In this study, researchers are testing a new method called Total Marrow and Lymphoid Irradiation (**TMLI**) to see if it is safe and effective for patients needing a special kind of treatment called a hematopoietic stem-cell transplant (**HSCT**). This transplant is used to treat a type of blood cancer known as Acute Lymphoblastic Leukemia (**ALL**). The study is for patients aged 16-45 who are either newly diagnosed or have had a relapse. TMLI aims to reduce damage to healthy tissues compared to traditional total body irradiation (**TBI**).

During the study, patients will receive TMLI along with medications like Fludarabine and Cyclophosphamide. After the transplant, additional medicines will help prevent complications. Patients will have regular blood tests and a bone marrow check-up 60 days after the transplant.

• The study takes place over several days, with intense treatment sessions.
• Eligibility is strict; patients must meet age and health criteria.
• Risks include potential side effects from radiation and medication.