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Biomedical subjects

G Grebe

Publications and source records attributed to G Grebe.

At least 19 recordsLinked to original sources
PubMed2003

Use of BANG polymer gel for dose measurements in a 68 MeV proton beam.

BANG polymer gel dosimetry using magnetic resonance imaging (MRI) was applied to an ophthalmologic 68 MeV proton beam. The object was to examine the use of BANG gel for the verification of proton fields in eye tumor therapy and to explore the applicability of polymer gel dosimetry in proton therapy under practical aspects. The gel phantoms were irradiated with monoenergetic and modulated proton beams. MRI analysis was carried out at clinical 1.5 and 3 T MR scanners. At constant LET, results show a linear relationship between spin-spin relaxation rates and dose. However, depth dose curves in BANG gel reveal a quenching of the Bragg maximum due to LET effects. The dose response of the gel for monoenergetic protons and spread-out depth dose distributions can be calculated based on ionization chamber measurements. Experiment and calculations show good agreement and indicate that BANG polymer gels might become a valuable tool in proton therapy quality assurance.

Equipment Failure Analysis↗
PubMed2001

Dynamic arc radiosurgery and radiotherapy: commissioning and verification of dose distributions.

PURPOSE: Conformal stereotactic radiosurgery and radiotherapy using a linear accelerator and a micromultileaf collimator (mMLC) offer the possibility of irradiating irregularly shaped target volumes. Dynamic arc radiosurgery and radiotherapy, i.e., stereotactic radiation therapy combining a moving gantry with a dynamic mMLC, enable the radiation even of lesions with concave structures. METHODS AND MATERIALS: The dynamic arc method requires additional tools for quality assurance (QA) and three-dimensional verification at a high spatial resolution. A QA program was developed. Dose distributions of planning target volumes with concavities were investigated in polymer gel phantoms. The radiation-induced change of the relaxation rate R(2) was measured by magnetic resonance imaging. The distributions were compared with image processing tools. RESULTS: Using the therapy-planning software BrainSCAN 4.0 (and 4.1 beta) in combination with the mMLC m3, deviations between the planned and measured 90% isodoses of about 2 mm were registered in the isocenter plane. Three-dimensional verification was feasible in the range of accuracy achieved in planning and dose measurement. CONCLUSIONS: Dynamic arc radiosurgery and radiotherapy offer excellent conformation even for complicated planning target volumes with concavities. The dose distribution calculated with the treatment-planning software used can be accomplished with the available equipment. Patients can be treated by dynamic arc radiosurgery and radiotherapy.

Calibration↗
PubMed1996

t(1;5)(q23;q33) in a patient with high-risk B-lineage acute lymphoblastic leukemia.

The t(1;5)(q23;q33) is a rare genetic anomaly that was reported previously in two infants with a myeloproliferative disorder and eosinophilia and in one adult patient with acute nonlymphocytic leukemia (ANLL). A 13-year-old boy with high-risk early pre-B acute lymphoblastic leukemia (ALL) who presented to our institution carried the t(1;5)(q23;q33). He had an initial blast count of 230 X 10(9)/L and responded poorly to prednisone. Complete remission (CR) was achieved, and he had a bone marrow (BM) relapse 3 months after despite intensive consolidation therapy. He underwent allogeneic BM transplantation (BMT) from a human leukocyte antigen (HLA)-identical siblings in early relapse with total body irradiation (TBI) and cyclophosphamide conditioning. He had a short second CR with a central nervous system (CNS) relapse on day + 106 after BMT. Two of the previously reported patients also did not respond to chemotherapy. The t(1;5)(q23;q33) appears to be a rare lineage nonspecific anomaly related to hematologic malignancies that are resistant to current therapy.

Adolescent↗
PubMed1995

[Imipenem/cilastatin versus ceftazidime-amikacin in the treatment of febrile neutropenic patients].

