25.3 Ultrasound-Guided Interventions, MSK & Superficial Masses

ARRT Sonography Primary

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1 Introduction & Exam Overview

1.1 Current Exam Facts & Logistics 1.2 Scoring, Section Minimums & the August 2026 Cut-Score Change 1.3 Official Blueprint & Study Strategy

2 Patient Care: Ethics, Legal Practice & Communication

2.1 Ethical & Legal Aspects of Patient Care 2.2 Interpersonal Communication & Patient Education 2.3 Physical Assistance, Monitoring & Sonographer Ergonomics

3 Patient Care: Safety, Emergencies & Infection Control

3.1 Medical Emergencies & Critical Findings 3.2 Infection Control & Hazardous Materials 3.3 Ultrasound Safety & Interventional Procedure Care

4 Image Production: Transducers & the Ultrasound Beam

4.1 Piezoelectric Effect & Transducer Construction 4.2 Beam Configuration: Near Field, Far Field & Focus 4.3 Transducer Types, Selection, Care & Malfunctions

5 Image Production: Pulse Characteristics & Resolution

5.1 Pulse Characteristics: PRF, PRP, SPL & Duty Factor 5.2 Resolution: Axial, Lateral, Temporal, Elevational & Contrast 5.3 Frequency, Bandwidth, Q Factor, Power, Pressure, Intensity & Amplitude

6 Image Production: Imaging Modes & Doppler Principles

6.1 B-Mode & M-Mode Imaging 6.2 Spectral Doppler: Pulsed Wave vs Continuous Wave 6.3 Color Doppler & Power Doppler

7 Image Production: Optimization Controls

7.1 Power, Gain, TGC, Depth & Focal Zone 7.2 Frame Rate, Line Density, Dynamic Range, Harmonics & Compounding 7.3 Doppler Optimization Controls

8 Image Production: Sound–Tissue Interactions

8.1 Speed of Sound & the Range Equation 8.2 Acoustic Impedance, Reflection, Refraction & Scattering 8.3 Attenuation, Absorption & Intensity

9 Image Production: Signal Processing, Display & Bioeffects

9.1 Receiver, Signal Processing & Analog-Digital Conversion 9.2 Postprocessing, Magnification, Panoramic & 3D/4D Imaging 9.3 Bioeffects & Output Display Measures

10 Image Production: Image Evaluation & Artifacts

10.1 Criteria for Diagnostic Quality & Annotation 10.2 Grayscale Artifacts 10.3 Doppler Artifacts

11 Image Production: Real-Time Interpretation & Informatics

11.1 Real-Time Imaging, Echogenicity & Echotexture 11.2 Color & Spectral Analysis: Measurements and Waveforms 11.3 Imaging Informatics: HIS, RIS, EMR, PACS & DICOM

12 Procedures: Abdominal & Transplant Vasculature

12.1 Aorta, Its Branches & the IVC 12.2 Portal Venous System & Hepatic Vasculature 12.3 Liver & Renal Transplant Sonography

13 Procedures: Liver

13.1 Liver Anatomy, Variants & Examination Technique 13.2 Diffuse Liver Disease 13.3 Focal Liver Lesions

14 Procedures: Biliary System, Pancreas & Spleen

14.1 Gallbladder & Bile Ducts 14.2 Pancreas 14.3 Spleen

15 Procedures: Urinary Tract, GI Tract & Other Abdominal Structures

15.1 Kidneys & Ureters 15.2 Bladder & Prostate 15.3 GI Tract, Adrenals, Lymph Nodes, Hernias & Peritoneal Cavity

16 Procedures: First-Trimester Obstetrics

16.1 Early Gestation: Normal Development & Structures 16.2 First-Trimester Measurements, Dating & Maternal Anatomy 16.3 First-Trimester Abnormalities

17 Procedures: Second/Third-Trimester Biometry & Fetal Survey

17.1 Standard Biometry: BPD, HC, AC, FL & Growth Assessment 17.2 Fetal Anatomic Survey: Head, CNS, Face & Spine 17.3 Fetal Anatomic Survey: Heart, Chest, GI, GU, Skeleton & Fetal Position

18 Procedures: Chromosomal, Genetic & Structural Abnormalities

18.1 Chromosomal & Genetic Abnormalities 18.2 Major Structural Anomalies by System 18.3 Fetal Infection, Neoplasms & Hydrops

