Nuclear medicine methods for evaluation of skeletal infection among other diagnostic modalities.

Skeletal infection continues to be a common and difficult condition in clinical practice and early accurate diagnosis is very challenging. Clinical and laboratory features of skeletal infections are not always present, may be confusing, and are nonspecific for bone infection in its early stages, therefore, several imaging modalities are used for early detection of osteomyelitis. Plain films should always be the first step in the imaging assessment of osteomyelitis, however, the sensitivity for X-ray radiography has been reported to range from 43% to 75%, and the specificity from 75% to 83%. Over years, scintigraphic procedures have become an essential part of the diagnostic procedure for osteomyelitis. The standard approach for bone scintigraphy with tech 99mTc labeled methylene diphosphonate to assess for osteomyelitis is to perform a three-phase procedure. The positive uptake on all three phases is highly sensitive for osteomyelitis (sensitivity 73% to 100%). 67Ga citrate gained more attention for the more specific diagnosis of osteomyelitis due to its known capacity to localize in cases of active infection and pus. The reported specificity for 67Ga scintigraphy in osteomyelitis is around 67-70% and the specificity is much higher (92%) when 67Ga single photon emission tomography was obtained. Labeled white blood cell (WBC) imaging has become the procedure of choice to diagnose most cases of skeletal infections except for those of the spine. Labeling of leucocytes can be done either by 111In or 99mTc labeled hexamethylpropylene amineoxime. The sensitivity and specificity for labeled WBCs are in the high range of 80% to 90%. [18F]fluorodeoxyglucose positron emission tomography (PET) has been found to accumulate non-specifically at sites of infection and inflammation. Investigational studies showed that PET is particularly valuable in the evaluation of chronic osteomyelitis and infected prostheses. Other imaging modalities include sonography, computed tomography (CT) and magnetic resonance imaging (MRI). The sensitivity and specificity of CT for the diagnosis of osteomyelitis has not been established clearly and are in the range of 65% to 75%. The sensitivity of MRI for osteomyelitis has been generally reported as being between 82% and 100%, and specificity between 75% and 96%. Cases of osteomyelitis commonly referred to diagnostic imaging departments include chronic osteomyelitis, diabetic foot infections, vertebral osteomyelitis, joint prostheses and patients with suspected reinfection. These specific entities need special attention and careful selection of the correct tracer or combination of imaging modalities that is best suited for the proper therapeutic management protocols.

Value of myocardial SPECT in early detection of ischaemia in children with sickle cell anaemia.

BACKGROUND: Cardiovascular complications of sickle cell anaemia (SCA) are relatively infrequent compared with other cerebral and skeletal insults. However, myocardial infarction and cardiac dysfunction have been reported in autopsied patients with SCA. When left ventricular functional parameters of gated SPECT and echocardiography were compared incidentally in children with SCA, some 26% of patients were found to have evident myocardial ischaemia. This stimulated the current work with the aim to further analyse these incidental findings and evaluate the possible role of SPECT in early detection of coronary insufficiency in children with SCA. PATIENTS AND METHODS: Twenty-seven patients (19 girls, 8 boys), mean age 9.2±4.2 years, with SCA were examined by baseline ECG, echocardiography and gated SPECT. They were all free from any cardiac symptoms. Intravenous injection of 5 to 10 mCi 99MTc-MIBI or 99MTc-Myoview was administered, according to the predetermined weight-dependent paediatric dose. Stress SPECT was obtained 45 to 60 minutes after tracer injection, which took place at peak physical exercise (6 patients) or 3 to 4 minutes after IV infusion of dipyridamole pharmacological stress (21 patients). Rest SPECT study was acquired 4 to 5 hours later after a second injection of 99MTc-MIBI/Myoview. A semiquantitative nine-segment stress/rest bull's eye model was used to assess to the presence/extent of myocardial ischaemia. RESULTS: Myocardial perfusion was normal in 20 patients (74%). Seven patients (26%) had significant perfusion defects in the stress images. Four of them showed perfusion defect in one or two segments. Complete reversibility in the rest study was seen in all patients. Two patients showed a mixture of reversible and fixed perfusion defects in four segments. One patient had evident left ventricular dilatation with multiple fixed and reversible defects (cardiomyopathy). In this case, a diffusely reduced myocardial wall contractility was seen and a low LVEF of 42% as assessed by echocardiography. This was the only case showing agreement between the echo and SPECT findings. In the whole cohort the EF% and FS% by echocardiography were 61.7±5.9% and 33.2±3.4% respectively (mean±SD). There were no significant relations between myocardial perfusion abnormalities when compared with EF% and FS%; (p>0.05). CONCLUSION: Cardiac involvement in the form of myocardial ischaemia should be regarded as a high-risk complication in patients with SCA. Myocardial perfusion scintigraphy succeeded in the early detection of myocardial perfusion abnormalities in patients with SCA.