Speckle-initialized dynamic segmentation of the prostate

Echography is a commonly used modality for prostate imaging. Prostate segmentation is the first step in analyzing echographic prostate images. Because of the nature of these images, traditional local image processing operators are inadequate for finding the prostate boundary. Most automated segmentations described in literature require user interaction for contour initializing or editing. Also shape templates are applied as prior knowledge. In this paper, an automatic segmentation method is presented, based on prostate specific image granulation and image intensity. First, a granulation detector is used to extract granulation. Subsequently, the Hessian is adopted to evaluate granulation shape and intensity for the extraction of the prostate-specific dot pattern. This dot pattern is used to construct the contour initialization. A smooth contour model (discrete dynamic contour; DDC) is evolved from this initialization to the final contour. The guiding vector field for the DDC deformation is the gradient vector flow field calculated from an edge map of the original image. The scale of the relevant edges (large compared to granulation) is estimated from the prostate-specific dot pattern. Comparison of automated segmentations with clinical expert manual segmentations reveals a mean sensitivity and accuracy of 0.90 and 0.93, respectively.

Transrectal contrast enhanced ultrasound for diagnosis of prostate cancer

The diagnosis of prostate cancer is based on histology. Prostate biopsies are obtained based on the triad of prostate specific antigen (PSA), digital rectal examination (DRE) and transrectal ultrasound. Because prostate biopsies still have a large percentage of negative outcomes, patient selection and biopsy direction need improvement. This paper describes the recent improvements in prostate cancer imaging, especially contrast-enhanced transrectal ultrasound.

[Advances in the ultrasound diagnosis of prostate cancer]

OBJECTIVES

Ultrasound guided biopsies are the mainstay in the diagnosis of prostate cancer. With the aim of improving diagnostic performances different protocols of prostate biopsy have been designed. The addition of vascular contrasts to the ultrasound allows for identification of hypervascular regions more likely to be cancer. The new ultrasound modalities enhance contrast signal and specifically differentiate its signal from the tissue reflections.

METHOD

A non structured review of the literature was conducted on the utility of the different ultrasound modalities and types in targeting the biopsies of the prostate.

RESULTS

There are four types of ultrasound guided biopsies of the prostate: ultrasound guided biopsy of hypoechoic nodes, systematic biopsy protocols, Doppler guided biopsy and Contrast Enhanced Doppler guided biopsy. In spite of the broad literature only few series possess a methodologically correct design related to the use of reference standards. The diagnostic performance of each one of the different types of biopsy varies widely. Sensitivity and specificity of ultrasound guided biopsy of hypoechoic nodes depends on the type of population included in the study but in general its positive predictive value is low. The protocols of systematic biopsy increase the sensitivity of the prostate biopsy but still specificity is low. The Doppler techniques offer a marginal benefit. Contrast Enhanced Doppler guided biopsies series have reported only a slightly increase in sensitivity and a significant improvement of the odds risk for diagnostic of prostate cancer. New arising ultrasound modalities present with promising preliminary results.

CONCLUSIONS

Ultrasound guided biopsy have an acceptable sensitivity in the diagnosis of prostate cancer, however specificity is overall low. Among the different ultrasound techniques only Contrast Enhanced Ultrasound improves significantly the diagnostic risk of the biopsy although the sensitivity remains quite stable. New specific contrast ultrasound techniques are currently under investigation.

Cryotherapy for renal-cell cancer: diagnosis, treatment, and contrast-enhanced ultrasonography for follow-up

Cryotherapy is a curative treatment option for patients with small (<4 cm) renal-cell cancers. For the followup of ablated lesions, imaging is the only available method, but the best tool has not yet been determined. The method selected should be able to determine the presence or absence of perfusion in the area and measure the lesion. Usually, contrast-enhanced CT or MRI is used. The accompanying video shows cryotherapy treatment along with contrast-enhanced ultrasound investigations before and afterward. We used a Siemens Acuson Sequoia device with contrast pulse sequence imaging and Sonovue (Bracco) as the contrast agent. The lesion could be identified and measured easily. Because this method enables selective detection of contrast, the presence and absence of perfusion can be determined objectively.

