Instead of by value

patient_dicom, study_dicom etc. should use streams, otherwise it's very inefficient.

• Your lib.rs can be divided into smaller modules.
• Maybe trait Entity should be sealed?
• fn parent_kind_name(&self) -> Option - maybe return Option<&str>?
• Some functions on Entity trait can be implemented inside impl dyn Entity, to disallow override and detach dependency from implementor. https://radicle.community/t/rust-s-impl-dyn-trait-syntax/102
• Using pub fields may render future changes to structs incompatible with previous major version of the lib (see #[non_exhaustive] https://doc.rust-lang.org/reference/attributes/type_system.html).
• You can apply #[serde(rename_all = "PascalCase")] to more structures instead of manual renaming.
• You still have TODOs in your code. Maybe resolve them or move into github issues?
• You can allow user to pass a &str as an argument where you need a String with arg: impl Into and acquire a String with arg.into() (in fn auth, for example).
• You should accept Read and Write by value, and not reference, see https://rust-lang.github.io/api-guidelines/interoperability.html#c-rw-value
• timeout != None => timeout.is_some() or if you need to access inner value if let Some(to) = timeout {
• I think Error could be better. What errors typical user of your crate would expect and in what form? How much details can you omit? You can hide pub fields, and instead lend message with Display.
• Option - you can use an enum inside of your Error to encapsulate different errors. Also, consider source https://doc.rust-lang.org/std/error/trait.Error.html#method.source
• You can move integration tests from lib.rs to /tests

https://github.com/jonasbb/serde_with looks like it could replace all the #[serde(skip_serializing_if = "Option::is_none")] (perhaps more).

Java(Version 1.8)
The file is stored with the encoding ISO_IR 192 on the server but the DICOM response of C-FIND is ISO_IR_100.
i use the code try other system is fine，it's made me not to know what the problem is

could you give me any idea

The library would be pretty much useless for dealing with large amounts of data without the ability to do it asynchronously.

        let search = Search {
            level: kind,
            query,
            expand: Some(true),
        };

The expand is hard-coded to true.