pet ct techniques and pit falls

PET-CT IDEAL TECHNIQUES & pit falls:

PET-CT IDEAL TECHNIQUES & pit falls DR.K.M.Lakshmipathy MBBS.PGDNM .( Ph.D ) Senior consultant nuclear scans & therapy Head PET-CT Centre. Dr.Kamakshi Memorial Hospital.Chennai . INDIA

PET-CT Ideal Techniques & Pitfalls :

PET-CT Ideal Techniques & Pitfalls PET, PET-CT PET radiotracers Proper preparation of patients Protocols for scans Normal variations in images. PET-CT Pitfalls Appropriate Interpretation of PET-CT.

PET,PET-CT.:

PET,PET-CT. Imaging Physics - better images by Detector design Spatial resolution Sensitivity Image processing Corrections for physical effects Image reconstruction algorithms Data Analysis & Biological Modeling - better interpretation of images

PET-CT:

PET-CT

Positron annihilation:

Positron annihilation Annihilation gives 2x 511 keV gamma rays 180 degrees apart Line of response 511 keV 511 keV e + e -

Prototypical PET Detector:

Scintillation Crystal PMT Pre-Amplifier + Electronics Gamma photon converts to optical photons (proportional to gamma energy, typ. 1000’s) photons are collected at the end of the crystal light is converted to an electrical signal & amplified Front-end electronics condition the signal for further processing Prototypical PET Detector Gamma Ray Optical reflector

PET daily quality control :

PET daily quality control Blank scan for which all detector parameters are within tolerance. Display results for 1 block detector are out of tolerance, indicated by black areas (arrows) in respective displays.

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PET-CT

PET TRACERS.:

PET TRACERS. cyclotron: PETtrace Particles and energies: negative ions p = 16.5 MeV, F18 by targeting O 18

PET-CT OUTPUT:

PET-CT OUTPUT

Preparation of patient:

Preparation of patient Patients should be fasting for at least 4 – 6 hrs. This must include chewing gum, candies and even glucose syrup based medications such as cough preparations. Patients should be well hydrated with water only on the day of the test. No glucose-containing IV fluids or enteral or parenteral nutrition for inpatients. Patient should not exercise strenuously on the day before or on the day of the test. No smoking on the day of the test. In diabetics, moderate to good control is imperative such that blood glucose at the time of the test is below 200 mg/dl. No short acting insulin, if possible, on the day of the test. If required for glucose >200 mg/dl, it must be given IV at least 90 min prior to the study time. No long acting insulin for at least 12 hrs prior to the study. Hold sulfonylureas on morning of the study unless patient is poorly controlled without it and hypoglycemia is unlikely with fasting. It is preferable to wait six (6) weeks after surgery or radiation therapy to perform the PET scan .

PROTOCOLS FOR PET-CT:

PROTOCOLS FOR PET-CT High-quality PET/CT studies - efficiently trained and motivated technologists and physicians. Tracer dose, timing of scan 2D/ 3D mode, MOVEMENT FREE acquisition ,

PET-CT TYPES OF ACQUISTION OF IMAGES:

PET-CT TYPES OF ACQUISTION OF IMAGES DYNAMIC / STATIC PET-CT. 1.TORSO PET-CT 2.TRUE WHOLE BODY PET-CT 3.WHOLE BODY PET-CT 4.REGIONAL PET-CT 5.COCKTAIL PET-CT

4D PET-CT:

4D PET-CT “Respiratory gated (RG) 4D PET/CT … represents an innovative methodology for accurate imaging of tumors, particularly those located in the thorax and upper abdomen,” accurately assess tumor volume and motion for radiation therapy applications. There are three essential tools required (i) an integrated PET/CT system; (ii) a respiratory monitoring system to detect and record a signal representative of the patient’s respiratory cycle, synchronized to 4D-CT and 4D-PET (iii) acquisition and processing protocols dedicated to RG 4DPET/CT studies.

