Fast Monte Carlo codes for occupational dosimetry in interventional radiology.

PURPOSE: Interventional radiology techniques cause radiation exposure both to patient and personnel. The radiation dose to the operator is usually measured with dosimeters located at specific points above or below the lead aprons. The aim of this study is to develop and validate two fast Monte Carlo (MC) codes for radiation transport in order to improve the assessment of individual doses in interventional radiology. The proposed methodology reduces the number of required dosemeters and provides immediate dose results. METHODS: Two fast MC simulation codes, PENELOPE/penEasyIR and MCGPU-IR, have been developed. Both codes have been validated by comparing fast MC calculations with the multipurpose PENELOPE MC code and with measurements during a realistic interventional procedure. RESULTS: The new codes were tested with a computation time of about 120 s to estimate operator doses while a standard simulation needs several days to obtain similar uncertainties. When compared with the standard calculation in simple set-ups, MCGPU-IR tends to underestimate doses (up to 5%), while PENELOPE/penEasyIR overestimates them (up to 18%). When comparing both fast MC codes with experimental values in realistic set-ups, differences are within 25%. These differences are within accepted uncertainties in individual monitoring. CONCLUSION: The study highlights the fact that computational dosimetry based on the use of fast MC codes can provide good estimates of the personal dose equivalent and overcome some of the limitations of occupational monitoring in interventional radiology. Notably, MCGPU-IR calculates both organ doses and effective dose, providing a better estimate of radiation risk.

[Malignant fibrous histiocytoma of the scrotal wall. Presentation of a case and review of the literature]. / Histiocitoma fibroso maligno de la pared escrotal. Aportación de un caso y revisión de la literatura.

A case of Malignant Fibrous Histiocytoma in a 64 years old man, its rarity consisting in the location, the scrotal wall, is presented. An exposition on this pathological form of presentation, symptomatology, A.P., diagnostic, natural history, prognosis and treatment is made. Also, we review the literature on Malignant Fibrous Histiocytomas on the scrotal wall.

[Current validity of urethroplasty in two stages]. / Vigencia actual de la uretroplastia en dos tiempos.

Review of 18 patients with complex urethral stenosis, who underwent a two-stage urethroplasty in our Unit over the last three years. Clinical results have been favourable in all patients and, from the radiological point of view, there has been only one re-stenosis. Complications rate has been low and can be superimposed to that of any urethroplasty procedure. The paper emphasizes the enormous relevance of the care taken between both surgical stages on the procedure's final result.

[Excretory azoospermia secondary to a cyst of the seminal vesicle]. / Azoospermia excretora secundaria a quiste de vesícula seminal.

A case report of malformation of the right mesonephric ductus, involving a seminal vesicle cyst and ipsilateral renal and ureteral agenesis. The infrequency of such pathology is recalled and the oddity, in our case, of its presentation in the fashion of infertility secondary to excretory azoospermia highlighted. The deferentovesiculography, ultrasound scanning, urography and CAT were highly illustrative in the diagnosis. The treatment of choice in symptomatic cases is surgical exeresis, which in our patient secured the resolution of the azoospermia.

[PSA in the staging and monitoring of cancer of the prostate]. / PSA en el estadiaje y monitorización del cáncer de próstata.

The prostatic surface antigen (PSA), exclusively secreted by the prostatic epithelial cells, can be raised in the sera of patients with various prostatic pathologies. Serum levels of this marker depend on many factors (prostatic manipulation, associated inflammation, volume of benign node hyperplasia, volume and grading of tumour differentiation), all of which will have to be taken into account when interpreting any specific level. The usefulness of this antigen has a distinctive role in the suspected diagnosis, staging and monitoring following treatment of prostate cancer. PSA has shown to be more effective than other markers in the diagnosis of prostate cancer. Following the review of 106 patients with prostate cancer in various clinical stages, PSA was higher in 76.5% and PAP only in 49%. There is also a correlation between PSA and the extension of the disease. Of 43 patients surgically (stages B, C, D1) or radiologically (stages D2) staged, increases PSA has been found in 25% B stages, 77.7% C stages and 88.4% D stages. With regard to post-treatment monitoring, PSA is highly useful to determine its effectiveness, detect any residual illness and predict a recurrence or progression.

[Analysis of a series of radical prostatectomies]. / Análisis de una serie de prostatectomías radicales.