19 Procedures: Placenta, Amniotic Fluid, Cord & Cervix

19.1 Placenta: Normal, Previa, Abruption & Accreta 19.2 Amniotic Fluid Assessment & Growth Disorders 19.3 Umbilical Cord & Cervical Assessment

20 Procedures: Fetal Assessment, Doppler & Multiple Gestation

20.1 Biophysical Profile & Fetal Surveillance 20.2 Fetal & Uteroplacental Doppler 20.3 Multiple Gestations, Assisted Reproduction & Maternal Disease

21 Procedures: Gynecology — Uterus

21.1 Uterine Anatomy, Myometrium & Fibroids 21.2 Endometrium: Cyclic Changes, Hyperplasia & Cancer 21.3 Cervix & Congenital Uterine Anomalies

22 Procedures: Gynecology — Adnexa & Pelvis

22.1 Ovaries: Normal, Functional Cysts & Benign Masses 22.2 Ovarian Malignancy, Torsion & Fallopian Tubes 22.3 Cul-de-Sac, Vagina & Pelvic Floor

23 Procedures: Neck & Scrotum

23.1 Thyroid & Parathyroid 23.2 Salivary Glands & Neck Lymph Nodes 23.3 Scrotum & Testes

24 Procedures: Breast & Peripheral Vascular

24.1 Breast & Axilla 24.2 Venous Extremity Doppler 24.3 Carotid Doppler & Post-Catheterization Complications

25 Procedures: Pediatric, Interventional & Miscellaneous

25.1 Neonatal Head, Spine & Hip Sonography 25.2 Pediatric GI & Noncardiac Chest 25.3 Ultrasound-Guided Interventions, MSK & Superficial Masses

25.3 Ultrasound-Guided Interventions, MSK & Superficial Masses

Key Takeaways Explain This Topic AI

Ultrasound guidance provides real-time needle visualization with no ionizing radiation, using either the freehand technique or a needle guide attached to the transducer

Fine-needle aspiration (22-25 gauge) yields cells for cytology, while core needle biopsy (14-18 gauge) preserves tissue architecture for histology

For paracentesis and thoracentesis, sonography marks the largest safe dependent fluid pocket and documents skin-to-fluid depth while avoiding vessels and solid organs

Abscesses typically show a hyperemic rim with no internal vascularity and swirling debris on compression, distinguishing them from simple cysts

• A lipoma is classically a compressible, isoechoic to mildly hyperechoic, well-circumscribed subcutaneous mass
• Last updated: July 2026

Ultrasound-Guided Interventional Technique

Ultrasound's chief advantage for guidance is real-time visualization : the operator watches the needle tip advance toward the target and steers around vessels, bowel, and pleura — all with no ionizing radiation and no contrast. Before any procedure, verify the order, obtain informed consent (risks include bleeding, infection, and injury to adjacent structures), perform a time-out confirming patient, site, and procedure, and review coagulation status and anticoagulant medications when relevant.

Two guidance approaches exist:

Freehand technique : the operator holds the transducer in one hand and the needle in the other. It is flexible — the needle angle can be adjusted continuously — but demands hand-eye coordination and constant attention to keeping the needle in the imaging plane

Needle guide : a bracket clipped to the transducer constrains the needle to a fixed angle displayed as an on-screen guideline. It improves accuracy for deep or small targets and for less experienced operators, at the cost of some flexibility

Sterile technique is mandatory: a sterile probe cover (with gel inside the cover for coupling), sterile gel on the skin, a sterile field, and skin antisepsis. Local anesthesia (for example, 1% lidocaine) is infiltrated along the planned track under direct visualization. Color Doppler maps vessels in the path before the needle is advanced. The needle tip — never the shaft — must be positively identified at the target before sampling or deployment; gentle tissue motion or a tiny injection of saline or anesthetic can confirm tip position.

Fine-Needle Aspiration vs. Core Needle Biopsy

• Feature Fine-Needle Aspiration (FNA) Core Needle Biopsy
• Needle 22-25 gauge 14-18 gauge cutting needle
• Sample Individual cells for cytology Tissue cylinder preserving architecture for histology

Strengths Quick, low complication rate, good for thyroid Definitive tumor typing, receptor status (breast), lymphoma architecture

Handling Smears on slides (air-dried or alcohol-fixed); cell block Formalin for routine histology; fresh tissue for flow cytometry or culture

Typical applications: thyroid nodules are sampled by FNA with several passes under ultrasound guidance; breast masses generally undergo core biopsy so hormone receptors and tumor grade can be assessed; liver lesions may be biopsied by either method, with Doppler used to avoid crossing large vessels; lymph nodes require core samples when lymphoma is suspected because architectural pattern matters. On-site cytopathology review, when available, confirms specimen adequacy before the patient leaves.

