TPT NOTES: An Analog of the Half-Life of a Radioactive Element

1968 ◽  
Vol 6 (9) ◽  
pp. 467-468 ◽  
Author(s):  
R. Castillo
Keyword(s):  
Half Life ◽  
Radioactive Element

The Scandium Group

2010 ◽  
Author(s):  
George K. Schweitzer ◽  
Lester L. Pesterfield
Keyword(s):  
Stable Isotope ◽  
Oxidation State ◽  
Half Life ◽  
Spontaneous Fission ◽  
Radioactive Element ◽  
Electron Level ◽  
Naturally Occurring ◽  
State Changes ◽  
And Tungsten

The members of the Sc Group are Sc scandium, Y yttrium, La lanthanum, Ce cerium, Pr praseodymium, Nd neodymium, Pm promethium, Sm samarium, Eu europium, Gd gadolinium, Tb terbium, Dy dysprosium, Ho holmium, Er erbium, Tm thulium, Yb ytterbium, Lu lutetium, and Ac actinium. All these elements resemble each other greatly, especially in the series La–Lu (called the lanthanoids). Their slight differences may be assigned largely to size similarities, but a few oxidation state changes give rise to marked differences. The predominant oxidation state is III, but the IV state for Ce, and the II state for Eu are also important in their aqueous chemistries. The electron structures of these elements along with some other of their pertinent properties are shown in Table 12.1. Note the progression in the sizes of M+3 rising from Sc to Ac, but decreasing from La to Lu. This behavior causes Y+3 to fall in between Dy+3 and Ho+3, which results in yttrium’s chemistry usually resembling the latter lanthanoids. For this reason, Y will be treated as a lanthanoid in succeeding sections. The successive filling of the 4f electron level from La through Lu should also be noted, as well as the interesting 5d occupancy for Gd. The richest ore of Sc is the rare mineral thorveitite Sc2Si2O7, but it also occurs in very small quantities in some lanthanoid, uranium, and tungsten ores. Yttrium and the lanthanoids (abbreviated Ln), except for Pm, occur in monazite LnPO4 (mostly light lanthanoids), bastnaesite LnCO3F (mostly light lanthanoids), xenotime LnPO4 (mostly heavy lanthanoids), loparite (mostly light lanthanoids), and lateritic clays (some with mostly light lanthanoids, others with mostly heavy lanthanoids). All isotopes of Pm are radioactive and it does not occur with the lanthanoids. Exceedingly small amounts are present in uranium ores where it has been produced by the spontaneous fission of U-238. Its major source is artificial production, the longest lived isotope being Pm-145 (half life of 17.7 years). Ac is also without a stable isotope, the radioactive element resulting from the decay of naturally occurring Th and U. The longest lived Ac species is Ac-227 which has a half life of 21.77 years.

The Half-Life of Mindless Psychology

1991 ◽  
Vol 36 (5) ◽  
pp. 455-455
Author(s):  
Michael J. Mahoney
Keyword(s):  
Half Life

Kinetics of Various 99mTc-Sn-Pyrophosphate Compounds in the Rat

1977 ◽  
Vol 16 (04) ◽  
pp. 157-162 ◽  
Author(s):  
C. Schümichen ◽  
B. Mackenbrock ◽  
G. Hoffmann
Keyword(s):  
Normal Saline ◽  
Half Life ◽  
Compound A ◽  
Short Half Life ◽  
Low Concentrations ◽  
The Stability ◽  
Kinetics Of ◽  
In Vitro Stability

SummaryThe bone-seeking 99mTc-Sn-pyrophosphate compound (compound A) was diluted both in vitro and in vivo and proved to be unstable both in vitro and in vivo. However, stability was much better in vivo than in vitro and thus the in vitro stability of compound A after dilution in various mediums could be followed up by a consecutive evaluation of the in vivo distribution in the rat. After dilution in neutral normal saline compound A is metastable and after a short half-life it is transformed into the other 99mTc-Sn-pyrophosphate compound A is metastable and after a short half-life in bone but in the kidneys. After dilution in normal saline of low pH and in buffering solutions the stability of compound A is increased. In human plasma compound A is relatively stable but not in plasma water. When compound B is formed in a buffering solution, uptake in the kidneys and excretion in urine is lowered and blood concentration increased.It is assumed that the association of protons to compound A will increase its stability at low concentrations while that to compound B will lead to a strong protein bond in plasma. It is concluded that compound A will not be stable in vivo because of a lack of stability in the extravascular space, and that the protein bond in plasma will be a measure of its in vivo stability.