OBJECTIVE: Radical prostatectomy (RP) is an elective therapeutical procedure for localized prostate cancer. The paper describes the critical analysis of our 10-year series. MATERIAL AND METHODS: A total of 216 RP have been performed between June 1986 and December 1996 (60 of them in the last year); with the purpose of securing a minimum follow-up of 4 months, the 204 procedures performed up to October 1996 were studied. Mean age was 64.9 years and PSA median 10.8 ng/ml. Intraglandular clinical stage was found in 192 cases versus 12 cases extraglandular. Up to the end of 1993 Walsh's technique with erectors' preservation was being used although the poor results obtained with regard to potency as well as the existence of positive borders have compelled us to perform the standard extracapsular technique since beginning of 1994. RESULTS: Mean follow-up in our series has been 29.62 months. Post-operative complications reached 29.9%, anastomosis fistula (21 cases) among the early ones and anastomosis stenosis (16 cases) among the late ones. 82.04% patients have total continence or minimal incontinence, the percentage of obstruction being 3.58%. Total impotence is estimated at 92.77%. One patient (0.49%) died in the immediate post-operative. Understaging was observed in 36.7%. 84 patients had extracapsular disease. Our percentage of positive surgical borders is of around 43.13%. Progression has been seen in 47 of 204 patients (23.03%): 8 local relapses, 12 metastasis, 3 with both conditions and 24 biological progression. Progression has been related to pathological stage, pre-operative PSA and Gleason's sum of the specimen. Difference was statistically significant. Overall survival at 1 and 5 years is 99.2% and 95.5% respectively while tumour specific survival is 97.8% and 75.8% at 1 and 5 years. CONCLUSIONS: RP is a surgery with minimal mortality but noticeable morbidity (incontinence 14.35%; impotence 92.77%; other complications from surgical technique 29.9%). Our clinical understaging is of around 36.7%. Progression is related to the specimen's pathological stage, and pre-operative PSA and Gleason. Our overall survival at 1 and 5 years is 99.2% and 95.5% respectively while tumour specific survival is 97.8% and 75.8%.

[Camey II type substitution ileocystoplasty. Our experience]. / Ileocistoplastia de sustitución tipo Camey II. Nuestra experiencia.

We present our experience in the performance of Camey II type substitution ileocystoplasty. The operation was performed between January 1988 and February 1989 on 11 patients who had been diagnosed as having vesical tumour by means of transurethral resection. All of them had received preoperative systemic chemotherapy. Technically, we single out the performance of ileo-obturating lymphadenectomy prior to the cystoprostatovesiculectomy in the same operation, creation of the neobladder with detubulized terminal ileum, uretero-ileal reimplantation according to Le Duc-Camey technique and use of mechanical sutures to reestablish intestinal continuity. Operative and postoperative mortality has been null. As complications, we may mention a urthro-ileal fistula as a result of the suture tension at this level, due to shortness of the mesointestine, and which yielded with conservative measures. Amongst tardive complications we may single out a urethro-ileal stenosis, which required performance of an internal urethrotomy. Daytime continence in all patients, except one. Night continence in six cases. Absence of ureteral reflux and upper urinary tract with correct function and morphology in all cases. The follow-up time ranges from 3 to 16 months. We conclude that this type of vesical substitution offers all patients a good quality of living and adequate mictional comfort.

[Metastasizing kidney cancer. Experience with interferon alfa-2a and vinblastine]. / Cáncer metastásico de riñón. Experiencia con interferón alpha-2a y vimblastina.

Management of renal cells carcinoma still remains a therapeutic challenge. Nephrectomy is the primary therapy when the disease has a definite location. In advanced or disseminated cases, the various traditional procedures, including radiotherapy, chemotherapy or hormonal regimes, have obtained poor responses. Survival shows a direct relationship with the biological aggressiveness of the tumour and histological factors. Results recorded in the literature using specific immunotherapeutic agents are encouraging although the real value of this regimes has not yet been established in large series of prospective studies. The Oncology Unit of our Urology Service has obtained optimal follow-up in a group of patients included in a combined protocol of interferon alpha-2a and vinblastine as cytotoxic agent.

[Metastasis in maxillary sinus as presentation form of adenocarcinoma of the prostate]. / Metástasis en seno maxilar como presentación de un adenocarcinoma de próstata.

Presentation of one case of prostate adenocarcinoma its initial clinical manifestation being the appearance of facial tumour secondary to metastatic affectation of left maxillar sinus. After stressing its rarity, the relevance of immunohistochemical studies for the specific prostatic antigen and acid phosphatase in determining the unconnected origin of metastatic lesions is addressed.

