Prostate Biopsy

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Revision as of 06:37, 17 December 2021 by Urology4all (talk | contribs) (Created page with "== Grayscale Trans-Rectal Ultrasound (TRUS) == * '''Probe frequency''' ** '''Increasing the frequency increases the resolution''' and decreases the depth of penetration ** '''Decreasing the frequency increases the depth of penetration''' and decreases the resolution ** '''The commonly used 7-MHz transducer''' produces a high-resolution image with a focal range from 1-4 cm from the transducer '''(best for peripheral zone where most cancers arise)''' ** Lower frequency tr...")
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Grayscale Trans-Rectal Ultrasound (TRUS)

  • Probe frequency
    • Increasing the frequency increases the resolution and decreases the depth of penetration
    • Decreasing the frequency increases the depth of penetration and decreases the resolution
    • The commonly used 7-MHz transducer produces a high-resolution image with a focal range from 1-4 cm from the transducer (best for peripheral zone where most cancers arise)
    • Lower frequency transducers (e.g., older 4-MHz transducers) have a focal range from 2-8 cm but at lower resolution
  • General urological uses of a TRUS (5):
    1. Assess prostate volume
    2. Locate focal prostate abnormalities
    3. Assess for obstructive cause of infertility (dilated seminal vesicles secondary to ejaculatory duct obstruction)
    4. Guide prostate biopsies
    5. Guide placement of brachytherapy seeds

TRUS Anatomy of the Prostate

  • Traditionally described based on a pathologic zonal architecture:
    • Anterior fibromuscular stroma (FS), which is devoid of glandular tissue
    • Transition zone (TZ)
    • Central zone (CZ)
    • Periurethral zone
    • Peripheral zone (PZ)
    • CZ and PZ cannot be distinguished from each other on US, and are often collectively referred to as the PZ on TRUS
    • The TZ is generally hyperechoic compared to the CZ and PZ
    • Click here for image
    • See video on GU Sonography of the Urinary Bladder, Scrotum & Prostate
  • Calcifications along the surgical capsule, known as the corpora amylacea, highlight the plane between the PZ and TZ (multiple diffuse calcifications are a normal, often incidental finding and represents a result of age rather than a pathologic entity)
  • Estimating Prostate Volume
    • Most formulas assume that the gland conforms to an ideal geometric shape: either an ellipse (π/6 × transverse diameter × AP diameter × longitudinal diameter), sphere (π/6 × transverse diameter3), or a prolate (eggshaped) spheroid (π/6 × transverse diameter2 × AP diameter).
      • All formulas reliably estimate gland volume and weight, with correlation coefficients > 0.90 with radical prostatectomy specimen weights, because 1 cm3 = approximately 1 g of prostate tissue.
      • Planimetry is the most accurate means of volume measurement by US
        • Planimetry allows for variation in shape as the area is calculated in consecutive ultrasonographic cross-sections. The area is multiplied with the distance between the cross-sections and the total volume is determined by summation of all contributions.§