Peter Acher

Indications, results and safety profile of transperineal sector biopsies (TPSB) of the prostate: a single centre experience of 634 cases

To describe a protocol for transperineal sector biopsies (TPSB) of the prostate and present the clinical experience of this technique in a UK population.

Diagnostic accuracy of magnetic resonance imaging (MRI) prostate imaging reporting and data system (PI-RADS) scoring in a transperineal prostate biopsy setting

To determine the sensitivity and specificity of multiparametric magnetic resonance imaging (mpMRI) for significant prostate cancer with transperineal sector biopsy (TPSB) as the reference standard.

TOWARDS A RATIONAL STRATEGY FOR THE SURVEILLANCE OF PATIENTS WITH LYNCH SYNDROME (HEREDITARY NON―POLYPOSIS COLON CANCER) FOR UPPER TRACT TRANSITIONAL CELL CARCINOMA

© 2 0 1 0 T H E A U T H O R S 3 0 0 J O U R N A L C O M P I L A T I O N

Using combined x-ray and MR imaging for prostate I-125 post-implant dosimetry : phantom validation and preliminary patient work

Post-implantation dosimetry is an important element of permanent prostate brachytherapy. This process relies on accurate localization of implanted seeds relative to the surrounding organs. Localization is commonly achieved using CT images, which provide suboptimal prostate delineation. On MR images, conversely, prostate visualization is excellent but seed localization is imprecise due to distortion and susceptibility artefacts. This paper presents a method based on fused MR and x-ray images acquired consecutively in a combined x-ray and MRI interventional suite. The method does not rely on any explicit registration step but on a combination of system calibration and tracking. A purpose-built phantom was imaged using MRI and x-rays, and the images were successfully registered. The same protocol was applied to three patients where combining soft tissue information from MRI with stereoscopic seed identification from x-ray imaging facilitated post-implant dosimetry. This technique has the potential to improve on dosimetry using either CT or MR alone.

Comparison of Combined X-Ray Radiography and Magnetic Resonance (XMR) Imaging–Versus Computed Tomography–Based Dosimetry for the Evaluation of Permanent Prostate Brachytherapy Implants

PURPOSE To present a method for the dosimetric analysis of permanent prostate brachytherapy implants using a combination of stereoscopic X-ray radiography and magnetic resonance (MR) imaging (XMR) in an XMR facility, and to compare the clinical results between XMR- and computed tomography (CT)-based dosimetry. METHODS AND MATERIALS Patients who had received nonstranded iodine-125 permanent prostate brachytherapy implants underwent XMR and CT imaging 4 weeks later. Four observers outlined the prostate gland on both sets of images. Dose-volume histograms (DVHs) were derived, and agreement was compared among the observers and between the modalities. RESULTS A total of 30 patients were evaluated. Inherent XMR registration based on prior calibration and optical tracking required a further automatic seed registration step that revealed a median root mean square registration error of 4.2 mm (range, 1.6-11.4). The observers agreed significantly more closely on prostate base and apex positions as well as outlining contours on the MR images than on those from CT. Coefficients of variation were significantly higher for observed prostate volumes, D90, and V100 parameters on CT-based dosimetry as opposed to XMR. The XMR-based dosimetry showed little agreement with that from CT for all observers, with D90 95% limits of agreement ranges of 65, 118, 79, and 73 Gy for Observers 1, 2, 3, and 4, respectively. CONCLUSIONS The study results showed that XMR-based dosimetry offers an alternative to other imaging modalities and registration methods with the advantages of MR-based prostate delineation and confident three-dimensional reconstruction of the implant. The XMR-derived dose-volume histograms differ from the CT-derived values and demonstrate less interobserver variability.

High-intensity focused ultrasound for treating prostate cancer.