The Bell-Shaped Nitinol Prostatic Stent in the Treatment of Lower Urinary Tract Symptoms: Experience in 108 Patients

OBJECTIVES

To assess the efficacy, safety, and durability of the bell-shaped nitinol prostatic stent in the treatment of moderate to severe lower urinary tract symptoms caused by benign prostatic enlargement in otherwise healthy patients.

METHODS

Stents were inserted in an outpatient setting under local anaesthesia. Assessments included maximum urinary flow (Qmax), postvoid residual (PVR) urine volume, International Prostate Symptom Score (IPSS), including quality of life (QoL) item, at baseline and follow-up visits.

RESULTS

108 men were enrolled in the trial. Stents were successfully inserted in 97% of the patients. Spontaneous voiding was achieved in all patients. After one month Qmax (+3.7 ml/s), PVR (-99 ml), IPSS (-12) and QoL (-1.7) all showed statistically significant improvements compared to baseline. Substantial improvements, however, were maintained for only one to two months. The main complications were haematuria (19%), urge incontinence (22%), and migration (15%). The median indwelling time was 105 days. The main reason for removal of stents was worsening of symptoms, which might be attributable to the tilting of stents within the prostatic urethra, found upon removal.

CONCLUSIONS

Insertion of the bell-shaped nitinol prostatic stent temporarily improves voiding parameters and symptom scores. Because of the limited durability, however, the bell-shaped prostatic stent is not suitable for clinical practice.

[Laparoscopic assisted cryoablation of small renal masses]

AIMS

To review the current status of cryoablation of small renal masses and to preliminary report our experience at the AMC.

MATERIAL AND METHODS

A bibliographic search was conducted (PubMed/Medline/Embase) and the most important series were analyzed. Our series includes 13 patients with a solitary small renal mass treated by Laparoscopic assisted Cryoblation with fine cryoprobes (1,5 cm diameter). Postoperative follow-up was done by means of CT and/or MRI every three months during the first year and every 6 months during the second year.

RESULTS

There are no randomized trials comparing Cryoblation of renal masses (<4 cm diameter) with either radical surgery or partial nephrectomy but only case series. Complication rate is low as it is the recurrence or persistence rate in most of the series but one referring to radiologically guided Cryoablation (8%). The maximal diameter of the masses treated in our series were 3,2 cm. Tumors were approached retro or transperitoneally depending on their localization in the kidney. Average surgical time were 208 minutes (108-379) and average time of exposition to temperatures lower than -20 degrees C in the tumor periphery was 10 minutes. AT a mean follow-up of 8 months no tumoral recurrence were objectivated.

CONCLUSIONS

Cryoablation of small renal masses may be an acceptable alternative of treatment although mean follow-up is still short in all the series.

LONG-TERM FUNCTIONAL AND URODYNAMIC RESULTS OF 50 PATIENTS RECEIVING A MODIFIED SIGMOID NEOBLADDER CREATED WITH A SHORT DISTAL SEGMENT

PURPOSE

We assessed the long-term functional and urodynamic outcomes of a modified sigmoid neobladder.

MATERIALS AND METHODS

A total of 50 patients received a sigmoid neobladder with a short distal segment after radical cystoprostatectomy. Patients were followed at 3-month intervals the first year and every 6 months thereafter. Continence and voiding patterns were assessed using questionnaires and interview. The International Continence Society classification was used after 1996. Urodynamic assessment was performed 3 times during followup.

RESULTS

Mean sigmoid segment length +/- SD was 18 cm (+/- 2.8). Mean followup was 38 months (+/- 24.8). Ureter stricture and reflux were present in 8% and 17% of the reimplanted units, respectively. Mean creatinine serum levels did not change after surgery and remained stable during followup. At 2 years 89% of the patients were continent in the daytime and 90% had good or satisfactory daytime continence according to the International Continence Society classification. At 3 years 77% of the patients voided every 3 or 4 hours during the day. Nighttime continence was poor. Only 10% of the patients complied with an alarm program. Mean maximal capacity of the reservoir was 300 ml and remained stable during followup. Mean intrareservoir pressure at maximal capacity decreased from 61 to 51 cm H2O from the first to the third urodynamic evaluation. No patient required clean intermittent catheterization.

