China
Africa
Explore chapters and articles related to this topic
Radiopharmaceuticals for Diagnostics
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Jim Ballinger, Jacek Koziorowski
The integrity of the arterial system in the lungs can be assessed using 99mTc-labelled macroaggregated human serum albumin particles (MAA). The diameter of capillaries is ~7 µm, so particles larger than this diameter will be trapped in capillaries. MAA particles are engineered to be 10–90 µm in diameter (90% within this range, none >150 µm; median typically 20–40 µm). The particles are formed by heat denaturation of human serum albumin in the presence of stannous chloride, which allows labelling of the particles by reduction of 99mTc-pertechnetate. When 99mTc-MAA is injected intravenously, it travels to the right ventricle, then to the pulmonary arterial system, where it encounters capillaries for the first time and is essentially completely trapped, outlining the pulmonary blood supply. This allows detection of pulmonary embolism as a cold spot. Lung perfusion imaging is routinely performed in conjunction with ventilation imaging to improve the differential diagnosis [18].
Regional Therapy of Liver Metastases: A Surgeon’s View
Published in Neville Willmott, John Daly, Microspheres and Regional Cancer Therapy, 2020
On the basis of the 99mTc-MAA scan patients were classified as having a “hot” or “cold” scan according to the localization of 99mTc-MAA in tumor regions. Ten of 15 patients evaluated had “cold” scans with 5 having a “hot” scan. Mean 3H-fluorodeoxyuridine levels in tumor were 6.9 ± 2.2 in the “cold” group and 14.8 ± 11.1 in the “hot” group. This difference fell just short of statistical significance (p = 0.07). Two months later the group was evaluated for tumor response. There were four partial responses to therapy, but this did not correlate with tumor fluo-rodeoxyuridine concentrations. The finding was explained as being due to small biopsy size and tumor tissue heterogeneity, which could lead to a tenfold variation in uptake of fluorodeoxyuridine within the same metastasis. The latter point was examined after infusion of 99mTc-MAA and 3H-fluorodeoxyuridine50 in four patients undergoing lobectomy or wedge resection where the whole tumor was available for analysis. In each case between 40 and 100 specimens of tumor and liver were assayed to map drug and MAA distribution. The study demonstrated a linear relationship between drug uptake (3H localization) and tissue perfusion (99mTc localization) for both tumor and liver tissue.
Clinical Applications and Protocols of Single Photon Emission Computed Tomography
Published in Bhagwat D. Ahluwalia, Tomographic Methods in Nuclear Medicine: Physical Principles, Instruments, and Clinical Applications, 2020
Efforts to find new applications of SPECT in detecting and characterizing hepatic tumors have been described recently by Gyves et al.154 Hepatic tumor microcirculation was investigated with SPECT by combining the results of transaxial tomography with 99mTc sulfur colloid with those obtained after hepatic-arterial injection of 99mTc macroaggregated human serum albumin (MAA). 99mTc MAA perfusion was used to assess hypo- and hypervascularization of colorectal and carcinoid tumors relative to normal liver. Figure 28 shows transaxial tomographic sections taken 48 h apart using 99mTc sulfur colloid uptake and 99mTc hepatic artery infusion of 99mTc MAA. A rim of increased activity around the tumor area is easily identified. Important differences in blood distribution can be quantified better with the SPECT approach than with contrast angiography. Tumors greater than 8 to 9 cm showed a hypovascularized cave surrounded by a rim of increased activity. The maximum radius of solid nodules was 4.2 cm, probably indicating a maximum depth of tumor hypervascularity of about 4 cm. The potential of designing a therapeutic protocol based on microspheres directed against hypervascularized tumors is presently being investigated.
Transarterial radioembolization: a systematic review on gaining control over the parameters that influence microsphere distribution
Published in Drug Delivery, 2023
T. J. Snoeijink, T. G. Vlogman, J. Roosen, E. Groot Jebbink, K. Jain, J.F.W. Nijsen
The influence of microsphere shape on the distribution has not been directly investigated. However there has been some research (Aramburu et al., 2017; Smits et al., 2020) concerning the predictive value of Tc-MAA particles used in the pretreatment dose-estimation procedure, which differ in shape from the therapeutic microspheres. These works show mixed results regarding the predictive value of Tc-MAA particles, but it remains unclear whether this is due to the difference in shape. Other factors, such as differences in injection velocity and catheter position between the pretreatment Tc-MAA infusion and the therapeutic microsphere injection, could also be responsible. Dedicated research isolating the effect of microsphere shape is thus needed to evaluate the effect of this parameter.
Progress in large field-of-view interventional planar scintigraphy and SPECT imaging
Published in Expert Review of Medical Devices, 2022
Martijn M.A. Dietze, Hugo W.A.M de Jong
Radioembolization is a treatment for liver cancer that is performed under fluoroscopic guidance in the intervention room [10,11]. In radioembolization, small radioactive spheres (microspheres) are injected into the liver bloodstream where the spheres lodge in the tumor vessels and deliver damaging radiation to the surrounding tissue. The microspheres must accumulate at the correct locations to realize the best treatment outcome. To this end, the radioembolization treatment is mimicked in a pre-treatment procedure in which 99mTc-MAA particles (which have similar kinetic behavior to the microspheres but are less ionizing) are injected instead.