The purpose of the study is to determine whether imaging techniques, such as magnetic resonance imaging (MRI), near infrared spectroscopy (NIRS), laser speckle contrast imaging (LSCI), and optical imaging (OI), can detect differences in blood flow and oxygen levels in different organ systems of participants with sickle cell disease (SCD). Differences in blood flow and oxygen levels detected by these techniques will be evaluated to determine their utility as biomarkers of clinical disease pathophysiology.

Key Inclusion Criteria:

1. Have a diagnosis of SCD confirmed by hemoglobin analysis.

2. Be in stable clinical condition, as determined by the Investigator.

   Subjects enrolled in Part B must also meet the following eligibility criterion at Screening:

3. Receiving scheduled standard of care RBC exchange transfusion therapy, with ≥3 transfusions already received.

4. Be deemed healthy, as determined by the Investigator, based on the physical examination, medical history, vital signs, 12-lead electrocardiogram (ECG), and clinical laboratory measurements.

Key Exclusion Criteria:

1. Inability to lie still for ≥5 minutes, claustrophobia sufficient to interfere with generating reliable MRI scans, body weight exceeding 320.0 lbs., or girth exceeding the magnet bore.
2. Presence of a metal device affected by MRI (e.g., any type of electronic, mechanical or magnetic implant, cardiac pacemaker, aneurysm clips, implanted cardiac defibrillator) or potential ferromagnetic foreign body (metal slivers, metal shavings, other metal objects) which would be a contraindication for MRI.
3. Acute pain crisis requiring hospitalization, with a discharge ≤4 weeks prior to the first imaging visit, or when determined by the Investigator to not be at steady state.
4. Recent (≤3 months) treatment with hydroxyurea therapy.

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.

Participants with mild to severe VOC