CONCLUSIONS

This modified sigmoid neobladder offers good daytime continence with low post-void residual and adequate daytime micturition frequency. Nighttime continence is poor. The presence of high intrareservoir pressures did not impair renal function.

The methodology of corpus cavernosum electromyography revisited

OBJECTIVE

The methodology of corpus cavernosum electromyography (CC-EMG) was revisited, in order to overcome current methodological difficulties that hinder its clinical application.

MATERIALS AND METHODS

Using an 8-channel device, CC-EMG was performed in 12 healthy volunteers. Surface electrodes were placed bilaterally on the penile shaft and the kneecap (reference electrode), the pubis region and the anterior superior iliac spine (ASIS). A band pass filter with cut-off frequencies of 0.1 and 20 Hz was used. At least 2 sessions of recordings were performed in each subject.

RESULTS

Thirty-five of 46 recordings were interpretable. Significant time delays between potentials recorded from different sites of the CC were detected. Clear spatial voltage gradients related to CC-potentials were observed on the pubis region. No voltage changes related to CC-potentials, but electrical activity from other sources were recorded from the ASIS. In contrast to frequency, a clear correlation could be demonstrated between amplitude, duration and polyphasity of CC-potentials recorded in 2 different sessions in the same individual.

CONCLUSIONS

Multichannel monopolar recording of CC-EMG with surface electrodes is practical and has several advantages compared with bipolar recording. The results provide evidence that the recorded signals indeed reflect electrical activity of the CC and therefore offer a basis to pursue further clinical validation studies.

The value of corpus cavernosum electromyography in erectile dysfunction: current status and future prospect

In the last decade, several investigators have tried to develop corpus cavernosum electromyography (CC-EMG) as a direct clinical method to evaluate the state of the penile autonomic innervation and the cavernous smooth muscle. Both basic and clinical studies have shown promising results. However, its application as a diagnostic tool with clinical relevance was hindered by insufficient knowledge of cavernous smooth muscle electrophysiology, lack of standardization, technical and practical difficulties and problems in the interpretation of the results. Recently, the European Commission created the so-called COST Action B18 (corpus cavernosum EMG in erectile dysfunction), aiming to strengthen the coordination of the European research groups and give the development of CC-EMG a new impetus. This review presents an overview of the physiological background, the current status of CC-EMG, and discusses possibilities for further developments.

Penile duplex pharmaco-ultrasonography revisited: revalidation of the parameters of the cavernous arterial response

PURPOSE

We revalidate parameters of the cavernous arterial response (peak systolic blood flow velocity) and acceleration time using penile duplex pharmaco-ultrasonography.

MATERIALS AND METHODS

Blood flow velocity in the cavernous artery following pharmaco-stimulation was determined with duplex ultrasonography in 106 patients with erectile dysfunction. Intima media thickness of the common carotid artery, a valid index for atherosclerosis and clinical diagnosis based on a comprehensive evaluation were used as references. The clinical diagnosis was used to determine cutoff values. For the statistical analysis, Pearson correlation and ROC curves were used.

RESULTS

When correlating peak systolic velocity and acceleration time to intima media thickness, acceleration time (r = 0.51, p <0.01) was the most valid parameter to detect cavernous atherosclerotic pathology (peak systolic velocity r = -0.18, p = 0.12). This finding was confirmed by a comparison of both parameters to the clinical diagnosis. AUC was 0.59, 95% CI 0.49-0.69 for peak systolic velocity and 0.72 (95% CI 0.62-0.80 for acceleration time). The cutoff point for acceleration time to discriminate between atherosclerotic and nonatherosclerotic erectile dysfunction was determined at acceleration time 100 milliseconds or greater. Sensitivity was 66% and specificity was 71%.

CONCLUSIONS

The results of this study show that acceleration time has more power than peak systolic velocity to diagnose atherosclerotic erectile dysfunction.

