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Andreas Bockisch

Publications and source records attributed to Andreas Bockisch.

36 records · Page 2Linked to original sources
PubMed2005

Optimized intravenous contrast administration for diagnostic whole-body 18F-FDG PET/CT.

UNLABELLED: Standard application of CT intravenous contrast agents in combined PET/CT may lead to high-density artifacts on CT and attenuation-corrected PET. To avoid associated diagnostic pitfalls, we designed and compared different intravenous contrast injection protocols for routine whole-body PET/CT. METHODS: Whole-body PET/CT included a topogram and a single spiral CT scan (2-row) with or without intravenous contrast, followed by an emission scan. The CT scan was used for attenuation correction of the emission data. Four groups of 10 whole-body PET/CT referrals each were investigated: (A) no intravenous contrast agent, (B) biphasic injection (90 and 50 mL at 3 and 1.5 mL/s, respectively) of intravenous contrast (300 mg/mL iodine) and CT in the craniocaudal direction with a 30-s delay, (C) triple-phase injection (90, 40, and 40 mL at 3, 2, and 1.5 mL/s, respectively) in the craniocaudal direction with a 50-s delay, and (D) dual-phase injection (80 and 60 mL at 3 and 1.5 mL/s, respectively) in the caudocranial direction with a 50-s delay. CT image quality was assessed on a scale from 1 to 3, and CT and attenuation-corrected PET images were reviewed separately for contrast-induced artifacts. RESULTS: Average CT image quality was poorest for protocol A (1.0) but improved to 2.8 when using intravenous contrast agents (protocols B-D). Only protocols B and C resulted in contrast-induced image artifacts that were limited to the thorax. The most homogeneous intravenous contrast enhancement without high-density image artifacts on either CT or PET after CT-based attenuation correction was achieved with protocol D. CONCLUSION: Dual-phase intravenous contrast injection and CT in the caudocranial direction with a 50-s delay yields reproducible high image quality and is now used routinely for combined diagnostic PET/CT at our hospital.

Contrast Media↗
PubMed2005

Assessment of liver tissue after radiofrequency ablation: findings with different imaging procedures.

UNLABELLED: Our goal was to assess the typical appearance of normal liver tissue immediately after radiofrequency ablation (RF-ablation) when imaged with contrast-enhanced ultrasound, CT, MRI, 18F-FDG PET, and PET/CT. METHODS: Nineteen RF-ablation sessions were performed on nontumorous liver tissue of 10 Göttingen Mini Pigs. CT, ultrasound, MRI, 18F-FDG PET, and PET/CT were performed immediately after the intervention. All imaging procedures were evaluated qualitatively for areas of increased contrast enhancement (morphologic imaging) and regions of elevated tracer uptake (functional imaging). Images were assessed quantitatively by determination of ratios (r(p/p)) comparing contrast enhancement/tracer uptake in the periphery of the necrosis with contrast enhancement/tracer uptake of normal liver parenchyma. RESULTS: On morphologic imaging, an increase in contrast enhancement surrounding the ablative necrosis was detected in all lesions. Quantification of this area of increased contrast enhancement revealed ratios of r(p/p) = 1.57 +/- 0.2 for CT and r(p/p) = 1.57 +/- 0.19 for MRI. On PET and PET/CT, homogeneous tracer utilization was found surrounding all lesions. There were no areas of a focal or rim-like increase in glucose metabolism. The ratio r(p/p) was found to be 1.05 +/- 0.08 for functional data. Histologic examination revealed pooling of blood in the sinusoids of the lesion's periphery that was caused by outflow obstruction due to the central necrosis. CONCLUSION: On morphologic imaging, a rim-like increase of contrast enhancement was found immediately after RF-ablation resembling peripheral hyperperfusion. This area of contrast enhancement may hamper detection of residual tumor. On the basis of homogeneous tracer distribution surrounding the area of necrosis, PET and PET/CT may serve for early assessment of patients after RF-ablation.

Animals↗
PubMed2005

1 + 1 = 3.

Explore the source record for details and available documents.

Austria↗
PubMed2004

Unknown primary tumors: detection with dual-modality PET/CT--initial experience.

