Perfusão cerebral e análise individual automatizada utilizando SPECT em uma população com transtorno obsessivo-compulsivo

Objective: To make individual assessments using automated quantification methodology in order to screen for perfusion abnormalities in cerebral SPECT examinations among a sample of subjects with OCD. Methods: Statistical parametric mapping (SPM) was used to compare 26 brain SPECT images from patients with OCD individually with an image bank of 32 normal subjects, using the statistical threshold of p < 0.05 (corrected for multiple comparisons at the level of individual voxels or clusters). The maps were analyzed, and regions presenting voxels that remained above this threshold were sought. results: Six patients from a sample of 26 OCD images showed abnormalities at cluster or voxel level, considering the criteria described above, which represented 23.07%. However, seven images from the normal group of 32 were also indicated as cases of perfusional abnormality, representing 21.8% of the sample. Conclusion: The automated quantification method was not considered to be a useful tool for clinical practice, for analyses complementary to visual inspection.

Radioimmuno positron emission tomography with monoclonal antibodies: a new approach to quantifying in vivo tumour concentration and biodistribution for radioimmunotherapy.

Radioimmunodetection of tumours with monoclonal antibodies is becoming an established procedure. Positron emission tomography (PET) shows better resolution than normal gamma camera single photon emission tomography and can provide more precise quantitative data. Thus, in the present study, these powerful methods have been combined to perform radioimmuno PET (RI-PET). Monoclonal antibodies directed against carcinoembryonic antigen (CEA) an IgG, its F(ab')2 and a mouse-human chimeric IgG derived from it were labelled with 124I, a positron-emitting radionuclide with a convenient physical half-life of four days. Mice, xenografted with a CEA-producing human colon carcinoma, were injected with the 124I-MAb and the tumours were visualized using PET. The concentrations of 124I in tumour and normal tissue were determined by both PET and direct radioactivity counting of the dissected animals, with very good agreement. To allow PET quantification, a procedure was established to account for the presence of radioactivity during the absorption correction measurement (transmission scan). Comparison of PET and tissue counting indicates that this novel combination of radioimmunolocalization and PET (RI-PET) will provide, in addition to more precise diagnosis, more accurate radiation dosimetry for radioimmunotherapy.

Budget impact from the incorporation of positron emission tomography – computed tomography for staging lung cancers

OBJECTIVE To estimate the budget impact from the incorporation of positron emission tomography (PET) in mediastinal and distant staging of non-small cell lung cancer.METHODS The estimates were calculated by the epidemiological method for years 2014 to 2018. Nation-wide data were used about the incidence; data on distribution of the disease´s prevalence and on the technologies’ accuracy were from the literature; data regarding involved costs were taken from a micro-costing study and from Brazilian Unified Health System (SUS) database. Two strategies for using PET were analyzed: the offer to all newly-diagnosed patients, and the restricted offer to the ones who had negative results in previous computed tomography (CT) exams. Univariate and extreme scenarios sensitivity analyses were conducted to evaluate the influence from sources of uncertainties in the parameters used.RESULTS The incorporation of PET-CT in SUS would imply the need for additional resources of 158.1 BRL (98.2 USD) million for the restricted offer and 202.7 BRL (125.9 USD) million for the inclusive offer in five years, with a difference of 44.6 BRL (27.7 USD) million between the two offer strategies within that period. In absolute terms, the total budget impact from its incorporation in SUS, in five years, would be 555 BRL (345 USD) and 600 BRL (372.8 USD) million, respectively. The costs from the PET-CT procedure were the most influential parameter in the results. In the most optimistic scenario, the additional budget impact would be reduced to 86.9 BRL (54 USD) and 103.8 BRL (64.5 USD) million, considering PET-CT for negative CT and PET-CT for all, respectively.CONCLUSIONS The incorporation of PET in the clinical staging of non-small cell lung cancer seems to be financially feasible considering the high budget of the Brazilian Ministry of Health. The potential reduction in the number of unnecessary surgeries may cause the available resources to be more efficiently allocated.

Assessment of coronary vasoreactivity by multidetector computed tomography: feasibility study with rubidium-82 cardiac positron emission tomography.