Drainage Procedures

Paracentesis : scan the lower abdomen and flank to find the largest dependent pocket of ascites. Mark the skin site, document skin-to-fluid depth and pocket depth, and use Doppler to avoid the inferior epigastric vessels (which course along the posterior rectus sheath) and any varices. A left lower quadrant or midline infraumbilical site is common

Thoracentesis : with the patient upright (or decubitus), identify the effusion in a costophrenic sulcus, confirm diaphragm position throughout the respiratory cycle, and mark an entry site in the intercostal space above the rib — the intercostal artery, vein, and nerve run in the groove along the rib's inferior margin. Confirm the pocket is large enough to avoid lung puncture, and never advance the needle deeper than the measured pocket

Abscess drainage : after confirming a drainable collection, most catheters are placed by the Seldinger technique — access needle, guidewire coiled within the cavity, serial dilators, then a pigtail drainage catheter secured at the skin. Output is recorded, and the catheter is flushed per protocol

Intraoperative ultrasound uses a sterile-draped transducer directly on an exposed organ — most often the liver — to localize sub-centimeter tumors, define their relationship to hepatic and portal veins, and guide resection margins or ablation probe placement.

Complications to counsel about and monitor for include bleeding (the most common), infection , pneumothorax after thoracic or subdiaphragmatic procedures, and vasovagal reactions. Post-procedure care includes vital signs, puncture-site checks, and a brief observation period scaled to the organ biopsied (longer for liver and kidney); patients receive written precautions and instructions for when to seek care.

Musculoskeletal Applications

Musculoskeletal sonography uses high-frequency linear transducers (10 MHz and above), generous gel or a stand-off pad for superficial structures, side-by-side comparison with the contralateral limb, and dynamic imaging through range of motion.

Rotator cuff tears : the supraspinatus is examined in the Crass or modified Crass position — extension, adduction, and internal rotation, with the hand behind the back or resting on the ipsilateral hip. A full-thickness tear appears as an anechoic or hypoechoic defect through the tendon, nonvisualization of tendon fibers with deltoid sagging against the humeral head, and flattening of the bursal contour; partial-thickness tears are focal hypoechoic defects on the bursal or articular surface

Tendon rupture : complete rupture shows a fiber gap, often filled with fluid or granulation tissue, and dynamic scanning demonstrates the torn ends separating with motion

Joint effusion : anechoic or complex fluid distends the joint recess (for example, the suprapatellar pouch of the knee), is compressible and displaceable, and can be targeted for aspiration

Foreign body localization : wood, glass, and metal are echogenic with posterior shadowing or comet-tail artifact; ultrasound excels at finding radiolucent objects like wooden splinters and marking the skin directly over them for removal

Superficial Masses and the Abdominal Wall

Mass Classic Sonographic Appearance

Lipoma Compressible, well-circumscribed, isoechoic to mildly hyperechoic, elliptical, thin echogenic septa, little or no flow

Epidermal inclusion (sebaceous) cyst Round, well-defined hypoechoic dermal/subcutaneous mass with posterior enhancement, often a connecting tract (punctum) to the skin and internal debris

Ganglion cyst Anechoic, multilobulated, noncompressible cyst adjacent to a joint or tendon sheath (wrist is classic)

Abscess Complex collection with thick irregular walls, swirling debris on compression, posterior enhancement, hyperemic rim on Doppler with no internal flow

Reactive lymph node Oval, hypoechoic cortex with a preserved echogenic fatty hilum and hilar vascularity; suspicious nodes are round, lose the hilum, and show peripheral flow

The swirling debris sign — gently compressing the mass and watching internal echoes shift in real time — is a favorite exam clue for abscess and for complicated cysts.

For the abdominal wall , ultrasound evaluates hernias dynamically: inguinal, femoral, umbilical, and incisional hernias are scanned at rest and with the Valsalva maneuver , which pushes contents through the fascial defect and demonstrates reducibility and the neck width. An abdominal wall endometrioma appears as a solid, hypoechoic, sometimes vascular mass within a cesarean-section or laparoscopic scar in a woman of reproductive age, with pain and swelling that wax and wane with the menstrual cycle. Desmoid tumors and rectus sheath hematomas round out the differential for solid and fluid abdominal wall lesions.