PURPOSE: To retrospectively evaluate fused positron emission tomography (PET)/computed tomography (CT) in depicting the primary lesion in cancer of an unknown primary tumor, compared with PET, CT, and PET and CT side-by-side evaluation. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. Forty-five patients (26 men and 19 women) with metastatic cervical adenopathy (n = 18) or extracervical metastases (n = 27) of unknown primary tumor were included. The mean age of the patients was 57 years (range, 29-95 years). PET/CT imaging was performed in all patients 1 hour after administration of 350 MBq of fluorodeoxyglucose with a whole-body field of view. Contrast agents were administered orally and intravenously in all patients to ensure diagnostic CT data. PET/CT data sets were evaluated for the primary tumor, and imaging results were compared with those of CT, PET, and PET and CT side-by-side evaluation. Differences in diagnostic performance were assessed by using the McNemar test with Bonferroni correction, which accounts for multiple comparisons. RESULTS: PET/CT depicted the primary tumor in 15 (33%) of 45 patients. In 30 (67%) patients, the primary tumor site remained occult (P > .05). PET and CT side-by-side evaluation depicted 13 (29%) of 45 tumors (P > .05). PET alone revealed the primary tumor in 11 (24%) of 45 patients (P > .05), while CT alone helped in the correct diagnosis in eight (18%) of 45 patients (P > .05). There were no significant differences between the diagnostic accuracies of PET/CT and the other imaging modalities. CONCLUSION: PET/CT was able to depict more primary tumors, though not significantly, than either of the other imaging modalities, but larger patient cohorts are required to finally judge its value for revealing the primary tumor site.

Adult↗
PubMed2004

Accuracy of whole-body dual-modality fluorine-18-2-fluoro-2-deoxy-D-glucose positron emission tomography and computed tomography (FDG-PET/CT) for tumor staging in solid tumors: comparison with CT and PET.

PURPOSE: To assess the accuracy of positron emission tomography/computed tomography (PET/CT) when staging different malignant diseases. PATIENTS AND METHODS: This was a retrospective, blinded, investigator-initiated study of 260 patients with various oncological diseases who underwent fluorine-18-2-fluoro-2-deoxy-d-glucose PET/CT for tumor staging. CT images alone, PET images alone, PET + CT data viewed side by side, and fused PET/CT images were evaluated separately according to the tumor-node-metastasis system. One hundred forty patients with tumors not staged according to the tumor-node-metastasis system or a lack of reference standard were excluded from data analysis; 260 patients were included. Diagnostic accuracies were determined for each of the four image sets. Histopathology and a clinical follow-up of 311 (+/- 125) days served as standards of reference. RESULTS: PET/CT proved significantly more accurate in assessing tumor-node-metastasis system stage compared with CT alone, PET alone, and side-by-side PET + CT (P < .0001). Of 260 patients, 218 (84%; 95% CI, 79% to 88%) were correctly staged with PET/CT, 197 (76%; 95% CI, 70% to 81%) with side-by-side PET + CT, 163 (63%; 95% CI, 57% to 69%) with CT alone, and 166 (64%; 95% CI, 58% to 70%) with PET alone. Combined PET/CT had an impact on the treatment plan in 16, 39, and 43 patients when compared with PET + CT, CT alone, and PET alone, respectively. CONCLUSION: Tumor staging with PET/CT is significantly more accurate than CT alone, PET alone, and side-by-side PET + CT. This diagnostic advantage translates into treatment plan changes in a substantial number of patients.

Adolescent↗
PubMed2004

Intraoperative radiation therapy in liver tissue in a pig model: monitoring with dual-modality PET/CT.

