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Biomedical subjects

B Nilsson

Publications and source records attributed to B Nilsson.

At least 757 records · Page 42Linked to original sources
PubMedDate not supplied

Fluence perturbation in photon beams under nonequilibrium conditions.

The perturbation effect in parallel-plate ionization chambers used for buildup measurements has been investigated. The fluence perturbation due to electrons emitted through the side walls are thoroughly investigated by measurements using film and extrapolation chambers and by calculations. The electron fluence varies both with side wall material and chamber geometry. In order to obtain a small perturbation effect, the chamber should have a large guard width compared to the electrode separation and the side walls should have as large an angle as possible with the central axis. The side wall should be of the same material as the rest of the chamber. The perturbation effect is also dependent on the electron contamination of the beam and angular distribution of the electron fluence. It is thus not possible to correct the perturbation effect in one parallel-plate chamber with fixed plate separation with correction factors obtained with extrapolation chambers of other dimensions. In order to make accurate surface dose measurements extrapolation chambers are therefore strongly recommended in favor of fixed parallel-plate chambers.

Electrons↗
PubMedDate not supplied

A study of interface effects in 60Co beams using a thin-walled parallel plate ionization chamber.

A large plane-parallel ionization chamber has been constructed to investigate interface effects in 60Co beam. The designed geometry yields negligible perturbation from the side walls, as opposed to the large effects existing in commercially available plane-parallel chambers. The chamber has been used to investigate interface phenomena in transition zones using a wide range of elements (Z = 4-82) as front- and back-scattering media and a clinically relevant 60Co gamma-ray field size. The effects of varying the chamber height discretely (0.5-11 mm) and increasing the wall thickness (1-9 mg/cm2) have been investigated. The variation of the measured ionization with the experimental setup (air gap between backscatter material and chamber wall, measurements at dmax and at 5-cm depth, varying the material both in front of and behind the chamber, etc.) has also been investigated. The simple geometry of the ion chamber has been found optimum for benchmark studies of Monte Carlo calculations. The ion chamber is suited for investigating experimentally the effects of varying transport parameters used in Monte Carlo simulations. The results presented show that the complex physical mechanisms governing 60Co interface dosimetry still make Monte Carlo condensed-history (macroscopic) techniques uncertain. It has been found that the EGS4 Monte Carlo system, together with the user code DOSRZ V4.0 and the PRESTA algorithm, yields good agreement with experiments for low and medium Z (main interest in dosimetry and radiotherapy), but may underestimate up to 10% the backscatter from high-Z materials even when transport parameters are optimized.

Algorithms↗
PubMedDate not supplied

Combined hepatocellular-cholangiocarcinoma. Diagnostic challenge in hepatic fine needle aspiration biopsy.

OBJECTIVE: To study the cytohistologic features of combined hepatocellular-cholangiocarcinoma (CHCC-CC) in fine needle aspiration biopsy (FNAB) material. STUDY DESIGN: Six hepatic FNAB cases with cell blocks (five) and hepatic resections (two) were analyzed cytohistologically and immunohistochemically. RESULTS: The six cases were diagnosed as CHCC-CC based on clinicopathologic correlation. Unequivocal hepatocellular carcinoma (HCC) cells corresponding to Edmondson and Steiner's grade 3 lesions were identified in the FNAB in three instances. Adenocarcinoma, represented by cohesive columnar cells with ovoid, basal nuclei displaying nuclear palisading, acini and/or papillary structures with variable intracytoplasmic intraacinar or brush border mucin production, was identified in all cases. Intermediate cells with hybrid/polymorphic cytologic features straddling malignant hepatocytes and glandular cells were identified in five instances. Tissue alpha-fetoprotein was negative. There was brush border and/or diffuse cytoplasmic p-carcinoembryonic antigen immunoreactivity in the glandular elements. CONCLUSION: FNAB diagnosis of CHCC-CC is possible if the clinical, cytohistologic and immunohistochemical findings support the presence of HCC and adenocarcinoma. Intermediate cells pose a great challenge to recognize and define: they tend to lose the classic cytologic features of malignant hepatocytes and acquire glandular characteristics. At the very least, there should be a high index of suspicion. These cases underscore the necessity for clinicopathologic correlation in enhancing the precision of FNAB diagnoses.