Penile duplex pharmaco-ultrasonography revisited: revalidation of the parameters of the cavernous arterial response

PURPOSE

We revalidate parameters of the cavernous arterial response (peak systolic blood flow velocity) and acceleration time using penile duplex pharmaco-ultrasonography.

MATERIALS AND METHODS

Blood flow velocity in the cavernous artery following pharmaco-stimulation was determined with duplex ultrasonography in 106 patients with erectile dysfunction. Intima media thickness of the common carotid artery, a valid index for atherosclerosis and clinical diagnosis based on a comprehensive evaluation were used as references. The clinical diagnosis was used to determine cutoff values. For the statistical analysis, Pearson correlation and ROC curves were used.

RESULTS

When correlating peak systolic velocity and acceleration time to intima media thickness, acceleration time (r = 0.51, p <0.01) was the most valid parameter to detect cavernous atherosclerotic pathology (peak systolic velocity r = -0.18, p = 0.12). This finding was confirmed by a comparison of both parameters to the clinical diagnosis. AUC was 0.59, 95% CI 0.49-0.69 for peak systolic velocity and 0.72 (95% CI 0.62-0.80 for acceleration time). The cutoff point for acceleration time to discriminate between atherosclerotic and nonatherosclerotic erectile dysfunction was determined at acceleration time 100 milliseconds or greater. Sensitivity was 66% and specificity was 71%.

CONCLUSIONS

The results of this study show that acceleration time has more power than peak systolic velocity to diagnose atherosclerotic erectile dysfunction.

Correlation of transrectal ultrasound, computer analysis of transrectal ultrasound and histopathology of radical prostatectomy specimen

A system for computerised analysis of ultrasonographic prostate images (AUDEX=Automated Urologic Diagnostic EXpert system) for the detection of prostate carcinoma was developed. The ultimate goal is to develop a system that is reliable and non-observer dependent. Results of an earlier study with a small group were encouraging and this study describes the results of the computerised analysis in a larger group. Sixty-two patients who were scheduled to undergo a radical prostatectomy were prospectively analysed. The radical prostatectomy specimens were step-sectioned in the transverse plane, corresponding to the ultrasound pictures. Malignant regions identified by each study were quantified and compared by computer calculation. No correlation was observed between ultrasound analysis and pathology result. For the AUDEX analysis an overall sensitivity of 85% and a specificity of 18% with only a diagnostic accuracy of 57% was noticed when presence or absence of malignancy was evaluated by octant (total 496). When applying a cut-off value of 0.5 ml the numbers were 71%, 33% and 55%, respectively. Correlation was significantly better for the ventral octants. In this study the earlier results of our AUDEX system could not be confirmed. Although sensitivity was good, specificity and especially diagnostic accuracy were lower than expected. We have to conclude that the current settings are inappropriate for routine clinical use. Prostate Cancer and Prostatic Diseases (2001) 4, 56-62

Value of contrast ultrasonography in the detection of significant prostate cancer: correlation with radical prostatectomy specimens

BACKGROUND

The presented study has investigated a possible improvement of imaging prostate cancer: three-dimensional contrast-enhanced power Doppler ultrasonography (3D-CE-PDU).

METHODS

Seventy patients with biopsy proven prostate cancer and scheduled for radical retropubic prostatectomy received a 3D-CE-PDU investigation before surgery. Two experts analyzed the ultrasound images. The ultrasound images were correlated to the whole-mount sections of the prostate specimen. The correlation protocol consisted of three evaluation steps.

RESULTS

In total, 153 prostate tumors were found in the 70 prostate specimens: 61 tumors <5 mm, 93 tumors >or=5 mm. The diagnosis of clinical significant and insignificant prostate cancer was made in 85 and 88% of the patients for expert I and II, respectively. Diagnosis by imaging improved from 61% (43 of 70 of the prostate cancers) for standard detection tools to an average 86% (60 of 70 prostate cancers) for 3D-CE-PDU.

CONCLUSION

3D-CE-PDU improves the detection of prostate cancer in this group of prostate cancer patients. The use of 3D-CE-PDU in the clinic is questionable as indications are still unclear.

