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Activity Quantification from Planar Images
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
where is the activity determined from SPECT/CT imaging at the th time point, is the planar-derived activity value at the same time point, and is the planar-derived activity at time point . Hence, by means of one SPECT/CT and sequential planar measurements, estimates of both the shape and the magnitude of the time-activity curve are obtained.
Breast imaging
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
Dynamic (flow) imaging can provide information useful for sentinel node localisation. Acquisition should be started immediately after completion of all injections. Patterns of uptake are analysed using the sequences of dynamic frames and time–activity curve.
Principles of Radioiodination and Iodine-Labeled Tracers in Biomedical Investigation †
Published in Garimella V. S. Rayudu, Lelio G. Colombetti, Radiotracers for Medical Applications, 2019
Mrinal K. Dewanjee, Shyam A. Rao
Considering the convenience of γ counting and the poor incorporation (<2%) of amino acid into protein, extensive studies404,405,422-430 have been done by means of radioiodinated plasma proteins, and the possibility of reutilization of the label is small. In a steady state, in which the amount of protein is constant, the calculation of protein turnover is based on the degradation and elimination of the labeled protein or the excretion rate of the label after the breakdown of the labeled protein. This technique is not applicable to tissue protein because no mixing of labeled tissue protein occurs in the tissue pool. The degradation and turnover study of radioiodinated protein can be made after an i.v. injection of the tracer and plotting the plasma radioactivity time curve (Figure 36). The plasma-clearance curve has two phases. Initially, the concentration declines rapidly owing to distribution in the extravascular space and total body and to metabolic degradation. The second phase is less rapid; at this time, there is an equilibrium between the extravascular and the intravascular pool. The slope of the time-activity curve is an index of the degradation rate of the protein, and turnover can be calculated from the slope and total protein content:
Effect of molecular size on interstitial pharmacokinetics and tissue catabolism of antibodies
Published in mAbs, 2022
Hanine Rafidi, Sharmila Rajan, Konnie Urban, Whitney Shatz-Binder, Keliana Hui, Gregory Z. Ferl, Amrita V. Kamath, C. Andrew Boswell
Blood and tissue time–activity curves are shown in terms of both 125I (Figure 2a) and 111In (Figure 2b) signals, which give readouts of intact and total (intact plus catabolized), respectively. Uncorrected tissue exposures largely mirror blood and serum profiles. These data allow assessment of the effect of molecular size in the absence of FcRn binding using non-FcRn-binding antibody variants IgG1-HAHQ (~150 kDa), F(ab’)2 (~100 kDa) and F(ab) (~50 kDa), as well as by comparing the two FcRn-binding molecules, IgG (~150 kDa) and one-armed IgG (~100 kDa). Serum and blood exposure of non-FcRn-binding molecules, particularly F(ab), appears to be higher for 125I-derived data than for 111In-derived data (Supplemental Figure S4). This result, however, is an artifact due to the rapid renal filtration, lysosomal degradation, and partial recirculation of non-residualized 125I-containing catabolites but not 111In-containing catabolites (see Discussion).
Pulmonary translocation of ultrafine carbon particles in COPD and IPF patients
Published in Inhalation Toxicology, 2022
Mikaela Qvarfordt, Martin Anderson, Alejandro Sanchez-Crespo, Maria Diakopoulou, Magnus Svartengren
In this study, the subject’s degree of alveolo-capillary permeability to water soluble substances was characterized by gamma camera measurement of the clearance of Technetium-99m-diethylenetriaminepentaacetic acid (99mTc-DTPA) aerosol to the systemic circulation (Wollmer and Evander 1994). The 99mTc-DTPA aerosol was prepared using a commercial kit (TechneScan DTPA; Mallinckrodt Medical, Kansas City, MO, USA) and inhaled using a SmartVent™ aerosol generating system (Diagnostic Imaging Limited, Welford, Great Britain). According to the manufacturer, the mass median aerodynamic diameter (MMAD) of the delivered droplets was 1.3 µm. Approximately 100 MBq 99mTc-DTPA were administered to each subject. 99mTc-DTPA was administered under normal tidal breathing using a mouthpiece and nose-clip and the subject lying in supine position in the gamma camera couch. Directly after administration, the pulmonary retention of 99mTc-DTPA was imaged for 45 minutes, at a sampling interval of 60 seconds. A two-headed gamma camera (Symbia T16, Siemens Healthcare, Erlangen, Germany) equipped with low energy high resolution parallel-hole collimators was used. A region of interest (ROI) covering both lungs was drawn and the time activity curve (TAC) corresponding to the pulmonary clearance of 99mTc-DTPA during the imaging period was then obtained. The TAC was then decay corrected and fitted to a mono-exponential equation from which the pulmonary clearance half-life of 99mTc-DTPA was obtained.
Formulation development and evaluation of nifedipine as pylorospasm inhibitor
Published in Drug Development and Industrial Pharmacy, 2018
Shaheen Sultana, Sushma Talegaonkar, Bhaskar Ray, Harvinder Singh, F. J. Ahmad, Gaurav Mittal, Aseem Bhatnagar
Figure 4(b) shows the time activity curve representing counts emptied per minute in (a) control (b) nifedipine treated patient. The heavy solid line of curve represents cumulative gastric emptying as a function of time. As clearly depicted from figure, percentage gastric emptying rate of two curves was slightly different during initial period of time (i.e. 20–30 min). After 30 min a significant difference can be seen in a curve of patients administered nifedipine formulation when compared with patients administered placebo formulation. This time may be needed for a formulation to disintegrate and release its content to show its action. One more image representing effect of formulation in patient with diabetic gastroparesis is shown in Figure 4(c) in which GER was found to be increase 2.02 times after formulation administration. Gastric emptying rate was found to be increased from 0.45% (Becosule capsule) to 1.037%/min (nifedipine loaded microcapsules).