AIM: To compare the efficacy of imipenem/cilastatine and ceftazidime-amikacin in the treatment of febrile neutropenic patients. DESIGN: Open, prospective and randomized clinical study. PATIENTS: Fifty two patients (26 female) aged 16 to 80 years old with 60 episodes of neutropenia were studied. They were randomly assigned to receive imipenem/cilastatine in doses of 500 mg iv qid or the combination of ceftazidime 1 to 1.5 g iv tid and amikacin 7.5 mg/kg iv bid. RESULTS: Global response to initial therapy was 53% in patients receiving imipenem/cilastatine and 37% in those receiving ceftazidime-amikacin (p = ns). When other antimicrobial were added, a 90 and 85% infection eradication success was achieved respectively. Six febrile episodes in the group receiving imipenem/cilastatine and 12 episodes in the group receiving ceftazidime-amikacin had Gram positive cocci as the sole infectious agent (p < 0.04). A lower duration of neutropenia had a favorable influence on treatment outcome. Three patients receiving imipenem/cilastatine (10%) and four receiving ceftazidime-amikacin (13%) died. Superinfections and toxicity related to antibiotics were minimal in both groups. CONCLUSIONS: Imipenem/cilastatine and the combination of ceftazidime with amikacin were equally effective in the treatment of febrile episodes in neutropenic patients.

Adolescent↗
PubMed1994

[Cytogenetic studies of Chilean children with acute lymphoblastic leukemia].

Acute lymphoblastic leukemia (ALL) is the most frequent childhood cancer. The leukemic cells of ALL patients show several well defined numeric and structural chromosomal abnormalities which are universally known for its prognostic implications. We studied a group of 44 children with ALL, to investigate the incidence of chromosome aberrations in ALL, its lymphocyte lineage and some clinical feature associations, and the finding of non previously described aberrations. A high proportion of patients (79.5%) showed chromosomal abnormalities. Most of them had a pseudodiploid karyotype (46 chromosomes), characterized mainly by a translocation. In relation to chromosome number, 27% of them were hyperdiploid with more than 50; 9% hyperdiploid between 47-50 and 7% hypodiploid (less than 46). Among structural aberrations found, were the following recurrent translocations: t (1; 19), t (4; 11), t (9; 22) in 6.8%, 9.1% and 2.3% of cases respectively, all related to an early B immunophenotype. Other translocations found, compromised regions 7q22, 9p21 - 24. Two new translocations in ALL were found: t (1; 5)(q23; q33), apparently balanced, and t (13; 21)(q14; q22), unbalanced. Other recurrent structural changes found were: deletion (6q), (7q), (9p), (11q), (12p), inversion (3q), isochromosome (7q), maker chromosomes and double minutes. The distribution of chromosome abnormalities in this group of patients was in agreement with previous reports from other investigators.

Adolescent↗
PubMed1994

[Anemia associated with acute post streptococcal glomerulonephritis].

Thirty-three children with post-streptococcal acute glomerulonephritis, age mean: 8.3 years (range: 6 - 12) were studied prospectively. Mean initial hematocrit (Hct) was 31.6% with 90% showing Hct under the normal lower limit for this age group. Reticulocyte index (RI) was < 0.5 in half of the cases. Serum iron concentration, total iron binding capacity (TIBC) and percentage of transferrin saturation were normal for this age group although 75% of the children had increased serum ferritin levels. At the time of discharge, Hct increased to 35.1% but 44% still had anemia. Hct increased spontaneously for 105 days stabilizing at 38%. Based on Hct changes, 3 groups were defined: Group I (3 individuals): normal upon discharge; Group II (19): partial recovery at discharge, slow recovery stabilizing after 105 days; Group III (11): lower Hct, slower recovery but with RI significantly higher than group II (0.96 vs 0.45 p < 0.01). Our data suggest that although hemodilution is present in all, it may be considered the solely factor only in 3 cases (Group I). In group II, evidence of bone marrow depression was indicated by the low RI. On the other hand, the intense anemia that could not be justified only by hemodilution and marrow depression in group III, suggests other pathogenic factors.

Acute Disease↗
PubMed1993

[Effect of the prolonged use of intrauterine devices and oral contraceptive on iron nutrition].

The aim of this work was to study the effect of prolonged use of intrauterine devices (IUD) and oral contraceptives (OCO) normally prescribed at outpatient clinics of the Health Service on iron nutrition. Two hundred twenty three healthy women, aged 20 to 39 years were studied. Of these, 100 were using IUD and 97 OCO for three to five years and 26 were not using any pharmacological or mechanical contraceptive method (control group). Serum ferritin was significantly higher in the OCO group compared to IUD and control groups (58.9 +/- 2.2; 26.2 +/- 2.1 and 21.1 +/- 2.4 ng/ml respectively). There was a positive correlation between serum ferritin and hemoglobin in IUD and control groups and between ferritin and transferrin saturation in the OCO and control groups. The frequency of storage iron depletion (defined as a serum ferritin < 12 ng/ml) was 6.3, 0 and 25% in the IUD, OCO and control groups respectively. The numbers for iron-deficient erythropoiesis (defined as a transferrin saturation < 15%) were 7, 3 and 4% and for iron deficiency anemia, 6.5, 0 and 8%. It is concluded that the chronic use of IUDs leads to iron depletion and that measures to improve iron nutrition among women using them should be adopted.

