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Biomedical subjects

G Karanikas

Publications and source records attributed to G Karanikas.

At least 19 recordsLinked to original sources
PubMed2002

Positron emission tomography with [18F]2-fluoro-D-2-deoxyglucose (FDG-PET) predicts relapse of malignant lymphoma after high-dose therapy with stem cell transplantation.

We have determined the predictive value of [18F]2-fluoro-2-deoxy-glucose (FDG-PET) in patients with Hodgkin's disease (HD) and aggressive non-Hodgkin's lymphoma (NHL) scheduled for high-dose therapy with stem cell transplantation (HDT/SCT). Inclusion criteria were the presence of an FDG-PET scan after chemotherapy (ChT) within 8 weeks prior to HDT/SCT and available follow-up data. Sixteen patients (10 NHL and six HD) were observed during a follow-up period of 4 to 28 months (median 13 months). Before SCT, five patients had a negative PET, three were weakly positive, two moderately positive, and six strongly positive. None of the five patients with a negative PET before HDT/SCT relapsed and two of three patients with a weakly positive scan are still in remission after HDT/SCT. Of eight patients with a moderate or high positive PET before HDT/SCT, seven relapsed and one died of early HDT/SCT related complications (P< 0.01). Three of eight relapsing patients died of lymphoma 5 to 10 months after SCT and in one additional patient not responding to HDT/SCT, the main cause of death was chronic toxicity 4 months after transplantation. After 12 months, in PET-negative patients the overall and relapse-free survival was 100%, in PET-positive patients 55% and 18%, respectively. In NHL, two patients with negative PET, but with an age-adjusted international prognostic index (AaIPI) of 2 and one with AaIPI = 1 are still in remission. In the seven PET-positive subjects, one patient with AaIPI = 0, three with AaIPI = 1, and two with AaIPI = 2 relapsed. We conclude that FDG-PET is accurate in the prediction of relapse prior to HDT/SCT in patients with lymphoma. It provides additional information when compared with the AaIPI.

Adult↗
PubMed2001

FDG-PET in adrenocortical carcinoma.

Adrenal cortical carcinoma (ACC) is a rare malignant neoplasm with a poor prognosis. Radical surgery of the primary tumor and of local as well as of distant recurrence is the only effective treatment, and requires accurate and early localization of recurrent tumors. In this regard, we prospectively scanned 10 patients with ACC, 8 during follow-up and 2 at primary work-up. In all patients PET scans from the neck to the upper thighs were obtained 45 minutes after injection of 370 MBq [18F]FDG. Reading was done visually, with the investigator blinded to the results of other diagnostic modalities. All known sites of ACC lesions showed markedly increased FDG uptake. In 3 patients, previously unknown lesions were identified by PET in the lung (one lesion), the abdomen (3 lesions), and the skeleton (multiple), respectively. One false positive liver focus was shown by PET aside from the true positive lung metastases in the same patient. The sensitivity/specificity of PET based on different organs was 100/97%, that based on the number of PET-detected lesions (N = 23) was 100/95%. PET altered or influenced the tumor stage in 3/10 patients, modifying the subsequent therapeutic management in 2/10 patients. We conclude that FDG-PET is highly useful in ACC and should be included in the work-up for initial staging as well as for follow-up.

Abdominal Neoplasms↗
PubMed2001

Radiation exposure from patients treated with 165Dy-ferric hydroxide.

In radiation synovectomy about 10 GBq 165Dy-ferric hydroxide is injected into major joints. Measurements of the dose rates were performed at distances of 5 cm, 0.5 m, 1 m and 2 m from the surface of the treated joints (knees) until 200 min after the application in 16 patients in order to estimate the radiation exposure of persons in the neighbourhood of the patients. The highest doses were estimated for the fingers of the technologist (320 microSv) and for the physician (700 microSv). Special shields for the syringes were constructed for dose reduction. The whole-body doses were 103 microSv for the technologist and 40 microSv for the physician. After the discharge of the patient to a ward or home, other persons at 1 m distance from the patient might receive 88 microSv, which is less than 9% of the annual permissible dose. Our results clearly demonstrate that the calculated radiation exposure to personnel and family members is well below the maximum annual dose limit for non-professionally exposed persons.

Algorithms↗
PubMed2000

Influence of drugs on myocardial iodine-123 metaiodobenzylguanidine uptake in rabbit myocardium.