PURPOSE: To assess, in a pig model, the value of dual-modality positron emission tomography (PET)/computed tomography (CT) for monitoring radiation therapy. MATERIALS AND METHODS: Central bile duct resection followed by creation of a biliodigestive anastomosis was performed in nine pigs. Six of these pigs were also treated with intraoperative radiation therapy (IORT) (20 Gy) in the area of the anastomosis. Two, 4, and 8 weeks postoperatively, contrast material-enhanced fluorine 18 fluorodeoxyglucose (FDG) PET/CT of the liver was performed in all of the animals. The radioactive tracer concentration in the region of the anastomosis was quantified, and the values were compared intraindividually with the values at the liver periphery. Histologic evaluation of the liver was performed 8 weeks postoperatively. The PET/CT images were assessed for changes in liver volume and bile duct diameter over time. RESULTS: In all nine pigs, the region of the anastomosis could be clearly defined on the fused PET/CT images. PET/CT revealed a decreased concentration of FDG in the irradiated field 2 and 4 weeks after IORT. At 8 weeks, however, the distribution of the tracer in the irradiated pigs did not differ from that in the nonirradiated pigs. Homogeneous tracer uptake in all liver regions was observed in the nonirradiated animals. The CT images showed an increase in liver volume in all pigs and bile duct dilatation that increased over time in the irradiated pigs. CONCLUSION: The morphologic and functional changes due to IORT in liver tissue can be accurately monitored with dual-modality PET/CT. By enabling the integration of functional and morphologic data, PET/CT may have an important role in monitoring radiation treatment.

Anastomosis, Roux-en-Y↗
PubMed2004

Acquisition protocol considerations for combined PET/CT imaging.

UNLABELLED: Since its introduction in 1998, dual-modality PET/CT imaging has received great attention in the medical community. For the first time, patients can be examined with both CT and PET in a single examination. A whole-body survey is the standard mode of acquisition. The CT images are used for anatomic reference of the tracer uptake patterns imaged in PET, as well as for attenuation correction of the PET data. The routine use of CT-based attenuation correction and user preferences for the quality and type of the CT examination have led to the introduction of different PET/CT scanning protocols. DISCUSSION: Two general approaches to PET/CT imaging can be distinguished today. One uses CT as a fast transmission source with little additional information for anatomic labeling. The other uses CT as a fast transmission source as well as a state-of-the-art diagnostic tool to maximize image quality using optimal acquisition parameters together with oral and intravenous contrast agents. Variations of these approaches share common concerns about image artifacts that result from mismatches in respiration and patient positioning between the CT and the PET examinations. Protocol requirements for the more complex radiologic PET/CT scenario also include alternative contrast application schemes or modifications to the attenuation correction procedure to handle CT contrast agents appropriately. CONCLUSION: High-quality PET/CT studies can be provided routinely with existing PET/CT technology that is used efficiently by trained and motivated technologists and physicians. Only then will the potential diagnostic benefit of this new imaging modality be explored fully.

Artifacts↗
PubMed2004

To enhance or not to enhance? 18F-FDG and CT contrast agents in dual-modality 18F-FDG PET/CT.

UNLABELLED: In combined PET/CT imaging, functional data provided by 18F-FDG increase diagnostic accuracy over conventional PET and CT in a variety of malignancies. The question to be raised is: how much is CT needed in PET/CT imaging? DISCUSSION: In stand-alone CT imaging, contrast agents are applied to aid differentiation of anatomic structures, improve lesion localization, and support lesion characterization. Based on our experience, the most important benefit when applying CT contrast agents in PET/CT imaging relates to more precise anatomic localization of pathology by differentiation of the lesion from its surrounding structures on CT. This benefit must be considered most profound in the head and neck as well as the abdomen and pelvis, where delineation of pathology from muscles, vascular structures, or the intestine is critical. CT contrast agents can be of additional value in tumors with only mild or no increase in 18F-FDG uptake by supporting lesion detection and characterization. The complementary role of CT contrast agents and molecular contrast for PET/CT imaging is addressed in this review. The authors provide specific indications as to which contrast-enhanced CT data provide additional diagnostic value. CONCLUSION: Functional contrast aids lesion detection and characterization, whereas morphologic contrast improves lesion localization. CT contrast agents and PET tracers do not compete but rather are complementary in combined PET/CT imaging.

Contrast Media↗
PubMed2004

Comparison of PET, CT, and dual-modality PET/CT imaging for monitoring of imatinib (STI571) therapy in patients with gastrointestinal stromal tumors.

