Diagnostic Radiology SC005: How Can Interventional Radiology Help Patient Management?

Question 1

Interventional Radiology

Answer 1

• Provide minimally invasive, image-guided therapy for conditions in virtually all body system
• Range of techniques which rely on the use radiological image guidance (X-ray fluoroscopy, ultrasound, CT, MRI) to precisely target therapy
• Most IR treatments are minimally invasive alternatives to open and laparoscopic (keyhole) surgery

Laparoscopy: Keyhole surgery
IR: Pinhole surgery

Scope of IR:

• Vascular (e.g. Prostate artery embolisation / Uterine fibroid embolisation (UAE))
• Oncology
• GI
• Genitourinary
• Neurointervention
• Head and Neck
• Musculoskeletal

Question 2

Prostate artery embolisation

Answer 2

• Minimally invasive treatment that helps improve lower urinary tract symptoms caused by BPH
• Lower risk of urinary incontinence / sexual SE (retrograde ejaculation / erectile dysfunction) when compared with TURP
• Significant improvement in IPSS, QoL, PV, PVR (Post-void residual urine), Qmax
• High safety profile
• PSA reduced / remained stable
• Alternative to medications, surgeries (esp. in elderly with comorbidities)

Mechanism:

• Infarcts with coagulative necrosis —> Volumetric reduction + LUTS improvement
• Increased elasticity with relaxation in smooth muscle —> less resistance to urinary flow
• Free of indwelling catheter + urodynamic obstruction

Indications:

1. BPH with LUTS (IPSS score, permanent catheter)
2. Large Prostate size (>35g)

CI:

1. Active infection (UTI, prostatitis)
2. Biopsy proven Ca prostate / bladder

Workup:

1. CBP, LRFT
2. PSA (exclude cancer)
3. CT pelvic angiogram

Process:

1. LA
2. Vascular access (femoral / radial)
3. +/- Foley balloon
4. Tackle prostatic artery (from internal iliac artery)
5. Beads for embolisation
6. Discharge next day

Risks:

1. Local vascular complications (haematoma, false aneurysm, distal embolisation)
2. Contrast reactions
3. AROU (0-25%)
4. Non-target embolisation (1-8%) (e.g. rectum —> PR bleed, bladder —> cystitis)
5. Transient haematospermia
6. Transient haematuria

TURP:

1. Mortality 0.2% (10% >80 yo)
2. Urinary incontinence common for 6-8 weeks + persistent in 2-4%
3. Impotent (5-10%)
4. Retrograde ejaculation (>80%)
5. Infertile

Question 3

Uterine fibroid embolisation (UAE)

Answer 3

Advantages over hysterectomy / myomectomy:

1. Shorter hospital stay (Next day)
2. Quicker return to full activity
3. Reduced likelihood of blood transfusions

Disadvantages:

1. Higher risk of minor complications
2. Higher reintervention rate (15-32% will require surgery within 2 years of UAE (vs 7% require surgery after hysterectomy / myomectomy))

Indications:

1. Symptomatic fibroid
2. Surgical indication (e.g. hysterectomy / multiple myomectomy)
3. No desire for future pregnancy
4. Multiple ***intramural fibroid
5. Adenomyosis

CI:

1. Viable pregnancy
2. Asymptomatic woman
3. Large pedunculated subserosal fibroid (MRI) (avoid dislodging into abdominal cavity)

History:

1. Chief complaint: bleeding vs bulk
2. Menstrual history
   - Duration and frequency; number of heavy days
   - Clots, “gushes”; frequency of pad / tampons
   - Intermenstrual bleeding
3. Polyps, hyperplasia, cancer
4. Pelvic symptoms
   - Pressure / “bloating”; pelvic pain; leg/back pain
   - Urinary frequency / nocturia or urinary obstruction
   - Dyspareunia
   - Constipation
5. Reproductive history
   - History of infertility, miscarriages
   - Desire for future fertility

Investigations:

1. USG
2. MRI pelvis
   - Does the patient actually have fibroids?
   - Where is / are the fibroid(s)?
   - Location is consistent with symptoms?
   - Intracavitary? Size?
   - Are the fibroids viable?
   - How large is the uterus?
   - Vascular anatomy?
   - Other pathologies?
3. MR angiogram
4. CBP, LRFT, clotting profile

