Multiparametric MRI-based 5-year Risk Prediction Model for Biochemical Recurrence of Prostate Cancer after Radical Prostatectomy.

Background Current predictive tools to estimate the risk of biochemical recurrence (BCR) after treatment of prostate cancer do not consider multiparametric MRI (mpMRI) information. Purpose To develop a risk prediction tool that considers mpMRI findings to assess the risk of 5-year BCR after radical prostatectomy. Materials and Methods In this retrospective single-center analysis in 1459 patients with prostate cancer who underwent mpMRI before radical prostatectomy (in 2012-2015), the outcome of interest was 5-year BCR (two consecutive prostate-specific antigen [PSA] levels > 0.2 ng/mL [0.2 µg/L]). Patients were randomly divided into training (70%) and test (30%) sets. Kaplan-Meier plots were applied to the training set to estimate survival probabilities. Multivariable Cox regression models were used to test the relationship between BCR and different sets of exploratory variables. The C-index of the final model was calculated for the training and test sets and was compared with European Association of Urology, University of California San Francisco Cancer of the Prostate Risk Assessment, Memorial Sloan-Kettering Cancer Center, and Partin risk tools using the partial likelihood ratio test. Five risk categories were created. Results The median duration of follow-up in the whole cohort was 59 months (IQR, 32-81 months); 376 of 1459 (25.8%) patients had BCR. A multivariable Cox regression model (referred to as PIPEN, and composed of PSA density, International Society of Urological Pathology grade group, Prostate Imaging Reporting and Data System category, European Society of Urogenital Radiology extraprostatic extension score, nodes) fitted to the training data yielded a C-index of 0.74, superior to that of other predictive tools (C-index 0.70 for all models; P ≤ .01) and a median higher C-index on 500 test set replications (C-index, 0.73). Five PIPEN risk categories were identified with 5-year BCR-free survival rates of 92%, 84%, 71%, 56%, and 26% in very low-, low-, intermediate-, high-, and very high-risk patients, respectively (all P < .001). Conclusion A five-item model for predicting the risk of 5-year BCR after radical prostatectomy for prostate cancer was developed and internally verified, and five risk categories were identified. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Aguirre and Ortegón in this issue.

Genomic surveillance of SARS-CoV-2 positive passengers on flights from China to Italy, December 2022.

With numbers of COVID-19 cases having substantially increased at the end of 2022 in China, some countries have started or expanded testing and genomic surveillance of travellers. We report screening results in Italy in late December 2022 of 556 flight passengers in provenance from two Chinese provinces. Among these passengers, 126 (22.7%) tested SARS-CoV-2 positive. Whole genome sequencing of 61 passengers' positive samples revealed Omicron variants, notably sub-lineages BA.5.2.48, BF.7.14 and BQ.1.1, in line with data released from China.

Association between previous negative biopsies and lower rates of progression during active surveillance for prostate cancer.

PURPOSE: To test any-cause discontinuation and ISUP GG upgrading rates during Active Surveillance (AS) in patients that underwent previous negative biopsies (PNBs) before prostate cancer (PCa) diagnosis vs. biopsy naive patients. METHODS: Retrospective analysis of 961 AS patients (2008-2020). Three definitions of PNBs were used: (1) PNBs status (biopsy naïve vs. PNBs); (2) number of PNBs (0 vs. 1 vs. ≥ 2); (3) histology at last PNB (no vs. negative vs. HGPIN/ASAP). Kaplan-Meier plots and multivariable Cox models tested any-cause and ISUP GG upgrading discontinuation rates. RESULTS: Overall, 760 (79.1%) vs. 201 (20.9%) patients were biopsy naïve vs. PNBs. Specifically, 760 (79.1%) vs. 138 (14.4%) vs. 63 (6.5%) patients had 0 vs. 1 vs. ≥ 2 PNBs. Last, 760 (79.1%) vs. 134 (13.9%) vs. 67 (7%) patients had no vs. negative PNB vs. HGPIN/ASAP. PNBs were not associated with any-cause discontinuation rates. Conversely, PNBs were associated with lower rates of ISUP GG upgrading: (1) PNBs vs. biopsy naïve (HR:0.6, p = 0.04); (2) 1 vs. 0 PNBs (HR:0.6, p = 0.1) and 2 vs. 0 PNBs, (HR:0.5, p = 0.1); (3) negative PNB vs. biopsy naïve (HR:0.7, p = 0.3) and HGPIN/ASAP vs. biopsy naïve (HR:0.4, p = 0.04). However, last PNB ≤ 18 months (HR:0.4, p = 0.02), but not last PNB > 18 months (HR:0.8, p = 0.5) were associated with lower rates of ISUP GG upgrading. CONCLUSION: PNBs status is associated with lower rates of ISUP GG upgrading during AS for PCa. The number of PNBs and time from last PNB to PCa diagnosis (≤ 18 months) appear also to be critical for patient selection.