Adult↗
PubMed1993

[Chronic myeloid leukemia: cytogenetic and molecular study and its relationship with the disease course].

The aim of this study was to perform a cytogenetic and molecular study in patients with chronic myelogenous leukemia and to seek a possible relation between bcr gene break points and the clinical evolution of the disease. The cytogenetic study allowed to establish the presence of Ph chromosome and the molecular study localized the break point in bcr region of chromosome 22 using the Southern technique, hybridizing with bcr fragment derived probes bcr1 and bcr2. Forty eight patients were studied, 27 male (aged 46.5 years) and 21 female (aged 56). Forty seven patients were Ph +. A rearrangement in 3' bcr region was found in 25 patients and in 5' region in 23. During the follow up period 20 patients developed a blast crisis or accelerated phase. In 11 of these the rearrangement was in region'3 and their chronic phase lasted a mean of 33.1 months; in 9 the rearrangement was in region 5' and their chronic phase lasted 44.1 months. There were no differences in event-free survival between those with rearrangement in region 3' or 5', however these was a tendency towards a longer chronic phase duration in those with 5' breaks. The lack of correlation between the location of break points and the evolution of the disease may be due to a selection of patients with a better evolution and the exclusion of those with a rapid progression to blast crisis or accelerated phase.

Adult↗
PubMed1992

[Infective complications of the use of permanent central venous catheters in oncology].

We analyzed the infectious complications associated with the use of permanent central venous catheters (PVC) in pediatric and adult cancer patients. 62 patients used 74 PVC (54 external, 20 subcutaneous), which were in place for an average of 200 days with a total observation period of 14,876 days, 152 febrile episodes occurred during this period, 87 in neutropenic patients (less than 500 neutrophils/mu, FN+) and 65 in non neutropenic patients (FN-). The incidence of bacteremia was 32% in febrile episodes in the first group (FN+C+ and 41% in the second (FN-C+). Overall there were 3.7 episodes of bacteremia per 1000 catheter days. We found a statistically significant difference in the incidence of bacteremia between the external and subcutaneous PVC in favor of the latter among patients over 15 years of age but not in the pediatric group. 14 PVC had to be removed due to an infection, 8 in patients with bacteremia and 6 in patients with exit site infections. We conclude that the use of PVC in the care of cancer patients is beneficial and safe, with a low incidence of infectious complications.

Adolescent↗
PubMed1991

[Intravascular coagulation in acute promyelocytic leukemia: analysis of coagulation and fibrinolysis parameters].

Eight pts with acute myeloid leukemia were studied to assess coagulation and fibrinolysis disturbances as a cause of hemorrhages associated to thrombopenia. Fibrinogen, products of fibrinogen to fibrin degradation, D-dimer, antithrombin III, protein C, plasminogen and alpha-2 antiplasmin determinations were performed at admission, during and after chemotherapy. All pts were on heparin during induction chemotherapy. Coagulation activation, which increased with the onset of chemotherapy (increases in D-dimer) and a decreasing trend at the end of the antileukemic therapy (normalization of fibrinogen levels) was observed. During the whole observation period alpha-2 antiplasmin levels remained very low. No significant changes were observed in antithrombin III or protein C levels. In conclusion, disseminated intravascular coagulation with associated thrombopenia is an important event in acute leukemia and an increased fibrinolytic activity due to low alpha-2 antiplasmin levels may take part in the genesis of hemorrhage. These data suggest that both heparin administration and the use of antifibrinolytic drugs may have a therapeutic effect.

Adolescent↗
PubMed1991

[Cytogenetic studies in myelodysplasias].

Cytogenetic studies were performed in 29 patients with myelodysplasia, 12 males and 17 females with a mean age of 61 years. The distribution of patients according to FAB groups were as follows: refractory anemia (RA) 7, sideroblastic refractory anemia SRA) 6, refractory anemia with excess blasts (RAEB) 12 and refractory anemia with transformation excess blasts (RAEB-t) 4. Cytogenetic anomalies were found in 48% over all, 78% in patients with RAEB and RAEB-t forms and only 23% in patients with simpler forms of myelodysplasia. Multiple and complex chromosomal alterations were found in 50% of abnormal studies, only in patients with complex forms. In general, structural rearrangements and deletions were less frequent than numeric defects, with a slight preponderance of chromosomal losses. Alterations of chromosomes 5, 7, 28, 21, 22, 8, 11 and 15 were the most commonly observed. Survival was decreased from 60 months in patients with normal karyotype to 6 months in those with chromosomal alterations. Thus, chromosomal abnormalities are related to excess blasts and to survival in patients with myelodysplasia.