UNLABELLED: This study was implemented to compare the value of PET, CT, and dual-modality PET/CT imaging for assessing gastrointestinal stromal tumor (GIST) response to imatinib therapy. METHODS: Twenty patients with histologically proven GIST underwent (18)F-FDG PET/CT imaging before and 1, 3, and 6 mo after the start of imatinib therapy. Separate PET and CT datasets, side-by-side PET and CT datasets, and fused PET/CT images were evaluated according to World Health Organization, Response Evaluation Criteria in Solid Tumors, and European Organisation for Research and Treatment of Cancer criteria for therapy response. Hounsfield units (HU) were assessed on CT images. A mean follow-up period of 381 +/- 134 d served as the standard of reference. RESULTS: The numbers of lesions detected in all patients were 135 with PET, 249 with CT, 279 on side-by-side evaluation, and 282 on fused PET/CT images. Tumor response was correctly characterized in 95% of patients after 1 mo and 100% after 3 and 6 mo with PET/CT. PET and CT images viewed side by side were correct in 90% of patients at 1 mo and 100% at 3 and 6 mo. PET accurately diagnosed tumor response in 85% of patients at 1 mo and 100% at 3 and 6 mo. CT was found to be accurate in 44% of patients at 1 mo, 60% at 3 mo, and 57% at 6 mo. HU were found to decrease by at least 25% in 12 of 14 responders after 1 mo. CONCLUSION: Tumor response to imatinib should be assessed with a combination of morphologic and functional imaging. Image fusion with combined PET/CT can provide additional information in individual cases when compared with side-by-side PET and CT.

Adult↗
PubMed2003

Whole-body dual-modality PET/CT and whole-body MRI for tumor staging in oncology.

CONTEXT: Deciding on the appropriate therapy for patients with malignant diseases mandates accurate tumor staging with whole-body coverage. Magnetic resonance imaging (MRI) and a combined modality including positron emission tomography (PET) and computed tomography (CT) provide whole-body tumor staging in a single session. OBJECTIVE: To determine the staging accuracies of both whole-body PET/CT and whole-body MRI for different malignant diseases. DESIGN, SETTING, AND PATIENTS: Prospective, blinded, investigator-initiated study of 98 patients (mean age, 58 years; range, 27-94 years) with various oncological diseases who underwent back-to-back whole-body glucose analog [18F]-fluorodeoxyglucose-PET/CT and whole-body MRI for tumor staging. The study was conducted at a university hospital from December 2001 through October 2002 and had a mean follow-up of 273 days (range, 75-515 days). The images were evaluated by 2 different, blinded reader teams. The diagnostic accuracies of the 2 imaging procedures were compared. MAIN OUTCOME MEASURES: Correct classification of the primary tumor, regional lymph nodes, and distant metastasis (overall TNM stage) using whole-body PET/CT and whole-body MRI. Secondary outcome measures were accurate assessment of T-stage, N-stage, and M-stage by the 2 imaging procedures. RESULTS: Of 98 patients, the overall TNM stage was correctly determined in 75 with PET/CT (77%; 95% confidence interval [CI], 67%-85%) and in 53 with MRI (54%; 95% CI, 44%-64%) (P<.001). Compared with MRI, PET/CT had a direct impact on patient management in 12 patients. Results from MRI changed the therapy regimen in 2 patients compared with PET/CT. Separate assessment of T-stage (with pathological verification) in 46 patients revealed PET/CT to be accurate in 37 (80%; 95% CI, 66%-91%) and MRI to be accurate in 24 (52%; 95% CI, 37%-67%) (P<.001). Of 98 patients, N-stage was correctly determined in 91 patients with PET/CT (93%; 95% CI, 86%-97%) and in 77 patients with MRI (79%; 95% CI, 69%-86%) (P =.001). Both imaging procedures showed a similar performance in detecting distant metastases. CONCLUSIONS: The feasibility and diagnostic accuracy of the whole-body staging strategies of PET/CT and MRI are established. Superior performance in overall TNM staging suggests the use of [18F]-fluorodeoxyglucose-PET/CT as a possible first-line modality for whole-body tumor staging.

Adult↗
PubMed2003

Non-small cell lung cancer: dual-modality PET/CT in preoperative staging.