Microvessel density: correlation between contrast ultrasonography and histology of prostate cancer

OBJECTIVE

Increased microvessel density (MVD) of prostate cancer seems to be associated with poor prognosis and higher stage. Assessment of MVD using noninvasive methods could be of use in the work-up of patients with prostate cancer. The aim of the present study was to correlate three-dimensional contrast-enhanced power Doppler ultrasound (3D-CE-PDU) findings with MVD characteristics of radical prostatectomy specimens.

METHODS

Seven patients with biopsy-proven prostate cancer had 3D-CE-PDU investigations 2-3 weeks after prostate biopsies were taken and prior to radical prostatectomy. The investigations were performed using Levovist contrast agent (Schering AG, Berlin, Germany) in combination with a Voluson 530D ultrasound scanner (Kretz AG, Zipf, Austria). The 7 patients were selected because of lateralization of the contrast enhancement. Histology slides were made of the side with 'contrast enhancement' and of the contralateral 'unenhanced' side and stained according to the catalyzed reporter deposition (CARD) amplification procedure, and MVD parameters were obtained.

RESULTS

In all patients the MVD count of the 'enhanced' side was higher than the MVD count of the 'unenhanced' side, averaging 1.93 times higher. On histology all enhanced lesions proved to contain prostate cancer tissue (average maximum diameter 25 mm (range 17-31)). Two patients had a small bilateral tumor lesion (4 and 5 mm respectively) and in total 5 patients had even smaller satellite lesions (1-2 mm). The smaller lesions were not identified using 3D-CE-PDU.

CONCLUSIONS

The present study shows that 3D power Doppler contrast ultrasonography is a minimally invasive imaging modality, which has the potential to visualize lesions with increased MVD. This property of 3D-CE-PDU could be used in the detection of prostate cancer.

The value of sildenafil as mode of stimulation in pharmaco-penile duplex ultrasonography

The purpose of this work was to assess whether a single intracavernous injection (ICI) of a low dose of the combination of papaverine-phentolamine is replaceable by a high dose of the oral erectogenic agent sildenafil as mode of stimulation during pharmaco-penile duplex ultrasonography (PPDU). Eleven patients with complaints of erectile dysfunction were included in a crossover study. With an interval of two weeks the patients were exposed to ICI with papaverine/phentolamine (3.75 mg/0.125 mg) and oral administration with sildenafil (100 mg) preceding PPDU. Five patients started with ICI. Six patients started with sildenafil. In the sildenafil stimulation mode, visual erotic stimulation (VES) was used to initiate erection. VES was applied by personal LCD monitor. Cut-off values to define sufficient arterial response were: peak flow velocity (PSV) >25 cm/s and acceleration time (AT) <72 ms. Cut-off value to define sufficient veno-occlusion was a resistance index > or =1.00. Statistical analysis of PPDU parameters shows no significant difference between the two modes of stimulation for arterial response (PSV, AT), whereas the resistance index, as a parameter of veno-occlusive response was significantly higher in the sildenafil mode. This finding is confirmed in the clinical translation of the results: two patients with an insufficient arterial response to ICI had a sufficient arterial response to sildenafil and only one patient showed an insufficient arterial response following sildenafil, whereas the response following ICI was sufficient. Analysis of veno-occlusive responses shows remarkable differences between both modes of stimulation. Whereas following the administration of sildenafil all veno-occlusive responses were classified as sufficient, seven patients showed an insufficient veno-occlusive response following ICI. As mode of stimulation in PPDU, high dose sildenafil yields significantly less false positive diagnoses of 'veno-occlusive dysfunction' than intracavernous injection of the combination papaverine/phentolamine. No difference was found in the quality of the arterial response. Based on this study we conclude that sildenafil may replace ICI as mode of stimulation during PPDU.

Three-dimensional grayscale ultrasound: evaluation of prostate cancer compared with benign prostatic hyperplasia

OBJECTIVES

To compare the accuracy of the detection, localization, and staging of prostate cancer using transrectal three-dimensional (3D) grayscale ultrasonography (3D-US) with conventional transrectal two-dimensional grayscale ultrasonography (2D-US).

