You are in: eMedicine Specialties > Urology > Urologic Imaging Transrectal Ultrasonography (TRUS) of the ProstateArticle Last Updated: May 1, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 11
 
Author: Sugandh Shetty, MD, Consulting Staff, Department of Urology, William Beaumont Hospital Sugandh Shetty is a member of the following medical societies: American Urological Association Editors: Martha K Terris, MD, FACS, Professor, Department of Surgery, Medical College of Georgia; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Martin I Resnick, MD †, Former Lester Persky Professor and Chair, Department of Urology, Former Professor, Department of Oncology, Case Western Reserve University School of Medicine; J Stuart Wolf, Jr, MD, FACS, David A Bloom Professor of Urology, Director, Division of Minimally Invasive Urology, Department of Urology, University of Michigan Medical Center; Bradley Fields Schwartz, DO, FACS, Associate Professor of Urology, Director, Center for Laparoscopy and Endourology, Department of Surgery, Southern Illinois University School of Medicine Author and Editor Disclosure Synonyms and related keywords: transrectal ultrasonography, prostatic ultrasonography, prostatic sonogram, prostatic sonography, prostatic echography, prostate ultrasound, prostate echography, transrectal ultrasound, TRUS, transrectal sonography, transrectal prostate ultrasound, prostate sonography, transrectal prostate sonography, prostate imaging, cryotherapy, prostate cancer, brachytherapy, carcinoma of the prostate, CAP, CAP diagnosis, azoospermia evaluation, ejaculatory cysts, seminal vesicular cysts, müllerian cysts, müllerian cysts, utricular cysts, prostate volume determination, benign prostatic hyperplasia, BPH, guided needle biopsy, neurogenic bladder, color Doppler scanning, contrast-enhanced prostate biopsy, intermittent ultrasonography, harmonic ultrasonography, intermittent ultrasound, harmonic ultrasound, high-intensity focused ultrasonography, high-intensity focused ultrasound, HIFU INTRODUCTION AND HISTORYSection 2 of 11
 
The use of sound waves to detect distant objects based on their reflective properties became popular after World War II. In medicine, the initial use of ultrasound waves was in the detection of brain tumors. In urology, ultrasound waves were first used to detect renal stones during surgery. While the early application of ultrasonography in medicine involved sound-wave generators, cathode-ray tubes, Polaroid photography, or 35-mm film recording, the invention of the silicone microchip gave birth to the modern ultrasonography revolution. Early investigators in prostatic ultrasonography included Hiroki Watanabe, William Boyce, Brian Peeling, and Hans Henrik Holm. These investigators conducted early experiments with ultrasound probes and recording devices. Improvements in gray-scale ultrasound display and multiplanar scanning have resulted in user-friendly hand-held probes that can be used by clinicians. One of the earliest devices was a chair-type apparatus with a probe mounted in the center of the chair. The patient sat on the probe, which was guided into the rectum. Earlier studies concentrated on the ultrasonic appearances of prostate abnormalities such as benign prostatic hyperplasia (BPH), carcinoma of the prostate (CAP), prostatitis, prostatic abscess, and prostatic calculi. Since the introduction of the prostate-specific antigen (PSA) screening test and early detection of prostate cancer, the role of transrectal ultrasonography (TRUS) has changed; it is mainly used to visualize the prostate and to aid in guided needle biopsy. ANATOMY AND INTERNAL STRUCTURE OF THE PROSTATE GLANDSection 3 of 11
Overview of Prostate AnatomyThe adult prostate is a chestnut-shaped organ enveloped in a fibrous capsule. The base of the prostate is attached to the bladder neck, and the apex is fixed to the urogenital diaphragm. The prostatic urethra traverses the gland. The verumontanum is a longitudinal ridge in the prostatic apex on which the ejaculatory ducts open. The prostate is located superiorly and posteriorly to the seminal vesicles. The ampullae of the vas deferens run medial to the seminal vesicles along the posterior surface of the prostate. Anteriorly, the fibrous capsule thickens at the level of the apex to form puboprostatic ligaments, which attach the prostate to the back of the symphysis pubis. The dorsal venous complex (ie, Santorini