SUMMARY Neuroreceptor imaging with radionuclide tracing in vivo has been greatly developed recently.Distribution,density,and activity of receptors in the brain can be visualized by the radioligands labeled for emission computed tomography(ECT),including PET(positron emission tomography)and SPECT(single photon emission computed tomography).The functional and quantitative imaging for several receptors,such as dopamine receptors,serotonin receptors,cholinergic receptors,benzodiazepine receptors,and opioid receptors,has clinical importance.The preparation of receptor imaging agents,foundation of the physio-mathematical model,and the development of nuclear medicine instruments are the main points.In the present review,we will concentrate on introducing the development of brain receptor imaging.

Tumor tissue hypoxia is taken as an important biologic character of malignant tumors,it could reduce the therapeutic efficacy of radiotherapy and chemotherapy. Presenting a noninvasive approach in detecting hypoxic state in tumors,hypoxia imaging of nuclear medicine can be used in the differential diagnosis,prognosis evaluation and guiding therapy of malignant tumors.

How to study a method that can significantly improve the therapeutic gain ratio of malignant tumor is one of the problems must be solved in the field of cancer therapy. However, how can effectively treat malignancy patients with contraindications of operation, radiotherapy and chemotherapy has been a difficult problem in cancer therapy. The 125I brachytherapy was suitable for malignancy patients with contraindications of operation, radiotherapy and chemotherapy. The guidance of multimodal imaging could contribute to the definitions of tissue density imaging target and biological target, and could ensure the targeting and conformity of treatment. Using the quality assurance and quality control measurements (QA/QC) optimized by radiation dosimetry; using therapy planning system (TPS) to make plan, and adopt optimizing radiation dosimetry and dose volume histogram (DVH) to evaluate TPS, and using image to guide particle implantation and adopt series of methods, such as real-time location verification, dosimetry verification post-implantation, therapy efficacy determination, follow-up and so on, to improve therapeutic gain ratio and partially control therapy efficacy, and then significantly reduce adverse reaction. All of these have important clinical value for increasing survival rate and quality of life.

To explore the effectiveness of positron emission tomography (PET) respiratory gating based on time and amplitude to improve the reconstructed image artifacts. It is necessary to appropriately select acquisition and processing methods which ensure the readability of myocardial imaging images in radionuclide medicine myocardial imaging. This summary mainly discusses the identification method and how to avoid adverse effect for images from myocardial imaging process, and includes similarities and differences of varieties methods: identification for image artifacts of myocardial imaging, image reconstruction algorithms and software processing and so on. It should be significant to choose the appropriate method to identify myocardial imaging artifacts in image collection. The pros and cons of myocardial imaging image reconstruction algorithm and various software processing methods still remain unknown. How to choose better appropriate acquisition, image reconstruction and software processing methods for myocardial imaging need further study.

Single nuclear medicine functional imaging (including SPECT and PET) couldn't fully meet the demand of clinical diagnosis because of its own limits, thus the multimodality imaging equipment integrated anatomical and functional images has became the development trend of the nuclear medicine and even the entire medical imaging. Following the earliest SPECT-CT and PET-CT which having been widely used in clinic, the newest PET-MR has also been applied to clinical practice. PET-MR combined MR images with PET function image is substantial to the clinical diagnosis of cerebral nervous system diseases, cardiovascular system diseases and tumor, etc. In this paper, we reviewed the current application situation and prospects of PET-MR in cerebral nervous system diseases.

The microRNA (miRNA) is a novel class of small noncoding RNA that regulate gene expression by targeting mRNA.It has been shown to play important roles in a broad range of biological processes,especially in the occurrence,development,invasion and metastasis of malignant tumors.Conventional detection methods,such as Northern blot and realtime PCR have been used to assess endogenous miRNA expression.However,these techniques are invasive and cannot be used repetitively in living animals.Recent remarkable advances of in vivo imaging techniques have provided the capability of noninvasive imaging of miRNA in vivo.The recent progress about the reporter gene,antisense luminescence,nanoparticle and multimodal imaging for visualizing miRNA expression in vivo was reviewed.

