SPECT-CT
Trinity Medical Imaging specialises in hybrid bone imaging by combining the functional information from a traditional bone scan, with high resolution three dimensional imaging from a CT (or CAT) scan. This is performed using our state of the art SPECT-CT scanner in one sitting. This hybrid SPECT-CT scan can localise problem areas with greater accuracy, improving diagnosis and potentially reducing the need for multiple examinations. Our team of radiologists have a specialist knowledge in musculoskeletal disease and have a wealth of experience of using SPECT-CT in diagnosing a range of sports injuries, back pain and painful joint replacements.
Spine and Low Back Pain
Spine and Low Back Pain
The demand for SPECT-CT scans of the cervical and lumbar spine, has been growing over the last few years. Healthcare professionals specialising in treating mechanical back pain are realising that they can take some of the guesswork out of diagnosing inflammatory causes of back pain.
SPECT-CT is a very sensitive test for intervertebral disc, facet joint and sacro-iliac joint inflammation. MRI scans are often performed in patients with difficult to diagnose neck and low back pain. Whilst this can be beneficial if patients have symptoms of nerve compression, MRI is of little use in the diagnosis and management of mechanical back pain. Often MRI scans can show abnormalities in intervertebral discs and in facet joints which do not correlate with patients’ symptoms.
SPECT-CT scans, on the other hand, show good correlation with the site of patients’ symptoms in mechanical back pain. The reason is that the scan can demonstrate the site of increased bone activity, which can be related to abnormal stress on the spine. It is this functional information which confers SPECT-CT greater accuracy than MRI in mechanical back pain.
The SPECT-CT scan can differentiate facet joint arthritis from intervertebral joint arthritis. It can accurately identify which joint is affected, and can be used to direct steroid injections into the site of disease. Potentially this can reduce the need for multiple unnecessary procedures.
The improved anatomical imaging that SPECT-CT provides can identify problems associated with congenital normal variants, such as fused vertebrae which may result in a pseudoarthrosis.
SPECT-CT can also be beneficial in identifying subtle pars interarticularis defects / fractures (spondylosis) which can often be missed on MRI scans.
SPECT-CT is invaluable in assessing the post-operative spine. Because the presence of metalwork in the spine degrades the quality of the images in MRI scans, their role in evaluating the post-surgical spine is limited. SPECT-CT is not limited by the presence of metalwork, and can be extremely useful in assessing loosening of prosthesis and is very sensitive in identifying post-operative infection.
SPECT-CT Indications in the spine
- Determining sites of active facet joint arthropathy prior to joint injection
- Detecting pars interarticularis defects / fractures (spondylosis)
- Determining the level of active degenerative disc disease
- Differentiating acute from chronic collapse prior to vertebroplasty
- Assessment of the post surgical spine
- Assessment of potential metastatic disease
- Early detection of osteomyelitis and diskitis
- Detection of active arthropathy associated with pseudoarthrosis
- Characterisation of focal spinal lesions e.g osteoblastoma or haemangioma
Finally SPECT-CT can be used to identify discitis and osteomyelitis earlier than MRI scans. The increased bone activity which occurs as a result of localised inflammation is much more sensitive than MRI. This, combined with the improved anatomical localisation of SPECT-CT, results in earlier and more accurate diagnosis of infection in the spine.
Foot and Ankle
Foot and Ankle
The ability to localise accurately sites of bone inflammation in the foot and ankle makes SPECT-CT an invaluable tool for many specialists in this area. Because of the complex anatomy in the foot, it can sometimes be difficult to confidently diagnose the cause of pain, particularly in patients with previous trauma or chronic conditions such as diabetes. Traditional imaging modalities such as x-rays and MRI are often used in the initial work up of patients, but they have poor specificity and can often be abnormal even if the patient doesn’t have pain.
SPECT-CT relies on assessing bone turnover and therefore is much more specific in identifying the cause of patients’ pain.
The latest generation CT technology available in our SPECT-CT scanner at Trinity Medical Imaging allows us to localise the cause of pain to within a few millimetres.