Performance Assessment of the LIAISON® SARS-CoV-2 Antigen Assay On Nasopharyngeal Swabs.

The SARS-CoV-2 pandemic is ongoing worldwide, causing prolonged pressure on molecular diagnostics. Viral antigen (Ag) assays have several advantages, ranging from lower cost to shorter turnaround time to detection. Given the rare occurrence of low-load viremia, antigen assays for SARSCoV-2 have focused on nasopharyngeal swab and saliva as biological matrices, but their effectiveness must be validated. We assayed here the performances of the novel quantitative Liaison® SARSCoV-2 Ag assay on 119 nasopharyngeal swabs and obtained results were compared with Hologic Panther and Abbott m2000 RT-qPCR. The Ag assay demonstrated a good correlation with viral load, shorter turnaround time, and favorable economics. The best performance was obtained in the acute phase of disease.

The role of MRI in the management of a prostate cancer patient with bone and lymph nodes metastases. A case report.

The use of multiparametric prostate magnetic resonance imaging (mpMRI) is recommended, in the European Association of Urology (EAU) guidelines, for local staging of patients with prostate cancer (PCa). Systemic staging is recommended only for patients with unfavourable intermediate and high-risk disease; with bone and lymph node assessments usually being performed using bone scan (BS) and computed tomography (CT), respectively. Magnetic resonance imaging (MRI) is the imaging technique with the highest sensitivity for the detection of bone metastases and has shown promising results also for lymph node assessments. In this report we illustrate how MRI provided a comprehensive assessment of local disease as well as bone and lymph node metastases in a patient with PCa. (www.actabiomedica.it).

Whole-body magnetic resonance imaging (WB-MRI) for cancer screening: recommendations for use.

Whole-body magnetic resonance imaging (WB-MRI) is currently recommended for cancer screening in adult and paediatric subjects with cancer predisposition syndromes, representing a substantial aid for prolonging health and survival of these subjects with a high oncological risk. Additionally, the number of studies exploring the use of WB-MRI for cancer screening in asymptomatic subjects from the general population is growing. The primary aim of this review was to analyse the acquisition protocols found in the literature, in order to identify common sequences across published studies and to discuss the need of additional ones for specific populations. The secondary aim of this review was to provide a synthesis of current recommendations regarding the use of WB-MRI for cancer screening.

Effects of Sex and Age on Fat Fraction, Diffusion-Weighted Image Signal Intensity and Apparent Diffusion Coefficient in the Bone Marrow of Asymptomatic Individuals: A Cross-Sectional Whole-Body MRI Study.

We aimed to describe the relationships between the relative fat fraction (%FF), muscle-normalized diffusion-weighted (DW) image signal intensity and water apparent diffusion coefficient (ADC), sex and age for normal bone marrow, in the normal population. Our retrospective cohort consisted of 100 asymptomatic individuals, equally divided by sex and 10-year age groups, who underwent whole-body MRI at 1.5 T for early cancer detection. Semi-automated segmentation of global bone marrow volume was performed using the DW images and the resulting segmentation masks were projected onto the ADC and %FF maps for extraction of parameter values. Differences in the parameter values between sexes at age ranges were assessed using the Mann-Whitney and Kruskal-Wallis tests. The Spearman correlation coefficient r was used to assess the relationship of each imaging parameter with age, and of %FF with ADC and normalized DW signal intensity values. The average %FF of normal bone marrow was 65.6 ± 7.2%, while nSIb50, nSIb900 and ADC were 1.7 ± 0.5, 3.2 ± 0.9 and 422 ± 67 µm2/s, respectively. The bone marrow %FF values increased with age in both sexes (r = 0.63 and r = 0.64, respectively, p < 0.001). Values of nSIb50 and nSIb900 were higher in younger women compared to men of the same age groups (p < 0.017), but this difference decreased with age. In our cohort of asymptomatic individuals, the values of bone marrow relative %FF, normalized DW image signal intensity and ADC indicate higher cellularity in premenopausal women, with increasing bone marrow fat with aging in both sexes.

