This is a contrast-enhanced magnetic resonance imaging (MRI) study conducted on a single-administration of polyglucose superparamagnetic iron oxide injection. Two dose groups are set up in this study, 2.5 mg/kg and 3 mg/kg, and two subjects in each group received the test drug for safety evaluation.

Inclusion Criteria:

• Signing the informed consent form before the trial and fully understanding the content, process and possible adverse effects of the trial;
• Be able to complete the study according to the requirements of the trial protocol;
• Male subjects aged 18 to 40 years old (including the threshold);
• Subjects weighing no less than 50 kilograms. Body mass index (BMI) = weight (kg)/height2 (m2), BMI within the range of 19~26 (including the critical value);
• Health status: no mental abnormality, no history of cardiovascular system, nervous system, respiratory system, digestive system, urinary system, endocrine system and metabolic abnormalities;
• Vital signs, physical examination, laboratory tests, electrocardiogram and imaging tests are normal or abnormal without clinical significance;
• No pregnancy and voluntary use of effective contraception for at least 6 months from 2 weeks prior to dosing to the last use of the study drug.

Exclusion Criteria:

• Previously suffered from neuropsychiatric, respiratory, cardiovascular, gastrointestinal, hematologic-lymphatic, hepatic or renal insufficiency, endocrine, or musculoskeletal disorders, or other diseases, and in the judgment of the investigator, the previous medical history may have an impact on the magnetic resonance imaging procedure, the quality of the images, or the safety of the subject;
• Subjects with internal metal foreign bodies (dentures, contraceptive rings, metal implants, metal clips, etc.) and persons who are claustrophobic;
• Those who are allergic to the study drug, its metabolites or its excipients;
• Subjects who have smoked more than 5 cigarettes per day for 3 months prior to the trial;
• History of drug and/or alcohol abuse (14 units of alcohol per week: 1 unit = 360 ml of beer or 45 ml of spirits of 40% alcohol or 150 ml of wine);
• Blood donation or significant blood loss (> 450 ml) within 2 months prior to dosing;
• Use of any drug that alters liver enzyme activity (e.g., liver enzyme inhibitors chlorpromazine, cimetidine, ciprofloxacin, metronidazole, etc.; liver enzyme inducers barbiturates, carbamazepine, rifampicin, dexamethasone, etc.) in the 28 days prior to dosing;
• Use of any prescription medication, over-the-counter medication, any vitamin product or herbal remedy within 14 days prior to dosing;
• The need to use tobacco, alcohol and caffeinated beverages, or certain foods that may affect metabolism (e.g., grapefruit, grapefruit juice, etc.) during the trial period, or a significant change in dietary or exercise habits prior to the trial, or any other factor that affects the absorption, distribution, metabolism, or excretion of the drug;
• Use of an investigational drug or participation in a clinical trial of a drug within 2 months prior to dosing;
• Screening positive for hepatitis (including hepatitis B and C) and for AIDS and syphilis;
• Screening positive for drugs or a history of drug abuse within the past 5 years or drug use within the 3 months prior to the trial;
• Persons who have difficulty with MRI scanning or who cannot tolerate MRI scanning;
• Acute illness occurring during the pre-study screening phase or prior to study drug administration;
• Subjects who are unable or incapable of complying with ward regulations.
• The subject is unable to complete the trial for personal reasons.
• Other circumstances which, in the judgment of the investigator, make enrollment in the study unsuitable.