Clinical FDG PET and PETCT

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Clinical FDG PET and PET-CT Half-Body and Brain
Scanning Protocols
Ed Somer UK PET SIG, June 2005
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UK PET Special Interest Group

• Established 1996
• Discuss technical aspects of PET scanning
• Almost all PET facilities in the UK participate
• Meet four times a year (usually in London)
• http//www-pet.umds.ac.uk/UKPET

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Participating Centres (PET-CT)
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Participating Centres (PET-CT)
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Participating Centres (PET Only)
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Participating Centres Summary

• 6 PET-CT sites
• 4 PET only (3 full-ring, 1 partial-ring)
• 8 static / 2 mobile units
• 300 - 350 scans/week
• gt 99 Oncology
• Predominantly half-body FDG PET scan
• 5 PET-CT and 1 PET only site also returned
  information on their FDG brain scanning protocol

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Overview

• Patient Preparation
• FDG Uptake
• When to scan?
• Uptake artefacts
• CT Protocols
• CT parameters dose
• Arm up or arms down?
• CT Contrast
• Breathing Protocol
• 2D versus 3D
• Injected Dose
• Scan Duration

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Patient Preparation
Insulin Dependent Diabetics Normal
diet Normal a.m. insulin. All other
patients Fasted (water only) for 6 hours prior
to the scan. Blood Sugar checked before
injection 4-10 mmol/L ideal gt 10mmol/L consider
rebooking
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FDG Uptake Period

• Referral Specific
• Is uptake increasing with time?
• Is background decreasing with time?
• SUV versus TBR
• Impacts directly on
• scheduling
• staff dose
• department design

Improved differentiation of benign and malignant
STS with delayed imaging - Lodge MA et al, Eur J
Nucl Med 1999 2622-30 FDG uptake at 2-hr p.i.
versus 1-hr, malignant tumour ?, nomal tissue
? - Kubota K et al, Eur J Nucl Med 2001
28696-703 In hepatocellular carcinoma, imaging
2-hr p.i. is more sensitive than 1-hr imaging -
Lin WY et al, Nucl Med Commun 2005 26315-321
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FDG Uptake Period (Half-Body Scan)
Centre 2 Ensures repeat studies have the same
uptake time (/- 3 min) Centre 3 Extend uptake
period to 90 min for ca pancreas and prostate
Centre 4 Extend uptake period to 90 min for ca
pancreas and sarcoma Centre 7 Available space
for hot patients sometimes limits uptake period
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FDG Uptake Period (Brain Scan)
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Brown Adipose Tissue (BAT) Artefact

• BAT regulates body temperature in new-born and
  hibernating mammals
• Heat production triggered by the sympathetic
  nervous system
• FDG uptake reduced by oral diazepam
• Artefact greater in younger patients and those
  exposed to a colder environment

Brown Adipose Tissue and Nuclear Medicine
Imaging - Weber WA et al, J Nucl Med 2004
451101-1103
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Vallium Administration
Centre 1 Also to ca breast, brown fat uptake
greater in 16-30 year olds Centre 2 Always give
vallium Centre 3 Also give to ca breast patients
and those under 35 years old Centre 4 Most
lymphoma patients lt 50 years old, ca breast,
paediatrics
Mobile units dont stock vallium so it must be
prescribed in advance Sites did not give vallium
as part of the brain scanning protocol
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Additional Uptake Period Protocols
The Diet Coke Protocol One centre administers
caffeine 15-30 minutes before injection in an
attempt to reduce cardiac uptake in patients were
the suspected mass is in the chest
Silence Protocol All centres ask head and neck
patients to remain silent for 20-30 minutes
before injection and throughout the uptake period
Laryngeal muscle uptake
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CT Scanning Protocol (Half-Body)
Currently (June 2005) only one of the 6
participating PET-CT centres is acquiring
diagnostic quality CT scans if requested,
although 2 others plan to offer this service in
the near future
Low (10mA, 0.5s) CT currents yield adequate PET
AC maps - Kamel E et al, Eur J Nucl Med Mol 2002
29346-350
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Position of Arms
Arms in the field of view cause truncation and
beam-hardening artifacts - Kinahan PE et al,
Semin Nucl Med 2003 33166-179
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Position of Arms

• All PET only centres scan patients with their
  arms by their sides
• 5/6 PET-CT sites scan with the arms raised above
  the head when possible
• One PET-CT site always scans arms down due to
  patient discomfort