The Effect of Carbimazole Following Radioiodine Therapy on Radiation Dose to the Thyroid

1981 ◽  
Vol 20 (02) ◽  
pp. 72-75 ◽  
Author(s):  
R. Kocak ◽  
R.G. Herbert ◽  
C.R. Squire ◽  
T.M.D. Gimlette
Keyword(s):  
Thyroid Gland ◽  
Radiation Dose ◽  
Half Life ◽  
Radioiodine Therapy

Radioiodine in the thyroid gland after a therapy dose of 131I was measured serially in 7 patients without Carbimazole, and in 11 patients starting Carbimazole 60 mg daily fourteen days after the therapy dose. Effective half-life for radioiodine in the gland initially 5.53±1.08 days fell to 4.26±1.12 days (p < 0.01) during Carbimazole, and returned to 5.83±1.21 days (NS) after stopping the drug. The radiation dose to the thyroid from a given therapy dose of 131I followed by Carbimazole was calculated to be 97% of that without Carbimazole when the drug was started after 14 days, and 90% and 75% when the drug was started after 7 days and 1 day respectively.

Radiation Mould with Radio Isotope Solutions Fluid „Iso-mould”

1961 ◽  
Vol 1 (03) ◽  
pp. 246-257
Author(s):  
M. O. Roxo-Nobre ◽  
D. M. Vizeu
Keyword(s):  
Clinical Practice ◽  
Remote Control ◽  
Lymph Nodes ◽  
Half Life ◽  
Radioactive Substances

SummaryA technique of mouldage, employing fluid radioactive substances is adopted, to replace the radium-moulding in the treatment of large surfaces. The technique is explained in detail, proving its greater safety by remote control and an adjustment of adequate means of protection. Distribution is obtained by means of a serpentine attached to the mould in question, which follows the Paterson-Parker system. The authors believe the distribution of radiation on curved anatomical areas to be much more uniform by mould system than any other process of application of the same radiation of rectilineal propagation, transmitted at greater focus-skin distances. The isotopes used up to now were the La140 and others of reduced half-life, in order to prevent the danger of eventual contaminations. Although the application of the process still has very little clinical practice, the technique is presented with a view to experimentation in extensive superficial tumours, or those of little depth, such as tumours of the skin, breast, penis, thyrreoid and lymph nodes.

Binding of 131I-Labeled Tissue-Type Plasminogen Activator on De-Endothelialized Lesions in Rabbits

1987 ◽  
Vol 26 (05) ◽  
pp. 224-228 ◽  
Author(s):  
Y. Isaka ◽  
H. Etani ◽  
K. Kimura ◽  
S. Yoneda ◽  
T. Kamada ◽  
...  
Keyword(s):  
Plasminogen Activator ◽  
Abdominal Aorta ◽  
Half Life ◽  
Balloon Catheter ◽  
Biochemical Properties ◽  
Tissue Type ◽  
Fibrin Deposition ◽  
Tissue Type Plasminogen Activator ◽  
High Affinity ◽  
Type Plasminogen Activator

Tissue-type plasminogen activator (t-PA) which has a high affinity for fibrin in the clot, was labeled with 131I by the iodogen method, and its binding to de-endothelialized lesions in the rabbit was measured to assess the detectability of thrombi. The de-endothelialized lesion was induced in the abdominal aorta with a Fogarty 4F balloon catheter. Two hours after the de-endothelialization, 131I-labeled t-PA (125 ± 46 μCi) was injected intravenously. The initial half-life of the agent in blood (n = 12) was 2.9 ± 0.4 min. The degree of binding of 131I-labeled t-PA to the de-endothelialized lesion was evaluated at 15 min (n = 6) or at 30 min (n = 6) after injection of the agent. In spite of the retention of the biochemical properties of 131I-labeled t-PA and the presence of fibrin deposition at the de-endothelialized lesion, the binding of t-PA to the lesion was not sufficiently strong. Lesion-to-control ratios (cpm/g/cpm/g) were 1.65 ± 0.40 (at 15 min) and 1.39 ± 1.31 (at 30 min), and lesion-to-blood ratios were 1.39 ± 0.32 (at 15 min) and 1.36 ± 0.23 (at 30 min). These results suggest that radiolabeled t-PA may be inappropriate as a radiopharmaceutical for the scintigraphic detection of a pre-existing thrombotic lesion.

