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In this paper, a network comprising wireless devices equipped with buffers transmitting deadline-constrained data packets over a slotted-ALOHA random-access channel is studied. Although communication protocols facilitating retransmissions increase reliability, a packet awaiting transmission from the queue experiences delays. Thus, packets with time constraints might be dropped before being successfully transmitted, while at the same time causing the queue size of the buffer to increase. To understand the trade-off between reliability and delays that might lead to packet drops due to deadline-constrained bursty traffic with retransmissions, the scenario of a wireless network utilizing a slotted-ALOHA random-access channel is investigated. The main focus is to reveal the trade-off between the number of retransmissions and the packet deadline as a function of the arrival rate. Towards this end, analysis of the system is performed by means of discrete-time Markov chains. Two scenarios are studied: (i) the collision channel model (in which a receiver can decode only when a single packet is transmitted), and (ii) the case for which receivers have multi-packet reception capabilities. A performance evaluation for a user with different transmit probabilities and number of retransmissions is conducted. We are able to determine numerically the optimal probability of transmissions and the number of retransmissions, given the packet arrival rate and the packet deadline. Furthermore, we highlight the impact of transmit probability and the number of retransmissions on the average drop rate and throughput.

Analysis of 32 patients operated on because of accidentally discovered adrenal tumors "incidentaloma" is presented. In 12 of them there was subclinical hormonal activity, in 9 of them tumors turned out to be pheochromocytoma and 3 of them were cortex adenoma. There were 20 hormonally inactive tumors, in 5 of them there were malignant lesions (4 of the cortex and 1 of the medulla). For evaluation of hormonal activity of adrenal tumors evaluation of chromogranin A and cortisol serum blood level or urine free cortisol level is recommended. For precise localization of the tumor beside USG also CT examination is of use. According to the high percentage of malignant lesions in "incidentaloma" type tumors, surgery treatment without delay is recommended. BAC or DHES in blood serum examinations were not found helpful in preoperative evaluating the lesions as benign or malignant. In case of preoperatively found subclinical hormonal hyperactivity of medulla pharmacological treatment with alpha and beta blockers in surgery preparation is recommended. Lateral extraperitoneal access for adrenalectomy is considered safe and provides good operational view. Laparoscopic procedure because of high percentage of malignant lesions in this group of patients is not justified.

A retrospective CT, MR, and clinical study was performed in 12 patients, five children and seven adults, with histologically proved primary CNS neuroblastoma. The CT and MR appearances of this neoplasia were more variable than generally recognized. Although seven tumors were predominantly intraparenchymal masses with calcification and cyst formation, five were intra- or juxtaventricular. CT was preferable to noncontrast MR both at initial diagnosis and follow-up for identification of calcification, recurrent tumor at surgical sites, and leptomeningeal disease. Noncontrast MR was useful primarily for localization of peri- and intraventricular lesions. We conclude that primary CNS neuroblastoma has a more variable radiographic appearance than is generally recognized, and that an intra- or periventricular epicenter is common.

Pneumothorax is the most common complication after CT-guided pulmonary interventional procedures and should be promptly diagnosed and treated. Because it is easier to obtain CT scans than chest radiographs after CT-guided interventional procedures, it is important to know the sensitivity of CT in detecting pneumothoraces. To determine the sensitivity of CT for detecting procedure-induced pneumothoraces, we retrospectively reviewed 70 pulmonary interventional procedures performed under CT guidance. The sensitivity for detecting pneumothoraces with CT was compared with the detection rate with expiratory chest radiographs. Thirty-two (46%) of 70 procedures resulted in pneumothorax. Twenty-nine (91%) of the pneumothoraces were detected on CT scans and 27 (84%) were detected on chest radiographs. The difference between these two detection rates was not statistically significant (p less than .90). We conclude that postprocedure CT scans can replace expiratory chest radiographs for the detection of pneumothoraces after CT-directed pulmonary procedures.