Revista Espanola De Medicina Nuclear最新文献

Objective

To develop a small-animal SPECT system using a low cost commercial portable gamma camera equipped with a pinhole collimator, a continuous scintillation crystal and a position-sensitive photomultiplier tube.

Material and methods

The gamma camera was attached to a variable radius system, which enabled us to optimize sensitivity and resolution by adjusting the radius of rotation to the size of the object. To investigate the capability of the SPECT system for small animal imaging, the dependence of resolution and calibration parameters on radius was assessed and acquisitions of small phantoms and mice were carried out.

Results

Resolution values, ranging from 1.0 mm for a radius of 21.4 mm and 1.4 mm for a radius of 37.2 mm were obtained, thereby justifying the interest of a variable radius SPECT system.

Conclusions

The image quality of phantoms and animals were satisfactory, thus confirming the usefulness of the system for small animal SPECT imaging.

The sentinel node biopsy procedure is based on the hypothesis of the existence of an orderly and predictable pattern of lymphatic drainage to a regional lymph node basin. This results in the consideration of all lymph nodes with direct drainage from the primary tumor as sentinel nodes. The sentinel node is not necessarily the hottest or the most nearby node, although this is often the case. Lymphoscintigraphy has been an essential component for preoperative sentinel node identification. With the new generation of multimodality gamma cameras, SPECT/CT has been incorporated into the sentinel node procedure. The resulting SPECT/CT fused images depict sentinel nodes in an anatomical landscape providing a helpful roadmap for surgeons. Therefore, it is necessary to define the role of SPECT/CT in relation to the classical planar lymphoscintigraphy for the identification of sentinel nodes. To understand the combined use of lymphoscintigraphy and SPECT/CT, the criteria for sentinel node identification on preoperative images must be specified. The authors, based on their experience in this field, present tentative criteria to identify lymph nodes as sentinel nodes both in planar and SPECT/CT images and classify them into different categories. The use of these scintigraphic categories to characterize radioactive lymph nodes is also helpful for surgical decision making.

We report the case of a 27 year-old man with symptoms of severe hypothyroidism that have evolved since his adolescence. He was found to have an 11 mm right lobe thyroid nodule. On thyroid ultrasound, the nodule was solid, heterogeneous with markedly atrophic hypoechoic surrounding tissue. Thyroid scintigraphy revealed increased ^99mTc pertechnetate and ¹³¹I uptake, with persistence of ¹³¹I hyperfixation after 24 h. There was no fixation of the radiotracer in the remaining tissue. Thyroid function tests found TSH > 100 mIU/l, free thyroxine level 0.9 pmol/l (normal values 11.5-21.8), anti-thyroid peroxydase antibodies strongly positive > 1,000 IU/ml, and anti-thyroglobulin antibodies negative. One year after levothyroxine therapy, the nodule decreased to 40% of its original size.

Hashimoto's thyroiditis may present as a single hot nodule and severe hypothyroidism. Data of reported cases suggest that the hot nodule corresponds to a localized hyperplasia of the less diseased portions of the thyroid. Chronic stimulation by TSH may have promoted nodular growth and isotopes uptake.

Background

Gallbladder carcinoma is a neoplasm having a poor prognosis in which the role of the positron emission tomography with ¹⁸F-fluordeoxyglucose as a diagnostic tool, although of possible usefulness, has not been well-defined.

Methods/design

It is a prospective cohort of patients with radiologically malignant suspicious gallbladder lesions. A staging diagnostic presurgical FDG-PET study was carried out in each patient using both dedicated PET and multimodality PET-CT scanners. Diagnostic accuracy parameters were calculated from the results of PET imaging and were correlated with the condition and/or the clinical course of the patients. The clinical impact of its implementation in the diagnosis of gallbladder carcinoma was also analyzed.

Results

A total of 42 patients were recruited (22 malignant lesions, 20 benign). Overall diagnostic accuracy was 83.33% for the diagnosis of the primary lesion, 88.89% for the evaluation of lymph node involvement and 85.1% for the evaluation of metastatic disease. Mean SUVmax in malignant gallbladder lesions was 6.14 ± 2.89. ROC curve showed a cut-off value of 3.65 in the SUVmax for malignancy. Accuracy of PET studies alone (n = 21) was slightly lower than that of the PET/CT (n = 21). FDG-PET changed the management of 14.8% of the population due to the identification of unsuspected metastatic disease.

Comments

FDG-PET accurately diagnoses malignancy or benignity of suspicious gallbladder lesions, with the addition of its capacity to identify unsuspected metastatic disease. PET-CT improves the diagnostic accuracy of the procedure, due to the metabolic-structural complementarity of their information. The SUVmax has a complementary value added to the visual analysis.

Intrathoracic splenosis is a generally asymptomatic entity incidentally diagnosed after the completion of an Rx, CT scan or MRI for another reason.

The performance of scintigraphy with ^99mTc-labelled heat-denatured erythrocytes allows the noninvasive diagnosis of this entity and avoids more aggressive diagnostic techniques such as FNAP or thoracotomy. Because this splenic tissue may be partially or fully functioning and therefore may have some beneficial immune function for the patient, the management of this entity should be conservative.

Radioisotopic scintigraphy with ^99mTc labelled heat-denatured erythrocytes is the technique with the greatest specificity in the demonstration of splenic tissue.

The presence of subpleural pulmonary nodules, associated or not with intra-abdominal nodules, together with the existence of previous partial or total splenectomy, traumatic or not, with or without associated rupture of the diaphragm, should raise suspicion of the presence of intrathoracic splenosis.

Background

Ankylosing spondilitis (AS) is a chronic inflammatory disease with prominent inflammation in joints and extraarticular organs. AS patients have approximately two times more risk of mortality than the normal population. One reason for this increase in mortality is increased cardiovascular risk. In this study, we have aimed to evaluate myocardial perfusion and left ventricular function using ^99mTc-MIBI gated myocardial perfusion single photon emission computed tomography (SPECT).

Material and methods

The study group consisted of 28 AS patients (19 men, 9 women), and mean age 39.46 ± 10.98 years. All patients underwent ^99mTc-MIBI gated myocardial perfusion SPECT with the same day protocol.

Results

We detected various risk factors including smoking habits in 12, family history of cardiovascular disease in 12, hypertension in 3, hyperlipidemia in 9 patients. We performed a myocardial perfusion SPECT for each patient and found normal perfusion pattern in SPECT images. Out of 28 patients, eight patients had normal perfusion but wall motion abnormalities.

Conclusion

We detected that myocardial perfusion is preserved in the patients with AS. However, left ventricular wall motion abnormalities are seen. We concluded that ankylosing spondylitis may be associated with microvascular dysfunction and gated myocardial perfusion scintigraphy could be valuable in AS patients for the evaluation of LV function even if the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score are low and the disease duration shorter.