An apparatus including an x-ray source and detector where the source is disposed behind the detector and the detector is configured with a hole through which an x-ray beam emitted by the source can be transmitted to target tissue is provided. During operation, the source emits an x-ray beam through the hole in the detector. The x-ray beam may then be incident on an area of a subject to be imaged and cause various reflections and/or absorptions. The detector can detect signals reflected by the subject and an x-ray image can be generated accordingly.