About 15 years ago, iodine-123 metaiodobenzylguanidine (MIBG) myocardial imaging was introduced for the evaluation of myocardial sympathetic nerve function. Two uptake mechanisms for MIBG have so far been identified: uptake type I, a saturable, energy-dependent mechanism, and uptake type II, a non-saturable, energy-independent mechanism. We incubated isolated rabbit myocardial tissue samples with 123I-MIBG in order to assess the uptake characteristics and the influence of varying incubation conditions. Furthermore, we examined the effects of several drugs and uptake inhibitors on the myocardial uptake of MIBG. The in vitro myocardial uptake of MIBG reached a steady plateau at 23.87%+/-3.63% after 1 h, i.e. a concentration gradient of 10, in a thermo-independent manner within a concentration range from 1.5 to 1500 microM. This indicates an unsaturable uptake process in the tested concentrations. Preincubation with the following drugs caused a significant inhibitory effect on myocardial MIBG uptake: haloperidol, levomepromazine, metoprolol, labetalol and clomipramine. According to our findings, the uptake mechanism seems to be an unspecific process, but the concentration gradient of 10 makes passive diffusion unlikely. Further studies with uptake-II-blocking substances as well as with isolated myocardial cells will be needed to clarify the nature of the myocardial MIBG uptake mechanism.

3-Iodobenzylguanidine↗
PubMed2000

Radioactive contamination of contact lenses during radioiodine therapy.

Although the secretion of radioiodine in tears is not unexpected, there are only few investigations in that field. We report the measurement of 131I in disposable contact lenses for daily use during radioiodine treatment. After administration of 740 MBq 131I, all contact lenses of a 59-year-old female used the day before and 5 days after radioiodine therapy were collected and measured in a gamma counter. Activities of 124 Bq (right) and 139 Bq (left) were measured in the contact lenses used during the first day after administration of radioiodine. The activity in the contact lenses of the following days was significantly lower. An initial dose rate of approximately 0.31 microSv x h(-1) was caused by the radioactivity resulting in a total dose of 13 microSv to the patient's eye lens. That dose is negligible compared to the dose caused by the incorporated radioactivity.

Contact Lenses, Hydrophilic↗
PubMed1999

Examination of co-complexes for radiolabeling of platelets in positron emission tomographic studies.

Oxine, tropolonate, and mercaptopyridine-N-oxide (MPO) have been widely used with 111In for platelet labeling. The use of positron emission tomography (PET) radioisotopes for platelet labeling would offer a higher sensitivity and resolution over conventional imaging. The medium half-life PET radioisotope 55Co (t1/2 = 18.2 hours) would enable quantitative uptake and cell kinetic studies with radiolabeled platelets. To identify the optimal complex for radiolabeling of platelets with 55Co, we investigated the platelet uptake of 57Co-oxine, 57Co-tropolonate, and 57Co-MPO in varying different parameters. The platelet uptake of Co-complexes was generally low (5-12%), dependent on time and temperature of incubation and density of platelets but independent of the amount of radioactivity. These findings are not promising for potential PET application.

Adult↗
PubMed1999

99m-Tc-tetrofosmin scintigraphy and breast cancer.

BACKGROUND: 99m-Tc-tetrofosmin holds significant interest among medical oncologists because of its high positive predictive value (>90%) in pilot trials, exceeding sensitivity and specificity rates of mammography. Objective. Our objective was to assess the diagnostic accuracy of 99m-Tc-tetrofosmin whole-body scintigraphy in outpatients. PATIENTS AND METHODS: Thirty-one patients with an abnormal mammograph (n = 22) or follow-up patients (n = 9), 7 of whom were known to have metastatic disease, were included. Tracer (550 MBq) was injected into the cubital vein. Whole-body planar and single photon emission computed tomography images of regions of interest were obtained. Histology, computed tomography (CT), or magnetic resonance imaging (MRI) were performed to confirm scintigraphic results. Correlation between scintigraphy and CT or MRI was assessed by two independent radiologists. Accuracy, sensitivity, and specificity rates for the diagnosis of local and distant breast cancer lesions were given. RESULTS: Of the 22 first-visit patients, 15 had breast cancer, and 7 had no evidence of any malignant disease. Of all patients examined (n = 31), 21 had distant metastases. Breast tumors were correctly diagnosed in 14/15 patients (93%), with only 1 false-negative result. Extrahepatic metastatic lesions (n = 16) were correctly diagnosed in 14 (88%) patients, whereas the method was not suitable for the diagnosis of liver metastases. CONCLUSION: Tetrofosmin scintigraphy has shown very high detection rates of breast tumors and of metastatic lesions and is therefore a valuable option in breast cancer diagnosis.

Adult↗
PubMed1999

Platelet labeling with 67Ga chelates.

68Ga-labeled platelets could be useful for positron emission tomographic (PET) studies. In order to identify the optimal chelate for radiolabeling of platelets with 68Ga, we investigated the platelet uptake of 67Ga-oxine, -tropolone and -MPO. The platelet uptake of 67Ga-oxine and -tropolone is very low (< 5%). The platelet uptake of 67Ga-MPO, in contrast, increases with platelet density (highest at 10(9) platelets/ml) up to 18%. Our data provide evidence that only 68Ga-MPO could be useful for PET-studies.

Adult↗
PubMed1999

The economy class syndrome--a survey of 19 cases.