SPECT-CT is often used in evaluating patients with degenerative disease of the joints in the ankle and foot. It can accurately localise the pain generator, and allows surgeons to target the correct joint for steroid and local anaesthetic injection. It is often used in pre-operative planning to differentiate joints prior to surgical fusion. For instance, SPECT-CT is particularly useful in differentiating ankle joint from subtalar joint arthritis; something that can be challenging by clinical examination alone.
Our experience has shown that joint injections that are performed by targeting with SPECT-CT are more successful than injections performed without SPECT-CT guidance.
At Trinity Medical Imaging SPECT-CT is often used to assess the post-operative foot and ankle. It can correctly determine whether a treated fracture has healed or whether an attempted joint fusion has been successful. SPECT-CT does not suffer from the same metal artefact that plagues MRI scans, and therefore should be considered the gold standard investigation in the post-operative foot and ankle.
SPECT-CT Indications in the foot and ankle
- Localising sites of symptomatic arthritis prior to intervention
- Assessing the post-surgical foot and ankle
- Evaluating union of fractures
- Identifying impingement syndromes
- Diagnosing symptomatic accessory ossicles
Finally, SPECT-CT can accurately diagnose impingement syndromes that can occur as a result of congenital or acquired deformities such as flat feet or accessory ossicles. The presence of abnormal tracer uptake can indicate that there is abnormal loading on the foot due to anatomical variation. This functional information cannot be determined by any another imaging modality.
Hip and Knee Joints
Hip and Knee Joints
Although MRI scans are still the most commonly performed examinations to evaluate painful hips and knees, SPECT-CT can be extremely useful when mechanical problems are suspected.
Recently we are using SPECT-CT to diagnose femoroacetabular impingement of the hip. In this condition, abnormalities of the femoral neck or acetabulum can contribute to restricted movement and pain. SPECT-CT is able to demonstrate sites of increased bone activity due to repetitive microtrauma during impingement, whilst providing high resolution three dimensional images to explain the cause of the symptoms. At Trinity Medical Imaging we can identify Ganz lesions, measure the alpha angle of the femoral neck and acetabular inclination and anteversion/retroversion to identify pincer deformities.
SPECT-CT indications in the hip and knee
- Differentiate patellofemoral from tibiofemoral arthropathy
- Identify patella maltracking with measurement of TTTG distance
- Identify causes of femoroacetabular impingement
- Evaluate joint prostheses for complications
- Assessing leg length discrepancies
In the knee, MRI remains the gold standard scan to evaluate the internal soft tissue structures, but SPECT-CT is able to provide a valuable insight into the cause of mechanical pain. For instance SPECT-CT is used to identify patella maltracking problems, osteochondral defects or subchondral fractures.
Joint Replacements
Joint Replacements
At Trinity Medical Imaging our consultants have been pioneering the use of hybrid SPECT-CT technology in evaluating painful joint replacements. Unlike other imaging modalities, SPECT-CT combines being able to image areas of increased bone turn-over that can occur in prosthetic complications, with detailed anatomical imaging.This anatomical imaging give surgeons a valuable insight into the positioning of prosthesis as well as allowing them to plan revision surgery if necessary.
At Trinity Medical Imaging we routinely perform SPECT-CT with component position measurements in hip and knee replacements. We also can evaluate joint replacements in the shoulder, wrist and ankle.
SPECT-CT is very sensitive for identifying infection in the joint replacement as well as periprosthetic fractures and component failures.
Loosening of the prosthesis is usually the result of either failure of a component of the prosthesis or abnormal stress on the joint. Sometimes this can be exacerbated by poor positioning of the prosthesis.
SPECT-CT has also successfully identified complications related to metallosis, as has been seen with recent metal-on-metal hip replacements. The CT component can identify soft tissue collections, often called psedotumours, around the joint.
At Trinity Medical Imaging, we provide detailed anatomical views of the joints to help surgeons determine the cause of the pain and plan therapy.
Musculoskeletal SPECT-CT preparation
In the case of a bone scan with SPECT-CT, you will receive an injection in your arm of a radiopharmaceutical. Usually we will perform an early phase scan and then a later scan at about 3–4 hours after the radiopharmaceutical has been absorbed by the bones.
