If a clinic offers diluted Radiesse for crepey neck and chest skin, slow down at the word diluted, because one clinic may mean something different by it than another. This guide does not say whether the treatment will work for you. It gives you the questions that let you compare what one clinic proposes with what another proposes. A good general reference for the filler family is the ASDS page on soft-tissue fillers for aging skin.
Ask what diluted means at this clinic
Radiesse is a product name, and diluted describes how it is prepared. Ask the clinic how they prepare it, why they chose that preparation for your neck and chest, and who prepares it. Ask whether they treat the neck and chest this way routinely or whether your case is unusual. The reason to ask is cause and effect: if you cannot get the same description from two clinics, you cannot compare their prices.
Ask about the product label
Ask whether this use is part of the product's official labeling or a use chosen by the clinician. Both can happen in practice. What matters is that you are told which one applies, so you can weigh it. Ask to see the labeling so you can check it yourself.
Ask what the clinic expects
Ask what change the clinician expects to see, over what period, and how they will judge whether it worked. Ask how many visits are planned and what each costs. If the answer is a promise instead of a plan, ask for the plan.
Read the research with questions in mind
Research on collagen stimulating injectables is technical. One example is a multicenter retrospective study on the safety of immediate reconstitution of poly-L-lactic acid for facial and body treatment. It concerns a different product, so use it to learn which questions about preparation are worth asking, and not as proof about how Radiesse behaves in your case. A second example is a laboratory study on poly-L-lactic acid particles and collagen synthesis, which shows how technical the evidence can get.
Four answers to get in writing
Before treating the neck and chest, get four answers in writing: what diluted means here, what the product label covers, what result the clinician expects and what the full plan costs. This site explains the questions rather than giving medical advice, and a licensed clinician who has examined your neck and chest should decide what suits you.