Adenocarcinoma↗
PubMedDate not supplied

Fine needle aspiration biopsy of hepatic leiomyosarcoma. An unusual epithelioid variant posing a potential diagnostic pitfall in a hepatocellular carcinoma-prevalent population.

OBJECTIVE: To study the cytomorphologic features of hepatic smooth muscle tumors on fine needle aspiration biopsy (FNAB) material in a hepatocellular carcinoma (HCC)-prevalent population, in which a potential diagnostic pitfall is an unusual variant of metastatic epithelioid leiomyosarcoma seen on aspiration cytology. STUDY DESIGN: FNABs of five cases of metastatic hepatic leiomyosarcomas were studied cytohistologically and immunocytochemically. In addition, ultrastructural studies were performed in one unusual case. Resected hepatic specimens and all other relevant histopathologic specimens were reviewed. RESULTS: Classically, aspirates of leiomyosarcoma produced syncytial masses of spindle cells characterized by overlapping, cigar-shaped nuclei and truncated ends. An unusual variant of metastatic epitheliod leiomyosarcoma was studied, with cytohistologic, immunohistochemical and ultrastructural correlation. CONCLUSION: Hepatic spindle cell lesions consist mainly of metastatic leiomyosarcomas. The diagnosis of malignancy and metastatic status of hepatic smooth muscle tumors is facilitated by the presence of an extrahepatic primary tumor. In a hepatitis B virus-endemic population, HCC, sarcomatoid type, has to be considered in the differential diagnosis of hepatic spindle cell lesions and the classic type, in epithelioid variants of smooth muscle tumors.

Adult↗
PubMedDate not supplied

pCEA canalicular immunostaining in fine needle aspiration biopsy diagnosis of hepatocellular carcinoma.

OBJECTIVE: To assess the usefulness of bile canalicular polyclonal carcinoembryonic antigen (pCEA) immunostaining in fine needle aspiration biopsy (FNAB) diagnosis of hepatocellular carcinoma (HCC). STUDY DESIGN: Hepatic FNAB with cell blocks of 72 confirmed and 6 possible HCC and 23 non-HCC malignancies (controls) were analyzed. Sections were stained with antibody to pCEA using the streptavidin biotin-immunoperoxidase method and results correlated with tumor grade and other parameters used in HCC diagnosis. RESULTS: Canalicular pCEA staining was observed in 60 (83%) of the 72 HCC. This category comprised 29%, 31%, 36% and 4% grade 1-4 tumors, including 7 small cell, 4 clear cell and 1 giant cell variants. With increasing anaplasia, the canaliculi became infrequent, irregularly distributed, and increasingly distorted and interrupted. Canalicular staining helped distinguish clear and small cell variants from metastatic renal cell carcinomas and neuroendocrine tumors, respectively. Of the six problematic cases, one was confirmed to be HCC with plasmacytoid features and five to be adenocarcinomas, of which three could have been combined hepatocellular-cholangiocarcinomas. Liver cell dysplasia also displayed an abnormal canalicular pattern. No cytoplasmic staining was seen in pure HCC. CONCLUSION: pCEA immunostaining cannot separate malignant, dysplastic or benign hepatocytes. It is usually not required in cytodiagnosis of most HCC. However, it is most helpful in confirming atypical variants of HCC, which may mimic other tumors.

Adenocarcinoma↗
PubMedDate not supplied

Fine needle aspiration biopsy of small/intermediate cell tumors in the liver. Considerations in a southeast Asian population.