BACKGROUND: Positron emission tomography (PET) during the cold pressor test (CPT) has been used to assess endothelium-dependent coronary vasoreactivity, a surrogate marker of cardiovascular events. However, its use remains limited by cardiac PET availability. As multidetector computed tomography (MDCT) is more widely available, we aimed to develop a measurement of endothelium-dependent coronary vasoreactivity with MDCT and similar radiation burden as with PET. METHODS AND RESULTS: A study group of 18 participants without known cardiovascular risk factor (9F/9M; age 60±6 years) underwent cardiac PET with (82)Rb and unenhanced ECG-gated MDCT within 4h, each time at rest and during CPT. The relation between absolute myocardial blood flow (MBF) response to CPT by PET (ml·min(-1)·g(1)) and relative changes in MDCT-measured coronary artery surface were assessed using linear regression analysis and Spearman's correlation. MDCT and PET/CT were analyzed in all participants. Hemodynamic conditions during CPT at MDCT and PET were similar (P>0.3). Relative changes in coronary artery surface because of CPT (2.0-21.2%) correlated to changes in MBF (-0.10-0.52ml·min(-1)·g(1)) (ρ=0.68, P=0.02). Effective dose was 1.3±0.2mSv for MDCT and 3.1mSv for PET/CT. CONCLUSIONS: Assessment of endothelium-dependent coronary vasoreactivity using MDCT CPT appears feasible. Because of its wider availability, shorter examination time and similar radiation burden, MDCT could be attractive in clinical research for coronary status assessment.

Peritoneal carcinomatosis due to ovarian cancer: comparison between MDCT, MRI and positron emission tomography-computed tomography with F18-fluorodeoxyglucose

Purpose: To compare MDCT, MRI and 18F-FDG PET/CT for the detection of peritoneal carcinomatosis due to ovarian cancerMethods and Materials: Fifteen women (mean age 65±) with clinical suspicion of ovarian cancer and peritoneal carcinomatosis underwent MDCT, MRI and 18F-FDG PET/CT, simultaneously and shortly performed before surgery (delay 8.1± days). According to the peritoneal cancer index nine abdominopelvic regions were defined. We applied four scores of lesion size on MDCT and MR images, while the maximal standard uptake value (SUVmax) was measured on 18F-FDG PET/CT. Three sites of lymphadenopathy and posterobasal pleural carcinomatosis were also analyzed. First, one radiologist blindly and separately read MDCT and MR images, while one nuclear physician blindly read PET/CT images grading each lesion according to four diagnostic certitudes. Secondly, all the images were reviewed jointly and compared with histopathology. Receiver operating characteristics (ROC) analysis was performed.Results: Peritoneal implants were proven in ten women (75%). Altogether, 228 abdominopelvic sites were compared. Sensitivity and specificity for MDCT was 90.2% and 90.6%, for MRI 93.5% and 86.3%, and for 18F-FDG PET/CT 92.7% and 95.7%, respectively. ROC area under the curve were 0.93 for MDCT and MRI, and 0.96 for 18F-FDG PET/CT respectively. No significant differences (p=0.11) were found between the three modalities.Conclusion: Although MRI revealed to be the most sensitive and 18F-FDG PET/CT the most specific modality, no significant differences were shown between the three techniques.

Micropapillary pattern in lung adenocarcinoma: aspect on 18F-fluorodeoxyglucose positron emission tomography/computed tomography imaging.

We diagnosed a non-small cell lung carcinoma in a 49-year-old female patient with the histopathological diagnosis of stage IIIB mixed bronchioloalveolar and papillary adenocarcinoma with extensive micropapillary feature, which was not visualized on the preoperative multimodality imaging with positron emission tomography (PET) and computed tomography (CT). The micropapillary component characterized by a unique growth pattern with particular morphological features can be observed in all subtypes of lung adenocarcinoma. Micropapillary component is increasingly recognized as a distinct entity associated with higher aggressiveness. Even the most modern multimodality PET/CT imaging technology may fail to adequately visualize this important component with highly relevant prognostic implications. Thus, the pathologist needs to consciously look for a micropapillary component in the surgical specimen or in preoperative biopsies or cytology. This may have potential future treatment implications, as adjuvant or neoadjuvant chemotherapy may be of relevance, even in the early stages of the disease.

18F-fluorodeoxyglucose positron emission tomography/computed tomography and magnetic resonance imaging in patients with liver metastases from uveal melanoma: results from a pilot study.

PURPOSE: F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and MRI are used for detecting liver metastases from uveal melanoma. The introduction of new treatment options in clinical trials might benefit from early response assessment. Here, we determine the value of FDG-PET/CT with respect to MRI at diagnosis and its potential for monitoring therapy. MATERIAL AND METHODS: Ten patients with biopsy-proven liver metastases of uveal melanoma enrolled in a randomized phase III trial (NCT00110123) underwent both FDG-PET coupled with unenhanced CT and gadolinium-diethylene triamine pentaacetic acid-enhanced liver MRI within 4 weeks. FDG-PET and MRI were evaluated blindly and then compared using the ratio of lesion to normal liver parenchyma PET-derived standardized uptake value (SUV). The influence of lesion size and response to chemotherapy were studied. RESULTS: Overall, 108 liver lesions were seen: 34 (31%) on both modalities (1-18 lesions/patient), four (4%) by PET/CT only, and 70 (65%) by MRI only. SUV correlated with MRI lesion size (r=0.81, P<0.0001). PET/CT detected 26 of 33 (79%) MRI lesions of more than or equal to 1.2 cm, whereas it detected only eight of 71 (11%) lesions of less than 1.2 cm (P<0.0001). MRI lesions without PET correspondence were small (0.6±0.2 vs. 2.1±1.1 cm, P<0.0001). During follow-up (six patients, 30 lesions), the ratio lesion-to-normal-liver SUV diminished in size-stable lesions (1.90±0.64-1.46±0.50, P<0.0001), whereas it increased in enlarging lesions (1.56±0.40-1.99±0.56, P=0.032). CONCLUSION: MRI outweighs PET/CT for detecting small liver metastases. However, PET/CT detected at least one liver metastasis per patient and changes in FDG uptake not related to size change, suggesting a role in assessing early therapy response.

