– The clinical utility of ultrafast
cardiocentric 3D SPECT novel
semi-conductor scanner
technology –
Berry Allen PhD 31 August 2013
Nuclear Medicine (Molecular Imaging)
Principles
• Functional clinical information derived from observing radiopharmaceutical
distribution / kinetics at a molecular level.
• Diagnostic data is provided by observing the pharmaceutical kinetics
• In vivo studies undertaken on a Gamma Camera / PET scanner.
• Radionuclide is ‘passive’; enabling the pharmaceutical to be localised.
•
99mTechnetium
is the most frequently used radioisotope
140 kev γ photon
6.02 hour physical half-life
Gamma Camera Principles
The gamma camera detector consists of:
- collimator
- scintillation crystal (Tl NaI)
- an array of photomultiplier tubes
- electronic system for detection and measurement of gamma energies
•
The emission of a single gamma ray is a very small
scale nuclear phenomenon
•
It is the role of the gamma camera detector to amplify
this photon into an electric signal that can be detected
By exploiting a large number of detected photons and resulting electric signals, it is
possible to map the radioactive nuclei responsible for the emission of gamma rays
Conventional (Gamma) camera configuration
Semi conductor (CZT) detectors
• Cadmium Zinc Telluride (Cd ZnTe), is a semiconductor material that directly
converts X-rays or Gamma-rays to electrons
• 15 -20 times increase in count rate sensitivity compared to NaI – shorter imaging times
• Capable of processing more than one million photons per second per square mm
• Spectroscopic resolution of CZT outperforms most other detectors
• True 3D volumetric acquisition
• No reconstruction resolution recovery or collimator recovery algorithms / processing
required
• 530c - 4.6 mm spatial resolution (pin hole collimation)
•
5% – 6% Energy resolution (NaI crystal ~ 11 - 13%)
Stationary semi conductor Cardiac scanners
530c Scanner
D-SPECT scanner
GE D530c Stationary Data (Gantry) Acquisition
•
Single Photon Emission Computed Tomography SPECT camera design
with standard parallel hole collimators is more than 50 years old
• ‘Conventional’ SPECT - inefficient as only small part of the
available crystal area is used to image the heart (Fig A)
• Novel dedicated scanner - all available detectors are constrained
to imaging just the cardiac field of view (Fig B)
Garcia et al JNM Vol. 52 • No. 2 • February 2011
GE D530c Stationary Data (Gantry) Acquisition
Indirect radiation conversion with
conventional SPECT detector
(Fig A)
Direct radiation conversion
with CZT detector
(Fig B)
Garcia et al JNM Vol. 52 • No. 2 • February 2011
Module / Detector/ Triplet Assembly
1 Triplet with 3 Detectors
1 CZT Module
4 Modules in a Detector
D530c Stationary Data Gantry Acquisition
•
Consisting of an array of 19 pinhole collimators,each with 4 solid-state
CZT pixilated modules
•
All 19 detectors simultaneously image the heart
•
Nine of the pinhole detectors are oriented perpendicular
to the patient’s long axis and 5 are angulated above
and 5 below the axis for a true 3-dimensional acquisition
geometry
Pathophysiology of Coronary Artery Disease
REST
EXERCISE
NORMAL
ANGINA
CORONARY
STENOSIS
Pathophysiology of Coronary Artery Disease
CORONARY FLOW RESERVE
EXERCISE
CORONARY
BLOOD
FLOW
REST
0
50
100
PERCENT
DIAMETER
STENOSIS
530c CZT / NaI Comparison
99mTc
based tracer
Patient:
67 yr female
weight: 50 kg
530 CZT
6 min scan
Indication:
Atypical chest pain
Presurgical assessment
Procedure:
Low dose stress
(pharmacologic)
NaI
20 min scan
530 CZT ‘Standard’ NaI
Dual energy 201Thallium – 99mTc cardiac imaging
The ‘Ideal‘ option
• This technique is not possible on standard gamma camera due to
poor photon energies separation characteristics
• ~ 65% injected radioactivity dose reduction
• The procedure is now a LOW dose study.