[Foreign body simulating kidney tumour]. / Cuerpo extraño simulando tumor renal.

A six cm kidney tumour is found in a prostate control ultrasonography, in a 70 aged men. A chirurgical remove is indicated the tumour presented a very few separation of the kidney. The kidney was only compressed by the mass which contained a chirurgical gauze inside it from a previous surgery 35 years before.

[Renal transplantation: results]. / Trasplante renal: resultados.

Between June 1986 and December 1991, 125 kidneys were transplanted in our hospital. Survival results of patients per annum was 94%, 90% of which represent grafts. Regarding the complications occurred in our series the most frequent ones were medical followed by surgical [urological (4%), vascular (2.4%) and others derived from the surgical procedure (20%)]. It was necessary to perform 5 transplantectomies.

[Incoercible hemorrhagic cystitis induced by pelvic radiotherapy and simultaneous treatment with cyclophosphamide]. / Cistitis hemorrágica incoercible inducida por la radioterapia pelviana y tratamiento simultáneo con ciclofosfamida.

We present a case of incoercible hemorrhagic cystitis provoked by the therapeutic association of systemic cyclophosphamide and pelvic radiotherapy in a woman with disseminated mammary carcinoma disease. The conservative treatment, including vesical irrigation with aluminum salts, did not succeed in stopping the bleeding. A "sauvatage" cystectomy was carried out with Bricher-Wallace II type urinary derivation. We conclude by pointing out how the simultaneity of two therapies with individual vesical toxicity risk were boosted and how cystectomy continues to be the definitive treatment once conservative measures have been used up.

[Bladder adenocarcinoma of urachal origin. A rare tumor]. / Adenocarcinoma vesical de orígen uracal. Un raro tumor.

With the description of this new case of urachal adenocarcinoma in the vesical cupula we provide a review on the clinical, pathological and immunohistochemical aspects of this rare tumour, as well as a diagnostic and therapeutical approach. Its subepithelial infiltrant nature delays discovery and denotes both an insidious evolution and poor prognosis. Mucinoid production, nodes pattern and certain immunohistochemical substances as well as abnormalities in the cell's DNA content are attributes of this entity. Only surgery, either partial or exeresis, is effective since this is a radioresistant and dubiously chemosensitive tumour.

[Urinary diversions and bladder enlargements]. / Derivaciones urinarias y ampliaciones vesicales.

Overall review that offers an integrated insight of the importance and repercussions of urinary by-pass and bladder replacement. Over the last decades there has been a growing interest in the possibility of reconstructing the urinary system and there are now an almost infinite number of surgical solutions. The history of the development of using the intestine for by-passes and the reconstruction of the urinary system is described. The secondary metabolic alterations, the possibility of secondary intestinal tumours and the rudiments of ureterointestinal anastomosis are dealt with. Bladder substitution techniques are highlighted, and the vast experience of the Urology Department of Hospital Miguel Servet explained, including criteria and conclusions that help to choose from the many urological surgery alternatives headed by urinary by-pass and bladder complications.

[Angiomyolipoma of the kidney with lymphatic involvement]. / Angiomiolipoma renal con afectación ganglionar.

We present a case of renal angiomyolipoma associated with tuberous sclerosis affecting the regional lymphatic ganglia. We analyse the possible etiopathogenesis of this affection and conclude, like most authors, that it may reflect the multifocalization of this tumour rather than malignity or metastatic lesion.

[Obstruction of the upper urinary tract caused by a malignant retrovesicular schwannoma. Therapeutic strategy]. / Obstrucción del tracto urinario superior causada por un Schwannoma maligno retrovesical. Estrategia terapéutica.

We present a case of malignant Schwannoma (MS) of uncommon, retroperitoneal and retrovesical localization in a 42-year-old male, which provoked bilateral ureteral obstruction as a urological manifestation. We show our therapeutic strategy by means of a schedule of systemic neoadjuvant chemotherapy with vincristine, adriamycin, cyclophosphamide, decarbacine combined with exeresis and urinary continuity reconstruction surgery. We point out that it is a low incidence but highly aggressive tumour and that treatment continues to be local radical excision, whilst chemotherapy probably continues to have little value.

[Analysis of our series of kidney transplants: urologic complications and survival]. / Análisis de nuestra serie de trasplantes renales: complicaciones urológicas y supervivencia.