Early diagnosis and precision medicine generally show significant differences in the prognosis of patients with carcinoma. Angiogenesis not only plays a key role in tumor pathophysiology but also acts as an important drug target. Peptides with specific se-quences can target specific molecules on the endothelial cellular membrane during tumor angiogenesis. Radionuclide-labeled molecu-lar probes exhibit many advantages in oncotherapy. This article focuses on the progress of radionuclide-labeled RGD and RRL in radio-immunoimaging and radioimmunotherapy targeting tumor angiogenesis.

Even though multimodal imaging system has already been applied in clinic, the PET-MRI still is a revolutionary progress of medical imaging, and it is a landmark after PET-CT imaging equipment. MRI not only can solve the limitations of CT, but also can provide abundant morphology and function information; at the same time, PET also play important role in the diagnosis of tumor, nervous system diseases and cardiovascular disease; and in the treatment decision, treatment effect evaluation and prognosis evaluation when it is applied in research of physiological and disease state at the levels of molecular activity and metabolism of human body. With the rapid development of science and technology, this article has summarized the imaging technology and clinical application of PET-MRI in recent years.

The radioactive iodine uptake(RAIU) has great value in determining the 131I treatment dosage of patients suffered from hyperthyroidism and judging thyroid function. Many factors which could interfere the results of RAIU were as follows: instrumental factors, thyroid radioactivity counts measurement, counts of a calibrated standard in a neck phantom and counts of room background, iodinated drugs and food, anti-thyroid medication, among other causes, have shown to induce varying degrees of errors in RAIU measurements. Irregular measurements which may interfere with radioactive iodine uptake are commonly seen in clinical practice, yet its actual influence has not been reported. Optimization, regularization and quality control of the radioiodine uptake measurement are essentials for clinical routine practice to guarantee appropriate values for clinical hyperthyroidism diagnosis and treatment. All the above factors affecting the measurement of thyroid function instrument for radioactive iodine uptake are analyzed and then put forward the corresponding solutions.

Objective To investigate the killing effect and molecular mechanism of different doses of ~(125)I seed interstitial brachytherapy for human hepatoma HepG2 cells in nude mice transplanted tumor.Methods Twenty nude mice bearing human hepatoma HepG2 cells were randomly divided into 4 groups (each n=5) and given ~(125)I seed interstitial brachytherapy at different doses including 18.5 MBq ~(125)I,29.6 MBq ~(125)I,37.0 MBq ~(125)I and 0 (the control group) ,respectively.~(125)I seeds were percutaneously implanted into tumors,each mouse with 1 ~(125)I seed implanted.Twenty-eight days later,nude mice were sacrificed and routine pathological examination was performed,.The expression of Bcl-2 and Bax was detected with immunohistochemical methods.Results Pathological examination showed serious coagulation necrosis of tumor cells surrounded by extensive fibrosis in all treatment groups,whereas rich tumor cells with proliferative growth were observqed in the control group.Immunohistochemical analysis showed that the expression of Bax in all treatment group were higher than that in the control group.the expression of which was up-regulated with increasing doses of ~(125)I seed.The expression of Bcl-2 and the ratio of Bcl-2/Bax in all treatment groups were lower than those in the control group.the expression of which was down-regulated with increasing doses of ~(125)I seed.The expression of Bcl-2.Bax and the ratio of Bcl-2/Bax among treatment groups and control group had statistical difference (P＜9.05) ,so as the difference among treatment groups (P＜0.05) .Conclusion ~(125)I seed interstitial brachytherapy induces apoptosis in human hepatoma HepG2 cells by reducing the ratio of Bcl-2/Bax and thereby inhibits the growth of tumor in nude mice,and the extent positively correlates with dosage in a certain range.