Reduction of metal artifact in single photon-counting computed tomography by spectral-driven iterative reconstruction technique.

PURPOSE: The exciting prospect of Spectral CT (SCT) using photon-counting detectors (PCD) will lead to new techniques in computed tomography (CT) that take advantage of the additional spectral information provided. We introduce a method to reduce metal artifact in X-ray tomography by incorporating knowledge obtained from SCT into a statistical iterative reconstruction scheme. We call our method Spectral-driven Iterative Reconstruction (SPIR). METHOD: The proposed algorithm consists of two main components: material decomposition and penalized maximum likelihood iterative reconstruction. In this study, the spectral data acquisitions with an energy-resolving PCD were simulated using a Monte-Carlo simulator based on EGSnrc C++ class library. A jaw phantom with a dental implant made of gold was used as an object in this study. A total of three dental implant shapes were simulated separately to test the influence of prior knowledge on the overall performance of the algorithm. The generated projection data was first decomposed into three basis functions: photoelectric absorption, Compton scattering and attenuation of gold. A pseudo-monochromatic sinogram was calculated and used as input in the reconstruction, while the spatial information of the gold implant was used as a prior. The results from the algorithm were assessed and benchmarked with state-of-the-art reconstruction methods. RESULTS: Decomposition results illustrate that gold implant of any shape can be distinguished from other components of the phantom. Additionally, the result from the penalized maximum likelihood iterative reconstruction shows that artifacts are significantly reduced in SPIR reconstructed slices in comparison to other known techniques, while at the same time details around the implant are preserved. Quantitatively, the SPIR algorithm best reflects the true attenuation value in comparison to other algorithms. CONCLUSION: It is demonstrated that the combination of the additional information from Spectral CT and statistical reconstruction can significantly improve image quality, especially streaking artifacts caused by the presence of materials with high atomic numbers.

Efficacy of tamsulosin oral controlled absorption system after extracorporeal shock wave lithotripsy to treat urolithiasis.

OBJECTIVE: To determine the efficacy of the tamsulosin oral controlled absorption system as an adjuvant therapy to extracorporeal shock wave lithotripsy (ESWL) for the expulsion of ureteral and renal stones. METHODS: A consecutive sample of 248 patients with ureteral or renal stones who underwent ESWL in an academic hospital was included in a 12-week, prospective, open-label, randomized clinical trial. Of the 248 patients, 186, including 77 with ureteral stones (mean size 9 mm) and 109 with renal stones (mean size 13 mm) completed the study. After successful ESWL, the patients were randomized to standard medical care (corticosteroids and analgesics) or standard care plus the tamsulosin oral controlled absorption system 0.4 mg/d for 1 month. The stone clearance rate, interval to the elimination of stone fragments, incidence of renal colic, and the need for rehospitalization were assessed at 4, 8, and 12 weeks. RESULTS: The stone clearance rate was significantly greater for the patients treated with tamsulosin than for those in the standard care group at 4 (73.4% vs 55.9%, respectively; P < .001) and 12 (91.3% vs 74.6%, respectively; P < .05) weeks. Tamsulosin treatment was also associated with a significantly lower interval to the elimination of stone fragments (P < .001), a significantly lower rehospitalization rate (P < .001), and a significantly lower proportion of patients with acute renal colic (P < .05) than standard care alone. No severe adverse events leading to treatment discontinuation were observed. CONCLUSION: Adjuvant treatment with tamsulosin, in addition to standard treatment with steroids and analgesics, improved the outcome of ESWL.

Organ transplantation in Bulgaria.

The transplantation program in Bulgaria started in 1968 with renal transplantations to a child and adult woman. In 1986 the first heart transplantation was performed. To date a total of 10 heart transplants have been performed, including one combined heart/lung. A liver transplantation program was launched in 2005 with a total number of 16 transplantations-7 from living donors and 9 from deceased donors. The highest transplantation activity is registered in the field of renal transplantation. During the period 1980-2006, 462 Bulgarian recipients of kidney were transplanted in Bulgaria. The ratio between transplantations from deceased and living related donors is approximately 1:0.9. Annual transplantation activity varies among the years from 1 to 12 renal transplantations p.m.p./per year. The 1- (80.7% vs. 63.1%), 5- (57.86% vs. 39.0%) and 10-year (42.65% vs. 23.62%) graft survival rates are higher for recipients of living donor kidneys compared to those of deceased donor. In 1983 a National kidney waiting list was established. Currently the number of the registered patients eligible for renal transplantation is 885. The proportion of sensitized patients in the waiting list is 20.45% and 4.34% of them are hyperimmunized. Recently HLAMatchmaker program has been implemented not only for sensitized patients but also for those with rare alleles and haplotypes. Post-transplant immunological monitoring showed a strong association between alloantibody presence and delayed graft function (Chi-square=10.73, P<0.001), acute rejection (Chi-square=14.504, P<0.001), chronic rejection (Chi-square=12.84, P<0.001) and graft loss (Chi-square=20.283, P<0.001). Based on the experience in our transplant center a strategy for improvement of long-term renal graft survival was developed and implemented.

Dorsal onlay augmentation urethroplasty with small intestinal submucosa: modified Barbagli technique for strictures of the bulbar urethra.

AIM: To present the results from one clinic's experience of using small intestinal submucosa (SIS) in augmentation urethroplasty for management of strictures of the bulbar urethra. METHODS: Urethral surgery was performed in nine men with strictures 4-6 cm. All of the patients were evaluated by history, physical examination, retrograde urethrogram, and uroflowmetry. Four layers of SIS were soaked in saline or Ringer's solution for 15 minutes at 37 degrees C, and the inner surface of the patch was gently fenestrated with a thin scalpel. The patch was spread-fixed onto the tunica albuginea. The mucosa was sutured to the submucosal graft first at 2-3 mm inwards from the SIS margins, then the spongiosum tissue was attached to the margins with interrupted absorbable sutures. RESULTS: Of the nine patients who underwent augmentation urethroplasty using SIS, only one had re-stricture at 6 months due to urethral infection. At 18 months after the surgery the uroflowmetry of the other eight patients was 20-21 mL/s. In terms of complications, six patients reported having post-micturition dribbling, and seven patients reported lack of morning erections for 35-69 days after surgery. CONCLUSIONS: Using SIS is a safe procedure; however, long-term follow-up is needed to substantiate the good short-term results.