METHODS

Fifty patients with clinical localized prostate cancer scheduled to undergo radical retropubic prostatectomy and 50 patients with clinical benign prostatic hyperplasia underwent transrectal ultrasound investigations (2D and 3D). The prostate images were retrospectively analyzed by two ultrasound experts unaware of the clinical findings. The images of the prostate cancer group were correlated with the whole-mount histologic specimens of the prostate.

RESULTS

All percentages are given for experts 1 and 2. The sensitivity, specificity, and accuracy for the detection of prostate cancer without considering the definitive localization of the tumor for 2D-US was 72% and 76%, 50% and 54%, and 63% and 64%, respectively; for 3D-US, the rates were 82% and 88%, 40% and 42%, and 61% and 65%. The sensitivity, specificity, and accuracy of the combination of 2D-US with 3D-US was 88% and 90%, 36% and 38%, and 62% and 64%, respectively. The sensitivity, specificity, and accuracy for the exact localization of the prostate tumor for 2D-US was 44% and 46%, 50% and 54%, and 47% and 50%, respectively; for 3D-US, they were 52% and 62%, 40% and 42%, and 46% and 52%. The staging of prostate cancer using 3D-US was correct in 49% (expert 1) and in 57% (expert 2) of patients. No difference was observed between 2D-US and 3D-US for accurate staging. Both experts judged the interpretation of 3D-US images as superior to that of 2D-US images.

CONCLUSIONS

Although 3D-US had statistically significant increased sensitivity in the detection of lesions and decreased specificity compared with 2D-US, 3D-US did not result in significant clinical improvement in the detection and staging of prostate cancer.

Reproducibility of contrast-enhanced transrectal ultrasound of the prostate

Transrectal three-dimensional (3-D) contrast-enhanced power Doppler ultrasound (US) is a novel technique for studying possible prostate malignancy. Before studies can be performed to investigate the clinical validity of the technique, reproducibility of the contrast US studies must be proven. Reproducibility of contrast US was studied in 10 patients with biopsy-proven prostate cancer. The studies performed included static investigations and dynamic investigations of the prostate vasculature. All studies were double performed. The assessment of reproducibility was done objectively using a computer program and, subjectively, by visual assessment. The results indicate high reproducibility of static contrast investigations, for both the objective and subjective assessment. The subjective assessment of the dynamic studies was also highly reproducible. The objective assessment of the dynamic contrast studies, however, was less reproducible, mainly due to motion artefact. We concluded that, especially static 3-D contrast-enhanced, power Doppler investigations of the prostate are highly reproducible.

Intra-prostatic vasculature studies: can they predict the outcome of transurethral microwave thermotherapy for the management of bladder outflow obstruction?

BACKGROUND

Blood perfusion regulates intraprostatic temperatures during transurethral microwave thermotherapy (TUMT). We evaluated baseline intraprostatic vasculature, as a predictor of efficacy of TUMT.

METHODS

Twenty-two patients, with lower urinary tract symptoms (LUTS) suggestive of bladder outflow obstruction, were treated with TUMT (Prostatron). At baseline, three-dimensional contrast-enhanced power-flow-Doppler prostate ultrasonography (3D-CE-PFD) was performed. Assuming that the percentage of perfused area (PPA) is a realistic measure of blood flow, it was used to quantify intraprostatic vasculature.

RESULTS

The median (range) age, prostate size, and energy delivered were 66 years (48-80), 47 cm(3) (30-121), 110 kJ (29-136), respectively. The response was 77% (5 failures). The median (range) PPA was 2.76% (0.7-11.3). No difference in PPA among good and poor responders was detected nor was any correlation between PPA and baseline parameters.

CONCLUSIONS

The baseline intraprostatic vascularization, documented by CE-PFD studies, has no predictive value for the efficacy of TUMT. It seems that "static" baseline blood flow does not reflect the "dynamic" thermoregulatory role of blood flow during treatment.

alpha-Blockade improves symptoms suggestive of bladder outlet obstruction but fails to relieve it

PURPOSE

We investigated the effect of the alpha-blockers alfuzosin, terazosin and tamsulosin on urodynamic parameters after 6 months of therapy.