Ambient radiation levels in positron emission tomography/computed tomography (PET/CT) imaging center

Objective: To evaluate the level of ambient radiation in a PET/CT center. Materials and Methods: Previously selected and calibrated TLD-100H thermoluminescent dosimeters were utilized to measure room radiation levels. During 32 days, the detectors were placed in several strategically selected points inside the PET/CT center and in adjacent buildings. After the exposure period the dosimeters were collected and processed to determine the radiation level. Results: In none of the points selected for measurements the values exceeded the radiation dose threshold for controlled area (5 mSv/year) or free area (0.5 mSv/year) as recommended by the Brazilian regulations. Conclusion: In the present study the authors demonstrated that the whole shielding system is appropriate and, consequently, the workers are exposed to doses below the threshold established by Brazilian standards, provided the radiation protection standards are followed.

Computed tomography-guided percutaneous trephine removal of the nidus in osteoid osteoma patients: experience of a single center in Brazil

AbstractObjective:To report the results of computed tomography (CT)-guided percutaneous resection of the nidus in 18 cases of osteoid osteoma.Materials and Methods:The medical records of 18 cases of osteoid osteoma in children, adolescents and young adults, who underwent CT-guided removal of the nidus between November, 2004 and March, 2009 were reviewed retrospectively for demographic data, lesion site, clinical outcome and complications after procedure.Results:Clinical follow-up was available for all cases at a median of 29 months (range 6–60 months). No persistence of pre-procedural pain was noted on 17 patients. Only one patient experienced recurrence of symptoms 12 months after percutaneous resection, and was successfully retreated by the same technique, resulting in a secondary success rate of 18/18 (100%).Conclusion:CT-guided removal or destruction of the nidus is a safe and effective alternative to surgical resection of the osteoid osteoma nidus.

Accuracy of positron emission tomography/computed tomography and clinical assessment in the detection of complete rectal tumor regression after neoadjuvant chemoradiation Long-Term Results of a Prospective Trial (National Clinical Trial 00254683)

BACKGROUND: Neoadjuvant chemoradiation (CRT) therapy may result in significant tumor regression in patients with rectal cancer. Patients who develop complete tumor regression have been managed by treatment strategies that are alternatives to standard total mesorectal excision. Therefore, assessment of tumor response with positron emission tomography/computed tomography (PET/CT) after neoadjuvant treatment may offer relevant information for the selection of patients to receive alternative treatment strategies. METHODS: Patients with clinical T2 (cT2) through cT4NxM0 rectal adenocarcinoma were included prospectively. Neoadjuvant therapy consisted of 54 grays of radiation and 5-fluorouracil-based chemotherapy. Baseline PET/CT studies were obtained before CRT followed by PET/CT studies at 6 weeks and 12 weeks after the completion of CRT. Clinical assessment was performed at 12 weeks after CRT completion. PET/CT results were compared with clinical and pathologic data. RESULTS: In total, 99 patients were included in the study. Twenty-three patients were complete responders (16 had a complete clinical response, and 7 had a complete pathologic response). The PET/CT response evaluation at 12 weeks indicated that 18 patients had a complete response, and 81 patients had an incomplete response. There were 5 false-negative and 10 false-positive PET/CT results. PET/CT for the detection of residual cancer had 93% sensitivity, 53% specificity, a 73% negative predictive value, an 87% positive predictive value, and 85% accuracy. Clinical assessment alone resulted in an accuracy of 91%. PET/CT information may have detected misdiagnoses made by clinical assessment alone, improving overall accuracy to 96%. CONCLUSIONS: Assessment of tumor response at 12 weeks after CRT completion with PET/CT imaging may provide a useful additional tool with good overall accuracy for the selection of patients who may avoid unnecessary radical resection after achieving a complete clinical response. Cancer 2012;35013511. (C) 2011 American Cancer Society.

