The goal of this clinical trial is to evaluate the biodistribution, radiation dosimetry, safety, and time-dependent image quality of ^68^Ga-EV203 injection in patients with hematological malignancies (multiple myeloma, non-Hodgkin lymphoma, or acute myeloid leukaemia), aged 18-75 years, who are able to lie still for 0.5 h and have no contraindications (e.g., pregnancy, recent radiotherapy, etc.).

The main questions it aims to answer are:

What are the biodistribution (organ uptake, %ID, SUV) and radiation absorbed doses (mGy/MBq) of ^68^Ga-EV203 in target organs and the whole body?

What is the safety profile of ^68^Ga-EV203, as measured by adverse events and serious adverse events?

How does the PET/CT image quality differ between the 30-, 60-, 90-, and 120-minute time points after injection?

If there is a comparison group: Researchers will compare the positive percent agreement (PPA) and positive predictive value agreement (PPrA) of ^68^Ga-EV203 PET/CT against ^18^F-FDG PET/CT to see if the new tracer offers comparable or superior diagnostic performance in detecting CXCR4-positive lesions.

Participants will:

Receive a single intravenous injection of 74-296 MBq of ^68^Ga-EV203.

Undergo whole-body PET/CT scans at 30 min, 60 min, 90 min, and 120 min post-injection on the same day.

Return within 3-7 days (but at least 2 days later) for a standard ^18^F-FDG PET/CT scan after fasting for ≥5 h.

Attend a safety follow-up visit at day 8-14 for physical examination, vital signs, and laboratory tests (blood count, coagulation, and biochemistry).

Inclusion Criteria:

• Age 18 to 75 years (inclusive) at screening.
• Able to lie still on the scanning bed for 0.5 hours.
• Willing to sign informed consent and able to comply with protocol requirements.
• Histologically/cytologically confirmed diagnosis of multiple myeloma (MM), non-Hodgkin lymphoma (NHL), or acute myeloid leukaemia (AML) according to the 2022 WHO Classification of Haematolymphoid Tumours.

Exclusion Criteria:

• Has claustrophobia or any other condition that prevents tolerance of imaging procedures
• Has undergone major surgery within 3 months prior to screening, or plans to undergo surgery during the study period.
• Has received any other radiopharmaceutical imaging agent or therapeutic radiopharmaceutical within 30 days prior to screening.
• Is pregnant or lactating at screening.
• Is a woman of childbearing potential or a man who does not agree to use effective contraception during the study (from signing informed consent) and for 3 months after study drug administration.
• Has a known allergy to alcohol or any component of the investigational product, or has other allergies judged by the investigator to increase the participant's risk.
• Has clinically significant cardiovascular disease within 6 months prior to screening (e.g., myocardial infarction, unstable angina, symptomatic congestive heart failure, uncontrolled severe arrhythmia).
• Has uncontrolled hypertension, or a history of coagulopathy or coagulation disorders.
• Has been diagnosed with another malignancy (other than the target haematological disease) within 5 years prior to 68Ga-EV203 administration.
• Has received any systemic anti-cancer therapy within 2 weeks prior to planned 68Ga-EV203 administration, or radiotherapy within 8 weeks prior to planned administration.
• Has any other condition that, in the investigator's judgment, makes the participant unsuitable for participation in the study.