already begun to be utilized in advanced hybrid imaging.
These new theranositc ligands will increase clinical demand for PET/CT and
help diagnose diseases not otherwise able to be targeted with standard
imaging.

40.  THANK YOU