PURPOSE: To determine the accuracy of dual-modality positron emission tomographic (PET)-computed tomographic (CT) imaging, as compared with PET alone and CT alone, in the staging of non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: Twenty-seven patients with NSCLC underwent staging with combined fluorine 18 fluorodeoxyglucose PET and CT. CT, PET, and coregistered PET/CT images were evaluated separately by two different physicians for each imaging modality, and disease stage was determined by using TNM and American Joint Committee on Cancer staging systems. Histopathologic results served as the reference standard. The statistical significance of differences among CT, PET, and PET/CT was determined by using the McNemar test. RESULTS: Overall tumor stage was correctly classified as 0-IV with CT in 19 patients, with PET in 20 patients, and with PET/CT in 26 patients. PET/CT findings when compared with PET findings led to a treatment change for four patients (15%) and when compared with CT findings led to a treatment change for five patients (19%). Differences in the accuracy of overall tumor staging between PET/CT and CT (P =.008) and between PET/CT and PET (P =.031) were significant. Primary tumor stage was correctly determined in more patients with PET/CT than with either PET alone or CT alone. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of regional lymph node staging, respectively, were 89%, 94%, 89%, 94%, and 93%, with PET/CT; 89%, 89%, 80%, 94%, and 89% with PET; and 70%, 59%, 50%, 77%, and 63% with CT. Fourteen distant metastases were detected in four patients with CT, four were detected in two patients with PET, and 17 were detected in four patients with PET/CT. CONCLUSION: Use of dual-modality PET/CT significantly increases the number of patients with correctly staged NSCLC and thus has a positive effect on treatment.

Adult↗
PubMed2003

Effect of oral contrast agents on computed tomography-based positron emission tomography attenuation correction in dual-modality positron emission tomography/computed tomography imaging.

RATIONALE AND OBJECTIVES: To evaluate the effect of iodine- and barium-based contrast agents on the computed tomography (CT)-based positron emission tomography (PET) attenuation correction in dual-modality PET/CT. METHODS: Experiments were conducted on a Society of Nuclear Medicine/National Electrical Manufacturers Association-PET phantom equipped with cylinders containing [18F]-2-fluoro-2-desoxy-D-glucose. The main compartment was filled with iodine (0.5-10%), barium (0.5-50%), or water (negative control). The error in attenuation correction was determined by comparison of measured tracer quantities in the presence of contrast agents with expected quantities. Contrast agent attenuation was demonstrated to be comparable to in vivo conditions. RESULTS: The presence of contrast agents resulted in an overestimation of the intracylindrical activity concentration on PET images and overestimation directly related to contrast concentrations (iodine 5-38%; barium 15-580%). Iodine and barium concentrations in clinical use resulted in an activity overestimation of 20 +/- 1.8% for iodine and 21 +/- 2.9% for barium. CONCLUSION: An overestimation of the tracer activity concentration is to be expected in the presence of oral contrast agents, if PET attenuation correction is attained CT-based.

Administration, Oral↗
PubMed2002

Impact of estrogen replacement therapy in a male with congenital aromatase deficiency caused by a novel mutation in the CYP19 gene.

