Patrick Veit

Respiration artifacts in whole-body 18F-FDG PET/CT studies with combined PET/CT tomographs employing spiral CT technology with 1 to 16 detector rows

PurposeCo-registration accuracy in combined whole-body (WB) PET/CT imaging is impaired by respiration-induced mismatches between the CT and the PET. Furthermore, PET/CT misregistration may bias the PET tracer distribution following CT-based attenuation correction (CT-AC). With the introduction of multi-row CT technology of up to 16 detector rows into PET/CT designs, we investigated the incidence of respiration artifacts in WB PET/CT examinations of patients who were unable to follow any breath-hold instructions.MethodsA total of 80 WB studies from six international sites operating PET/CT tomographs with 1-, 2-, 4-, 6-, 8-, and 16-row spiral CT were included. PET/CT examinations were acquired with the patients breathing normally during both the CT and the PET scan, and CT-AC was performed routinely. All studies were anonymized and reviewed independently by three radiologists and three nuclear medicine specialists. We report the frequency and severity of artifacts on CT and PET for the thorax and the abdomen.ResultsIn WB PET/CT imaging of normally breathing patients, significant gains in diagnostic image quality can be expected from employing CT technology with six or more detector rows. In our study, fewer PET images appear distorted than corresponding CT images, which is due to the limited propagation of only mild CT image artifacts after the resampling of the CT-based attenuation map during CT-AC.ConclusionIn whole-body PET/CT imaging of normally breathing patients, respiration-induced artifacts are reduced in both magnitude and prominence for PET/CT systems employing CT components of six or more detector rows.

Morphologic and Functional Changes in Nontumorous Liver Tissue After Radiofrequency Ablation in an In Vivo Model: Comparison of 18F-FDG PET/CT, MRI, Ultrasound, and CT

Rimlike contrast enhancement on morphologic imaging and increased tracer uptake on 18F-FDG PET in the periphery of the necrosis can hamper differentiation of residual tumor from regenerative tissue after radiofrequency ablation of liver lesions. This study used MRI, CT, ultrasound, and 18F-FDG PET/CT to assess the typical appearance of lesions in nontumorous animal liver tissue after radiofrequency ablation. Methods: Lesions were created by radiofrequency ablation of normal liver parenchyma in 21 minipigs. Follow-up was performed by 3 contrast-enhanced morphologic modalities—MRI, CT, and ultrasound—and by 18F-FDG PET/CT immediately, 3 and 10 d, and 1, 2, 3, and 6 mo after radiofrequency ablation. Images were evaluated qualitatively for areas of increased enhancement and regions of elevated tracer uptake. Furthermore, all images were assessed quantitatively by determination of ratios comparing enhancement/tracer uptake in the periphery of the necrosis with enhancement/tracer uptake in normal liver parenchyma. Imaging findings were compared with histopathology findings. Results: Immediately after radiofrequency ablation, no increase in 18F-FDG uptake was visible, whereas elevated enhancement was noticed in the periphery of the necrosis on all morphologic imaging procedures. At further follow-up, an area of rimlike increase in 18F-FDG uptake surrounding the necrosis was detected on PET/CT. The rimlike pattern of increased enhancement in the arterial phase was present for all liver lesions on CT, MRI, and ultrasound, especially between day 3 and month 1 after the radiofrequency ablation. Both elevated glucose metabolism and enhancement persisted for 6 mo postinterventionally. Histologic examination showed a hemorrhagic border converting into a regeneration capsule. Conclusion: If performed immediately after radiofrequency ablation, 18F-FDG PET/CT probably has benefits over those of morphologic imaging procedures when assessing liver tissue for residual tumor. Later follow-up may be hampered by visualization of peripheral hyperperfusion and tissue regeneration. Further studies on a patient population are essential.

Optimization of contrast dosage for gadobenate dimeglumine-enhanced high-resolution whole-body 3D magnetic resonance angiography.

