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Biomedical subjects

J Petrek

Publications and source records attributed to J Petrek.

At least 19 recordsLinked to original sources
PubMed2004

[Brain activity during language processing].

The neural system, responsible for language comprehension, must quickly process and integrate a large amount of heterogenous linguistic data. There is no appropriate and generally acceptable description of the architecture of this system. This means that no model of language processing is available that will allow, without problems, to interpret the wide range of disorders of language functions in neurological patients with focal lesions and explain the no less inconsistent results of experiments dealing with various aspects of language processing both in healthy people and in patients. In this paper are summed up the main findings from works of several authors who with electrophysiological recording techniques and metabolic imaging techniques (PET and MRI) sought answers to the question "where" and "how" in the brain are processed open class words and closed class words, nouns and verbs, or perhaps what is the temporal co-ordination and laterality of semantic and syntactic processes in language processing. The frequent contradictions in the findings, which a reader may quickly discover, are probably due to the design of the experiment, the properties of the stimulus applied, the type of the task to be solved during the experiment by its participants. In patients it may be also due to the accuracy of the determination of the anatomical localization and the extent of the lesions in nervous structures. In this context, however, it is necessary to be reminded that applied methods have their strong as well as weak points. Metabolic imaging techniques reliably inform of the exact localization of metabolically active brain structures, but they only give a rough picture of temporal dynamics of brain processes. On the other hand, electrophysiological techniques reflect precisely the temporal dynamics of neuronal activation near the recording electrode, but they say little about the activity of neuronal assemblies in areas remote from the site of registration.

Brain↗
PubMed2001

A trend analysis of the relative value of blue dye and isotope localization in 2,000 consecutive cases of sentinel node biopsy for breast cancer.

BACKGROUND: Among the advocates of blue dye, isotope, or combined dye-isotope mapping of the sentinel lymph node (SLN) for breast cancer, there is no universal consensus as to which technique is optimal and whether the relative value of each method changes with increasing experience. The objective of this study was to examine the relative contributions of blue dye and radioisotope to successful identification of the SLN as the SLN-mapping technique evolved over our first 2,000 consecutive cases. STUDY DESIGN: Using the first 2,000 consecutive SLN biopsy procedures for breast cancer, performed by eight surgeons (none previously experienced in SLN techniques) at one institution, using a combined technique of blue dye and isotope mapping, we report the institutional learning curve and the relative contributions of dye and isotope to identifying both the SLN and the positive SLN, by increments of 500 cases. RESULTS: Comparing the first 500 with the most recent 500 cases, success in identifying the SLN by blue dye did not improve with experience, although success in isotope localization steadily increased, from 86% to 94% (p < 0.00005). With the increasing success of isotope mapping, the marginal benefit of blue dye (the proportion of cases in which the SLN was identified by blue dye alone) steadily declined, from 9% to 3% (p = 0.0001). Parallel to this trend, the proportion of positive SLNs identified by blue dye did not change with experience (89% to 90%), but isotope success steadily increased, from 88% to 98% (p = 0.0015). The proportion of positive SLNs identified by blue dye alone declined from 12% to 2% (p = 0.0015). CONCLUSIONS: Using a combined technique of blue dye and radioisotope mapping, and with refinement of the radioisotope technique, we report 97% success identifying the SLN. Although we continue to recommend the use of both methods in SLN mapping for breast cancer, we observe with experience a declining marginal benefit for blue dye.

Breast Neoplasms↗
PubMed2001

Intradermal isotope injection is superior to intramammary in sentinel node biopsy for breast cancer.