Apparent Diffusion Coefficient and Other Preoperative Magnetic Resonance Imaging Features for the Prediction of Positive Surgical Margins in Prostate Cancer Patients Undergoing Radical Prostatectomy.

PURPOSE: To investigate the use of apparent diffusion coefficient (ADC) values and other MRI features for predicting positive surgical margins (PSMs) in patients undergoing radical prostatectomy. MATERIALS AND METHODS: We retrospectively identified 400 consecutive patients who underwent surgery for prostate cancer between January 2015 and June 2016. ADC values of the index lesion and other preoperative magnetic resonance imaging features, including tumor site, laterality, level, Prostate Imaging Reporting and Data System category, European Society of Urogenital Radiology extracapsular extension score, and prostate volume, were assessed. Univariate and multivariable logistic regression were performed. Performance in predicting the occurrence of PSMs was measured using the area under the curve (AUC). AUC differences were evaluated with the DeLong method. The Youden index was calculated to identify the ADC threshold to best discriminate patients with PSMs. RESULTS: Of the 400 patients, 105 (26.2%) had PSMs after radical prostatectomy. ADC values, Prostate Imaging Reporting and Data System category, extracapsular extension score, tumor site, and laterality were significantly associated with PSMs (P < .001) in univariate analysis. The AUC of the predictive model based on ADC alone was 68.2% (95% confidence interval, 62.2-74.2%) and did not significantly differ from the best multivariable predictive model which combined laterality, and site with ADC to attain an AUC of 70.0% (95% confidence interval, 64.2-75.8%; DeLong P = .318). The ADC threshold that maximized the Youden index was 960.3 µm2/s. CONCLUSION: ADC values and preoperative magnetic resonance imaging features can help estimate the risk of PSMs after radical prostatectomy.

Semi-Automated Segmentation of Bone Metastases from Whole-Body MRI: Reproducibility of Apparent Diffusion Coefficient Measurements.

Using semi-automated software simplifies quantitative analysis of the visible burden of disease on whole-body MRI diffusion-weighted images. To establish the intra- and inter-observer reproducibility of apparent diffusion coefficient (ADC) measures, we retrospectively analyzed data from 20 patients with bone metastases from breast (BCa; n = 10; aged 62.3 ± 14.8) or prostate cancer (PCa; n = 10; aged 67.4 ± 9.0) who had undergone examinations at two timepoints, before and after hormone-therapy. Four independent observers processed all images twice, first segmenting the entire skeleton on diffusion-weighted images, and then isolating bone metastases via ADC histogram thresholding (ADC: 650-1400 µm2/s). Dice Similarity, Bland-Altman method, and Intraclass Correlation Coefficient were used to assess reproducibility. Inter-observer Dice similarity was moderate (0.71) for women with BCa and poor (0.40) for men with PCa. Nonetheless, the limits of agreement of the mean ADC were just ±6% for women with BCa and ±10% for men with PCa (mean ADCs: 941 and 999 µm2/s, respectively). Inter-observer Intraclass Correlation Coefficients of the ADC histogram parameters were consistently greater in women with BCa than in men with PCa. While scope remains for improving consistency of the volume segmented, the observer-dependent variability measured in this study was appropriate to distinguish the clinically meaningful changes of ADC observed in patients responding to therapy, as changes of at least 25% are of interest.

Whole-body magnetic resonance imaging: technique, guidelines and key applications.

Whole-body magnetic resonance imaging (WB-MRI) is an imaging method without ionising radiation that can provide WB coverage with a core protocol of essential imaging contrasts in less than 40 minutes, and it can be complemented with sequences to evaluate specific body regions as needed. In many cases, WB-MRI surpasses bone scintigraphy and computed tomography in detecting and characterising lesions, evaluating their response to therapy and in screening of high-risk patients. Consequently, international guidelines now recommend the use of WB-MRI in the management of patients with multiple myeloma, prostate cancer, melanoma and individuals with certain cancer predisposition syndromes. The use of WB-MRI is also growing for metastatic breast cancer, ovarian cancer and lymphoma as well as for cancer screening amongst the general population. In light of the increasing interest from clinicians and patients in WB-MRI as a radiation-free technique for guiding the management of cancer and for cancer screening, we review its technical basis, current international guidelines for its use and key applications.

