Editing Prostate Biopsy

== 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):'''
*# '''Assess prostate volume'''
*# '''Locate focal prostate abnormalities'''
*# '''Assess for obstructive cause of infertility''' (dilated seminal vesicles secondary to ejaculatory duct obstruction)
*# '''Guide prostate biopsies'''
*# '''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.§