Nebojša Stojanović

Evaluation of optimal bandwidth in optical FSK system influenced by laser phase noise

In this paper, an optical frequency shift keying (FSK) system with TFS (two-filter structure), also known as dual-filter FSK, is observed in the presence of laser phase noise. Sensitivity of the receiver is shown as a function of intermediate frequency (IF) bandwidth and a bandwidth of the low-pass postdetection filter. It is shown that there is an optimal pair of bandwidths which minimizes required sensitivity; a few figures for different amounts of phase noise are given. The results in this paper are based on truncated Taylor expansion method and a method based on complex analysis is used to evaluate the integrals involved.

Influence of imperfect carrier recovery on satellite QPSK communication system performance

The purpose of this paper is to provide the theoretical approach for determining the bit error probability in detecting a coherent quaternary phase-shift-keyed signal transmitted over a soft-limited channel in the presence of the uplink and downlink noise, as well as the noisy carrier reference signal. The uplink noise is considered in the specific way through the envelope variations and the frequency offset of the signal remitted by the satellite station having influence on the variations of the phase-locked loop parameters in the receiving ground station, consequently on the probability density function of the phase error, i.e. the average bit error probability. The downlink noise is also taken into consideration. The determined results are based on the non-linear phase-locked loop model with primary emphasis on the degradations in the system performance produced by the imperfect carrier signal extraction. Copyright

ADC is not reliable in determinating subtypes of meningiomas

ObjectiveTo verify the reliability of apparent diffusion coefficient (ADC) measurements in determining subtypes of meningiomas.Material and methodsThirty patients (20 women and 10 men; average age, 53±15 years) with meningiomas were prospectively studied using DWI with b values of 0 and 1000. ADC values of the neoplastic tissue were obtained as the mean of measurements from three regions of interests within the mass and compared with histologic subtypes using ANOVA test (SPSS16).ResultsThe meningothelial subtype was found in 15 (50%) patients, fibroblastic in 10 (33.33%) patients and cystic in 5 (16.67%) patients. All meningiomas belonged to the WHO Grade 1 — benign meningiomas. There was no significant statistical difference between meningothelial, fibroblastic and cystic meningiomas when considering mean ADC values (0.000411+/−0.000066 mm2/s vs. 0.000750+/−0.001045 mm2/s vs. 0.000688+/−0.000063 mm2/s (p>0.05). Perifocal edema was present only with fibroblastic meningioma with mean ADC 0.000683 mm2/s. The ADC of the cystic component was statistically significantly higher in cystic meningeomas (0.001283 mm2/s) compared with fibroblastic (0.000224 mm2/s) and meningothelial meningiomas (0.000088 mm2/s) (p<0.001). The ADC of meningiomas was higher compared with contralateral healthy brain tissue (0.000642 mm2/s vs. 0.000404 mm2/s; n.s).ConclusionADC measurement do not seem reliable in identifying histological subtypes of Grade I meningiomas.

A rare case of retroperitoneal malignant Triton tumor invading renal vein and small intestine.

INTRODUCTION Malignant Triton tumor is a very rare malignant peripheral nerve sheath tumor with rhabdomyosarcomatous differentiation. Most of those tumors occur in patients with von Recklinghausens disease or as a late complication of irradiation and commonly seen in the head, neck, extremities and trunk. CASE REPORT We reported retroperitoneal malignant Triton tumor in a 57-year-old female patient. Skin lesions were not present, and there was no family history of neurofibromatosis or previous irradiation. The presented case is one of a few recorded in the specialized literature that occurs in the retroperitoneal space in sporadic form. In this case, tumor consisted of a multilobular mass was in close relation with the abdominal aorta and inferior vena cava and involved the renal vein with gross invasion of the small intestine. The patient underwent total resection of the tumor and left nefrectomy was performed. The small intestine 10 cm in length was also resected and end-to-end anastomosis was conducted. The postoperative course was uneventful and the patient was discharged from the hospital ten days after the surgery. CONCLUSION Diagnostically, it is crucial to recognize this uncommon histological variant because malignant Triton tumor has a worse prognosis than classic malignant peripheral nerve sheath tumor does. The use of the immunohistochemistry is essential in making the correct diagnosis. Only appropriate pathological evaluation supported by immunostaining with S-100 protein and desmin confirmed the diagnosis. Aggressive surgical management treatment improves the prognosis of such cases with adjuvant radiotherapy.

