Multiparametric-magnetic resonance imaging (mp-MRI) of the prostate and Urolift: Identifying artefact size, location and clinical implications

Abstract

Objectives: We sought to define the degree of artefact caused by prostatic urethral lift (PUL) on multiparametric-magnetic resonance imaging (mp-MRI) to determine the location, size of artefact and if the device could potentially obscure a diagnosis of prostate cancer.

Methods: Ten patients were prospectively enrolled to undergo PUL for treatment of benign prostatic hyperplasia and follow-up imaging. A standard mp-MRI protocol using a 3.0 Tesla scanner was performed prior to and following Urolift insertion. Pre- and post-PUL images were compared to measure maximum artefact diameter around each implant in each MRI parameter. A transverse relaxation time weighted (T2) artefact reduction protocol was also evaluated. The location of each artefact was then compared to a separate database of 225 consecutive patients who underwent magnetic resonance guided prostate biopsies.

Results: Artefact occurred around the stainless steel urethral implant component only. Mean T2 artefact maximum diameter was 7.7 mm (sd = 1.71 mm), with an artefact reduction protocol reducing this to 5.4 mm (sd = 1.43). Mean dynamic-contrast-enhancement artefact was 10 mm (sd = 2.5 mm), and mean diffusion-weighted-imaging artefact was 28.2 mm (sd = 7.8 mm). All artefacts were confined to the posterior transition zone only. In the 225 consecutive patients who had undergone magnetic resonance guided prostate biopsies, there were 55 positive biopsies with prostate cancer, with 13 cases found in the transition zones and no cancer identified solely in the posterior transitional zone.

Conclusions: The stainless steel urethral component of the PUL does cause artefact, which is confined to the posterior transition zone only. PUL artefact occurs in an area of the prostate that has a very low incidence of a single focus of prostate cancer. If there is concern for prostate cancer in the posterior TZ (e.g. if every other area is clear with a high PSA), this area can undergo targeted biopsy.

Keywords: artefacts; magnetic resonance imaging; minimally invasive surgical procedures; prostatic hyperplasia; prostatic urethral lift.

FIGURE 1

Axial Plane. Horizontal line at the confluence of Peripheral Zone and Transition Zone joining the tips of the Peripheral Zone anteriorly (yellow line). Anterior to the yellow line is the Anterior Transition Zone, posterior to the yellow line is the Posterior Transition Zone. The Peripheral Zone appears much brighter and is easily seen on the T2 phase. Figure 2B ‐ Sagittal Plane midline position. Line from the anterior urethra to the distal extension of the Peripheral Zone (yellow line). Anterior Transition Zone is outlined in pink. Posterior Transition Zone is outlined in green. Peripheral Zone is outlined in blue. [Correction added on 19 June 2024, after first online publication: Figure 1 caption has been corrected.]

FIGURE 2

Multiparametic Magnetic Resonance Imaging Pre and Post PUL insertion. Artifact can be appreciated particularly in the T2 phase and DCE phases as dark areas (white arrows). [Correction added on 19 June 2024, after first online publication: Figure 2 caption has been corrected.]