PURPOSE: To review our series of 416 renal transplants, with special reference to the surgical complications and their management. METHODS: From June, 1986 to October 1997, we are performed 416 heterotopic renal transplants, harvested from cadavers. Reconstruction of the urinary tract reconstruction was by ureteroneocystostomy in practically all the cases. RESULTS: There were some urological complications in 80 patients (19.2%). The most common urological complication was obstruction of the urinary tract arising from stenosis (3.3%), lymphocele (4.3%) and clotting (1.2%). 78.1% of these urological complications were resolved by endourological techniques. Urinary fistula was observed in 12 cases (2.8%). Vascular complications in 22 (6.9%), lithiasis in 5 (1.2%), and eventrations in 11 (2.6%). The treatment of these complications is described. The actuarial survival rates were 87.8% and 77.3% at one and five years respectively for the graft, and 92.4% and 83.5% for the patients. CONCLUSIONS: Our surgical complication rate in patients undergoing renal transplantation was 19.2%. The most common complication was urinary tract obstruction from stenosis (3.3%), lymphocele (4.3%) and clotting (1.6%); 78.1% of these obstructive complications were resolved by endourologic techniques. Percutaneous drainage and esclerotherapy of the lymphoceles resolved 66.6% of them. Renal biopsy performed with a 14G needle caused 5 severe hemorrhagic complications. There were no complications when an 18G needle was utilized.

Monte Carlo study of the effects of system geometry and antiscatter grids on cone-beam CT scatter distributions.

PURPOSE: The proliferation of cone-beam CT (CBCT) has created interest in performance optimization, with x-ray scatter identified among the main limitations to image quality. CBCT often contends with elevated scatter, but the wide variety of imaging geometry in different CBCT configurations suggests that not all configurations are affected to the same extent. Graphics processing unit (GPU) accelerated Monte Carlo (MC) simulations are employed over a range of imaging geometries to elucidate the factors governing scatter characteristics, efficacy of antiscatter grids, guide system design, and augment development of scatter correction. METHODS: A MC x-ray simulator implemented on GPU was accelerated by inclusion of variance reduction techniques (interaction splitting, forced scattering, and forced detection) and extended to include x-ray spectra and analytical models of antiscatter grids and flat-panel detectors. The simulator was applied to small animal (SA), musculoskeletal (MSK) extremity, otolaryngology (Head), breast, interventional C-arm, and on-board (kilovoltage) linear accelerator (Linac) imaging, with an axis-to-detector distance (ADD) of 5, 12, 22, 32, 60, and 50 cm, respectively. Each configuration was modeled with and without an antiscatter grid and with (i) an elliptical cylinder varying 70-280 mm in major axis; and (ii) digital murine and anthropomorphic models. The effects of scatter were evaluated in terms of the angular distribution of scatter incident upon the detector, scatter-to-primary ratio (SPR), artifact magnitude, contrast, contrast-to-noise ratio (CNR), and visual assessment. RESULTS: Variance reduction yielded improvements in MC simulation efficiency ranging from ∼17-fold (for SA CBCT) to ∼35-fold (for Head and C-arm), with the most significant acceleration due to interaction splitting (∼6 to ∼10-fold increase in efficiency). The benefit of a more extended geometry was evident by virtue of a larger air gap-e.g., for a 16 cm diameter object, the SPR reduced from 1.5 for ADD = 12 cm (MSK geometry) to 1.1 for ADD = 22 cm (Head) and to 0.5 for ADD = 60 cm (C-arm). Grid efficiency was higher for configurations with shorter air gap due to a broader angular distribution of scattered photons-e.g., scatter rejection factor ∼0.8 for MSK geometry versus ∼0.65 for C-arm. Grids reduced cupping for all configurations but had limited improvement on scatter-induced streaks and resulted in a loss of CNR for the SA, Breast, and C-arm. Relative contribution of forward-directed scatter increased with a grid (e.g., Rayleigh scatter fraction increasing from ∼0.15 without a grid to ∼0.25 with a grid for the MSK configuration), resulting in scatter distributions with greater spatial variation (the form of which depended on grid orientation). CONCLUSIONS: A fast MC simulator combining GPU acceleration with variance reduction provided a systematic examination of a range of CBCT configurations in relation to scatter, highlighting the magnitude and spatial uniformity of individual scatter components, illustrating tradeoffs in CNR and artifacts and identifying the system geometries for which grids are more beneficial (e.g., MSK) from those in which an extended geometry is the better defense (e.g., C-arm head imaging). Compact geometries with an antiscatter grid challenge assumptions of slowly varying scatter distributions due to increased contribution of Rayleigh scatter.