plexus) runs along the puboprostatic ligaments. The prostate gland lies beneath the endopelvic fascia. Posteriorly, the 2 layers of Denonvilliers fascia separate the prostate from the rectum. The rectourethralis muscle attaches the rectum to the prostatic apex. A rich plexus of veins encompasses the prostate gland between the true fibrous capsule of the gland and the lateral prostatic fascia; these are visible landmarks on sonograms. The neurovascular bundles run craniocaudally along the posterolateral aspects of the prostate. The prostate gland is supplied by the prostatic artery, which is usually a branch of the inferior vesical artery. The prostate is divided into a urethral branch, which supplies the adenoma, and a capsular branch. Venous drainage from the prostate moves into the Santorini plexus and eventually into the internal iliac vein. The prostatic venous plexus communicates freely with the extradural venous plexus (ie, Batson plexus), which is thought to be factor in the spread of prostate cancer. Initially, lymphatic drainage of the prostate is into the obturator lymph nodes and into the hypogastric chain. The nerve supply to the prostate is both sympathetic, from the hypogastric plexus (L1-2), and parasympathetic, from the pelvic nerve (nervi erigentes, S2-S4). Although the cavernous nerves run along the posterior aspect of the prostate, the 2 distinct areas from which prostatic nerves leave the gland are thought to be the superior and inferior pedicles. These areas are the first sites of extraprostatic spread of cancer. Internal Architecture and Anatomy of the ProstateAccording to the classic work by McNeal, the prostatic urethra, which is the main reference point of the prostate, divides the gland into an anterior fibromuscular stroma and a posterior glandular organ. The urethra angulates 35° anteriorly in the proximal portion of the prostate. The ejaculatory ducts run in the same plane as the distal prostatic urethra to join the verumontanum. Lowsley's concept of a 5-lobed prostate has been replaced by McNeal's concept of zonal architecture. The prostate has 4 glandular zones, each with their own ductal system. The peripheral zone, transition zone, and periurethral glands have similar histological appearance and are derived from the urogenital sinus. However, the central zone is histologically distinct and is derived from mesonephric tissues (ie, wolffian tissue). Peripheral zone The peripheral zone constitutes almost 75% of the normal prostate gland. It occupies the distal prostate gland, the area around the urethra distal to the verumontanum. The acini are small, round, and smooth-walled, and their ducts drain distal to the verumontanum into the urethra. The stroma is loosely woven with randomly oriented muscle fibers. Approximately 70% of carcinoma of the prostate (CAP) cases arise in this zone. Central zone The central zone constitutes 25% of the normal prostate and occupies the part of the prostate behind the proximal prostatic urethra. The ejaculatory ducts traverse through the central zone. The acini are large and irregular with significant intraluminal folds and ridges. They are also surrounded by muscular tissue that closely follows the shape of the acini. The central zone is embryologically distinct from other zones and is derived from the mesonephric system (wolffian). Approximately 5-10% of CAP cases arise in this zone. Transition zone The transition zone makes up approximately 5-10% of the normal prostate gland. The transition zone lies on either side of the proximal prostatic urethra lateral to the internal sphincter. The glandular architecture is similar to the peripheral zone; however, the stroma is more compact. The transition zone is where benign prostatic hyperplasia (BPH) originates, and approximately 20% of CAP cases arise in the transition zone. Periurethral glands The periurethral glands comprise less than 1% of the glandular tissue. These glands are embedded in the smooth muscle of the prostatic sphincter. This is the site of origin of the large median lobe of BPH. Anterior fibromuscular stroma The anterior part of the prostate is composed mainly of fibromuscular stroma, which is continuous with detrusor fibers. Toward the apex of the gland, this fibromuscular tissue blends with striated muscle from the levator. Puboprostatic ligaments also blend with this area. Invaginated extraprostatic space As the ejaculatory ducts