BACKGROUND: The optimal sentinel lymph node (SLN) biopsy technique remains undefined in breast cancer. Injecting radiotracer or blue dye by a variety of routes seems to stage the axilla with comparable accuracy, and we have hypothesized that the dermal and the parenchymal lymphatics of the breast drain to the same SLN in most patients. Two previous studies from our institution support this concept: (1) a single-surgeon series of 200 consecutive SLN biopsy procedures demonstrating a high dye-isotope concordance for both intradermal (ID) and intraparenchymal (IP) isotope injection, and (2) a series of 100 procedures validated by a backup axillary dissection (ALND) in which the false-negative rate following ID isotope injection was comparable to that of our previous results with IP injection. Here, we directly compare the results of SLN biopsy using either ID or IP isotope injection for our entire experience of SLN biopsy procedures in which a backup ALND was done. METHODS: This is a retrospective, nonrandomized study of 298 clinical stage I to II breast cancer patients having SLN biopsy with a backup ALND planned in advance, comparing the results of ID (n = 164) and IP (n = 134) isotope injection. All patients had IP injection of blue dye. Endpoints included (1) successful SLN identification, (2) false-negative rate, (3) dye-isotope concordance, and (4) the SLN/axillary background isotope count ratio. RESULTS: ID isotope was more successful than IP, identifying the SLN in 98% versus 89% of cases, respectively. False-negative results (4.8% vs 4.4%) and dye-isotope concordance (92% vs 93%) were comparable between the 2 groups, and SLN/axillary background isotope count ratios were significantly higher with ID than with IP injection (288/1 vs 59/1). CONCLUSIONS: ID isotope injection identifies the SLN more often than IP, stages the axilla with comparable accuracy, and is associated with higher levels of SLN isotope uptake. The dermal and parenchymal lymphatics of the breast drain to the same axillary SLN in most breast cancer patients, and ID isotope injection is the procedure of choice in this setting.

Adult↗
PubMed2000

Sentinel lymphadenectomy accurately predicts nodal status in T2 breast cancer.

BACKGROUND: Sentinel lymph node biopsy (SLNB) has emerged as a reliable, accurate method of staging the axilla for early breast cancer. Although widely accepted for T1 lesions, its use in larger tumors remains controversial. This study was undertaken to define the role of SLNB for T2 breast cancer. STUDY DESIGN: From a prospective breast sentinel lymph node database of 1,627 patients accrued between September 1996 and November 1999, we identified 223 patients with clinical T1-2N0 breast cancer who underwent 224 lymphatic mapping procedures and SLNB followed by a standard axillary lymph node dissection (ALND). Preoperative lymphatic mapping was performed by injection of unfiltered technetium 99 sulfur colloid and isosulfan blue dye. Data about patient and tumor characteristics and the status of the sentinel lymph nodes and the axillary nodes were analyzed. Statistics were performed using Fisher's exact test. RESULTS: Two hundred four of 224 sentinel lymph node mapping procedures (91%) were successful. Median tumor size was 2.0 cm (range 0.2 to 4.8 cm). One hundred forty-five of the 204 patients had T1 lesions and 59 patients had T2 lesions. There were 92 pathologically positive axillae, 5 (5%) of which were not evident either by SLNB or by intraoperative clinical examination. The false-negative rate and accuracy were not significantly different between the two groups, but axillary node metastases were observed more frequently with T2 than with T1 tumors (p = 0.005); other factors, including patient age, prior surgical biopsy, upper-outer quadrant tumor location, and tumor lymphovascular invasion were not associated with a higher incidence of false-negative SLNB in either T1 or T2 tumors. CONCLUSIONS: SLNB is as accurate for T2 tumors as it is for T1 tumors. Because no tumor or patient characteristics predict a high false-negative rate, all patients with T1-2N0 breast cancer should be considered candidates for the procedure. Complete clinical examination of the axilla should be undertaken to avoid missing palpable axillary nodal metastases.

Adult↗
PubMed1997

[Use of personal computers for simulation experiments in the teaching of physiology--methods].

The paper describes the use of PC in laboratory courses in physiology for the simulation of animal experiments or for simulation of behaviour of some functional systems of an organism in various experimental situation. It presents simple and non expensive system enabling to a large group of students (up to 24) to follow simultaneously on their monitors the course and results of the computer simulation.

