Post on 20-Mar-2018
Aquilion One - Genesis
A Radiologist’s Perspective
Dr Jenny Bramley
Canberra Imaging Groupjbramley@cig.com.au
Aquilion One - Genesis
• Radiation dose - very low
• Coronary Artery CT (CTCA)
• CT peripheral joints
• Dual Energy CT and Adrenal Lesions
RADIATION DOSE
• Xrays: if increase dose - image is compromised (over-exposed)
• CT scans: no penalty for increased dose
- 11% imaging is CT, which contributes 65% of radiation dose for all diagnostic imaging
Radiation Dose
• The New York Times on August 01, 2010
SI UNITS OF RADIATION
Radiation Dose and Effects (mSv)
CT Radiation Dose
• CTDIvol - CT dose index (mGy)
• DLP - Dose Length Product (mGy.cm)
• Effective Dose = DLP x k factor (mSv)
K factors
• AAPM report No 96, 2008
• *http://msct.eu/PDF_FILES/Appendix%20MSCT%20Dosimetry.pdf
Body Region 0 year old 1 year old 5 year old 10 year old Adult
Head 0.011 0.0067 0.004 0.0032 0.0021
Neck 0.017 0.012 0.011 0.0079 0.0059
Chest 0.039 0.026 0.018 0.013 0.014
Abdo/pelvis 0.049 0.03 0.02 0.015 0.015
Extremities 0.0008*
CT CORONARY ARTERIES
• Faster rotation
• Superior detectors
• 16cm coverage
• Improve reconstruction algorithms
• Prospective ECG gating
Markedly reduced radiation dose
Dose Comparison
Jan - Sept 2016 Genesis
CTCA Dose Genesis
0
50
100
150
200
250
300
1 2 3 4 5 6 7 8 9
Patient
Do
se
(D
LP
mG
y)
CTCA Doses Prime
0
200
400
600
800
1000
1200
1400
1600
1 13 25 37 49 61 73 85 97 109
Patients
Do
se
(D
LP
mG
y)
Posterior Descending
CTCA Results
• CTCA has a high negative predictive value.
• This means that a coronary event in the next
five years is extremely low.
Dr John Faulder (Radiologist) 6203 2025
Dr Ganesh Shesthra (Nuclear medicine
physician) 6203 2039
CT Extremities
CT Extremities
• CT of extremities can now be performed at or near plain x-ray dose levels
• CT provides additional information
• Plain x-ray dose for an extremity can be between 0.003 – 0.07mSv
• DLP 27 and 113.8mGy.cm (k factor = 0.0008)
• Effective Dose = 0.02 and 0.091 mSv
CT Extremities
• Inconclusive or suspicious xrays
• Persistent symptoms
• Scaphoid fractures
• Mapping of the bony fragments
• SEMAR - metal artefact reduction
Scaphoid
Scaphoid
Scaphoid CT
Ankle Fracture
CT Ankle
Metal Artefact Reduction
SEMAR SEMAR
Metal Artefact Reduction
Metal Artefact Reduction
SEMAR
SEMAR
DUAL ENERGY CT
80 and 140kVp
• Every element produces a different
signature (spectra) when exposed to Xrays
• Photoelectric effect = Z3p/E3
Photoelectric Effect/Absorption
Detector/film
Attenuation
K edges
Element Atomic Number K edge (meV)
Hydrogen 1 0.01
Carbon 6 0.3
Nitrogen 7 0.4
Oxygen 8 0.5
Sodium 11 1.07
Calcium 20 4.0
Iodine 53 33.4
DECT - Gout
• Monosodium
Urate crystals
vs Calcium
• C5H3N4NaO3
DECT - Gout
Tim Bongartz et al. Ann Rheum Dis doi:10.1136/annrheumdis-2013-205095
Renal Calculi
• Calcium vs Uric Acid
(and further differentiation)
• C5H4N4O3
• Aids in planning of
treatment
DECT Images - 80 & 140kVp
140 kVp Optimised contrast
DOI:10.2214/AJR.12.9116 Dual Energy CT General Principals
Iodine and Calcium -in colour Ca subtraction - angiographic work
DECT Images
DOI:10.2214/AJR.12.9116 Dual Energy CT General Principals
140 kVp
Virtual unenhanced
Iodine mapping
CT ADRENALS
• 4 - 5% on CT abdomen have adrenal lesions -
incidentalomas - in a patient without a known
malignancy
• Need to exclude malignancy and/or hormone
secreting
• Current imaging criteria for adenoma
– <10 HU on NON-CONTRAST CT (lipid rich - 70%)
– 3 phase study with calculation of washout.
CT Adrenal
Why dual energy CT?
• Most adrenal lesions found on post-contrast CT abdomen scan
• Patient needs to return for a diagnostic adrenal study (Non-contrast +/- contrast and delayed scans)
• Increased radiation
• Virtual non-enhanced images from DECT -subtract the Iodine
CT Density VNCT vs Unenhanced CT
DOI:10.2214/AJR.11.7316 L. Ho et al., Characterization of Adrenal Nodules With Dual Energy CT: Can Virtual Unenhanced Attenuation Values Replace True Unenhanced Attenuation Values?
Light grey - VNCT, Dark grey - Unenhanced CT
Functioning Adrenal Nodules
• 5-10% subclinical or early Cushing syndrome
• 5% phaeochromocytoma
• 1% aldosteronoma
• Routine hormone evaluation:
– 1mg dexamethasone suppression test (or 24 hr
urinary cortisol level)
– Plasma (or urine) metanephrines
– Aldosterone-to-renin activity ratio (if patient
hypertensive or with low potassium)
Development of Secreting
Adrenal Nodules
• Adrenal lesions may develop cortisol
hyperfunction over time
• Lesion size >2.4cm increased risk of becoming
hormonally active (47% at 5 years)
• So - annual hormonal testing for 4 years
Adrenal Incidentalomas: Clinical Controversies and Modified Recommendations. AJR:206,June 2016
ANY QUESTIONS?
Thank you for your time and attention.