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Gerald Antoch

Publications and source records attributed to Gerald Antoch.

33 records · Page 2Linked to original sources
PubMed2004

Dual-modality PET/CT scanning with negative oral contrast agent to avoid artifacts: introduction and evaluation.

The authors qualitatively and quantitatively assessed a solution containing 0.2% locust bean gum (LBG) and 2.5% mannitol (mannitol-LBG) dissolved in water to provide a negative oral contrast material in dual-modality positron emission tomography (PET)/computed tomography (CT) scanning. PET/CT was performed in 60 patients with cancer after oral administration of barium, water, or mannitol-LBG. Qualitative and quantitative analyses were conducted to determine bowel distention and a potential influence of the contrast agents on the PET data. Intestinal distention with mannitol-LBG proved superior to that with water or barium. Findings at both quantitative and qualitative analysis revealed apparently increased tracer uptake in the small bowel with barium in comparison to that with mannitol-LBG or water. Mannitol-LBG may, therefore, be used as a negative oral contrast agent at PET/CT scanning because it provides excellent bowel distention while avoiding contrast material-induced PET artifacts.

Administration, Oral↗
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

Response to imatinib mesylate of a gastrointestinal stromal tumor with very low expression of KIT.

More than 90% of gastrointestinal stromal tumors (GISTs) express the receptor tyrosine kinase KIT, and activating mutations of the KIT gene are detectable in the vast majority of these tumors. Imatinib mesylate (formerly STI571) is a potent inhibitor of KIT kinase activity and has been proven to be highly active in patients with unresectable or metastatic GIST expressing immunohistochemically detectable KIT protein. Here we report a patient with metastatic GIST who responded well to imatinib mesylate treatment despite the near absence of KIT expression in two different samples of his tumor. The tumor was morphologically typical for a GIST, stained positively for CD34, and harbored an in-frame deletion (WK 557-558) in KIT exon 11 that is common in GISTs. Our experience with this patient suggests that even GISTs with very low levels of KIT expression may respond to imatinib mesylate therapy.

Adult↗
PubMed2003

Dual-modality PET/CT imaging: the effect of respiratory motion on combined image quality in clinical oncology.

To reduce potential mis-registration from differences in the breathing pattern between two complementary PET and CT data sets, patients are generally allowed to breathe quietly during a dual-modality scan using a combined PET/CT tomograph. Frequently, however, local mis-registration between the CT and the PET is observed. We have evaluated the appearance, magnitude, and frequency of respiration-induced artefacts in CT images of dual-modality PET/CT studies of 62 patients. Combined PET/CT scans during normal respiration were acquired in 43 subjects using single- or dual-slice CT. Nineteen patients were scanned with a special breathing protocol (limited breath-hold technique) on a single-slice PET/CT tomograph. All subjects were injected with approximately 370 MBq of FDG, and PET/CT scanning commenced 1 h post injection. The CT images were reconstructed and, after appropriate scaling, used for on-line attenuation correction of the PET emission data. We found that respiration artefacts can occur in the majority of cases if no respiration protocol is used. When applying the limited breath-hold technique, the frequency of severe artefacts in the area of the diaphragm was reduced by half, and the spatial extent of respiration-induced artefacts was reduced by at least 40% compared with the acquisition protocols without any breathing instructions. In conclusion, special breathing protocols are effective and should be used for CT scans as part of combined imaging protocols using a dual-modality PET/CT tomograph. The results of this study can also be applied to multi-slice CT to potentially reduce further breathing artefacts in PET/CT imaging and to improve overall image quality.

Abdominal Neoplasms↗
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

Value of CT volume imaging for optimal placement of radiofrequency ablation probes in liver lesions.

PURPOSE: To determine the value of multiplanar and volume-rendered modes of analysis versus axial imaging for the optimal placement of probes in spiral image computed tomography (CT)-guided radiofrequency (RF) ablation of liver lesions. MATERIALS AND METHODS: Thirty-two malignant hepatic lesions in 21 patients with hepatocellular carcinoma (n = 10) or metastases (n = 11) were treated with percutaneous RF ablation. After axial CT-guided placement (biopsy mode) of the probe in the tumor, a contrast-enhanced spiral image set was obtained and data were viewed in contiguous axial sections and the multiplanar and volume-rendered modes. The position of the probe was characterized as "central," "marginal," or "outside," corresponding with its position in the lesion. Outside positioning was corrected before ablation was performed and, in cases of "marginal" positioning, the probe was redirected after initial ablative therapy in the same session. RESULTS: Multiplanar and volume-rendered analysis reclassified the needle position before 14 of 32 RF ablation procedures (44%; P =.0034, McNemar test). In 10 cases, probe positions considered "central" on biopsy-mode images were found to be "marginal" with multiplanar/volume-rendered analysis. In three cases, probe positions considered "marginal" on biopsy-mode images were found to be "outside" with multiplanar/volume-rendered analysis. In one lesion, multiplanar/volume-rendered analysis upgraded the probe position from "marginal" to "central." Comparison of multiplanar and volume-rendered analysis revealed no difference in probe positioning. The time requirements to obtain additional data were 159 seconds +/- 49 for multiplanar analysis and 434 seconds +/- 78 for volume-rendered analysis. CONCLUSION: A contrast-enhanced spiral CT image data set with multiplanar reformations to verify an optimal probe location after axial CT-guided needle placement should be obtained before RF ablation of liver lesions.

Aged↗
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↗