Advanced ortho imaging

February 5, 2019 0 By FM

X-rays revolutionized orthopedic management in fundamental ways, especially in the diagnosis of conditions and their management. However, there are limitations to X-rays that have paved the way for the further advancements in this field.
An analysis of the limitations reveals that X-rays cannot visualise cartilages, occult fractures and stress fractures. Also, early detection of osteomyelitis, tumours with marrow involvement and micrometastasis or soft tissue component are not possible.
Many hospitals nowadays utilise PACS (Picture Archival and Communicating System). PACS is an imaging technology which transmits images and reports digitally in the universal format DICOM (Digital Imaging and Communications in Medicine). The major components of PACS include the imaging modalities (like X-ray, CT, MRI), a secured network, and workstations for interpreting the images, and archives for the storage and retrieval of images and reports. The system offers some major benefits. A soft copy of X-ray films replaces the costlier hard copy film. In teleradiology and telediagnosis, it facilitates the effective and efficient management of various medical conditions. It also allows for electronic image integration with Hospital Information System, Radiology Information System, Electronic Medical Record, thus enabling a seamless flow of information across the system.

MRIs for occult fractures
Since the development of MRI back in the 1970s, it has become the best choice for diagnostic medicine and biomedical research. With rapid advancements in this imaging technique, it has become the 1st choice in detecting occult fractures, stress fractures, osteomyelitis, tumours with marrow involvement, micrometastasis or soft tissue component. MRI studies are useful in evaluating the internal structure and surface of the meniscus, peripheral and inferior surface tears of the meniscus and multiple tears. MRI should be done in every patient of suspected ligamentous injury posted for arthroscopy to prevent unwanted arthroscopies. Many anatomic variants can erroneously look like tears on MRI. MRIs are always advised before surgery or biopsy, because it reveals the extent of a tumour better than X- ray. For example, in enchondroma, X-rays may not appreciate the involvement of the shaft fully. Surgery based on X-rays alone would not be adequate. Contrast in MRI is used to identify cystic or necrotic areas from where we do not take a representative biopsy; viable areas appear bright. Contrast can also help to differentiate between edema and a tumour, as the latter takes contrast intensely. A dynamic contrast MRI can also be used to assess the response to treatment given. It is always advisable to get a scale for measurement while doing CT. In DICOM format, we can take measurements to plan the surgeries, particularly limb salvage procedures.
Orthopedicians experience great challenge in interpreting the MRI of people with implants in situ. With newer MRI sequences with MARS (Metal Artifact Reducing Sequences), this traditional problem of imaging can be overcome. MAVRIC (Multi Acquisition Variable Resonance Image Combination) and SEMAC (Slice Encoding for Metal Artifact Correction) and the use of materials that produce less artifacts, like titanium, have overcome the limitations of MRI to a certain extent. Interventional radiology, like RFA (Radiofrequency ablation), is used to treat osteoid osteoma, metastasis etc.

PET choice
When F18 Fluro Deoxy Glucose is injected into a patient, a PET (Positron Emission Tomography) scanner can form a 2D or 3D image of its distribution in the whole body. Its uptake is analysed by SUV (Standard Uptake Value). PET can be utilized for diagnosing Hodgkin’s disease, Non-Hodgkin’s lymphoma, colorectal cancer, breast cancer, melanoma, lung cancer and Alzheimer’s disease. PET provides functional information of tissue metabolism, helping in initial evaluation and to measure the response to treatment.
PET, CT/MRI combines functional and spatial resolution. PET-CT is more useful than a bone scan as it can identify primary and is more specific for tumour cells. But it has its own limitations when it comes to osteoblastic lesions, which have limited uptake on PET, and a bone scan may be more appropriate in such cases. A Tc-labelled bone scan can pick up osteoblastic activity; methylene diphosphonate is taken up by osteoblasts on scanning the whole skeleton. However, in multiple metastases, a PET scan is the first choice.
Similarly, ultrasound-guided biopsy and CT-guided biopsy have revolutionized the ease of diagnosis even in a routine set up.