Non-uniform delta modulation for coding of the service channel in optical systems

A new algorithm for non-uniform delta modulation is presented. It is called statistical delta modulation (SDM) due to the statistical nature of clock instants. SDM is especially suitable for the modulation of the service channel based on the line code redundancy, where no other known delta modulation with uniform clock can be applied. SDM and linear delta modulation (LDM) are compared by computer simulation.

Spontaneous chronic subdural hematoma in elderly people – Arterial hypertension and other risk factors

Background: The risk factors implicated in the genesis of chronic subdural hematomas include old age, alcoholism, diabetes mellitus, arachnoid cysts, coagulopathy, anticoagulant (ACTh) and antiplatelet drugs. However, no study has reported an association between arterial hypertension (HTA) and chronic subdural hematomas. Therefore, the aim of this study was to investigate whether HTA is a risk factor for spontaneous chronic subdural hematomas (SCSDHs). Methods: This multicenter study included patients aged over 60 years and was conducted from January 2009 to the end of 2015. One hundred and twenty‐two patients with SCSDHs and 111 controls treated for other reasons with no evidence of intracranial hemorrhages on brain computed tomography were enrolled. The patients were separated into three age subgroups to provide a better insight into the role of risk factors with age. Results: The average age in the SCSDH group was 74.45 ± 8.16 years, compared to 71.28 ± 6.69 years in the control group. The SCSDH group was significantly older than the control group (p = 0.0014). The patients in the 60–69 years age group diagnosed with SCSDHs had significantly higher rates of HTA (p = 0.0519), ACTh treatment (p = 0.0292) and alcoholism (p = 0.0300) than the control group. The patients in the 70–79 years age group diagnosed with SCSDHs had significantly higher rates of HTA (p = 0.0071) and ACTh treatment (p = 0.0158) than the control group. In the subgroup of patients older than 80 years, there were no statistical differences. Conclusion: The incidence of HTA had borderline significance in the patients aged 60–69 years with SCSDHs and statistical significance in the patients aged 70–79 years with SCSDHs. Anticoagulant therapy was the most significant risk factor. Among the patients with SCSDHs aged 60–69 years, the percentage of heavy drinkers was significantly higher than in the control group.

SURGICAL TREATMENT OF MENINGIOMA WITH VENTRAL AND VENTROLATERAL LOCALIZATION IN THE REGION OF THE FORAMEN MAGNUM

Meningiomas localized in the ventral part of the foramen magnum always represent a surgical challenge. Analysis was performed on the surgical approach to meningiomas with ventral localization in the craniocervical region in 6 patients. Two posterolateral surgical approaches were used, depending on whether the tumor was at the level of the foramen magnum or it transited into the cervical spinal canal. In the case of a tumor at the level of the foramen magnum, posterolateral approach was used, with the suboccipital bone removal, and removal of part of the occipital condyles, with the resection of the atlas arch and mobilization of a.vertbralis. In tumors propagated in the spinal canal, the same resection of the occipital bone and occipital condyle was done, with the removal of the atlas and part of the atlantoaxial joint. Due to destabilization, occipitocervical fixation was performed in the second posterolateral approach. The posterolateral approach with the suboccipital removal of the bones and the atlas or, if necessary, with the resection of the occipital condyle or atlantoaxial joint, enables a good ventral separation of the tumor attachment and subsequent gradual complete removal. Fixation is required in the event of a removal of the atlantoaxial joint or removal of more than half of the occipital condyle. Posterolateral approach is an absolute indication in all cases of the ventral and ventrolateral localization of meningiomas in the area of the cervico-occipital junction, because it provides complete visualization of the tumor and allows for its safe removal.