enter the prostate posteriorly, an invaginated extraprostatic space (IES) surrounds them and invaginates into the prostate. The IES surrounds the ejaculatory ducts, ends at the verumontanum, and communicates with the periurethral space. In 1989, Lee first introduced the concept that invasion of the IES may be the first sign of extraprostatic extension of prostate cancer and an early sign of invasion of seminal vesicles. In 2005, Amin et al evaluated the pathological significance of the invasion of IES in 80 patients with prostate cancer and concluded that IES involvement was consistently seen in cases with seminal vesicle invasion.1 Bladder neck and the internal sphincter The internal sphincter runs from the bladder neck to the level of the verumontanum. The smooth muscle fibers of the sphincter are continuous with the superficial layer of the trigone. In healthy males, the bladder neck and the internal sphincter are closed. In males with a neurogenic bladder, the bladder neck and the prostatic urethra are wide open, and some investigators have used transrectal ultrasonography (TRUS) to monitor the lower urinary tract in patients with spinal injuries. TRANSRECTAL ULTRASONOGRAPHY TECHNIQUESection 4 of 11
Preparation, positioning, and contraindications More than 80% of urologists administer an enema prior to transrectal ultrasonography (TRUS) and prostate biopsy, but some authors feel this is unnecessary. More than 90% of urologists administer oral agents for prophylactic antibiotic coverage. A total of 11 different antibiotics with 20 different dosages and durations of treatment, ranging from 1-17 days, have been reported. Increasing support has been garnered for single-dose prophylaxis in patients with uncomplicated medical conditions. A fluoroquinolone antibiotic prior to the procedure and a second dose 12 hours later is the protocol most commonly recommended for antibiotic coverage. In patients with prosthetic implants or valvular heart disease, additional prophylaxis with 1 g of intramuscular ampicillin (or 1 g IV vancomycin in patients who are allergic to penicillins) and 80 mg of intramuscular gentamicin is recommended. Positioning should be left lateral, lithotomy, or knee-elbow. Contraindications to biopsy include an acute painful perianal disorder and hemorrhagic diathesis. Patients should be discouraged from taking aspirin or nonsteroidal anti-inflammatory drugs for 10 days prior to the procedure, but recent use should not be considered an absolute contraindication to biopsy. Local anesthesia and the procedure Although the procedure was performed without any infiltrative anesthesia in the past it is a common practice to use lidocaine infiltration in the periprostatic area. In 2001, Pareek et al described a technique of periprostatic nerve blockade.2 They injected 2.5 mL of lidocaine on each side at the prostate base at the junction of the prostate and the seminal vesicle (using a 5-in 22-gauge spinal needle through the ultrasound probe). In a randomized, double-blind, placebo-controlled study, they showed significant pain control during and after biopsy. Alavi et al compared the efficacy of intrarectal lidocaine gel with that of periprostatic nerve block and concluded that the nerve block was superior for pain control. Using this technique, saturation biopsies, with up to 20 cores, could be performed. In 2005, Mutaguchi et al reported a comparison of 2 techniques of local anesthesia for prostate biopsy.3 In the periprostatic block technique, 5 mL of 1% lidocaine was injected via a 7-in, 22-gauge spinal needle into the region of the prostatic vascular pedicle just lateral to the junction of seminal vesicles and the prostate. The needle is slowly withdrawn to the prostatic apex, and an additional 5 mL of lidocaine is injected at the apex. In the intraprostatic block technique, 10 mL of 1% lidocaine was injected into 2-3 sites of each prostate lobe. In this study, the intraprostatic block provided superior pain control during the prostate biopsy. Currently, the most widely used probe is a 7-MHz transducer within an endorectal probe, which can produce images in both the sagittal and axial planes. Scanning begins in the axial plane, and the base of the prostate and seminal vesicles are visualized first. A small amount of urine in the bladder facilitates the examination. Seminal vesicles are identified bilaterally, with the ampullae of the vas on either