Recent reports of the impact of estrogen receptor alpha and aromatase deficiency have shed new light on the importance of estrogen for bone formation in man. We describe a novel mutation of the CYP19 gene in a 27-yr-old homozygous male of consanguinous parents. A C to A substitution in intron V, at position -3 of the splicing acceptor site before exon VI of the CYP19 gene, is the likely cause of loss of aromatase activity. The mRNA of the patient leads to a frameshift and a premature stop codon 8 nucleotides downstream the end of exon V. Both parents were shown to be heterozygous for the same mutation. Apart from genua valga, kyphoscoliosis, and pectus carniatus, the physical examination was normal including secondary male characteristics with normal testicular size. To substitute for the deficiency, the patient was treated with 50 micro g transdermal estradiol twice weekly for 3 months, followed by 25 micro g twice weekly. After 6 months estrogen levels (<20 at baseline and 45 pg/ml at 6 months; normal range, 10-50) and estrone levels (17 and 34 ng/ml; normal range, 30-85) had normalized. Bone maturation progressed and the initially unfused carpal and phalangeal epiphyses began to close within 3 months and were almost completely closed after 6 months. The bone age, assessed by roentgenographic standards for bone development by Gruelich and Pyle, was 16.5 at baseline and 18-18.5 yr after 6 months of treatment. Bone density of the distal radius (left), assessed by quantitative computed tomography, increased from 52 to 83 mg/cm(3) (normal range, 120-160) and bone mineral density of the lumbar spine, assessed by dual-energy x-ray-absorptiometry, increased from 0.971 to 1.043 g/cm(2) (normal range, >1.150). Osteocalcin as a bone formation parameter increased from 13 to 52 micro g/l (normal range, 24-70) and aminoterminal collagen type I telopeptide as a bone resorption parameter increased from 62.9 to 92.4 nmol/mmol creatinine (normal range, 5-54). Semen analysis revealed oligoazoospermia (17.4 million/ml; normal >20) at baseline. After 3 months of treatment, the sperm count increased (23.1 million/ml) and decreased rapidly (1.1 million/ml) during the following 3 months. The sperm motility was reduced at baseline and decreased further during treatment. Area under the curve of insulin, C-peptide, and blood glucose levels during oral glucose tolerance test decreased after 6 months (insulin: 277 vs. 139 micro U/ml.h; C-peptide 52 vs. 15 ng/m.h; area under the curve glucose: 17316 vs. 12780 mg/d.min). Triglycerides (268 vs. 261 mmol/liter) and total cholesterol levels (176 vs. 198 mmol/liter) did not change significantly, but the low-density lipoprotein/high-density lipoprotein ratio decreased from 5.37 to 3.56 and lipoprotein (a) increased from 19.9 to 60.0 mg/dl (normal range, <30). In this rare incidence of estrogen deficiency, estrogen replacement demonstrated its importance for bone mineralization and maturation and glucose metabolism in a male carrying a novel mutation in the CYP19 gene.

Adult↗
PubMed2002

Whole-body positron emission tomography-CT: optimized CT using oral and IV contrast materials.

OBJECTIVE: Our objective was to show that oral and IV contrast materials improve CT image quality in dual-modality positron emission tomography (PET) and CT, resulting in an increase in diagnostic capacity. We also present a standardized scanning protocol for whole-body PET-CT with oral and IV contrast materials. SUBJECTS AND METHODS: To evaluate the use of whole-body PET-CT in clinical practice, we examined 30 patients according to the protocol. The CT images were evaluated quantitatively by signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) analyses and qualitatively by two radiologists in consensus. PET quality was assessed quantitatively by measurements of standard uptake values that were compared with standard uptake values in 10 PET-CT examinations without contrast agents. RESULTS: . The application of oral and IV contrast materials led to a highly sufficient delineation of vascular and intestinal structures in 26 of 30 patients. Quantitative analysis revealed a mean vascular SNR of 15.8 +/- 7.71 for the 30 patients who received contrast materials compared with 4.79 +/- 1.45 for the 10 control group patients (p < 0.001). Similarly, the mean intestinal SNR of 17.06 +/- 7.96 far exceeded that seen in the control group of 3.83 +/- 1.16 (p < 0.001). Analyses led to a vessel-to-muscle CNR of 10.78 +/- 5.89 (control group, -1.21 +/- 0.89; p < 0.001) and an intestine-to-muscle CNR of 12.04 +/- 6.07 (control group, -2.17 +/- 1.22; p = 0.001) in the 30 patients. An evaluation of PET quality in patients who received contrast materials showed a mean standard uptake value of 2.09 +/- 1.16 compared with 2.04 +/- 0.83 in the control group (p = 0.702). CONCLUSION: Our whole-body PET-CT protocol provided good vascular and intestinal enhancement without compromising PET quality, leading to a potential improvement in the diagnostic capacity of the combined PET-CT examination.

Administration, Oral↗
PubMed2002

Focal tracer uptake: a potential artifact in contrast-enhanced dual-modality PET/CT scans.