OBJECTIVE: To assess the diagnostic problems and accuracy involved in rendering an exact cytologic diagnosis, including reference to a primary site of origin, on fine needle aspiration biopsies (FNABs) of small/intermediate cell tumors of the liver. STUDY DESIGN: Thirty-five hepatic FNABs of small/ intermediate tumors, neuroendocrine tumors (NETs) and poorly differentiated or undifferentiated cancers occurring in adults were analyzed. Ancillary studies, including immunohistochemistry, were performed whenever necessary. All other relevant histopathologic sections and medical records were reviewed. RESULTS: There were 26 metastases, while 9 were considered primary lesions. The aspirates were categorized into 11 NETs (pancreas 5, lung 1, liver 2, unknown primary 3); 9 undifferentiated nasopharyngeal carcinomas; 2 small cell undifferentiated carcinomas (lung 2); 4 undifferentiated carcinomas, not otherwise specified (lung 1, pancreas 1, liver 1, unknown 1); 1 lobular-ductal carcinoma (breast); 1 glioblastoma multiforme (brain); 1 ovarian carcinoma; 1 non-Hodgkin's lymphoma (liver); and 5 primary hepatocellular carcinomas. CONCLUSION: There was histologic and/or immunohistochemical confirmation in 25 cases (71%). Some of the limitations in categorization of such tumors obtained by FNAB can be overcome by immunohistochemistry. Information gleaned from a precise cytologic diagnosis can sometimes only favor a particular primary site.

Adult↗
PubMedDate not supplied

Cerebral vasomotor reactivity in normotensive and spontaneously hypertensive rats.

Intravenously injected metaraminol induced a larger blood pressure increase in spontaneously hypertensive rats (SHR) than in normotensive controls (NR) when the pressure was raised from the same starting level. Cerebral blood flow (CBF) response in NR was either perfect autoregulation, partial autoregulation or "break-through." When present, the autoregulatory response was very rapid, i.e. the flow returned to the initial value within 10-15 sec. All SHR showed an initial prompt vasoconstrictor response which was followed after 30-40 sec by a gradual flow increase. The blood pressure elevation was highest in SHR when hypertension was induced by compression of the aorta, which supports the hypothesis that the enhanced response is, at least in part, a consequence of an increased vessel wall to lumen ratio. The characteristic CBF pattern observed in SHR after a metaraminol-induced rise in blood pressure was not seen when the blood pressure was increased by aortic compression, which suggests an effect of the drug separate from its pressor effect. During maximum vasodilatation the cerebrovascular resistance (CVR) was considerably higher in SHR than in NR. Assuming an equivalent vessel density in the 2 groups, our results suggest that structural changes in resistance vessels in SHR encroach on the lumen.

Animals↗
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rCBF in patients with carotid occlusion. Resting and hypercapnic flow related to collateral pattern.

rCBF was measured by 133Xenon inhalation technique in 39 patients with unilateral carotid artery occlusion in a subacute-chronic stage. Resting flow values (ISI) varied between 23.7 and 52.4 ml/100 g/min. An almost constant finding was interhemispheric asymmetry, the degree of which was correlated with the severity of the initial symptoms. An ischemic focus was an insignificant finding. The CO2 response was normal in patients with angiographic signs of circle of Willis collateral flow and without significant contralateral carotid stenosis, whereas it was impaired in patients with a retrograde ophthalmic flow or collateral flow via the circle of Willis and contralateral carotid stenosis greater than or equal to 50%. It is concluded that the CO2 response in useful rCBF variable and may be applied for analysis of collateral flow capacity in patients with carotid artery occlusion considered for bypass surgery.

Adult↗
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A venous outflow method for measurement of rapid changes of the cerebral blood flow and oxygen consumption in the rat.

