Negotiate and transcode DICOM transfer syntaxes during C-STORE association to handle modality and PACS incompatibilities

Verified steps

1. Inspect the Proposed Presentation Contexts in the association request from the sending SCU; each context pairs an Abstract Syntax (SOP class UID) with one or more Transfer Syntax UIDs the SCU can send
2. The SCP accepts each Presentation Context with a single agreed Transfer Syntax; prefer the lossless or uncompressed transfer syntax (Explicit VR Little Endian 1.2.840.10008.1.2.1) when the SCP's storage or downstream systems do not support the proposed compressed syntax
3. If the SCP receives data in a compressed transfer syntax it cannot store natively (e.g., JPEG 2000 Lossless 1.2.840.10008.1.2.4.90), invoke transcoding to the agreed syntax before storing — libraries such as dcmtk dcmcjpeg or pydicom with gdcm provide transcoding pipelines
4. For multi-frame objects ensure that transcoding preserves PhotometricInterpretation (e.g., YBR_FULL_422 for JPEG, MONOCHROME2 for CT) as changing this tag invalidates the pixel data interpretation
5. Log rejected Presentation Contexts (Result 3 = Abstract Syntax Not Supported) from association negotiations to identify SOP classes that need to be added to the SCP's configured Supported SOP Classes list