Animals↗
PubMed1996

[Computer simulation of the activity of selected functional systems in the body during maintenance of homeostasis].

A computer with an appropriate software may greatly contribute to the understanding of relationships and interactions among physiological processes in the body and thus to influence the speed and effectiveness of learning. Presented computer model "The Internal Environment", briefly described in this paper, illustrates this fact. This model allows to simulate behavior of some functional systems in various experimental situations. The subsequent evaluation of the activity changes in these systems can help students to understand and interpret principles of the activity of the homeostatic mechanisms. That is why the computer simulation is an appropriate starting point at seminars where problems of the internal environment stability maintenance are to be discussed.

Computer Simulation↗
PubMed1991

Arm edema in conservatively managed breast cancer: obesity is a major predictive factor.

To identify risk factors in the development of arm edema (AE) after conservative management of breast cancer, the authors prospectively measured differences in upper and lower arm circumference in 282 patients with stage I or II breast cancer who received radiation. AE was defined as a difference of 2.5 cm or more in either measurement between treated and untreated arms. Median follow-up was 37 months (range, 7-109 months). The crude frequency of AE overall was 19.5% (55 patients). In 21 patients (7.4%) AE was transient; 34 patients (12.1%) had persistent AE, which is the focus of this article. The 5-year actuarial incidence of persistent AE was 16%. The crude risk of persistent severe AE was 3.9%. Various factors were examined for their ability to enable prediction of AE. Treatment-related factors did not significantly enable prediction of AE, whereas factors related to patient size, such as body mass index, were strongly associated with both the frequency and severity of AE.

Adult↗
PubMed1991

Auditory brain stem responses recorded and processed by analyser HEAD/TNS: normative data.

In 31 healthy people (14 men, 17 women) the authors analysed the shape of auditory brain stem responses (ABR) registered on short acoustic stimulus (click) in the vertex. Beside the shape of the responses was also evaluated the dependence of the latencies of each peak of ABR on the position of the reference electrode, on the character of the stimulus and on sex. The data obtained made possible producing one's own laboratory norm for measuring the normality of ABR recorded on the registration apparatus, with TNS microcomputer as its central component.

Adolescent↗
PubMed1987

Limited resection for breast cancer: a study of inked specimen margins before radiotherapy.

This is an analysis of tumor margins of 108 patients who underwent a limited resection for infiltrating breast cancer, prior to starting radiation therapy. This represented the initial resection (IR) in 75 patients, and a re-excision (RE) after biopsy elsewhere in 33 patients. All specimens were processed by the India ink method prior to frozen and paraffin section analysis. Overall, the incidence of involved margins was 28% for the IR group, and 15% for the RE group. No correlation was found with the axillary node status, or with the type of prior surgery in the RE group. The data suggest a correlation between increasing tumor size and margin involvement. Further surgery in the IR group with involved margins yielded negative margins in all cases; the finding of residual carcinoma was correlated with the type of secondary surgery, that is, further re-excision or mastectomy.

Biopsy↗
PubMed1987

Fibroadenomas with stromal cellularity. A clinicopathologic study of 21 patients.

Data on clinical and pathologic features of tumors from 21 patients who had breast tumors compatible with juvenile (cellular) fibroadenomas (JCF) were reviewed. All patients were black females ranging in age at time of presentation from 10 to 39 years, with a median age of 15 years. Follow-up (median period, six years) was obtained for 20 patients. Patients were categorized into two groups; 13 had solitary lesions and eight had multiple and successive lesions. No histologic differences were observed between JCF occurring as solitary or multiple tumors or between lesions occurring in patients younger and older than age 20 years. The JCF was shown to be a fairly distinct clinicopathologic entity that characteristically occurred in adolescents, but which was occasionally seen in young adults. It had a benign course, characterized by synchronous and metachronous multicentricity, rather than local recurrence.

Adenofibroma↗