A technique for continuous measurement of cerebral venous outflow in the rat is described. The method involves cannulation of one retroglenoid vein close to its exit from the skull, and diversion of cerebral venous blood through a closed extracorporal circuit with a drop recording device, the blood being returned to the central venous circulation via a catheter in the external jugular vein. Occlusion of the contralateral retroglenoid vein increases measured flow and minimizes extracerebral contamination of the diverted cerebral venous blood. The venous outflow system is not further isolated from cerebral or potential extracerebral collaterals. Thus, the mass of tissue drained cannot be exactly defined anatomically. However, the experiments involving changes of PP, arterial CO2 tension, and induction of epileptic seizure activity, and simultaneous indirect measurements with radioactive tracer technique, indicate that significant extracerebral contamination does not occur and that in short term measurements the venous outflow represents cerebral blood flow (CBF) in a constant mass of (dorsal and central, mainly forebrain) cerebral tissue. Measurement of arterial blood pressure and pressure in the cisterna magna allows calculation of cerebral perfusion pressure (PP). By simultaneous measurement of arterial and cerebral venous oxygen content changes in cerebral oxygen consumption (CMRO2) can be calculated. The method has been applied to document several situations of transient CBF and CMRO2 changes.

Animals↗
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Hinged cast after knee ligament surgery.

One hundred thirteen patients scheduled for repair of knee ligament injuries were randomized to postoperative immobilization in either a hinged or a long leg cast. The time of disability (i.e., sick leave) was significantly shorter (6 weeks) with a hinged cast, but only in ACL cases. All types of injuries regained their range of motion more rapidly after use of a hinged cast. There was no evidence that the motion permitted in a hinged cast hampers the result as regards to stability.

Adolescent↗
PubMedDate not supplied

Immunodeficiency and prognosis in patients with non-Hodgkin's lymphomas.

Monocyte depleted blood lymphocyte subpopulations, their functions and relation to prognosis were studied in 68 untreated adult patients with non-Hodgkin's lymphomas classified according to the Kiel nomenclature. The median observation time was 48 months (range 41-60). The mean total blood lymphocyte and T (SRBC-rosetting) cell counts were significantly decreased as compared with age-matched controls (n = 57). Twenty-five per cent of the patients had a monoclonal blood B lymphocyte population. The spontaneous lymphocyte DNA synthesis, measured as incorporation of 14C-thymidine, was increased and the response to mitogen and antigen stimulation was decreased. Blood lymphocyte counts and functions before treatment were not related to the rates of remission or survival.

Adult↗
PubMedDate not supplied

Relapse factors during maintenance therapy of acute lymphoblastic leukemia in children.

A statistical analysis of possible risk factors for relapse during maintenance therapy (MT) for acute lymphoblastic leukemia (ALL) has been performed. The patient material consists of 64 patients. Twenty-six patients were classified as standard risk (SR), 21 as intermediate risk (IR), and 17 as high-risk (HR) patients. Seventeen patients relapsed and 50 patients (78%) are alive at a median observation period of 86 months (range 39-146 months). Mean white blood cell count (mean WBC) based on weekly determinations, duration of treatment interruption, and the number of infectious episodes were calculated in each patient during the first 6 months of MT. In analyses starting at 6 months after the beginning of MT, these factors were related to relapse risk, time to relapse, and time to infection. Using the median WBC value (3.9 x 10(9)/L) of all patients during the first 6 months as a cutoff point, 14 patients with levels higher, and 3 patients with levels lower relapsed (p = .0004). Adjustment of mean WBC for leukemia risk groups had no influence on the analysis. Time to relapse was related to duration of interruption of MT (p less than .01). Time to relapse was not related to leukemia risk groups. Infection frequency was higher in HR patients compared to SR and IR risk patients (p = .04). As WBC level had a prognostic value and was previously shown to be related to 6-mercaptopurine (6-MP) peak plasma concentration, monitoring 6-MP plasma levels during MT could be helpful for optimizing treatment.

Antineoplastic Combined Chemotherapy Protocols↗
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Silicon diodes as detectors for backscatter radiation in photon fields.

