Estimation of additional dosimetry from low-dose CT scan to 99mTc-HMDP SPECT/CT.

INTRODUCTION: Currently, the addition of computed tomography (CT) to a gamma-camera has revolutionized nuclear medicine. Indeed the CT, because of its good spatial resolution, of the attenuation correction of the single photon emission computed tomography (SPECT) images and of a better anatomical localization of lesions, improves the sensitivity, specificity and accuracy of the examination. Despite the fact that the hybrid camera uses a low-dose non-diagnostic scanner, increases the overall delivered dose of radiation. METHODS: The aim of this study was to evaluate the contribution of CT to the total effective dose of 99mTc-HMDP (hydroxymethylenediphosphonate labelled with technetium 99 metastable) SPECT/CT for an adult oncologic population. This prospective study included 103 patients (75 women and 28 men) aged 28 to 79 years. RESULTS: The mean effective doses of SPECT, CT and SPECT/CT were respectively 3.8 mSv, 3.3 mSv and 7.1 mSv, respectively. The average contribution of CT scans to the total effective dose for SPECT/CT examination was 45 ± 9.7%, and ranged from 10 to 67.4%. The lowest value was for the thorax area. CONCLUSION: This radiation dose is not negligible. But, taking into account the benefit of hybrid imaging, this additional radiation remains justifiable. Nevertheless, the "As Low as Reasonably Achievable (ALARA)'' principle must be respected to ensure that the patient is not subjected to unnecessarily high levels of radiation.

Does the Incremental Value of 123I-Metaiodobenzylguanidine SPECT/CT over Planar Imaging Justify the Increase in Radiation Exposure?

PURPOSE: Planar scintigraphy with 123I-radiolabeled metaiodobenzylguanidine (123I-mIBG) is an important imaging modality to evaluate neuroblastoma. In recent years, Single Photon Emission Computed Tomography combined with Computed Tomography (SPECT/CT) has revolutionized nuclear medicine. Nevertheless, the addition of the CT has increased the patients' irradiation. We aimed to evaluate the incremental benefits of 123I-mIBG SPECT/CT over conventional planar imaging and to estimate the relative increase of radiation dose. METHODS: We retrospectively evaluated the added value of 56 SPECT/CT performed in 40 children in terms of better characterization of the lesion and its locoregional extension, better lymph node staging, detection of new lesions, and elimination of false positives by a paired comparison between the planar images and the SPECT/CT ones. Then, we calculated the percentage contribution of the additional radiation of the CT in this hybrid imagery. RESULTS: In 88% (49 out of 56) of the examinations, SPECT/CT provided additional information, which was crucial in 20% of the cases. It allowed a better characterization of the lesion and its locoregional extension in 44 cases, a better lymph node staging in 28 cases, the detection of 33 new lesions, and the elimination of 9 false positives. The CT effective dose was significantly lower than the SPECT one. The average additional radiation exposure due to CT was 12% (4-23%). CONCLUSION: 123I-mIBG SPECT/CT has an undeniable added value that improves planar imaging interpretation and impacts patient management. These potential benefits would justify the low additional radiation induced by the CT.

New Hybrid Method for Left Ventricular Ejection Fraction Assessment from Radionuclide Ventriculography Images.

BACKGROUND: In this paper, we propose a new efficient method of radionuclide ventriculography image segmentation to estimate the left ventricular ejection fraction. This parameter is an important prognostic factor for diagnosing abnormal cardiac function. METHODS: The proposed method combines the Chan-Vese and the mathematical morphology algorithms. It was applied to diastolic and systolic images obtained from the Nuclear Medicine Department of Salah AZAIEZ Institute. In order to validate our proposed method, we compare the obtained results to those of two methods present in the literature. The first one is based on mathematical morphology, while the second one uses the basic Chan-Vese algorithm. To evaluate the quality of segmentation, we compute accuracy, positive predictive value and area under the ROC curve. We also compare the left ventricle ejection fraction estimated by our method to that of the reference given by the software of the gamma-camera and validated by the expert, using Pearson's correlation coefficient, ANOVA test and linear regression. RESULTS: Static results show that the proposed method is very efficient for the detection of the left ventricle. The accuracy was 98.60%, higher than that of the other two methods (95.52% and 98.50%). CONCLUSION: Likewise, the positive predictive value was the highest (86.40% vs. 83.63% 71.82%). The area under the ROC curve was also the most important (0.998% vs. 0.926% 0.919%). On the other hand, Pearson's correlation coefficient was the highest (99% vs. 98% 37%). The correlation was significantly positive (p<0.001).