Process:

1. LA
2. Vascular access (femoral / radial)
3. Tackle uterine artery (from internal iliac artery)
4. Beads for embolisation
5. Discharge next day

Complications:
- Transient amenorrhea ~10%
- Permanent amenorrhea
—> <45 years ~3%
—> >45 years ~15%
- Fibroid expulsion ~5%
- Access complications ~<3% (e.g. pseudoaneurysm)
- Uterine infection ~2%
- Venous thromboembolism <1%

Question 4

Benefit of Wrist over Groin vascular access

Answer 4

Groin: more retroperitoneal bleeding
Wrist: easier to take care of wound

Question 5

Embolic agent

Answer 5

1. PVA
   - 355-500 um
   - 500-700 um
2. Embosphere
   - 500-900 um

Question 6

Trans-arterial Chemoembolisation (TACE)

Answer 6

• HCC is a vascular tumor supplied almost solely by the hepatic artery
• Iodized oil is selectively taken up by HCC cells
• Cytotoxic agent (Cisplatin) mixed into an emulsion with Lipiodol will thus be carried to the tumor cells in high concentration to be released slowly
• Potentially curative now

Complications:

1. Post-embolisation syndrome (common)
   - N+V, abdominal pain, loss of appetite, fever
2. Others (Uncommon)
   - Cholecystitis, upper GI bleeding, gastric/duodenal necrosis, acute pancreatitis, hepatic abscess, rupture

CI:

1. Main portal vein tumor thrombosis
   - Embolisation of hepatic artery may cause complete occlusion and total ischaemia to liver
2. Extrahepatic metastases
3. Poor liver function (serum bilirubin >50 μmol/L)

Question 7

Ablation in interventional oncology

Answer 7

Indications:

1. HCC
2. Kidney
3. Bone
4. Soft tissue tumor
5. Thyroid
6. Lung

Ablative devices:

1. Radiofrequency ablation (RFA)
2. Microwave (MW)
3. Cryoablation
4. High intensity focused ultrasound (HIFU)
5. Percutaneous ethanol injection
6. Irreversible electroporation (IRE)

Question 8

Radiofrequency ablation (RFA)

Answer 8

• Radiofrequency + Microwave energy
• Ionic excitation —> frictional heating —> thermal energy to cause tumour necrosis
• 60-100oC: instant protein coagulation + irreversible cellular damage
• Patient used to complete the circuit
  —> needle tip —> small surface area —> high concentration of energy —> tumour necrosis
  —> grounding pad —> large surface area —> low energy concentration —> decreased skin burn
• Ablation zone should cover the tumour: usual ablation zone 3-5cm
• Plus margin (~ to surgical resection margin): 5-10mm margin
• Reality: ablation zone is more elliptical and 5-10% smaller than advertised

Advantage:

• Most evidence
• Fast (10 mins)
• Better cosmesis
• Lower morbidity
• Day procedure
• Preserve thyroid function (in thyroid nodule ablation)

Disadvantage:

• Heat sink effect
• Incomplete ablation of large tumour

Complications (e.g. thyroid):

• Minor: Haematoma, transient hoarseness, skin burn, hypothyroid, hypoparathyroid
• Major: Persistent hoarseness, vessel injury, abscess or haematoma requiring surgery, thyrotoxic storm, septic shock, stroke, death

Question 9

Microwave ablation

Answer 9

Principle: Dielectric heating / Hysteresis

• Apply electromagnetic field to tissue
• EM field alternates with current
• Water molecule tries to “line up” with field
• Water molecule rocks —> kinetic energy —> heat

Advantage:
- No heat sink, more homogenous heat distribution
—> Create heat >100 times faster than RFA
—> Heat is still carried away but heat creation is even faster
- Variable field size with power and time
—> More tailored treatment
—> Larger ablation zone than RFA
- Faster ablation time (6 mins)
- No need to complete circuit with grounding pads
- Can deliver heat through charred tissue (EM wave not impeded by charred tissue vs RFA)