Normal variations:

Normal variations

Normal variations:

Normal variations

Normal variations in PET scan:

Normal variations in PET scan

Diabetics – avoid insulin and antihyperglyemic drugs on the day of test:

Diabetics – avoid insulin and antihyperglyemic drugs on the day of test

Avoid insulin administration.:

Avoid insulin administration.

abnormal variations:

abnormal variations

False negative & false negatives:

False negative & false negatives

Most common troubles :

Most common troubles

PET-CT Artifacts:

PET-CT Artifacts

Pit falls of PET-CT:

Pit falls of PET-CT Differences in Breathing patterns between CT and PET scans

Pit falls of PET-CT:

Pit falls of PET-CT 66-year-old woman with non–small cell lung cancer. Axial fused image confirms FDG-avid sacral insufficiency fracture. FDG uptake overlaps fracture.

Pit falls of PET-CT.:

Pit falls of PET-CT. MUTIPLE MYELOMA unfused bone window sagittal reformation reveals loss of white cortical endplates ( arrow). This lack of cortical definition, in addition to loss of disk space, is diagnostic of infectious spondylitis rather than degenerative change. Note that area of FDG uptake obscures this critical clue to cause of abnormality.

Pit falls of PET-CT:

Pit falls of PET-CT Uterine fibroid. (a) Fused PET-CT scan shows a hypermetabolic focus (arrowhead) in the uterine body. This finding corresponds to a hypoattenuating fibroid that was seen at CT. Approximately one-fifth of fibroids demonstrate this pattern at FDG PET. (b) Contrast-enhanced CT scan shows a focal hypoattenuating fibroid (arrowhead) in the left wall of the uterine body.

Pit falls of PET-CT:

Pit falls of PET-CT 43 y/f Trophoblatic tumor with lung metastasis Metstasis demonstarted in both CT AND PET images in the lower lobe of left lung Focal abnormal fdg uptake in right lung noted however no abnormality seen in the CT SCAN-MICROTHROMBO EMBOLI Due to extravasation of tracer i.v. injection.

PET-CT image analysis:

PET-CT image analysis Qualitative. Visual scoring –reference organs ex: head & neck –brain lymph nodes, adrenals-Liver and mediastinum uptake Contra lateral area SEMI Quantitative. SUV Either SUVmaximum or SUVmean ? Nevertheless majority prefers to report the case by the Maximum SUV. Because the maximum SUV is least affected by partial volume effect, It has a strong positive correlation with weight if calculated the SUV in body weight

S U V & its AVATAR’S:

S U V & its AVATAR’S

S U V -SILLY:

S U V -SILLY

SUV major flaw (1& 2):

SUV major flaw (1& 2)

SUV other possible flaws:

SUV other possible flaws SUV-VARIES WITH BODY WEIGHT KG/BW BODY SURFACE AREA LEAN BODY MASS LBM

So why silly? Is thier any hope?:

So why silly? Is thier any hope?

Monitoring of patients:

Monitoring of patients

Suv neither Silly nor Smart but Simple………….:

S uv neither S illy nor S mart but S imple…………. S ecret U nique V alue

Variations in Clinical PET/CT Operations: Results of an International Survey of Active PET/CT Users. :

Variations in Clinical PET/CT Operations: Results of an International Survey of Active PET/CT Users. 18 F-FDG PET/CT Protocols A Web-based survey of PET/CT users was initiated in November 2009 through e-mail advertising using Academy of Molecular Imaging databases.128 centres. The major areas of variation were---- (18)F-FDG dose [7-20 mCi]) uptake time (45-90 min), sedation (never to frequently), handling of diabetic patients, imaging time (2-7 min/bed position), performance of diagnostic CT scans as a part of PET/CT, type of acquisition (2-D vs. 3-D), duration of fasting (4 or 6 h), and (varying widely) acquisition, processing, display The Journal of Nuclear Medicine Vol. 52 No. 2 303-310,2011

PET-CT PIT FALLS-STEPPING STONES OF SUCCESS:

PET-CT PIT FALLS -STEPPING STONES OF SUCCESS Normal / Abnormal VARIATIONS False POSITIVE/Falls NEGATIVES Patient preparations, avoiding movement artifacts , proper windowing of images and Optimum usage of utilization of SUV

THANK YOU our dedicated cyclotron & Pet-CT team :

THANK YOU our dedicated cyclotron & Pet-CT team