side of the midline. The seminal vesicles are convoluted cystic structures that are darkly anechoic. Men who have abstained from ejaculation for a long period may have dilated seminal vesicles. Next, the base of the prostate is visualized. The central zone comprises the posterior part of the gland and is often hyperechoic. The mid gland is the widest portion of the gland. The peripheral zone forms most of the gland volume. Echoes are described as isoechoic and closely packed. The transition zone is the central part of the gland and is hypoechoic. The junction of the peripheral zone and the transition zone is distinct posteriorly and is characterized by a hyperechoic region, which results from prostatic calculi or corpora amylacea. The transition zone is often filled with cystic spaces in patients with benign prostatic hyperplasia (BPH). Scanning at the level of the verumontanum and observing the Eiffel tower sign (anterior shadowing) help to identify the urethra and the verumontanum. The prostate distal to the verumontanum is composed mainly of the peripheral zone. The capsule is a hyperechoic structure that can be identified all around the prostate gland. Several hypoechoic rounded structures can be identified around the prostate gland. These are the prostatic venous plexi. The position of the neurovascular bundles can often be identified by the vascular structures. Imaging in the sagittal plane allows visualization of the urethra. The median lobes of the prostate are often visualized. Volume measurement Volume assessment of the prostate is an important and integral part of this procedure. Several formulas have been used, the most common of which is the ellipsoid formula, which requires measurement of 3 prostate dimensions. Dimensions are first determined in the axial plane by measuring the transverse and anteroposterior dimension at the estimated point of widest transverse dimension. The longitudinal dimension is measured in the sagittal plane just off the midline because the bladder neck often obscures the cephalad extent of the gland. The ellipsoid volume formula is then applied, as follows:
Biopsy Biopsies are best performed with a spring-driven needle core biopsy device (or biopsy gun), which can be passed through the needle guide attached to the ultrasound probe. Most instrumentation provides optimal visualization of the biopsy needle path in the sagittal plane. In general, 18-gauge needles are used, and the tips of the needles are etched with small ridges or pits to render them more echogenic. Sonograms should be superimposed with a ruled puncture trajectory that corresponds to the needle guide of the probe, which allows anticipation of the needle path. Directed biopsies are obtained from any area deemed as suggestive (ie, hyperechoic) based on ultrasonographic findings or based on palpable abnormalities after digital rectal examination. Because the incidence of nonpalpable isoechoic prostate tumors is high, limiting biopsy sites to either ultrasonographically hypoechoic lesions or to areas of palpable abnormality tends to miss many malignancies. Obtain separate biopsy samples from each sextant of the prostate, which improves the odds of sampling clinically inapparent tumors. Originally, these biopsy sites included the midlobe parasagittal plane at the apex, the mid gland, and the base, bilaterally. Many authors subsequently recommended that (1) these 6 biopsy samples be obtained from the lateral third of each lobe rather than from the mid lobe or that (2) 2 lateral biopsy samples be obtained from each lobe in addition to the original sextant samples (termed the 10-biopsy scheme). Obtaining even larger numbers of biopsy cores has been recommended by some authors to increase the diagnostic sensitivity. Complications of prostate biopsy include hematuria, rectal bleeding, hematospermia, urosepsis, and perineal pain. Although most of these complications subside within 48-72 hours, patients should be warned that hematospermia can last for 3-4 weeks. In rare cases (<1%), patients develop bacteremia that requires hospitalization and administration of intravenous antibiotics. Diagnostic indications include the following:
Therapeutic indications include the following:
Local anesthesia with the above techniques can be used during minimally invasive procedures for BPH, such as transurethral needle ablation of the prostate (TUNA), photoselective evaporation of the prostate (PVP), and interstitial laser coagulation (ILC) of the prostate. Gill has recently reported on the use of TRUS monitoring using Doppler during laparoscopic radical prostatectomy to identify the blood flow in the neurovascular bundles. By identifying and preserving vascular flow, neurovascular bundles can be preserved, which could lead to enhanced postoperative erectile activity. TRANSRECTAL ULTRASONOGRAPHY IN THE EARLY DIAGNOSIS OF PROSTATE CANCERSection 5 of 11
Advances in transrectal ultrasonography (TRUS) coincided with the development of prostate-specific antigen (PSA) testing, the most valuable tumor marker test for carcinoma of the prostate (CAP). PSA levels were found to be abnormal in more than 75% of patients with CAP, and abnormal PSA levels precede symptoms of CAP by several years. Therefore, PSA testing was the logical choice for early diagnosis of CAP. An abnormal PSA level (eg, >4 ng/mL) and/or abnormal digital rectal examination findings (eg, asymmetry, nodule, firmness) became indications for prostate biopsy. TRUS was also evaluated to determine if it could be used for CAP screening. However, lack of specificity made this difficult; CAP lesions appear hypoechoic, hyperechoic, or isoechoic. Therefore, TRUS is used to direct the physician to suggestive areas in the prostate or to perform systematic biopsies. In 2004, Thompson et al reported on the results of the Prostate Cancer Prevention Trial (PCPT), which suggested PSA levels of 2.1-3 ng/mL and PSA levels of 3.1-4 ng/mL correctly predicted prostate cancer in 24% and 27% of cases, respectively.4 This suggests that a significant number of men with PSA levels of 2-4 ng/mL have CAP and should be counseled regarding prostate biopsy. Prostate volume is assessed during the TRUS examination. The decision to perform biopsy in patients with abnormal PSA levels can be bolstered by PSA density (PSAD), which is defined as the PSA level divided by the prostate volume. Sensitivity of PSAD was enhanced by a cut-off value of 1.5. Benign prostatic hyperplasia (BPH) tissue produces one tenth of PSA per gram as compared to cancer tissue; therefore, a large BPH gland indicates an elevated PSA level. CAP is diagnosed in 30% patients with a PSA value of 4-10 ng/mL and in 60% of patients with a PSA value of 10-20 ng/mL. PSAD has been used to decrease the number of prostate biopsies performed. Another concept popularized by Lee is the expected PSA value for a given prostate volume, which can be used to decide if a biopsy should be performed. The volume of the transition zone and the PSAD of the transition zone have also been used to determine the need for biopsy. A PSA value that increases at a velocity greater than 0.75 ng/mL/y has also been used to determine the need for biopsy. The volume of the prostate gland can also be used to determine treatment options. Both perineal prostatectomy and brachytherapy are easier to perform when the gland is smaller than 50 g. In large glands, the anterolateral portion of the gland is behind the pubic arch, and these areas cannot be reached with the perineal brachytherapy needles. Hormonal downsizing is useful in such cases, and TRUS is used to monitor gland size. Measuring prostate volume is also useful in large BPH glands to help decide if transurethral resection or an open procedure is appropriate for prostatectomy. Whether TRUS has a role in staging prostate cancer is debatable. Most early cancers are confined to the organ. Lee and colleagues popularized staging biopsies of the neurovascular bundles and the seminal vesicles. Positive results from biopsy of the neurovascular bundles and seminal vesicles signified extracapsular disease and a poor outcome. However, presently, most information is available on the PSA value and the Gleason score of prostate cancer based on several published nomograms (ie, Partin nomograms). Moreover, biopsy of the periprostatic venous plexus may result from pelvic hematoma. Perineural invasion found on prostate biopsy samples should not be considered an indicator of extraprostatic spread. TRUS can help identify extraprostatic CAP in advanced-stage T3 cases. Brachytherapy Localized prostate cancer can be treated with brachytherapy using permanent radioactive iodine seeds with or without preimplant external beam irradiation (depending on tumor grade). After initial volume assessment, the seeds are placed according to a computer-generated grid