UNLABELLED: This study was performed to evaluate a possible artifact related to the administration of intravascular contrast agent in dual-modality PET/CT imaging. METHODS: Thirty oncology patients underwent whole-body PET/CT. CT images, which were collected in the presence of intravenous and oral iodinated contrast agent, were used for PET attenuation correction. PET images were assessed for the artifact, defined as a region of high count rate on attenuation-corrected images in accurate coregistration with a contrast-enhanced blood vessel. Intravascular enhancement of thoracic veins was quantified by application of regions of interest, and quantities in patients with the artifact (group 1) and without the artifact (group 2) were correlated. Body surface area was calculated for all patients. RESULTS: The contrast-induced PET artifact was present in 4 (13%) of 30 patients. Mean density differences in intravascular enhancement were highly significant (P < 0.001) in a comparison of group 1 (2,262 +/- 304 Hounsfield units [HU]) and group 2 (1,058 +/- 209 HU). Body surface area was significantly lower (P = 0.035) in the patients of group 1 (1.67 +/- 0.11 m(2)) than in the patients of group 2 (2.01 +/- 0.18 m(2)). CONCLUSION: Contrast-enhanced dual-modality PET/CT examinations may result in a PET artifact that is due to the transient bolus passage of undiluted intravenous contrast agent.

Artifacts↗
PubMedDate not supplied

Positron emission tomography/computed tomography--imaging protocols, artifacts, and pitfalls.

There has been a longstanding interest in fused images of anatomical information, such as that provided by computed tomography (CT) or magnetic resonance imaging (MRI) systems, with biological information obtainable by positron emission tomography (PET). The near-simultaneous data acquisition in a fixed combination of a PET and a CT scanner in a combined PET/CT imaging system minimizes spatial and temporal mismatches between the modalities by eliminating the need to move the patient in between exams. In addition, using the fast CT scan for PET attenuation correction, the duration of the examination is significantly reduced compared to standalone PET imaging with standard rod-transmission sources. The main source of artifacts arises from the use of the CT-data for scatter and attenuation correction of the PET images. Today, CT reconstruction algorithms cannot account for the presence of metal implants, such as dental fillings or prostheses, properly, thus resulting in streak artifacts, which are propagated into the PET image by the attenuation correction. The transformation of attenuation coefficients at X-ray energies to those at 511 keV works well for soft tissues, bone, and air, but again is insufficient for dense CT contrast agents, such as iodine or barium. Finally, mismatches, for example, due to uncoordinated respiration result in incorrect attenuation-corrected PET images. These artifacts, however, can be minimized or avoided prospectively by careful acquisition protocol considerations. In doubt, the uncorrected images almost always allow discrimination between true and artificial finding. PET/CT has to be integrated into the diagnostic workflow for harvesting the full potential of the new modality. In particular, the diagnostic power of both, the CT and the PET within the combination must not be underestimated. By combining multiple diagnostic studies within a single examination, significant logistic advantages can be expected if the combined PET/CT examination is to replace separate state-of-the-art PET and CT exams, thus resulting in significantly accelerated diagnostics.

Humans↗
PubMedDate not supplied

Dual modality of 18F-fluorodeoxyglucose-positron emission tomography/computed tomography in patients with cervical carcinoma of unknown primary.

OBJECTIVE: To evaluate an optimized F-18-flurodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) acquisition protocol for head and neck cancer and assess the usefulness of combined FDG-PET/CT in locating unknown primary tumors in patients with biopsy-proven cervical lymph node metastases. SUBJECTS AND METHODS: Twenty-one patients with cervical lymph node metastases of unknown primary tumors underwent staging with FDG-PET/CT. The images of FDG-PET alone, CT alone, FDG-PET/CT read side by side and fused and FDG-PET/CT were evaluated separately by 2 physicians. Imaging results were correlated with either histology (n = 14) or clinical follow-up (n = 7). RESULTS: On the fused FDG-PET/CT images, primary tumors were identified in 12 patients (57%); with FDG-PET alone and FDG-PET and CT read side by side 11 (52%) primary tumors were found while CT alone identified 5 (23%) primary tumors. CONCLUSION: Our data indicate that fused FDG-PET and CT images increased the sensitivity of detecting carcinoma of unknown primary (CUP) tumors compared to CT alone, but not to FDG-PET alone or FDG-PET and CT read side by side. Hence accurate fusion of functional and morphologic data by FDG-PET/CT is a promising imaging modality in the clinical workup of patients with cervical CUP tumors.

Aged↗