Introduction of SARS-CoV-2 variant of concern 20h/501Y.V2 (B.1.351) from Malawi to Italy.

We report here an imported case of SARS-CoV-2 variant of concern B.1.1.351 (also known as 20H/501Y.V2 or "South African variant" or VOC 202012/02) in a 66-years old symptomatic male who returned from Malawi to Italy.

Imported SARS-CoV-2 Variant P.1 in Traveler Returning from Brazil to Italy.

We report an imported case of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant P.1 detected in an asymptomatic traveler who arrived in Italy on an indirect flight from Brazil. This case shows the risk for introduction of SARS-CoV-2 variants from indirect flights and the need for continued SARS-CoV-2 surveillance.

Comparison of three therapeutic regimens for genotype-3 hepatitis C virus infection in a large real-life multicentre cohort.

BACKGROUND & AIMS: In the direct-acting antiviral era, treatment of genotype-3 HCV (HCV-GT3) is still challenging. Real-life comparisons between recommended regimens, sofosbuvir (SOF)+daclatasvir (DAC), SOF/velpatasvir (VEL), glecaprevir/pibrentasvir (GLE/PIB), are scarce. We aimed at filling this data gap. METHODS: Sustained virological response 12 weeks after treatment completion (SVR12) was assessed for all HCV-GT3 patients consecutively treated within the Lombardia web-based Navigatore HCV-Network; differences in SVR12 across regimens were evaluated by logistic regression. RESULTS: Of the 2082 subjects with HCV-GT3, 1544 were evaluable for comparisons between regimens: SOF + DAC (1023, 66.2%), SOF/VEL (369, 23.9%), GLE/PIB (152, 9.8%). Patients treated with former regimens were more frequently male, cirrhotic, HIV-positive, pretreated, used ribavirin in their regimen, and had lower baseline HCV-RNA. SVR12 was similar across groups: 94.8% in SOF + DAC, 97.6% in SOF/VEL, 96.7% in GLE/PIB (P = .065). At univariate analysis, SVR12 was associated with female gender (97.9% vs 94.8%, P = .007) and lower median pretreatment Log10 HCV-RNA (5.87 vs 6.20, P = .001). At multivariate logistic regression analysis, treatment with SOF/VEL was associated with a higher likelihood of SVR12 than SOF + DAC, but only in the absence of ribavirin (98% vs 90.3%). Female gender and lower pretreatment HCV-RNA were independently associated with SVR12. CONCLUSIONS: In a large real-life setting of HCV-GT3-infected patients with a high proportion of cirrhosis, the success rate was remarkable. The slight advantage of SOF/VEL on SOF + DAC was significant only without ribavirin. The current prescription shift towards novel regimens (ie SOF/VEL and GLE/PIB) in easier-to-treat patients allows ribavirin-free and shorter schedules without mining SVR12 in this <> genotype.

Renal safety in 3264 HCV patients treated with DAA-based regimens: Results from a large Italian real-life study.

BACKGROUND: Sofosbuvir (SOF)-based regimens have been associated with renal function worsening in HCV patients with estimated glomerular filtration rate (eGFR) ≤ 45 ml/min, but further investigations are lacking. AIM: To assess renal safety in a large cohort of DAA-treated HCV patients with any chronic kidney disease (CKD). METHODS: All HCV patients treated with DAA in Lombardy (December 2014-November 2017) with available kidney function tests during and off-treatment were included. RESULTS: Among 3264 patients [65% males, 67% cirrhotics, eGFR 88 (9-264) ml/min], CKD stage was 3 in 9.5% and 4/5 in 0.7%. 79% and 73% patients received SOF and RBV, respectively. During DAA, eGFR declined in CKD-1 (p < 0.0001) and CKD-2 (p = 0.0002) patients, with corresponding rates of CKD stage reduction of 25% and 8%. Conversely, eGFR improved in lower CKD stages (p < 0.0001 in CKD-3a, p = 0.0007 in CKD-3b, p = 0.024 in CKD-4/5), with 33-45% rates of CKD improvement. Changes in eGFR and CKD distribution persisted at SVR. Baseline independent predictors of CKD worsening at EOT and SVR were age (p < 0.0001), higher baseline CKD stages (p < 0.0001) and AH (p = 0.010 and p < 0.0001, respectively). CONCLUSIONS: During DAA, eGFR significantly declined in patients with preserved renal function and improved in those with lower CKD stages, without reverting upon drug discontinuation.