under ultrasonographic guidance. To exclude violation of the urethra or bladder, cystoscopic evaluation is necessary at the end of the procedure. Iodine seeds are commonly used; however, palladium seeds are often used to treat more aggressive cancers, usually defined as a Gleason score of higher than 7 and a PSA value of greater than 10 ng/mL. Alternatively, patients with more aggressive tumors may receive high-dose radiation therapy consisting of external beam radiation therapy during the second and the fourth week, with a brachytherapy boost with temporary implants. With temporary seeds, trocars are placed under ultrasonographic guidance according to a computer-generated grid, and the radioactive source is threaded in and out of each of these trocars. TRANSRECTAL ULTRASONOGRAPHY AND CRYOTHERAPY FOR PROSTATE CANCERSection 6 of 11
Gonder and associates were the first to use cryoablation in urological disorders in the 1960s. In 1988, Onik et al used real-time ultrasonography to monitor the freezing process during radical cryoablation of the prostate. Radical cryoablation is defined as the freezing of the entire prostate, periprostatic tissue, neurovascular pedicles, and proximal seminal vesicles. Probes are placed in the prostate gland via the perineum under ultrasonographic guidance, and cryotherapy is begun. The ice ball, which is an anechoic lesion with a hyperechoic edge that can be seen advancing or receding, is directly monitored as it occupies the entire prostate gland. Most centers use a urethral warming device to prevent urethral necrosis. Three types of techniques have been used—single and double freeze-thaw cycles and the pullback freeze technique. A suprapubic catheter is kept in place until the patient is able to void satisfactorily with minimal residual urine. Follow-up biopsies are performed at 6 months, 1 year, and 2 years. Using the current double freeze-thaw technique, Cohen et al reported an 11% positive biopsy rate after 4 years of follow-up, and all positive results occurred in patients with a prostate-specific antigen (PSA) value of greater than 10 ng/mL or tumors at stage T3.5 In 2001, Ghafar et al reported their results on salvage cryotherapy for recurrence after external beam radiation therapy.6 Using an argon-based system, 38 men were treated with the double freeze-thaw technique. The biochemical recurrence-free survival rate using actuarial analysis was 86% at 1 year and 74% at 2 years. Complications included rectal pain in 39.5%, urinary tract infection in 2.6%, incontinence in 7.9%, hematuria in 7.9%, and scrotal edema in 10%. No patients developed rectourethral fistula, urethral sloughing, or retention. Currently, cryotherapy is acceptable as salvage therapy for radiation failures. TRANSRECTAL ULTRASONOGRAPHY IN THE MANAGEMENT OF MALE INFERTILITYSection 7 of 11
Normal seminal vesicle dimensions are 3 cm in length (±0.5 cm), 1.5 cm in width (±0.4 cm), and 13.7 mL in volume (±3.7 mL). Patients with low ejaculate volumes may be evaluated with transrectal ultrasonography (TRUS) to help rule out ejaculatory duct obstruction. Absence of fructose in the semen suggests ejaculatory duct obstruction. The absence of unilateral or bilateral vas deferens is associated with seminal vesicular anomalies, such as cysts and renal agenesis. Seminal vesicular cysts are often associated with a dysplastic kidney that is receiving drainage from an ectopic ureter. Cystic lesions in the prostate are either midline or lateral. Utricular cysts are intraprostatic and midline. Müllerian cysts are large and extraprostatic in the midline. Ejaculatory cysts may be midline or paramedian. TRUS can be used to deroof ejaculatory cysts. TRANSRECTAL ULTRASONOGRAPHY TO EVALUATE FOR NEUROGENIC BLADDERSection 8 of 11
High-resolution images of the bladder neck and the proximal urethra obtained using transrectal ultrasonography (TRUS) have been used to monitor patients with spinal cord injuries or neurogenic bladder. While the sector or electronic ultrasound transducers offer better visualization of the prostate when investigating for cancer, benign prostatic hyperplasia (BPH), and infertility, linear array scanners are more suitable for imaging as part of a neurological evaluation. Linear array scanners allow simultaneous sagittal imaging of the bladder, bladder neck, prostate, external sphincter, and proximal bulbar urethra. This imaging technique is usually performed in conjunction with urodynamic testing. In patients with detrusor-sphincter dyssynergia, the bladder neck is open when the bladder is at rest and can be seen to close with bladder contraction. Patients on intermittent catheterization can develop a ledge of tissue at the bladder neck from chronic trauma and bladder irritation. Using TRUS to determine prostate volume in these patients can help distinguish outlet obstruction from BPH and/or detrusor-sphincter dyssynergia. FUTURE APPLICATIONSSection 9 of 11