Recombinant Variants of Tissue-Type Plasminogen Activator Containing Amino Acid Substitutions in the Finger Domain

1992 ◽  
Vol 68 (06) ◽  
pp. 672-677 ◽  
Author(s):  
Hitoshi Yahara ◽  
Keiji Matsumoto ◽  
Hiroyuki Maruyama ◽  
Tetsuya Nagaoka ◽  
Yasuhiro Ikenaka ◽  
...  
Keyword(s):  
Amino Acid ◽  
Plasminogen Activator ◽  
Half Life ◽  
Tissue Type ◽  
Clot Lysis ◽  
Amino Acid Substitutions ◽  
Wild Type ◽  
Plasma Clot ◽  
Tissue Type Plasminogen Activator ◽  
Type Plasminogen Activator

SummaryTissue-type plasminogen activator (t-PA) is a fibrin-specific agent which has been used to treat acute myocardial infarction. In an attempt to clarify the determinants for its rapid clearance in vivo and high affinity for fibrin clots, we produced five variants containing amino acid substitutions in the finger domain, at amino acid residues 7–9, 10–14, 15–19, 28–33, and 37–42. All the variants had a prolonged half-life and a decreased affinity for fibrin of various degrees. The 37–42 variant demonstrated about a 6-fold longer half-life with a lower affinity for fibrin. Human plasma clot lysis assay estimated the fibrinolytic activity of the 37–42 variant to be 1.4-fold less effective than that of the wild-type rt-PA. In a rabbit jugular vein clot lysis model, doses of 1.0 and 0.15 mg/kg were required for about 70% lysis in the wild-type and 37–42 variant, respectively. Fibrinogen was degraded only when the wild-type rt-PA was administered at a dose of 1.0 mg/kg. These findings suggest that the 37–42 variant can be employed at a lower dosage and that it is a more fibrin-specific thrombolytic agent than the wild-type rt-PA.

Plasma Thrombospondin as an Indicator of Intravascular Platelet Activation in Patients with Vasculitis

1987 ◽  
Vol 58 (03) ◽  
pp. 850-852 ◽  
Author(s):  
M B McCrohan ◽  
S W Huang ◽  
J W Sleasman ◽  
P A Klein ◽  
K J Kao
Keyword(s):  
Platelet Activation ◽  
Plasma Levels ◽  
Half Life ◽  
Degradation Products ◽  
Plasma Concentrations ◽  
Primary Source ◽  
Positive Correlation ◽  
Activation Marker ◽  
Fibrin Degradation Products ◽  
The Mean

SummaryThe use of plasma thrombospondin (TSP) concentration was investigated as an indicator of intravascular platelet activation. Patients (n = 20) with diseases that have known vasculitis were included in the study. The range and the mean of plasma TSP concentrations of patients with vasculitis were 117 ng/ml to 6500 ng/ml and 791±1412 ng/ml (mean ± SD); the range and the mean of plasma TSP concentrations of control individuals (n = 33) were 13 ng/ml to 137 ng/ml and 59±29 ng/ml. When plasma TSP concentrations were correlated with plasma concentrations of another platelet activation marker, β-thromboglobulin (P-TG), it was found that the TSP concentration inei eased exponentially as the plasma β-TG level rose. A positive correlation between plasma levels of plasma TSP and serum fibrin degradation products was also observed. The results suggest that platelets are the primary source of plasma TSP in patients with various vasculitis and that plasma TSP can be a better indicator than β-TG to assess intravascular platelet activation due to its longer circulation half life.

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