Animal studies using the highly metastatic Dunning R3327 model in rats showed that HIFU could be used to destroy prostatic carcinoma without causing metastasis [2,3]. Subsequent canine studies showed that foci could be applied transrectally to the prostate without damaging the rectal wall [4]. Initial in vivo human studies showed defined margins of tissue necrosis in benign tissue before a Millin prostatectomy [5], and studies on cancerous prostates several days before radical prostatectomy showed delineated areas of coagulative necrosis in the treated areas [6,7]. HIFU is repeatable, and it is not uncommon for more than one treatment session to be needed for a satisfactory response. The gland must be small enough for the anterior part to be reached by the lesion ( < 40–50 mL), and with no large calcifications ( > 5 mm) that might interfere with the ultrasound signal.

Prostate biopsy: will transperineal replace transrectal?

Contemporary data concerning the outcomes of transrectal biopsy are available from 1000 participants in the ProtecT study [2]. Fever was reported in 18% of men, and 1.3% of men were admitted to hospital. A fifth of men stated that having a further biopsy would be a moderate or major problem, largely because of pain and infective complications – an important statistic in view of the quoted 38% rebiopsy rate within 5 years. A recent focus group at our unit highlighted patient concerns with the uncertainties associated with transrectal biopsy: a negative result is commonly misleading and the misclassification of low-risk disease may lead to the undertreatment of a third of men or overtreatment of the remainder [3].

Positive visualization of implanted devices with susceptibility gradient mapping using the original resolution

In magnetic resonance imaging, implantable devices are usually visualized with a negative contrast. Recently, positive contrast techniques have been proposed, such as susceptibility gradient mapping (SGM). However, SGM reduces the spatial resolution making positive visualization of small structures difficult. Here, a development of SGM using the original resolution (SUMO) is presented. For this, a filter is applied in k‐space and the signal amplitude is analyzed in the image domain to determine quantitatively the susceptibility gradient for each pixel. It is shown in simulations and experiments that SUMO results in a better visualization of small structures in comparison to SGM. SUMO is applied to patient datasets for visualization of stent and prostate brachytherapy seeds. In addition, SUMO also provides quantitative information about the number of prostate brachytherapy seeds. The method might be extended to application for visualization of other interventional devices, and, like SGM, it might also be used to visualize magnetically labelled cells. Magn Reson Med, 2011.

An analysis of intraoperative versus post-operative dosimetry with CT, CT-MRI fusion and XMR for the evaluation of permanent prostate brachytherapy implants.

BACKGROUND AND PURPOSE To assess the agreement between intraoperative and post-operative dosimetry and to identify factors that influence dose calculations of prostate brachytherapy implants. MATERIALS AND METHODS Patients treated with prostate brachytherapy implants underwent post-operative CT and XMR (combined X-ray and MR) imaging. Dose-volume histograms were calculated from CT, XMR and CT-MR fusion data and compared with intraoperative values for two observers. Multiple linear regression models assessed the influences of intraoperative D90, gland oedema, gland volume, source loss and migration, and implanted activity/volume prostate on post-operative D90. RESULTS Forty-nine patients were studied. The mean D90 differences (95% confidence limits) between intraoperative and post-operative CT, XMR and CT-MR fusion assessments were: 11 Gy (-22, 45), 18 Gy (-13, 49) and 20 Gy (-17, 58) for Observer 1; and 15 Gy (-34, 63), 13 Gy (-29, 55) and 14 Gy (-27, 54) for Observer 2. Multiple linear regression modelling showed that the observed oedema and intraoperative D90 were significant independent variables for the prediction of post-operative D90 values for both observers using all modalities. CONCLUSION This is the first study to report Bland-Altman agreement analysis between intraoperative and post-operative dosimetry. Agreement is poor. Post-operative dosimetry is dependent on the intraoperative D90 and the subjectively outlined gland volume.

Demonstration of erectile management techniques to men scheduled for radical prostatectomy reduces long‐term regret: a comparative cohort study

Study Type – Outcomes (case series)