Centre 1 Acquires a local view with arms down in
HN referrals and a local view of the injection
site if body scan shows axillary node
uptake Centre 2 HN and melanoma referrals are
scanned with arms down
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Breathing Protocol
Breathing Protocols Special protocols,
particularly limited breath-hold technique
improve image quality - Beyer T et al, Eur J
Nucl Med Mol 2003 30558-596 Respiratory motion
artefacts noted in most patients using tidal
breathing protocol - Osman MM et al, Eur J Nucl
Med Mol 2003 30603-606 Free breathing and normal
expiration breath-hold are both suitable for
PET-CT - Goerres GW et al, Eur Radiol 2003
13734-739
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Limited Breath Hold vrs Free Breathing
Those using the limited breath-hold technique
carefully assess patients and revert to normal
breathing if theres any chance on
non-compliance. Two centres using the normal
breathing protocol have found fewer artefacts
occur than when using limited breath-hold
technique. Breath-hold techniques seem most
appropriate on 2-slice CT systems
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Intravenous CT Contrast Agents
Diagnostic CT often requires the administration
of contrast agents for delineation of vessels or
bowel
Antoch et al
Intravenous Contrast Artefacts in 4/30 mimicking
focal tracer uptake - Antoch G et al, J Nucl
Med 2002 431339-1342 No abnormal focal increased
FDG activity (n54) - Yau YY et al, J Nucl Med
2005 46283-291 Optimised IV contrast protocol -
no artefacts - Beyer T et al, J Nucl Med 2005
46429-435
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Oral CT Contrast Agents
Antoch et al
Oral Contrast No obvious foci of artefactual
uptake (n91, 900ml 1.3 Barium) - Cohade C et
al, J Nucl Med 2003 44412-416 Small, but
clinically insignificant, effect on SUV -
Dizendorf E et al, J Nucl Med 2003
44732-738 Barium as a ve contrast agent can
introduce attenuation artefacts - Antoch G et
al, Radiology 2004 230879-885 Focal or diffuse
FDG uptake due to CT AC and physiological
reaction - Otsuka H et al, Ann Nucl Med 2005
19101-108
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CT Contrast Agents
1 Never 2 Oral 700ml Barium Sulphate 1-hour prior
to injection for all (except ca lung and HN),
another cup before scan 3 Oral Water given as
contrast in all GI patients 4 Never (but dilute
bowel contrast is under consideration) 5 Oral Wate
r given as contrast when required 6 Never
No centres routinely use intravenous contrast at
this time
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CT Scanning Protocol (Brain)

• All centres scanned with arms down at patients
  side
• Breathing and contrast protocols are not relevant

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Acquisition Mode 2D versus 3D

• 2D
• Reduced scatter, randoms and dead-time
• Better image quality in larger patients?
• Imaging with high injected activity e.g.
  15O-Water studies
• 3D
• Greater sensitivity - option to reduce dose /
  scan time
• Simpler construction and operation
• Widely accepted for brain imaging, under
  evaluation in body

• Where possible all centres acquire half-body
  scans in 2D mode
• 3/10 sites had 3D only scanners
• Half of the PET-CT sites switch from 2D to 3D for
  brains

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Scan Duration and Injected Dose
Injected Dose LSO 3D PET (3min/bed emission,
60min pi). ? 8MBq/Kg (mean 584MBq) - Everaert H
et al, Eur J Nucl Med Mol 2003 301615-1619 EANM
FDG PET Guidelines suggest 6MBq/Kg - Bombardieri
E et al, Eur J Nucl Med 2003 30BP115-BP124 Scan
duration LSO 3D PET 1-3min/bed scans provide
similar lesion detectability to 4min/bed -
Halpern BS et al, J Nucl Med 2004
45797-801 5min/bed sufficient LSO 3D PET/CT in
obese (? 91Kg) patients - Halpern BS et al, J
Nucl Med 2005 46603-607
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Scan Duration and Injected Dose (Half-body)
Centres 2 3 Reduce acquisition time to 4min
for low BMI patients (lt65-70Kg) Centre 4 Has
scanned at 3min/bed with acceptable image
quality Centre 3 Increases dose for those gt
120Kg Centre 5 8 Always scale dose to patient
weight Centres 3, 4 8 Acquire half-body scans
in 3D mode
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Scan Duration and Injected Dose (Brain)
Centre 5 Acquire as 10 x 2min frames and
sum Centres 10 Mostly research, dose of 100MBq
in normal volunteers
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Local Views
Reasons for acquiring local views include

• Head and Neck (arms down)
• If requested following abnormal half-body scan
• Patient movement
• Legs in melanoma patients (whole-body scan)
• Urine drainage
• Soft-tissue sarcoma at 4-hours post-injection
• To apply transmission rod AC

2 PET-CT centres perform local views with a CT
beam current of 10mA
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Disagreements - Opportunities

• Optimum FDG uptake period
• 3D PET dose/scan time reduction
• CT dose reduction, especially in paediatrics
• Breathing protocols
• Diagnostic CT contrast protocols
• Brain scan duration, injected dose CT protocol

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Thanks to...
Leisl Anderson Nigel Benatar Chris
Constable Olivia de Courcey Bernadette
Cronin Michelle Cunneen
John Lowe Peter Julyan Lucy Rahman Fiona
Roberts Paul Schleyer Andy Welch