Goyen M, Herborn CU, Lauenstein TC, et al. Optimization of contrast dosage for gadobenate dimeglumine-enhanced high-resolution whole body 3D magnetic resonance angiography. Invest Radiol 2002;37:263–268. rationale and objectives. To determine the optimal dose of gadobenate dimeglumine for diagnostic high-resolution whole-body 3D-MR angiography. methods. Ten healthy volunteers were examined three times with an ascending dose of Gd-BOPTA (0.1/0.2/0.3 mmol/kg BW). Three-dimensional data sets were collected with a rolling table platform (AngioSURF; MR-Innovation GmbH, Essen, Germany) which integrates the torso surface coil, using a 3D FLASH sequence at five stations from carotid arteries to the trifurcation vessels in 72 seconds. SNR- and contrast-to-noise-values were calculated for 30 segments per patient. For qualitative evaluation a 4-point-visualization scale was used. results. Overall, significantly (P < 0.05) higher signal-to-noise values and CNR values were determined for Gd-BOPTA at a dose of 0.2 and 0.3 mmol/kg compared with 0.1 mmol/kg. Similarly, the qualitative analysis demonstrated image quality to be superior with 0.2 and 0.3 mmol/kg compared with 0.1 mmol/kg (P < 0.05). Qualitative and quantitative assessment failed to demonstrate a statistically significant difference between 0.2 and 0.3 mmol/kg BW (P > 0.05). conclusion. A dose of 0.2 mmol/kg BW Gd-BOPTA rendered diagnostic image quality in all vascular segments of all volunteers.

Positron emission tomography/computed tomography improves diagnostics of inflammatory arteritis.

Based on the unique property of fluorine-18 fluorodeoxyglucose, localization and follow-up of hypermetabolic processes is possible with positron emission tomography (PET). The dual-modality PET/computed tomography (CT) systems provide intrinsically fused morphologic and functional data in a single examination. We report on two patients with inflammatory aortitis and positive PET/CT findings. A 57-year-old woman with an inflammatory process involving the thoracolumbal aorta with an aneurysm and a 48-year-old woman with an aneurysm of the thoracic aorta and pronounced fluorodeoxyglucose-uptake. The advantages in differentiation of vessel wall structures compared with PET or CT alone are pointed out.

Digital subtraction dark-lumen MR colonography: initial experience.

To evaluate image subtraction for the detection of colonic pathologies in a dark‐lumen MR colonography exam.

Contrast-Enhanced Dark Lumen PET/CT and MR Colonography in a Rodent Polyp Model: Initial Results with Histopathologic Correlation

OBJECTIVE The objective of this study was to assess the feasibility of PET/CT for the detection of colorectal masses in a rodent polyp model in an intraindividual comparison with dark-lumen MR colonography. CONCLUSION Detection of small tumors with PET/CT and MR colonography is possible in a rodent model. The technique thus warrants further evaluation in animal studies as well as in patients with suspected colorectal disease.