Color Doppler scanning Color Doppler has been used to enhance the diagnosis of carcinoma of the prostate (CAP) as an adjunct to transrectal ultrasonography (TRUS). Several investigators have demonstrated that the addition of color Doppler improved prostate biopsy finding specificity. However, differentiating a focus of prostatitis from cancer was difficult. The addition of power Doppler was not advantageous. Contrast-enhanced prostate biopsy The use of microbubble contrast agents can enhance gray-scale imaging and Doppler imaging. Newer agents that remain in the vascular compartment have been used for prostate imaging. EchoGen, Levovist, Imavist, Echovist, DMP 115, and NC100-100 are the agents that are currently available. Several investigators have evaluated contrast-enhanced prostate ultrasonography. Using EchoGen, Ragde and colleagues studied 15 patients with rising prostate-specific antigen (PSA) levels and previous negative biopsy findings.7 Only 2 of the 8 patients with abnormal vascular patterns were diagnosed with cancer. Similarly, Watanabe and colleagues studied 9 cases in which Levovist was used and demonstrated enhanced images of all cancers. Halpern and colleagues evaluated 26 patients with elevated PSA levels and found significant image enhancement after using Imavist.8 However, the extra cost of this technique may be the limiting factor in its widespread use. Intermittent and harmonic ultrasonography Conventional ultrasonography destroys the microbubbles of the contrast agents used in ultrasonographic imaging. Intermittent ultrasonography increases the enhancement provided by the contrast agents. In harmonic imaging, the reverberations produced by the contrast agent are visualized at a different frequency than the insonating frequency, which can provide a better image. High-intensity focused ultrasound Using extracorporeal high-intensity focused ultrasound (HIFU), temperatures of greater than 60°C can be achieved in the target tissue. The prostate can be easily treated with this modality via a transrectal probe. The size of the thermal lesion can be controlled by the power and the duration of the ultrasound pulse. Higher in situ intensities (>3055 W/cm2) create the cavitation phenomenon and bubble effect, which are difficult to monitor. The currently available HIFU devices use transducers with 3-4 MHz. Experimental studies have shown core temperatures of 75°C with a peak of 99°C during insonification. Gelet et al pioneered the use of transrectal HIFU in the treatment of prostate cancer.9 Currently, the procedure is used in In a multicenter trial of 402 patients treated with HIFU, the median duration for catheter use was 5 days.10 Nine percent experienced prolonged retention, and 3.6% developed urethral strictures. Incontinence following HIFU was rare (0.6%). Rectourethral fistula developed in 1.2% of the patients. Complication rates are higher with salvage HIFU after radiation therapy, radical prostatectomy, or HIFU. Erectile function can be preserved in 20-46% of patients who undergo only one session of HIFU. After a minimum follow-up period of 6 months, Thuroff et al reported negative biopsy results in 87% of patients and a median nadir PSA level of 0.4 ng/mL. Gelet at al reported that 78% of low-risk patients were disease-free and had negative biopsy results at an actuarial 5-year follow-up. Gelet et al has also reported salvage HIFU after failed radiation in 71 patients. Among these patients, biopsy results were negative in 80%, and 61% had a PSA level nadir of less than 0.5 ng/mL. The complications following salvage HIFU were higher; 6% developed total incontinence, 6% developed rectourethral fistula, and 17% developed vesical neck contracture.11 MULTIMEDIASection 10 of 11
REFERENCESSection 11 of 11
Transrectal Ultrasonography (TRUS) of the Prostate excerpt Article Last Updated: May 1, 2008 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
