2017 Vol. 41, No. 2
Exosomes are small extracellular vesicles released from normal and tumor cells. These vesicles contain proteins, lipids, and noncoding RNAs, and can mediate intercellular communication among different cell types in the body, thus affecting physiological and pathological processes. Emerging evidence indicates that radiation-induced exosomes facilitates the interaction between a tumor and its microenvironment. This article reviewed the biological effects of radiation-induced exosomes on tumor radiotherapy and discussed the role of such exosomes in tumor angiogenesis.
Differentiated thyroid cancers(DTC) are generally considered low-risk malignant tumors. Radioiodine ablation following thyroidectomy and thyroid hormone suppression therapy are standard treatment in patients with metastatic DTC. Patients with DTC obtain many benefits from a three-step therapy schedule(i.e., thyroidectomy+radioiodine ablation+thyroid hormone). A proportion of patients with locally advanced or metastatic disease and poorly differentiated or dedifferentiated thyroid cancer become refractory to radioactive 131I therapy. After sensitizer and/or redifferentiation inducer treatment, thyroid cancer cells in patients with refractory thyroid cancer increase 131I uptake and the effects of 131I treatment are improved for patients with refractory thyroid cancer. The emergence of targeted drug treatment technology provides a broad prospect for thyroid cancer refractory to 131I therapy. Progress in the areas of sensitizers, redifferentiation inducers, and targeted drug treatment techniques for treating thyroid cancer refractory to 131I therapy is discussed in this review.
The differential diagnosis of Parkinson disease can be challenging. Radionuclide imaging can provide the molecular and metabolic information so that it is helpful for differential diagnosis of Parkinson disease from atypical parkinsonism or other neurological disability such as essential tremor. The application of radionuclide imaging in the differential diagnosis of Parkinson disease was reviewed in this article.
Chemisorption or ion exchange of 99Tcm-MDP on the surface of hydroxyapatite crystals can facilitate bone imaging, which can be used for the diagnosis of various bone disorders. However, extraosseous uptake in soft tissue structures on bone scans has been observed in some instances. Although the exact mechanism of its occurrence is currently unclear, most researchers have proposed that its mechanism include calcification of soft tissues(e.g., dystrophic calcification, and metastatic calcification), increased regional vascularity, technical artifacts, and radiopharmaceutical binding to macromolecules in the tissues. Identifying the specific mechanisms and detecting the occurrence of extraosseous uptake on the bone scan can facilitate the detection of disorders in other systems, thus reducing examinations and enhancing the diagnostic value of the study. The present essay reviews all the related articles and illustrates the commonly encountered extraosseous uptake and its possible mechanisms.
Myocardial perfusion imaging(MPI) plays an increasingly important role in the diagnosis, risk stratification, and prognosis of coronary heart disease, and coronary artery calcification scoring(CACS) can refine the risk stratification and prognosis of coronary heart disease. However, both methods possess limitations and deficiencies. The combination of CACS and MPI compensates for these deficiencies and provides detailed information to the physician. SPECT/CT generates CT images for attenuation correction when collecting MPI. CACS scans acquired during normal expiration can also be used for attenuation correction. The use of these scans not only reduces the radiological dose but also provides detailed information to the physician. This review focuses on the clinical values of CACS, MPI, and their combination and presents the latest developments in obtaining MPI and CACS images in one scan.
Cadmium-Zinc-Telluride(CZT) SPECT and IQ·SPECT are new technologies used in myocardial perfusion imaging and are important in the development of nuclear cardiology. These technologies exhibit higher sensitivity and spatial resolution, shorter acquisition time, and lower injection and radiation doses than conventional SPECT. In contrast to the conventional SPECT system equipped with standard low-energy high-resolution collimators, IQ·SPECT adopts SMART-ROOM collimators and cardiac-centric acquisition to improve detection sensitivity. The detectors of CZT SPECT consist of semiconductor materials, instead of conventional sodium iodide(NaI) crystals, to improve energy resolution, spatial resolution, sensitivity, and signal-to-noise ratio. These detectors can also quantitatively analyze myocardial flow reserve. This paper reviews the imaging principle, performance parameters, and clinical application of three SPECT systems.