Leydig cell tumor as a cause of hirsutism in a postmenopausal woman

ZusammenfassungHintergrund:Als Ursache eines Hirsutismus bei postmenopausalen Frauen mit sehr hohen Testosteronwerten kommen differentialdiagnostisch androgenproduzierende Tumoren (Ovarialtumoren, Nebennierentumoren) in Frage. Eine präoperative Lokalisation des Tumors kann sich als schwierig erweisen.Fallbeschreibung:Eine 61-jährige Patientin klagte seit Einsetzen der Menopause vor 9 Jahren über zunehmende Behaarung im Gesichts-, Brust- sowie Ober- und Unterschenkelbereich und über eine tiefer werdende Stimme. Ursächlich wurden deutlich erhöhte Testosteronwerte von knapp 30 nmol/l gemessen. Die initiale bildgebende Darstellung der Nebennieren sowie die gynäkologische Untersuchung ergaben keinen Anhalt für einen zugrundeliegenden Tumor. Zur weiteren Lokalisationsdiagnostik wurden bildgebende ([18F]FDG-PET/CT) und invasive Verfahren (Stufenkatheteruntersuchung) eingesetzt. Bei Verdacht auf einen androgenproduzierenden Adnextumor rechts erfolgte eine Adnexektomie. Histologisch konnte die Diagnose eines Leydig-Zell-Tumors des rechten Ovars gestellt werden. Postoperativ sank der Testosteronspiegel auf 2,28 nmol/l ab.Schlussfolgerung:Bei Hirsutismus und hohen Testosteronwerten stellt sich der Verdacht auf einen androgenproduzierenden Tumor des Ovars oder der Nebenniere. Zur Lokalisation des androgenproduzierenden Tumors können eine [18F]FDG-PET- und Stufenkatheteruntersuchung ergänzende diagnostische Optionen darstellen.AbstractBackground:Hirsutism or virilization in postmenopausal women may be due to increased testosterone levels caused by an androgen-secreting tumor. The preoperative localization of small ovarian or adrenal androgen-secreting tumors is difficult.Case Report:A 61-year-old, postmenopausal woman presented with progressive hirsutism and deepening of voice over the last 9 years. Serum testosterone was very high (almost 30 nmol/l). Computed tomographic (CT) scans of the adrenals and ultrasonography of the pelvis were negative. Selective catheterization and [18F]FDG-PET/CT investigation raised the suspicion of an androgen-secreting tumor of the right ovary. Oophorectomy was performed, and a Leydig cell tumor of the right ovary was confirmed on histological examination.Conclusion:Selective catheterization and [18F]FDG-PET investigation may aid the detection of androgen-secreting tumors.

Androgenproduzierender Leydig-Zell-Tumor des Ovars als Ursache von Hirsutismus bei einer postmenopausalen Frau

ZusammenfassungHintergrund:Als Ursache eines Hirsutismus bei postmenopausalen Frauen mit sehr hohen Testosteronwerten kommen differentialdiagnostisch androgenproduzierende Tumoren (Ovarialtumoren, Nebennierentumoren) in Frage. Eine präoperative Lokalisation des Tumors kann sich als schwierig erweisen.Fallbeschreibung:Eine 61-jährige Patientin klagte seit Einsetzen der Menopause vor 9 Jahren über zunehmende Behaarung im Gesichts-, Brust- sowie Ober- und Unterschenkelbereich und über eine tiefer werdende Stimme. Ursächlich wurden deutlich erhöhte Testosteronwerte von knapp 30 nmol/l gemessen. Die initiale bildgebende Darstellung der Nebennieren sowie die gynäkologische Untersuchung ergaben keinen Anhalt für einen zugrundeliegenden Tumor. Zur weiteren Lokalisationsdiagnostik wurden bildgebende ([18F]FDG-PET/CT) und invasive Verfahren (Stufenkatheteruntersuchung) eingesetzt. Bei Verdacht auf einen androgenproduzierenden Adnextumor rechts erfolgte eine Adnexektomie. Histologisch konnte die Diagnose eines Leydig-Zell-Tumors des rechten Ovars gestellt werden. Postoperativ sank der Testosteronspiegel auf 2,28 nmol/l ab.Schlussfolgerung:Bei Hirsutismus und hohen Testosteronwerten stellt sich der Verdacht auf einen androgenproduzierenden Tumor des Ovars oder der Nebenniere. Zur Lokalisation des androgenproduzierenden Tumors können eine [18F]FDG-PET- und Stufenkatheteruntersuchung ergänzende diagnostische Optionen darstellen.AbstractBackground:Hirsutism or virilization in postmenopausal women may be due to increased testosterone levels caused by an androgen-secreting tumor. The preoperative localization of small ovarian or adrenal androgen-secreting tumors is difficult.Case Report:A 61-year-old, postmenopausal woman presented with progressive hirsutism and deepening of voice over the last 9 years. Serum testosterone was very high (almost 30 nmol/l). Computed tomographic (CT) scans of the adrenals and ultrasonography of the pelvis were negative. Selective catheterization and [18F]FDG-PET/CT investigation raised the suspicion of an androgen-secreting tumor of the right ovary. Oophorectomy was performed, and a Leydig cell tumor of the right ovary was confirmed on histological examination.Conclusion:Selective catheterization and [18F]FDG-PET investigation may aid the detection of androgen-secreting tumors.

