UTZ Interventional

Interventional ultrasound

Percutaneous image-guided procedures performed for diagnosis or therapy

Common ultrasound-guided procedures

Biopsy, aspiration, drainage, ablation, localization, and injection

Major advantage of ultrasound guidance

Real-time visualization of needle tip and adjacent structures

Needle guidance methods

Freehand and needle guide attachment

Freehand technique

Operator manually aligns needle and transducer; flexible angle but requires experience

Needle guide technique

Pre-set path attached to transducer; fixed entry angle for predictable trajectory

Coaxial technique

Outer guide needle remains while multiple inner biopsy passes are taken

Fine needle aspiration (FNA)

Uses small gauge (20–25G) needle to obtain cytologic samples

Core biopsy

Uses larger gauge (14–18G) needle to obtain tissue cores for histology

Common biopsy targets

Liver, thyroid, kidney, lymph nodes, breast, prostate, pancreas

Liver biopsy contraindications

Uncorrectable coagulopathy, vascular lesions, ascites, hydatid cyst

Renal biopsy indication

Evaluation of renal parenchymal disease or transplant rejection

Breast biopsy positioning

Patient supine with ipsilateral arm raised; transducer parallel to chest wall

Thyroid biopsy

Performed under sterile field with patient supine and neck hyperextended

Abscess drainage

Placement of catheter for evacuation of infected fluid; monitored by ultrasound

Paracentesis

Removal of ascitic fluid from peritoneal cavity; done with full bladder empty

Thoracentesis

Drainage of pleural effusion; performed with patient upright and transducer above diaphragm

Amniocentesis

Ultrasound-guided aspiration of amniotic fluid; performed ≥15 weeks gestation

Chorionic villus sampling (CVS)

Transcervical or transabdominal sampling of chorionic villi; performed 10–13 weeks

Pericardiocentesis

Needle aspiration of pericardial fluid; done under ultrasound for effusion or tamponade

Hydrocele aspiration

Drainage of scrotal fluid collection; sterile field required

Biopsy track seeding risk

Higher in malignancies; minimized by coaxial technique and limited passes

Bleeding complication

Most common; minimized by checking coagulation profile before procedure

Pneumothorax complication

Possible in thoracic biopsies; prevented by shallow approach and post-procedure scan

Infection prevention

Sterile technique, skin prep, and probe covers mandatory

Patient monitoring

Observe vital signs and puncture site for 1–2 hours post-procedure

Local anesthesia

1% lidocaine commonly used; infiltrated up to capsule or lesion margin

Needle visualization technique

Needle seen as echogenic line or bright dot depending on angle of insonation

In-plane approach

Needle visualized along full length within ultrasound beam

Out-of-plane approach

Needle appears as bright dot; requires frequent repositioning

Color Doppler use

Avoids puncture of vascular structures

Transducer sterilization

Use high-level disinfectant (glutaraldehyde, hydrogen peroxide)

Biopsy specimen handling

Placed in formalin for histology or saline for culture studies

Documentation

Includes patient ID, indication, method, number of passes, and complications

Informed consent

Required before all interventional procedures

Ultrasound-guided injection

Used for cyst sclerosis, steroid therapy, or anesthetic delivery

Localization procedures

Preoperative wire or marker placement for lesion removal

Ablation techniques

Ethanol injection, radiofrequency, microwave, or cryoablation under ultrasound

Thermal index (TI)

Safety indicator for tissue heating; keep TI ≤ 1.0 for obstetric and sensitive studies

Mechanical index (MI)

Indicates cavitation potential; keep MI ≤ 1.9 for diagnostic imaging

Output display standard (ODS)

Real-time display of MI and TI on ultrasound monitor

Acoustic power setting

Use ALARA principle (As Low As Reasonably Achievable)

Quality assurance (QA)

Predictive maintenance and performance verification of ultrasound systems

QA frequency

Weekly for image quality, semiannual for full performance check

Phantom test purpose

Ensures system consistency and accurate measurements

Types of phantoms

Tissue-equivalent, string, and hydrophone phantoms

Tissue-equivalent phantom

Assesses grayscale, depth, and distance accuracy

String phantom

Tests Doppler sensitivity and velocity accuracy

Hydrophone testing

Measures acoustic output, MI, and TI

Depth of penetration test

Evaluates maximum visible depth of tissue echoes

Axial resolution test

Determined by shortest distance between two reflectors along beam axis

Lateral resolution test

Measured by ability to distinguish side-by-side reflectors

Vertical distance accuracy test

Measures spacing of targets along sound beam direction

Horizontal distance accuracy test

Measures spacing perpendicular to sound beam

Dead zone test

Assesses near-field region where transducer cannot display echoes accurately

Contrast resolution test

Assesses ability to display subtle differences in echo intensity

Sensitivity test

Assesses weakest echo signals detectable by system

Uniformity test

Checks even brightness across image field; detects dead elements

Image registration test

Assesses spatial accuracy between modes (B-mode vs Doppler)

Signal-to-noise ratio (SNR)

Higher ratio = cleaner image; affected by gain and noise

Power Doppler sensitivity

Evaluated with low-flow phantom; tests detection of slow flow

Display monitor QC

Contrast, brightness, and resolution evaluated visually

Transducer integrity test

Detects crystal failure or cable breakage

System warm-up stability

Verifies consistent image after 5–10 min of operation

Record-keeping

QA logs maintained for each test and corrective action

Acceptance testing

Performed after new equipment installation before clinical use

Preventive maintenance

Scheduled servicing to minimize downtime and preserve accuracy

Cleaning protocol

Use manufacturer-approved non-alcohol wipes for probe surface

Electrical safety check

Leakage current test; ensures safe grounding and insulation

Maximum scanning time

Limit exposure to necessary duration; especially for fetal and neonatal scans

Thermal safety

Increase in temperature ≤ 1°C considered safe

Patient dose reduction

Use lowest power, shortest scan time, and intermittent scanning

Acoustic output labeling

Displayed as MI and TI values on screen for operator awareness