Use of Magnetic Induction to Activate a "Touchless" Shape Memory Alloy Implantable Penile Prosthesis.

INTRODUCTION: We describe a novel physiologic penile prosthesis that uses shape memory alloy properties to mimic the transition between a flaccid and erect penis using magnetic induction instead of hydraulic pressure. AIM: To evaluate the parameters of magnetic induction to activate a shape memory alloy implantable penile prosthesis. METHODS: We prototyped an implantable penile prosthesis cylinder using temperature-tuned nickel titanium alloy tubes laser cut to specifications. The device was then tested implanted in an animal tissue model and in cadaveric tissue. Testing consisted of placing the device deactivated in its more malleable and compressed state, then activating it using an external inducer wand while measuring temperature changes that occur on the surface of the device, within the tissue, and at the skin surface. MAIN OUTCOME MEASURES: Our main outcome measures were the efficiency of activation and thermal safety of this approach. RESULTS: Using a handheld magnetic inductor, we were able to successfully activate the SMA penile prosthesis with no direct contact under 45 seconds. This handheld wand produced a magnetic field that penetrated tissue and caused the appropriate phase change within the prosthesis. Tissue temperature (middle and surface probes) in the animal tissue model increased only a few degrees Celsius during the activation process, and never exceeded 28 degrees Celsius from a baseline at room temperature ∼ 25 degrees Celsius. We encountered similar results without a notable change in tissue temperature in the cadaveric tests. The fully activated device resisted buckling forces of 2.66 kgf ± 0.045. CLINICAL IMPLICATIONS: This non-hydraulic shape memory prosthesis obviates the needs for reservoirs and pumps, and the wand-based interaction with the device may be easier to use. STRENGTH & LIMITATIONS: This technology represents a fundamental departure from the hydraulic-based penile prosthesis and has comparable mechanical properties as current-marked devices. It appears to show thermal safety in controlled environments, however real-world use would need further studies. Further optimization of prototypes needs to be done prior to human clinical trials. CONCLUSION: A shape memory penile prosthesis is a promising alternative to hydraulic-based penile prostheses and can be activated safely and efficiently using magnetic induction in our models of the human penis. Le BV, McVary KT, McKenna K, et al. Use of Magnetic Induction to Activate a "Touchless" Shape Memory Alloy Implantable Penile Prosthesis. J Sex Med 2019;16:596-601.

The diabetes pandemic and associated infections: suggestions for clinical microbiology.

There are 425 million people with diabetes mellitus in the world. By 2045, this figure will grow to over 600 million. Diabetes mellitus is classified among noncommunicable diseases. Evidence points to a key role of microbes in diabetes mellitus, both as infectious agents associated with the diabetic status and as possible causative factors of diabetes mellitus. This review takes into account the different forms of diabetes mellitus, the genetic determinants that predispose to type 1 and type 2 diabetes mellitus (especially those with possible immunologic impact), the immune dysfunctions that have been documented in diabetes mellitus. Common infections occurring more frequently in diabetic vs. nondiabetic individuals are reviewed. Infectious agents that are suspected of playing an etiologic/triggering role in diabetes mellitus are presented, with emphasis on enteroviruses, the hygiene hypothesis, and the environment. Among biological agents possibly linked to diabetes mellitus, the gut microbiome, hepatitis C virus, and prion-like protein aggregates are discussed. Finally, preventive vaccines recommended in the management of diabetic patients are considered, including the bacillus calmette-Guerin vaccine that is being tested for type 1 diabetes mellitus. Evidence supports the notion that attenuation of immune defenses (both congenital and secondary to metabolic disturbances as well as to microangiopathy and neuropathy) makes diabetic people more prone to certain infections. Attentive microbiologic monitoring of diabetic patients is thus recommendable. As genetic predisposition cannot be changed, research needs to identify the biological agents that may have an etiologic role in diabetes mellitus, and to envisage curative and preventive ways to limit the diabetes pandemic.