Application of CT Contrast Agents in PET-CT Imaging

For a number of indications, a clinical contrast-enhanced CT scan may provide additional information compared with a nonenhanced PET-CT scan. The main benefit of oral and IV contrast is more accurate anatomic correlation with PET. Areas of focally increased tracer uptake may be more precisely localized by differentiation of the lesion from its surrounding structures. In addition, contrast-enhanced CT may provide valuable information for lesion detection and characterization in PET-negative tumors. The effects of positive CT contrast agents on PET attenuation correction can be avoided by using water-equivalent oral contrast and adapting the acquisition protocol after IV contrast administration. CT contrast agents should be considered with PET-CT imaging since they not only enhance the CT image but also enhance the quality of PET-CT.

Androgenproduzierender Leydig-Zell-Tumor des Ovars als Ursache von Hirsutismus bei einer postmenopausalen Frau@@@Leydig Cell Tumor as a Cause of Hirsutism in a Postmenopausal Woman

ZusammenfassungHintergrund:Als Ursache eines Hirsutismus bei postmenopausalen Frauen mit sehr hohen Testosteronwerten kommen differentialdiagnostisch androgenproduzierende Tumoren (Ovarialtumoren, Nebennierentumoren) in Frage. Eine präoperative Lokalisation des Tumors kann sich als schwierig erweisen.Fallbeschreibung:Eine 61-jährige Patientin klagte seit Einsetzen der Menopause vor 9 Jahren über zunehmende Behaarung im Gesichts-, Brust- sowie Ober- und Unterschenkelbereich und über eine tiefer werdende Stimme. Ursächlich wurden deutlich erhöhte Testosteronwerte von knapp 30 nmol/l gemessen. Die initiale bildgebende Darstellung der Nebennieren sowie die gynäkologische Untersuchung ergaben keinen Anhalt für einen zugrundeliegenden Tumor. Zur weiteren Lokalisationsdiagnostik wurden bildgebende ([18F]FDG-PET/CT) und invasive Verfahren (Stufenkatheteruntersuchung) eingesetzt. Bei Verdacht auf einen androgenproduzierenden Adnextumor rechts erfolgte eine Adnexektomie. Histologisch konnte die Diagnose eines Leydig-Zell-Tumors des rechten Ovars gestellt werden. Postoperativ sank der Testosteronspiegel auf 2,28 nmol/l ab.Schlussfolgerung:Bei Hirsutismus und hohen Testosteronwerten stellt sich der Verdacht auf einen androgenproduzierenden Tumor des Ovars oder der Nebenniere. Zur Lokalisation des androgenproduzierenden Tumors können eine [18F]FDG-PET- und Stufenkatheteruntersuchung ergänzende diagnostische Optionen darstellen.AbstractBackground:Hirsutism or virilization in postmenopausal women may be due to increased testosterone levels caused by an androgen-secreting tumor. The preoperative localization of small ovarian or adrenal androgen-secreting tumors is difficult.Case Report:A 61-year-old, postmenopausal woman presented with progressive hirsutism and deepening of voice over the last 9 years. Serum testosterone was very high (almost 30 nmol/l). Computed tomographic (CT) scans of the adrenals and ultrasonography of the pelvis were negative. Selective catheterization and [18F]FDG-PET/CT investigation raised the suspicion of an androgen-secreting tumor of the right ovary. Oophorectomy was performed, and a Leydig cell tumor of the right ovary was confirmed on histological examination.Conclusion:Selective catheterization and [18F]FDG-PET investigation may aid the detection of androgen-secreting tumors.