BACKGROUND: Thromboembolic events during or immediately after long-distance flights (economy class syndrome--ECS) are gaining more importance due to the rapidly increasing number of flights. Systematic data on haemostatic parameters in these patients are not available yet. PATIENTS AND METHODS: We were therefore analyzing the anamnestic, laboratory and clinical findings in 19 patients (17 males, 2 females, aged 33-75 years) with the final clinical diagnosis ECS. RESULTS: Symptoms commenced either immediately or up to 93 hours after disembarkation (mean 42.3 hours). In the great majority (84.2%) myocardial infarction was the initial diagnosis. No defect in the coagulation and/or prostaglandin system was discovered in either of the patients. Prevalence of smoking (26.3%) was even lower than in the normal population. No predisposing factors were found. Apparent anamnestic similarities were flu and fever (47.4%) while 4 of the patients (26.3%) had severe diarrhoea and dehydration before the flight. Almost all the patients (78.9%) were drinking alcohol during the flight and not actively moving their legs (84.2%). ECS occurred also in business and first class passengers. CONCLUSION: Surprisingly the onset of ECS is definitely not associated with haemostatic defects and not necessarily associated with the clinical risk factors reported.

Adult↗
PubMed1999

6-Oxo-PGF1alpha and 8-epi-PGF2alpha in human atherosclerotic vascular tissue.

Isoprostanes are a new family of compounds generated by the free radical catalyzed action on arachidonic acid. Formed during oxidation they have been claimed to be a reliable indicator of in vivo oxidation injury. We assessed the amount of 8-epi-PGF2alpha in human surgical specimens as compared to PGI2 (via its stable metabolite 6-oxo-PGF1alpha), the major compound generated by vascular tissue. 8-epi-PGF2alpha is low in normal vascular tissue as is the 8-epi-PGF2alpha/6-oxo-PGF1alpha ratio. The vessels of smokers in general exhibited an increased 8-epi-PGF2alpha (r=0.82) and a decreased 6-oxo-PGF1alpha (r=0.71). The 8-epi-PGF2alpha/6-oxo-PGF1alpha ratio is, not significantly, increased in vessels derived from hyperlipidemics and hypertensives. These findings indicate that lipid peroxidation occurs within the human arterial wall as evidenced by 8-epi-PGF2alpha, probably further decreasing the synthesis of PGI2 and promoting atherogenic mechanisms.

6-Ketoprostaglandin F1 alpha↗
PubMed1996

Passive smoking and platelet thromboxane.

While active smoking is known to enhance platelet thromboxane production, no data on passive smoking is available yet. The influence of single and repeated exposure to passive smoke for 60 minutes in a 18 m3 room was assessed in non-smokers as compared to sex and age matched smokers. All the evaluated measures (malondialdehyde, plasma thromboxane B2, 11-dehydro-thromboxane B2, serum thromboxane B2, conversion of exogenous arachidonic acid to thromboxane B2 and to hydroxy-5, 8,10-heptadecatrienoic acid) were higher in smokers than non-smokers at baseline, immediately and 6 hours after passive exposure to cigarette smoke. Repeated exposure of non-smokers rendered their platelets more activated becoming close to the behaviour of smokers. These results indicate that passive smoking may activate thromboxane A2 release from the platelets, contributing to the development of hemostatic imbalance.

Adult↗
PubMed1995

[Thrombocyte function of healthy probands taking 50 mg of acetylsalicylic acid per day].

The antithrombotic effect of acetylsalicylic acid (ASS) is attributed in part to its inhibitory action on platelet cyclooxygenase and, thereby, thromboxane A2 (TXA2) formation. The therapeutic goal of low-dose ASS regimens was the development of a preparation showing a high inhibitory capacity on platelet TXA2 generation whilst leaving vascular prostaglandin I2 (PGI2) synthesis unaffected, thereby minimizing side effects. The effect of a new acid-resistant preparation of 50 mg ASS (Thrombo-ASS 50 mg) on plasma levels of ASS, salicylate, TXB2, 11-dehydro-thromboxane B2, serum thromboxane B2 and malonyl dialdehyde, the conversion of exogenous 14C-arachidonic acid to TXB2 and hydroxy-5,8,10-heptadecatrienoic acid (HHT), as well as on the urinary metabolites 2,3-dinor-6-oxo-PGF1 alpha and 2,3-dinor TXB2, were compared in a crossover trial to those of a marketed preparation (Aspirin 100 mg) in healthy volunteers after a single dose and repeated administration of ASS. While platelet activity was inhibited by both the test and the reference substance to a comparable extent, vascular PGI2 production (as determined by urinary 2,3-dinor-6-oxo-PGF1 alpha excretion) was less affected by the test substance. These findings confirm the claim that a dosage of 50 mg ASS administered daily as an enteric coated or uncoated tablet is sufficient to almost completely block platelet cyclooxygenase, while the respective vascular enzyme is only minimally affected.

Adult↗