Real-world effectiveness and safety of glecaprevir/pibrentasvir in 723 patients with chronic hepatitis C.

BACKGROUND AND AIMS: The efficacy and safety of glecaprevir/pibrentasvir (G/P) for patients infected with hepatitis C virus (HCV) have only been investigated in clinical trials, with no real-world data currently available. The aim of our study was to investigate the effectiveness and safety of G/P in a real-world setting. METHODS: All patients with HCV consecutively starting G/P between October 2017 and January 2018 within the NAVIGATORE-Lombardia Network were analyzed. G/P was administered according to drug label (8, 12 or 16 weeks). Fibrosis was staged either histologically or by liver stiffness measurement. Sustained virological response (SVR) was defined as undetectable HCV-RNA 12 weeks after the end of treatment. RESULTS: A total of 723 patients (50% males) were treated with G/P, 89% for 8 weeks. The median age of our cohort was 58 years, with a median body mass index of 23.9 kg/m2, and median liver stiffness measurement of 6.1 kPa; 84% were F0-2 and 16% were interferon-experienced. Median HCV-RNA was 1,102,600 IU/ml, and 49% of patients had HCV genotype 1 (32% 1b), 28% genotype 2, 10% genotype 3 and 13% genotype 4. The median estimated glomerular filtration rate was 90.2 ml/min, platelet count 209x103/mm3 and albumin 4.3 g/dl. The SVR rates were 94% in intention-to-treat and 99.3% in per protocol analysis (8-week vs. 12 or 16-week: 99.2% vs. 100%). Five patients failed therapy because of post-treatment relapse; a post-treatment NS5A resistance-associated substitution was detected in 1 case. SVR rates were lower in males (p = 0.002) and in HCV genotype-3 (p = 0.046) patients treated for 8 weeks, but independent of treatment duration, fibrosis stage, baseline HCV-RNA, HIV co-infection, chronic kidney disease stage and viral kinetics. Mild adverse events were reported in 8.3% of the patients, and 0.7% of them prematurely withdrew treatment. Three patients died of drug-unrelated causes. CONCLUSIONS: In a large real-world cohort of Italian patients, we confirmed the excellent effectiveness and safety of G/P administered for 8, 12 or 16 weeks. LAY SUMMARY: A large number of patients with hepatitis C virus have been treated with glecaprevir/pibrentasvir (G/P) within the NAVIGATORE-Lombardia Network, in Italy. This is the first real-world study evaluating effectiveness and safety of G/P in patients with hepatitis C virus treated according to international recommendations. This study demonstrated excellent effectiveness (with sustained virological response rates of 99.3%) and safety profiles.

A Novel Thermal-activated Shape Memory Penile Prosthesis: Comparative Mechanical Testing.

OBJECTIVE: To compare a novel nickel-titanium (Ni-Ti) shape memory alloy (SMA) penile prosthesis of our own design with commercially available prostheses using a format similar to mechanical testing done at major penile prosthesis manufacturers. We evaluated the mechanical parameters of commercially available penile prostheses and used this information to guide the development of the Ni-Ti-based physiological penile prosthesis that expands and becomes erect with a small amount of heat applied. METHODS: A penile prosthesis consisting of an exoskeleton of temperature-tuned Nitinol was designed and prototyped. Mechanical testing was performed in a model of penile buckling, penile lateral deviation, and original penile shape recovery commonly used by penile prosthesis manufacturers for testing. RESULTS: Our SMA penile prosthesis demonstrated useful mechanical characteristics, including rigidity to buckling when activated similar to an inflatable penile prosthesis (2.62 kgf SMA vs 1.42 kgf inflatable penile prosthesis vs 6.45 kgf for a malleable prosthesis). The Ni-Ti also became more pliable when deactivated within acceptable mechanical ranges of existing devices. It could be repeatedly cycled and generate a restorative force to become erect. CONCLUSION: An SMA-based penile prosthesis represents a promising new technology in the treatment of erectile dysfunction. We demonstrated that an Ni-Ti-based prosthesis can produce the mechanical forces necessary for producing a simulated erection without the need for a pump or reservoir, comparable with existing prostheses.