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.