We investigated the use of unencapsulated silicon semiconductor detectors for backscatter radiation detection. The results were compared with Monte Carlo (MC) calculations modelling the experimental set-up. A special diode was manufactured, which was designed so that it allowed the positioning of different materials in close contact with the detector surface. Polymethylmethacrylate (PMMA), Pb, Ti and Fe (stainless steel) were used as backscatter materials. The diode signal was measured by integrating the current when irradiating the diode with an equal photon fluence obtained from a medical Co-60 source. When compared to the signal with PMMA as backscatter material the increase in signal was 21%, 27% and 73% for Ti, Fe and Pb, respectively. This is in reasonable agreement with the MC calculations, when taking the effective measurement depth in the Si diode detector into account.

Cobalt Radioisotopes↗
PubMedDate not supplied

Recovery of extracellular human insulin-like growth factor-I and II as a fusion protein from Escherichia coli culture broth by aqueous two-phase extraction.

The primary purification of human insulin-like growth factor-I (IGF-I) and IGF-II, produced extracellularly in Escherichia coli as a fusion to two domains (ZZ) derived from staphylococcal protein A, has been studied. First, the partitioning of IgG-affinity purified ZZ-IGF-I and ZZ-IGF-II, respectively, to the top phase in poly(ethylene glycol)/potassium phosphate aqueous two-phase systems were investigated. Thereafter, the extraction of ZZ-IGF-I with a poly(ethylene glycol) 1500/potassium phosphate system was performed directly in the bioreactor after the cultivation. This resulted in a reduction of the cultivation volume more than 3-fold with a recovery of about 90% of target protein in a poly(ethylene glycol)-rich phase. The majority of the cells partitioned to the potassium phosphate-rich bottom phase, while a smaller fraction was collected at the interface, and/or as a densely packed cake on top of the interface. Contaminating proteins were also eliminated to some extent, which resulted in an almost 2-fold protein purification. Some obvious benefits offered by the aqueous two-phase system in the primary purification have been demonstrated: Firstly, the possibility to an early process volume reduction and thereby a concentration of the target protein. Secondly, a simultaneous protein purification was achieved. From this work it can be concluded that aqueous two-phase extraction should be considered as an attractive candidate for the primary steps during the design of new purification processes for extracellular proteins.

Cell Separation↗
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Bilateral carcinoid tumor of the breast. Report of a case with diagnosis by fine needle aspiration cytology.

A case of bilateral carcinoid tumors of the breast was studied by cytology, histology, immunohistochemistry and electron microscopy. The preoperative aspiration cytologic findings strongly suggested a carcinoid tumor of the breast. The differential diagnosis with fine needle aspiration cytology of other breast lesions, the bilaterality of the condition and terminology are discussed.

Biopsy, Needle↗
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Fine needle aspiration biopsy of hepatocellular carcinoma. Some unusual features.

The cytologic features of fine needle aspiration smears from 28 hepatocellular carcinomas (HCC) were reviewed. All aspirations except one were guided. There were 14 well-, 11 moderately and 3 poorly differentiated HCC. The better-differentiated HCC were characterized by similarity of the tumor cells to hepatocytes (83%), cohesive cell clusters with a trabecular arrangement (72%) and presence of sinusoidal endothelial cells (66%). Other features included bile production (38%), atypical hepatocytic naked nuclei (52%), acinar formation (31%), intracytoplasmic vacuoles (14%) and abnormal vascular patterns (14%). Poorly differentiated HCC showed dyshesive pleomorphic cells. Unusual cytologic features from a well-differentiated HCC with fatty change and an HCC with a prominent acinar component are described. The identification of fatty change in dissociated well-differentiated hepatocytes or cytologic features suggestive of an adenocarcinoma do not preclude the diagnosis of HCC. The usefulness of cell blocks is emphasized.

Adult↗
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Clinical results in patients provided with conical crown retained dentures.

During 1985 and 1986, 25 patients were treated with conical crown retained dentures, 26 in the maxillary arch and four in the mandible. The primary indication for having used these dentures was the presence of only a few teeth, mostly in unfavorable positions. Clinical findings after 24 to 43 months are reported and considered promising. Patients were generally satisfied and only comparatively small tissue changes were found.

Adult↗