def case_seed(global_seed: int, source_id: str) -> int:
    """Per-image deterministic seed derived from global seed and source path."""
    h = hashlib.sha256(f"{global_seed}|{source_id}".encode()).hexdigest()
    return int(h[:8], 16)


def generate_phi(seed: int) -> dict:
    fake = Faker()
    Faker.seed(seed)
    rng = random.Random(seed)

    last = fake.last_name()
    first = fake.first_name()
    middle = fake.random_letter().upper()
    mrn = f"{rng.randint(1000000, 9999999)}"
    dob = fake.date_of_birth(minimum_age=18, maximum_age=95)
    study_date = fake.date_time_this_decade()
    institution = rng.choice(INSTITUTION_POOL)

    return {
        "case_uuid": f"SYNTH-{uuid.UUID(int=rng.getrandbits(128))}",
        "patient_name_display": f"{last}, {first} {middle}.",
        "patient_name_dicom": f"{last}^{first}^{middle}",   # DICOM PN VR format
        "patient_id": mrn,
        "dob": dob,
        "study_date": study_date,
        "institution_name": institution,
    }