Disadvantage:
- Increase risk of inadvertent damage to adjacent organ (∵ hotter, 100oC vs RFA 60oC)

Question 10

Cryoablation

Answer 10

Mechanism:

• Rapid cooling to cause cell death
• Intra + Extracellular ice crystals are directly cytotoxic —> cell dehydration + rupture
• When frozen tissue thawed —> microvascular occlusion with cell hypoxia —> indirect ischaemic injury
• Thaw —> water influx —> bursting of cells
• Process: Freeze —> Thaw —> Freeze —> Thaw
• Clinical success 90% + even greater for tumours <3cm

Process:
- Cooling needle insertion
—> Needle cooled by liquid gas (argon / helium)
—> Formation of ice ball
—> Cell death is time + temp-dependent, with critical threshold for cell death -19.4- -40oC
—> Cryoprobe reaches -190
—> Ablation time: 12 mins freeze-thaw cycle
—> 2 cycles
—> Can use multiple needles simultaneously

Advantages:

1. No need for GA, LA only
2. Not that painful
3. ***Ablation zone is visible immediately + during mid-cycle of ablation —> avoid damage to nearby tissue
4. Very little damage to adjacent tissue (esp. renal collecting system)

Question 11

High Intensity Focused Ultrasound (HIFU)

Answer 11

Non-incisional, transcutaneous tumour ablation technique

Mechanism of HIFU ablation:

• Thermal coagulative necrosis
• Acoustic cavitation
• Damage to tumour vasculature
• US / MRI guidance

Advantage:

• Avoid risk + complication of needle or electrode placement
• Ability to treat large tumor >5cm

Disadvantages:

• Long treatment time
• Require GA

Question 12

Musculoskeletal biopsy by IR

Answer 12

1. US
   - Real time guidance
   - Soft tissue
2. CT
   - Precise localization
3. Fluoroscopy
   - Real time guidance
   - 3D views / DynaCT

Surgical anatomy:
- Biopsy at Anterior deltoid (can be sacrificed even if seeding)
- Avoid
—> Deltopectoral groove
—> Posterior deltoid
—> Neurovascular bundle

Question 13

Cementoplasty

Answer 13

Indications:

1. Stability and prevention of pathological fracture from RT / Percutaneous ablation
2. Painful metastasis

Vertebroplasty:

1. Pain relief (80-97%)
   - Mechanical stabilisation
   - Vascular, chemical, thermal forces
2. Reduces vertebral bulge
3. Reduces risk of burst fracture
4. Antitumoural effect of PMMA

Indications for Vertebroplasty:

1. Painful bone tumour
2. Aggressive vertebral haemangioma
3. Osteoporotic fracture
4. Kummel’s disease

Post-op:

• Prone until cement is hard
• Bed rest 1-2 hours
• CT: Cement distribution
• Pain score (VAS)
• Discharge next day

Other locations:

• Acetabulum
• Femoral condyles
• Tibial ends
• Talus + Calcaneus

PMMA:

• Radio-opaque
• Powder + monomer mixture
• Exothermic polymerisation
• Liquid —> paste —> solid

Question 14

Neurointerevntion

Answer 14

Complications of IA thrombolysis:

1. Thromboembolic
   - clot formation on coil ball, catheter
   - push clot out of aneurysm
2. Aneurysm rupture
   - more likely in ruptured aneurysms
3. Device malfunction
   - premature detachment of coil
   - unraveling
4. Vascular damage
   - spasm, dissection

Question 15

Interventional Radiology

Answer 15

Advantages:

1. Minimally invasive procedures
2. Provide alternative to surgery in suitable patients
3. Hospital admission often not required
4. Quick recover, less pain and complications
5. Generally safe + effective

Roles:
Diagnostic:
- Histological sampling / Biopsy
- Treatment planning

Therapeutic:

• Vascular intervention
• Non-vascular intervention
• Interventional oncology

Arterial:

• Balloon angioplasty and stenting
• Thrombolysis
• Haemorrhage control + Embolisation

Venous:

• Central venous access
• IVC filter
• Fistula intervention