cardiovascular imaging

Question 1

imaging techniques

Answer 1

1. x-ray methods:
   - catheter or direct puncture angiography: invasive
   - radiography, fluoroscopy (non-invasive)
2. ultrasound - Doppler methods (non-invasive)
3. CT, CT-angiography (non-invasive)
4. MR, MR-angiography (non-invasive)

Question 2

radiography

Answer 2

• digital is preferred over analog
• summation images: high spatial resolution, low contrast resolution
• bi-directional (PA, lateral) CXR -> heart + great vessels are in the mediastinal shadow, well contoured by air-containing lungs
• information on: heart size, dilation + course of mediastinal vessels, calliber of pulmonary vessels, cardiac + vessel wall calcification, inserted IV lines, devices, pacemakers
• fluoroscopy: pulsation of heart + vessels

Question 3

signs of congestive heart failure

Answer 3

• cephalization of pulmonary vasculature -> pulmonary venous pressure increases
• Kerley lines: interlobular septal thickening - interstitial edema
• diffuse alveolar edema: perihilar distribution, butterfly or bat-wing pattern, coalescing fluffy opacities, air-bronchogram
• pleural effusion
• enlarged heart (+/-)

Question 4

ultrasonography

Answer 4

• fluids: hypo- or an-echoic -> blood-filled vessels + heart chambers are dark on 2D ultrasound images
• real time imaging (echocardiography)
• high resolution imaging of vessel wall & lumen: for superficial vessels, plaque analysis
• bones & air are not penetrated by US. “Acoustic window” is needed
• Doppler techniques: accurate velocity measurements - haemodynamic analysis. Color Doppler - flow map.
• 2D ultrasound images + spectrum Doppler = duplex ultrasound

Question 5

main indications of duplex sonography

Answer 5

• cerebrovascular disease (carotid stenosis, transcranial Doppler)
• obliterative arterial disease of extremities (atherosclerotic chronic disease, acute embolic occlusion)
• deep venous thrombosis of the extremities
• abdominal vessels (AAA - aneurysm of the abdominal aorta, renal artery stenosis, abdominal angina - mesenteric artery stenosis, portal HTN)
• soft tissue vascularisation (eg tumors)
• post-surgical conditions - complications

Question 6

significant arterial stenosis

Answer 6

• vessel wall irregularity
• plaques causing stenosis
• > 50% stenosis - quantification is more accurate on haemodynamic basis
• elevated end-systolic & end-diastolic peak velocity
• sign of turbulence - filling of :systolic window”

Question 7

patent deep venous trunk

Answer 7

• echo-free compressible lumen
• spontaneous flow with preserved respiratory fluctuations
• augmentable with manoeuvres

Question 8

acute thrombosis

Answer 8

• dilated non-compressible lumen
• lack of spontaneous flow
• restricted augmentation
• intraluminal echoes +/-

Question 9

chronic thrombosis

Answer 9

• difficult diagnosis
• deliniation of lumen is less clear, irregular “braid-like” collaterals
• variable spontaneous flow, restricted respiratory fluctuation, reflux augmentable

Question 10

advanced CT & MRI techniques in cardiovascular imaging

Answer 10

• spiral CT-angiography
• ECG-gated cardio-CT
• MR-angiography
• ECG-triggered cardio-MR

Question 11

vascular imaging by CT

Answer 11

• non-contrast CT: pathologic mural calcification, coronary Ca scoring
• contrasted-enhanced CT -> “conventional” technique: aorta (d >/= 1cm)
• spiral CT-angiography: single detector row spiral CT ( branches of aorta, d >/= 2-3 mm), multidetector row spiral CT (peripheral vessels, d >/= 1 mm)

Question 12

helical (spiral) CT angiography

Answer 12

• dynamic IV administration of contrast material
• scan-delay optimised for the selected circulation phase
• helical scanning with thin collimation during the first pass of contrast bolus
• post-processing of primary scan data: multiplanar and 3D reformatted images resembling DSA

Question 13

vascular imaging by CT - scanning parameters

Answer 13

• slice thickness as thin as possible (isotropic imaging): 4-16 slice CT: 1 - 1,25 mm / 16-256 slice CT: 0,5 - 1,25 mm
• multiphase examination if necessary: venous filling, vessel walls, perivascular tissues, parenchymal organs
• ECG-gating: coronary CTA, congenital anomalies, “triple rule-out” approach for acute chest pain

Question 14

vascular imaging by CT - contrast administration

Answer 14

• type: non-ionic, preferably low osmolality
• dose: MDCT: 1 - 1,5 cc/kgBW
• automatic injection: 2,5 - 5 cc/sec, second phase saline flush
• scan timing to achieve optimal “first pass” effect: empiric -> variable circulation times, bolus detecting program (bolus tracking) -> automatic detection of intravascular density elevation at arrival of contrast bolus

Question 15

MR angiography: without contrast - TOF (time-of-flight)

Answer 15

short repetition time results in the saturation of stationary tissues; signal is generated only by the unsaturated spins in the blood entering the examination plane (inflow effect)

application: intracranial arteries

Question 16

MR angiography: without contrast - PC (phase contrast)