When the pictures are being taken, the gamma camera moves over the body to detect the gamma rays coming from the radiopharmaceutical in the bones. This creates an image of the bones, as determined by the activity of the bone to remodel. This can highlight information which helps the doctor to diagnose your condition.
Are there are any risks?
As the gamma rays are similar to X-rays, there are small risks associated with being exposed to radiation. However, the radiation decays away over a few hours and the amount of radiation used in medical imaging is very low. This is comparable to the natural radiation we all receive from the environment over about two years. In fact, the risks from missing a disorder by not having a bone scan may be considerably greater than the risks of the radiation. If you are concerned about the risks of the radiation, please speak to a member of our team.
Are you required to make any special preparations?
No specific preparations are required. You may eat and drink normally and you should take any medicines you need as usual. After the injection you should drink plenty of fluids – unless you normally have to restrict your fluid intake. If you leave the department, you do not need to take any special precautions, but if you stay then you should use the special toilet for nuclear medicine patients. Your technologist will show you where the toilet in the department is.
If you are pregnant or breastfeeding
If you are pregnant, or think you may be pregnant, you mustinform the department before attending, and certainly before the radiopharmaceutical is administered.
If you are breastfeeding, please inform the department before attending and you will be advised as to whether you will need to take any precautions. You may be advised to avoid breastfeeding for a few hours afterwards and you may need to express milk before your scan.
Can you bring a relative/friend?
Yes you can, but for reasons of safety, they may not be able to accompany you into the examination room, except in very special circumstances. Please do not bring children with you as they will potentially be exposed to radiation from other patients.
Arriving for your appointment
When you arrive for your appointment, please go to the reception desk, after which you will be shown where to wait until collected by a technologist.
The technologist will explain the procedure, and you can ask any questions. You may be asked some questions about your health, or whether you have had this examination before.
The technologist will then give you the injection of radiopharmaceuitcal preparation into a vein in the arm. This is just like having blood taken.
What happens during the scan?
You do not need to undress but please remove any jewellery or metallic objects such as keys, coins or buckles. You will be taken to the scanner room and made comfortable lying on the couch. The technologist will position the gamma camera over the main joint being examined and this early phase of the study will last up to 15 minutes.
You will then be free to leave the department and asked to return in approximately three hours, during which time you can eat and drink as normal. On your return, you will be asked to visit the special toilet to empty your bladder. The technologist will position the gamma camera over one end of your body and ask you to lie still. You can breathe normally throughout. Usually, the camera will slowly scan the whole length of your body. Sometimes the camera takes pictures in segments.
The technologist will remain in the control room and watch you through the glass screen in the examination room. It may be necessary to take one or two more localised views, if more detail is required. Afterwards, it will usually be necessary to perform a special scan called a CT (or CAT) scan. Your technologist will tell you if this is going to happen. During this scan, the table will move forwards and backwards through the ‘doughnut’ shaped scanner.
Will it be uncomfortable?
No. Apart from the injection, you will not feel anything.
Can I listen to music while I have my scan?
Your technologist will ask you whether you would like to listen to music during your scan. You may bring in a CD or select music from our selection.
How long will it take?
Apart from the 3 hours while the isotope is absorbed into the bones, the scanning process usually takes about 30 minutes, and your total time in the department will usually be less than one hour.
Are there any side-effects?
No, the injection causes no side-effects, nor will you feel drowsy. You can drive home afterwards and go about your normal activities.
In addition to mothers who are breastfeeding, parents with young children should notify the technologist, who will explain that it is advisable not to have prolonged close contact with them for the rest of the day. This is to avoid their being exposed to unnecessary radiation.
When will you get the results?
The scan will be examined after your visit and a written report on the findings will be sent to your referring doctor within 7 days.
Please remember
The radiopharmaceutical required for this examination is ordered especially for you. If you cannot attend your appointment, please let the department know as soon as possible, so that we can use it for someone else.
We hope that this leaflet has answered your questions, but remember that this is only a starting point for discussion about your treatment with the doctors looking after you. Make sure you are satisfied that you have received enough information about the procedure.