MATERIALS AND METHODS

Between February 1992 and June 1998, 163 patients with lower urinary tract symptoms suggestive of bladder outlet obstruction were treated with alfuzosin (60), terazosin (66) and tamsulosin (37). Patients were evaluated with urodynamic studies, including pressure flow analysis, before treatment and after 6 months of therapy. Initially, all patients were also assessed by the International Prostate Symptom Score questionnaire and measurement of urinary flow rate.

RESULTS

The majority of patients had no clear improvement in obstructive parameters, regardless of the alpha-blocker used, as urethral resistance factor and detrusor pressure maximum flow rate decreased by only 4 cm. H2O. There was a clear subjective and statistically significant decrease in International Prostate Symptom Score and quality of life scores of 6 and 2 points, respectively. No relevant statistical difference was noted among the effects of the 3 alpha-blockers on relieving symptoms or improving urodynamic parameters of obstruction.

CONCLUSIONS

The alpha-blockers are effective for treating symptoms suggestive of bladder outlet obstruction in patients presenting with lower urinary tract symptoms but not for treating the obstruction.

Computerized artifact detection and correction of uroflow curves: towards a more consistent quantitative assessment of maximum flow

OBJECTIVES

To evaluate a computerized method of artifact detection and correction of uroflow and compare the quantitative assessment of maximum flow obtained by the computer with visual correction by experts.

METHODS

A total of 90 randomly chosen flows was scanned into the computer whereafter automated artifact detection and correction was performed according to pre-established rules implemented in the software. Three experts visually corrected the flows using the same artifact detection and correction specifications as the computer. Measuring agreement between different methods of assessment of maximum flow was evaluated by calculating the difference and the standard deviation (SD) of the differences. The repeatability of assessing the maximum flow value by the computer and by expert 1 was assessed by calculating the difference between 2 readings and the coefficient of repeatability.

RESULTS

The coefficient of repeatability of maximum flow after detection and correction of artifacts by the computer (0.38 ml/s) was slightly better when compared with the coefficient of repeatability between 2 observations by 1 expert (1.12 ml/s). The interobserver variation for the quantitative assessment of maximum flow appeared to be great. A total of 51% of the maximum flow values assessed by expert 2 was 1 ml/s or more greater than those assessed by expert 1. When comparing the results of the computer with those of the experts, the mean value of maximum flow from expert 1 was 0.71 ml/s smaller than the computer value (p < 0.01), the mean value from expert 2 was 0.53 ml/s greater (p < 0.01) and the mean value from expert 3 was not significantly different (0.25 ml/s greater). The SD of maximum flow after correction by the computer was 0.3 ml/s smaller than the SD of the raw data from the flowmeter and the corrected values by 2 experts.

CONCLUSIONS

Computerized artifact detection and correction eliminates an important fraction of the variability of manually corrected maximum flow values. This may lead to smaller sample size requirements, especially in studies where the primary objective is to assess a small (+/- 1 ml/s) difference in mean maximum flow between groups.

Intraprostatic temperature monitoring during transurethral microwave thermotherapy: status and future developments

Transurethral microwave thermotherapy is being applied as a minimally invasive treatment for alleviating the symptoms of urinary outlet obstruction associated with benign prostatic hyperplasia. Treatment progress has traditionally been guided in its effective power by rectally and urethrally measured temperatures, whereas intraprostatic temperatures would be preferred for feedback purposes. A critical evaluation is presented of intraprostatic thermometry techniques that have been suggested, the techniques currently being used and investigated, and the problems that remain to be solved. Techniques for noninvasive temperature measurement and detecting tissue response during thermal therapy are discussed in more detail. Results presented in the literature have shown magnetic resonance imaging and ultrasonic imaging to be adequate thermometry modalities. For treatment monitoring of transurethral microwave thermotherapy, ultrasonic imaging is especially promising. Future research will indicate whether the promise evolves into a sound clinical technique.