Answer 16

flow (depending on its direction and velocity) changes the phase of precessing spins

• flow direction determination
• flow velocity determination

application: haemodynamic analysis

Question 17

MR angiography: with contrast material (CE-MRA)

Answer 17

sequences based on the marked T1 shortening effect of paramagnetic Gd

• dynamic IV administration of contrast material (Gd)
• scan-delay optimised for the selected circulation phase
• T1 weighted 3D gradient echo fast sequence during the first pass of contrast material

Question 18

CE-MRA post-processing

Answer 18

a. 2D reformatted images:
- multiplanar (MPR)
- curved (analog the course of vessels)

b. 3D reformatted images:
- maximun intensity projection (MIP)
- volume rendering (VR)
- shaded surface display (SSD)

c. semi-automatic analysis programs:
- automatic segmentation, “bone-removal”
- stenosis quantification based on diameter and/or cross-sectional area reduction measurement
- aneurysm sizing for stent-graft implantation

Question 19

CE-MRA evaluation

Answer 19

1. primary slices: these contain all the information provided by the study. Any further processing may result in data loss
2. MIP (maximum intensity projection): DSA-like demonstration of global vascular anatomy. “slab MIP” -> target volume, stenosis analysis
3. MPR (multiplanar reconstruction), CR: stenosis, plaque analysis
4. 3D volume rendering (VR), SSD: demonstration of complex anatomy of vessels / bones / parenchymal organs

Question 20

CT/MRA main indications: emergency conditions

Answer 20

• acute chest pain: acute aortic syndrome, acute pulmonary embolism, acute coronary syndrome
• acute abdominal pain: rupture or pending rupture of AAA, mesenterial ishcemia
• subarachnoid bleeding: aneurysm of the circle of Willis, vascular malformation
• traumatic injury of great vessels
• massive bleeding with haemodynamic instability: tracheo-bronchial, gastrointestinal, genito-urinary

Question 21

thoracoabdominal aorta - aneurysms

Answer 21

PRIMARY ASSESSMENT:

• diameter, length
• anatomy of proximal and distal necks
• origin of branches
• intraluminal thrombus
• vessel wall thickness, periaortic tissues (inflammation?)
• signs of imminent rupture

FOLLOW UP:

• growth
• d > 5,5 - 6 cm is indication for intervention
• postoperative follow-up: anastomoses, signs of pseudoaneurysm formation, early complications, late complications (aorto-duodenal fistula)

Question 22

aortic dissection - acute

Answer 22

• type: Stanford A or B?
• possible dissection variant
• intramural hematoma
• penetrating ulcer, circumscribed dissection
• anatomy of true + false lumen, diameter
• side branches (supraaortic, renal, splanchnic, iliac)
• origin from true or false lumen
• dissection affecting the aortic branch
• signs of stenosis, thrombosis, hypoperfusion

Question 23

aortic dissection - chronic

Answer 23

• progression of secondary aneurysm
• signs of imminent rupture
• side branches

Question 24

planning and follow-up of endovascular interventions

Answer 24

1. sizing before stent-graft implantation:
   - accurate diameters of proximal and distal vessel segments
   - distance from proximal and distal branches, bifurcations
2. post-intervention follow-up:
   - endoleak?
   * type (source)
   * degree, progression

Question 25

endovascular interventions: indications

Answer 25

• atherosclerotic obliterative arterial disease
• cerebrovascular disease
• renovascular hypertension
• mesenteric ischemia
• limb ischemia
• (ischemic heart disease)

Question 26

renal arteries - pathology

Answer 26

1. renovascular hypertension:
   - clinical suspicion of RAS with equivocal examination results (clinical data, US, nuclear medicine)
   - after catheter angiography: complex anatomy
   - AAA +/- RAS?
   - assessment of the arterial supply of transplanted kidney
   - post-operative / stent follow-up
2. renal artery aneurysm
3. renal artery anomalies: lower polar artery causing ureteral stenosis?

Question 27

extremity arteries - pathology

Answer 27

1. obliterative disease:
   - for the selection of optimal treatment choice: CTA or MRA, instead of DSA -> able to map the whole extremity arterial tree
   - special MRA technique with table stepping
   - only MDCT enables the imaging of long segments (whole extremity) with reasonable contrast amount & x-ray exposure
2. femoro-popliteal aneurysms
3. popliteal entrapment syndrome
4. vascular injuries associated to pelvic and long bone fractures

Question 28

indications of CTA - MRA: pulmonary circulation

Answer 28

1. acute pulmonary embolism:
   - direct visualization of emboli filling the lumen completely or partially
   - peripheral branches down to subsegmental level are adequately assessed
   - IV contrast administration
   - feasible in critically ill, non-cooperative patients as well
   - DDX: ptx, pneumonia, tumor, etc
2. chronic pulmonary thrombo-embolic disease:
   - clinical signs of pulmonary arterial HTN
   - known embolic episode in clinical history