I have lost my hair from the crown. Have undergone 3 PRP sessions since Jan 2018 but no noticeable change. (Photos)

In my  opinion, there could be a number of reasons why you haven't noticed any change. Firstly, if your hair loss has been greater than three to five years in the crown, You may not get regrowth. Secondly, you need to wait a minimum of four to six months to see growth changes. Thirdly, discontinuation of the minoxidil can cause hair loss. I would reinstitute the minoxidil. Furthermore, If you've noticed a decrease in hair loss (shedding) in the other areas, PRP is working and you need to be patient.

Thank you for your question and the pictures.
The PRP treatment you have had three times since January - this is more often that I give for treatments and tend to leave it atleast 3 months between treatments to adequately assess the hair growth. 
You are thinning on the crown and over the front of your scalp also and i think you would be a good candidate for a hair transplant. The PRP will help also as this will not only thicken your existing hair but provide growth factors for the transplanted hair. usually I administer the PRP a couple of weeks before I carry out hair transplants.
It would be advisable to see a hair transplant surgeon and they can assess you properly.
I hope this helps 
Best wishes
Rohit Seth
Plastic, reconstructive, aesthetic and hair transplant surgery

It takes 6-9 months to determine if PRP will help. In your case, if minoxidil is stopped you will likely lose hair simply from stopping minoxidil and this will amen even more difficult to determine if PRP is working or not. You may wish to discuss your situation with a hair loss expert. Going for a hair transplant right now when you are actively losing hair wouldn't be the best idea. You need to get back on a plan to stabilize loss.

Treatment for androgenic alopecia is very limited. Topical minoxidil (side effects headache and increase in body hair elsewhere), oral finasteride (loss of libido and contraindicated in pregnancy) alone or in combination and PRP. Mesotherapy with PRP is safe and effective treatment of androgenic alopecia, but needs to be repeated 4-6 times (2 weeks apart). In 80% of patients it is effective, but the long term studies are limited.
Dr. Anna Sylwestrowicz MD, FRCP(C)
Victoria, BC

There is a lot of confusion in the community regarding PRP treatments.  Everyone agrees long term maintenance such as laser hats or propecia should be used for the long term and not stopped.  I do not understand why most practices recommend otherwise for PRP.  Just like the other treatments out there, as soon as you stop any treatment you will in time loose the benefits of that treatment.  For this reason, we have a clinical haircare membership with monthly treatments alternating between PRP sessions and microneedling sessions.  For your particular case, you can consider restoration, but keep in mind, restoration will give you back hair you have lost but not help to maintain your existing hair - that is what PRP and other maintenance options are for.  You may also be a good candidate for scalp camouflage which does not require any donor harvesting and lasts about 5 years.  Good luck! Dr. Rome

Although We recommend 4 treatments over 4 months and wait a couple of months to see change, three treatments are sufficient to see improvement. I think you need to wait a few more months before concluding it doesn’t work. Technique, type of centrifuge used to prepare the PRP matters. Finally adjunctive treatments like minoxidil, 6 alpha reductase inhibitors, vitamin supplements, laser therapy should be incorporated.

Thanks for your question. It is quite normal to take several months to notice any change. In most patients by the three month mark they may feel it is slightly thicker but for most it is really hard to notice a difference clinically that early. Almost all studies are structured that their before and after pictures are 6 months from beginning treatment as this is how long in most cases it takes to notice an appreciable difference. In my own practice I will do a series of 3 treatments a month a part and then re-evaluate 3-4 months later to truly evaluate whether they are getting any benefit. In most cases I encourage patients to continue minoxidil to really appreciate if the PRP is working because if they stop at that time they can have some loss from the discontinuation so it is hard to tell how much benefit the PRP is offering because they may be losing from stopping the minoxidil.
If you are seriously considering a hair transplant I would recommend you have an evaluation by a hair transplant surgeon. I don’t look at PRP as a hair transplant replacement but for some it will delay the process before proceeding with a transplant but can also be used very effectively in conjunction with transplant. Good luck.