The role of choline positron emission tomography/computed tomography in the management of patients with prostate-specific antigen progression after radical treatment of prostate cancer

Choline positron emission tomography (PET)/computed tomography (CT) is a currently used diagnostic tool in restaging prostate cancer (PCa) patients with increasing prostate-specific antigen (PSA) after either radical prostatectomy (RP) or external-beam radiation therapy (EBRT). However, no final recommendations have been made on the use of this modality for patient management.

Novel positron emission tomography/computed tomography of diffuse parenchymal lung disease combining a labeled somatostatin receptor analogue and 2-deoxy-2[¹⁸F]fluoro-D-glucose

We prospectively investigated the potential of positron emission tomography (PET) using the somatostatin receptor (SSTR) analogue ⁶⁸Ga-DOTATATE and 2-deoxy-2[¹⁸F]fluoro-D-glucose (¹⁸F-FDG) in diffuse parenchymal lung disease (DPLD). Twenty-six patients (mean age 68.9 ± 11.0 years) with DPLD were recruited for ⁶⁸Ga-DOTATATE and ¹⁸F-FDG combined PET/high-resolution computed tomography (HRCT) studies. Ten patients had idiopathic pulmonary fibrosis (IPF), 12 patients had nonspecific interstitial pneumonia (NSIP), and 4 patients had other forms of DPLD. Using PET, the pulmonary tracer uptake (maximum standardized uptake value [SUV(max)]) was calculated. The distribution of PET tracer was compared to the distribution of lung parenchymal changes on HRCT. All patients demonstrated increased pulmonary PET signal with ⁶⁸Ga-DOTATATE and ¹⁸F-FDG. The distribution of parenchymal uptake was similar, with both tracers corresponding to the distribution of HRCT changes. The mean SUV(max) was 2.2 ± 0.7 for ⁶⁸Ga-DOTATATE and 2.8 ± 1.0 (t-test, p  =  .018) for ¹⁸F-FDG. The mean ⁶⁸Ga-DOTATATE SUV(max) in IPF patients was 2.5 ± 0.9, whereas it was 2.0 ± 0.7 (p  =  .235) in NSIP patients. The correlation between ⁶⁸Ga-DOTATATE SUV(max) and gas transfer (transfer factor of the lung for carbon monoxide [TLCO]) was r  =  -.34 (p  =  .127) and r  =  -.49 (p  =  .028) between ¹⁸F-FDG SUV(max) and TLCO. We provide noninvasive in vivo evidence in humans showing that SSTRs may be detected in the lungs of patients with DPLD in a similar distribution to sites of increased uptake of ¹⁸F-FDG on PET.

Added value of dual-energy computed tomography versus single-energy computed tomography in assessing ferromagnetic properties of ballistic projectiles: implications for magnetic resonance imaging of gunshot victims.

OBJECTIVE The objective of this study was to assess the discriminative power of dual-energy computed tomography (DECT) versus single-energy CT (SECT) to distinguish between ferromagnetic and non-ferromagnetic ballistic projectiles to improve safety regarding magnetic resonance (MR) imaging studies in patients with retained projectiles. MATERIALS AND METHODS Twenty-seven ballistic projectiles including 25 bullets (diameter, 3-15 mm) and 2 shotgun pellets (2 mm each) were examined in an anthropomorphic chest phantom using 128-section dual-source CT. Data acquisition was performed with tube voltages set at 80, 100, 120, and 140 kV(p). Two readers independently assessed CT numbers of the projectile's core on images reconstructed with an extended CT scale. Dual-energy indices (DEIs) were calculated from both 80-/140-kV(p) and 100-/140-kV(p) pairs; receiver operating characteristics curves were fitted to assess ferromagnetic properties by means of CT numbers and DEI. RESULTS Nine (33%) of the projectiles were ferromagnetic; 18 were nonferromagnetic (67%). Interreader and intrareader correlations of CT number measurements were excellent (intraclass correlation coefficients, >0.906; P<0.001). The DEI calculated from both 80/140 and 100/140 kV(p) were significantly (P<0.05) different between the ferromagnetic and non-ferromagnetic projectiles. The area under the curve (AUC) was 0.75 and 0.8 for the tube voltage pairs of 80/140 and 100/140 kV(p) (P<0.05; 95% confidence interval, 0.57-0.94 and 0.62-0.97, respectively) to differentiate between the ferromagnetic and non-ferromagnetic ballistic projectiles; which increased to 0.83 and 0.85 when shotgun pellets were excluded from the analysis. The AUC for SECT was 0.69 and 0.73 (80 and 100 kV[p], respectively). CONCLUSIONS Measurements of DECT combined with an extended CT scale allow for the discrimination of projectiles with non-ferromagnetic from those with ferromagnetic properties in an anthropomorphic chest phantom with a higher AUC compared with SECT. This study indicates that DECT may have the potential to contribute to MR safety and allow for MR imaging of patients with retained projectiles. However, further studies are necessary before this concept may be used to triage clinical patients before MR.