• Was a HIGH dose procedure
• Immediate imaging
•
60% reduction in imaging time relative to standard gamma camera
• 1 hour proceed versus 5 hours on standard gamma camera
Pre angioplasty stress 201-thallium stress test
Klein J J et al. Circulation 2004;109:e191-e193
Dual Isotope 201Tl 5 Min Stress / 99mTc Rest MIBI 3 Min
Dual Isotope LAD Territory 201Tl Pharmacologic / 99mTc Rest
Patient:
67 yr male
weight: 79 kg
Indication:
CABG 2006
PCI to LAD
No chest pain / SOB
MVA
LOC
Angiography : Normal grafts
Procedure:
Low dose 201Tl / 99mTc-MIBI
Average Dose Reduction
99m
Tc Activities (MBq)
Dual Detector
Sodium Iodide
CZT
Reduction
Rest First
400
220
-45%
Stress
900
590
-45%
201
Tl Activities (MBq)
Stress
Redistribution
Dual Detector
Sodium Iodide
CZT
Reduction
150
56
-63%
50
15
-70%
Ultrafast Parathyroid 3D CZT SPECT
• ‘Standard’ tracer administered radioactivities – 10 minute scan
• Does however allow for lower injected activities - ~30 - 50%
reduction
• Dual isotope 201Thallium / 99mTc (Thyroid) protocol possible
• Markedly improved study sensitivity and specificity over
‘standard’ NaI technology
• Excellent for the claustrophobic patient
Clinical features of parathyroid adenomas
Characteristics
%
Gender
Female
90
Male
10
Age (median 54.5 yrs)
20-40
9
40-70
83
>70
8
Localisation
Right superior
6
Left superior
2
Right inferior
48
Left inferior
40
Intrathyroidal
2
Bilateral inferior
2
Smj 2006, vol:27
Parathyroid
Ultrafast parathyroid SPECT
Ultrafast parathyroid SPECT
Patient:
60 yr female
weight: 65 kg
Indication:
1º Hyperparthyroidism
Decreased Bone density
Elevated Ca2+ and PTH
Ultrafast parathyroid 3D SPECT
Patient:
60 yr female
weight: 65 kg
Indication:
1º Hyperparthyroidism
Decreased Bone density
Elevated Ca++ and PTH
Procedure:
‘Small patient’
6 minute scan
Parathyroid scan – ‘Conventional scanner’
Patient:
55 yr female
weight: 75 kg
Indication:
1º Hyperparthyroidism
Elevated Ca++ and PTH
Previous Parathyroid
(other institution) scan
NAD
Procedure:
‘Small patient’
8 minute scan
Ultrafast parathyroid 3D SPECT
Patient:
55 yr female
weight: 75 kg
Indication:
1º Hyperparthyroidism
Elevated Ca++ and PTH
Previous Parathyroid
(other institution) scan
NAD
Procedure:
‘Small patient’
8 minute scan
‘Standard’ MPI filter
Customised filter
The Sentinel Node Concept
Breast sentinel node 3D SPECT
Patient:
39 yr female
weight: 65 kg
Indication:
Left Breast cancer
?
Breast sentinel node 3D SPECT
Patient:
39 yr female
weight: 65 kg
Indication:
Left Breast cancer
Discussion
What has been the impact of this innovative technology?
•
Significantly reduced patient radiation burden
•
Markedly improved image quality
•
‘Real time’ 3D volumetric acquisition and reconstruction
•
Significantly reduced scanning times
•
Myocardial perfusion and ‘Other’ structures imaging proving to be fast,
demonstrating excellent image resolution, and clinical improved sensitivity
•
Improved patient journey and comfort
•
As production costs decline, the technology will become more ‘mainstream
White light
Ultraviolet light
Thank you