Giant renal oncocytoma

BACKGROUND Renal onkocytoma is a distinctive benign tumor derived from epithelial cells of the distal renal tubules. These tumors are often clinically asymptomatic, diagnosed accidentally and difficult to distinguish from renal cell carcinoma. CASE REPORT We presented a giant renal onkocytoma in a man aged 64, without any signs or symptoms of the urogenital system disorder. The preoperative diagnosis described the tumor mass of the right kidney, size 16 x 14 cm, and indicated a malignant tumor of kidney. The patient underwent radical nephrectomy. The tumor was encapsulated at the intersection with the characteristic central hyaline scar. Microscopically, it was built of uniform polygonal cells with abundant eosinophilic cytoplasm. Immunohystochemiclly, tumor cells were immunoreactive to CK AE1/AE3 and CD 117, but showed negative immunoreactivity to CK 7, RCC marker and Vimentin. CONCLUSION Giant renal oncocytomas are rare tumors with benign clinical course. As a rule, they are discovered by accident. Clinical differentiation from malignant tumors of the kidney is not possible. They are treated surgically, mainly by radical nephrectomy. A definitive diagnosis is made only by histopathological examination of tumors using immunohistochemical marker panels.

Mature Intracranial Teratoma

SUMMARY Teratomas constitute a group of nongerminomatous germ cell tumors that are composed of an admixture of different tissue types representative of ectoderm, endoderm and mesoderm. Intracranial teratomas are rare, comprising approximately 0.5% of all intracranial tumors. They preferentially involve the midline structures, and occur primarily in children. We presented an unusual case of mature intracranial teratoma with extracranial extension in a 24-year-old man who complained of headache, nausea and vomiting. The intracranial expansive lesion was localized in the left frontotemporobasal region extending into the ipsilateral orbit. The patient underwent total resection of the tumor. No adjuvant treatment was given. On gross examination, the resected tumor was lobulated, containing heterogeneous solid and cystic components. Histologic investigation revealed the presence of various fully differentiated tissues representative of the three germ cell layers, including adipose tissue, cartilage, bone, striated muscle bundles, brain tissue, respiratory epithelium and glandular structures. The diagnosis of mature teratoma was established. Follow-up at four years did not show any evidence of recurrence. The presented case is an unusual example of mature teratoma with regards to the age of the patient and, especially, to the location of the tumor, both intraand extracranially. It is critical to recognize this rare entity by extensive sampling to rule out the presence of immature elements which may constitute only a minor part of the tumor. Sažetak Teratomi predstavljaju grupu negerminomskih tumora germinativnih ćelija, koji su građeni od mešavine različitih tipova tkiva ektoderma, endoderma i mezoderma. Intrakranijalni teratomi su retki i čine oko 0.5% svih intrakranijalnih tumora. Pretežno zahvataju strukture srednje linije i javljaju se primarno kod dece. U radu je prikazan bolesnik star 24 godine sa zrelim intrakranijalnim teratomom uz ekstrakranijalno širenje, što je praćeno glavoboljom, mukom i povraćanjem. Intrakranijalna ekspanzivna lezija bila je lokalizovana frontotemporobazalno levo sa širenjem u istostranu orbitu. Tumor je odstranjen u celini. Adjuvantna terapija nije primenjena. Makroskopskim pregledom, odstranjeni tumor bio je lobuliran sa heterogenom solidnom i cističnom komponentom. Histološkom analizom utvrđeno je prisustvo različitih diferentovanih tkiva sva tri germinativna ćelijska sloja, uključujući masno tkivo, hrskavicu, kost, snopove poprečno-prugastih mišićnih ćelija, moždano tkivo, respiratorni epitel i žlezdane strukture. Postavljena je dijagnoza zrelog teratoma. Nakon četiri godine praćenja nije otkrivena pojava recidiva. Prikazani slučaj zrelog teratoma je neuobičajen primer u pogledu godina starosti bolesnika i, posebno, lokalizacije tumora, intra- i ekstrakranijalno. Prepoznavanje ovog retkog entiteta ispitivanjem brojnih preseka tkiva je od presudnog značaja, budući da nezreli elementi mogu da čine samo minorni deo tumora.

Optimal bandwidth in optical FSK system influenced by laser phase noise

In this paper, an optical FSK system with TFS (two-filter structure) also known as dual-filter FSK is observed in the presence of laser phase noise. Sensitivity of the receiver is shown as a function of IF bandwidth and a bandwidth of the low-pass postdetection filter. It is shown that there is an optimal pair of bandwidths witch minimizes required receiver sensitivity: a few figures for different amounts of phase noise are given. The results in this paper are based on truncated Taylor expansion method.