Final answer:
The lateral view is the best for determining the size of the spleen on a 99mTc-sulfur colloid liver/spleen image, providing a clear measurement without interference.
Step-by-step explanation:
The best view for determining the size of the spleen in a 99mTc-sulfur colloid liver/spleen image is the lateral view. This view allows for a clear measurement of the spleen's dimensions without superposition of other abdominal structures. The spleen is a critical organ in the lymphatic system, functioning as a blood filter and an immune response location. Its close attachment to the stomach via the gastrosplenic ligament and its lack of a strong capsule make the lateral view more favorable for evaluating its size accurately.