Logic Masters Deutschland e.V.

This puzzle is a variant and extension of a puzzle type I've discovered recently called "Circle 9".

The Rules:

1. [Circle 18] Use blue to shade exactly 18 of the cells containing numbers such that there are two shaded cells in every row, column, and 3x3 box, and each digit from 1-9 is shaded exactly twice. Shade the remaining cells gray.
2. [Sudoku] Then normal sudoku rules apply - so every row, column and 3x3 box will need the digits placed from 1-9. Cells shaded blue are given digits. The digits in cells shaded gray cannot be correct digits in the final sudoku.
3. [Sandwich] Clues outside the grid, which must be deduced, are the sum of the digits between the blue shaded cells. These totals are all different prime numbers. (2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37)

The Puzzle: Try it on Sudokupad