[Thyroglobulin: usefulness and limits in monitoring patients with thyroid carcinoma]. / La thyroglobuline: place et limites dans le suivi du cancer différencié de la thyroïde.

UNLABELLED: The aim of this study was to assess the role of thyroglobulin in monitoring patients with differentiated thyroid carcinoma. METHODS: We retrospectively sudied thirty patients who had total thyroidectomy and had been followed beteween 1999 and 2004 in nuclear medicine department. They have had iodine 131 whole body scans, repeated determination of thyroglobulin, thyreostimulin and thyroglobulin antibodies. RESULTS: One hundred twelve samples of thyroglobulin were done. In post surgical period thyroglobulin was ranging from 0.3 to 600 ng/ml. In 38 months follow up 4 patients (11.4%) had shown reccurent disease. Thyroglobulin sensitivity was 75%. One patient had diffuse lung metastases with high thyroglobulin level 600 ng/ml wich decreased after iodine 131 therapy. CONCLUSION: Serum thyroglobulin is the differentiated thyroid carcinoma marker of choice nevertheless one should establish the level of thyroid stimulation and seek for the antithyroglobulin antibodies.

Dual-isotope 99mTc-MIBI/123I parathyroid scintigraphy in primary hyperparathyroidism: comparison of subtraction SPECT/CT and pinhole planar scan.

PURPOSE: In patients with primary hyperparathyroidism, the preoperative imaging objective is to locate accurately and reliably uniglandular or multiglandular hyperfunctioning parathyroid, to guide surgery, particularly for minimally invasive method. Subtraction planar scintigraphy with dual-isotope (I/Tc-MIBI) is an efficient examination to specify abnormal parathyroid location, but without accurate anatomic reference. This lack should be avoided by a hybrid SPECT/CT image acquisition. METHODS: We compared planar scans (neck and mediastinum parallel-hole, associated with anterior neck pinhole) to neck and mediastinum SPECT/CT, all with subtraction (I/Tc-MIBI) method, in exact location of abnormal parathyroid in 50 patients with sporadic primary hyperparathyroidism. Surgical and histological findings were used as the standard of comparison. RESULTS: Sensitivity is equivalent for the 2 protocols (86% and 75% for SPECT/CT and planar protocol, respectively, P = 0.15), but SPECT/CT was highly specific (specificity 100% and 90% for SPECT/CT and planar protocol, respectively, P = 0.04). In patients with concomitant thyroid disease, subtraction SPECT/CT appeared to be more sensitive than planar protocol (88% and 62% for SPECT/CT and planar protocol, respectively, P = 0.04). CONCLUSIONS: In preoperative assessment of primary hyperparathyroidism and to guide surgery, we propose to perform first subtraction SPECT/CT and to complete it with neck pinhole, only if tomoscintigraphy is negative.

Desmoplastic small round cell tumor: impact of F-FDG PET induced treatment strategy in a patient with long-term outcome.

The desmoplastic small round cell tumor (DSRCT) is an uncommon and highly aggressive cancer. The role of (18)F-FDG PET in management of DSRCT is little reported. We report a case of metastasized abdominal DSRCT detected in a 43-year old patient whose diagnostic and therapeutic approaches were influenced by (18)F-FDG PET-CT. The patient is still alive ten years after diagnosis. (18)F-FDG PET-CT seems to be a useful method for assessing therapeutic efficiency and detecting early recurrences even in rare malignancies such as DSRCT.

Osteoblastoma and osteoid osteoma: morphofunctional characterization by MRI and dynamic F-18 FDG PET/CT before and after radiofrequency ablation.

Osteoblastoma (OB) and osteoid osteoma (OO) are benign bone-forming tumors frequently involving vertebrae and long bones of the extremities. Because of their similar histopathological features, distinction between OB and OO is mostly based on size criteria. CT and MRI represent the cornerstone of noninvasive diagnostic procedures, as they provide excellent morphologic details and often obviate the need for confirmatory biopsy. Bone scan is a complementary, highly sensitive functional technique particularly useful for detection of vertebral OO. F-18 FDG PET/CT could have potentiality in diagnosis and post therapeutic evaluation of patients with OB and OO. We report MRI and dynamic F-18 FDG PET/CT results obtained before radiofrequency or laser ablation from 3 patients with an OB of the right L5 pedicle, an OB of the left talus and an OO of the right acetabulum. Both patients with OB underwent posttherapeutic evaluation to confirm the effectiveness of percutaneous radiofrequency ablation.