Adolescent↗
PubMed1990

[Myelodysplasias: clinical experience with 35 patients].

Myelodysplasia, characterized by varied reductions of peripheral blood elements with normal or hypercellular bone marrow, is relatively frequent among older patients and may evolve to acute leukemia. We reviewed findings in 35 patients whom, according to the FAB classification were distributed as follows: simple refractory anemia (RA) 34%, sideroblastic refractory anemia (SRA) 14%, refractory anemia with excess blast forms (RAEB) 31%, chromic myelomonocytic leukemia (CMML) 12% and refractory anemia with excess blast forms in transformation (RAEBT) 9%. Cytogenetic studies performed in 16 patients were abnormal in 5 (31%), all among patients with poor prognosis forms of the disorder. All patients had anemia; thrombopenia and neutropenia were more frequent in subtypes RAEB, CMML and RAEBT). Mean survival rate was 30 months, significantly greater in RA and SRA compared to the other groups. Infections and development of acute leukemia were the causes of death.

Actuarial Analysis↗
PubMed1990

[Hemoglobin, serum iron and transferrin saturation among users of intrauterine devices and oral contraceptive agents].

We studied 60 females using either intrauterine device or taking oral contraceptive pills. Hemoglobin, serum iron, total iron binding capacity and saturation of transferrin were determined before and 4 and 10 months after starting a responsible paternity program. Women with a basal hemoglobin level below 12 g/dl were excluded. Age, parity and hematologic parameters were similar for both groups. A significant decrease in hemoglobin level and saturation of transferrin was observed at 10 months in intrauterine device users (13.6 to 13.1 g/dl and 36.2 to 26.9%, respectively). Use of oral contraceptive pills was not associated to hemoglobin decrease but a significant rise in saturation of transferrin was observed (36.2 to 43.9%, p less than 0.05).

Adult↗
PubMed1989

[Beta 2 microglobulin in some hematologic neoplasms].

Beta 2 microglobulin is a low molecular weight protein integrating the light chain HLA antigens. Its serum concentration is increased in different neoplasias and in renal failure. Using solid phase RIA we determined the concentration of beta 2 microglobulin in plasma and spinal fluid of 57 healthy individuals and patients with hematologic neoplasia. Serum levels were 1.34 +/- 0.34 mg/l and spinal fluid levels were 1.3 +/- 0.7 mg/l in healthy subjects. Serum levels in 29 patients with myeloma was 7.51 mg/l, significantly higher in those with renal failure (12.35 mg/l) compared to those without (4.54). In 30 patients with non-Hodgkin lymphoma the mean serum levels were 2.90 mg/l, significantly greater in those with active disease (3.18) than in those with remission (1.5). No difference was found according to the degree of malignancy. Patients with acute lymphatic leukemia had elevated values of beta 2 microglobulin while the disease was active (3.37 mg/l), decreasing to normal levels after remission (1.79 mg/l). Spinal fluid levels of beta 2 microglobulin were elevated only in patients with central nervous system involvement. Our results indicate that serum levels of beta 2 microglobulin are helpful in patients with hematologic neoplasia in assessing the activity of the disease and tumor mass, especially in multiple myeloma.

Adolescent↗
PubMed1989

[Deficiency of folates in pregnancy: effect of supplementary folic acid].

Higher folate needs are present during pregnancy, which may lead to tissular deficiency in the mother and to depleted newborn folate reserves. The aim of this work was to assess the prevalence of folate deficiency and to establish the rates of serum and red cell folate in two groups of mothers and newborn infants, one receiving only iron and the other iron and folate during pregnancy. The rates of serum and red cell folate found at the end of pregnancy were significantly higher in the group which received folate; however, the percentage of cases with tissular folate deficiency was low in both groups, with no significant difference (3.8% and 1.3%, respectively). These findings, along with the lack of effect of supplemental folate on erythropoiesis, pose some questions on the usefulness of supplemental folate during pregnancy in our country.

Adult↗