Florian F Behrendt

University Hospital RWTH Aachen, Aachen, North Rhine-Westphalia, Germany

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Publications (69)179.73 Total impact

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    ABSTRACT: The aim of this study is to evaluate the impact of a high resolution (HR) image reconstruction with a voxel size of 2mm in comparison to the most routinely used standard reconstruction with 4mm voxels in patients suffering from prostate cancer having undergone (18)F-methylcholine PET/CT. Phantom studies were performed using a Jaszczak phantom and a custom made phantom containing small hot lesions (size 2-10mm). Clinical evaluation was performed on PET/CT scans of 50 patients. Images were reconstructed with 4mm and 2mm voxel size and analyzed quantitatively using AMIDE and MATLAB. Clinical images were judged by two observers concerning TNM staging, image quality and the correlation of PET and CT data. Phantom studies revealed increased SUVmean and SUVmax values in the HR images (P<0.01). The lower detection limit was approximately 3mm in the HR and 4-5mm in the conventional images. Lower FWHM values were found in the HR images. No significant difference was found concerning the image quality and the correlation of PET and CT (each P>0.5). For both reconstructions, a comparable total amount of lesions was reported (P>0.5) with no impact on the TNM staging. In conclusion, the HR PET reconstruction provides semi-quantitative advantages in the sense of an improved lower detection limit and increased semi-quantitative tumour-to-background ratios. In the setting of choline PET/CT for prostate cancer the high resolution reconstruction could be implemented clinically as there are no relevant qualitative differences between this and the conventional image resolution in terms of image quality, assessment confidence and lesion identification rate.
    Hellenic journal of nuclear medicine 11/2014; · 0.68 Impact Factor
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    ABSTRACT: To determine the frequency of seemingly pathological retroperitoneal uptake in the location of the coeliac ganglia in patients undergoing [(68)Ga]PSMA-HBED PET/CT.
    European journal of nuclear medicine and molecular imaging 09/2014; · 5.11 Impact Factor
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    ABSTRACT: Background: Ventilation/perfusion single-emission photon CT (V/P-SPECT) is widely used to detect pulmonary embolism (PE). Any pathological deficit on P-SPECT with a corresponding unremarkable V-SPECT is considered an embolism. This means that a deficit on P-SPECT with a corresponding deficit on the ventilation scan correlates with other lung pathologies such as pneumonia, bullous emphysema or tumor. In principle, it is possible to identify any of these lung pathologies on nonenhanced chest CT and so this technique has the potential to replace V-SPECT in the diagnosis of PE. Today, SPECT/CT hybrid imaging systems are increasingly applied in clinical routines. Objectives: We investigated whether embolism can be diagnosed using a combined P-SPECT/CT hybrid imaging approach without V-SPECT. Methods: Ninety-three patients with clinically suspected embolism were investigated with standard V/P-SPECT and a nonenhanced CT scan on a combined SPECT/CT system. A diagnosis of embolism was based on V/P-SPECT (gold standard). P-SPECT/CT datasets were blinded and analyzed without any knowledge of the V-SPECT data. The accuracy of P-SPECT/CT was compared to the gold standard. Results: Embolism was diagnosed in 24/93 patients using V/P-SPECT. In total, 57 lung lobes were affected. P-SPECT/CT significantly (p < 0.01) overdiagnosed embolism in nonaffected patients. In total, 36 cases with 88 affected lung lobes were shown. The sensitivity was 95.8%, the specificity 82.6%, the false-negative rate 4.2% and the false-positive rate 17.3%. Conclusions: Our results demonstrate that a nonenhanced CT scan in a novel hybrid imaging system cannot replace V-SPECT in the scintigraphy-based diagnosis of PE. V-SPECT increases specificity and reduces the number of false-positive results when compared to 'perfusion-only' SPECT/CT. © 2014 S. Karger AG, Basel.
    08/2014;
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    ABSTRACT: Context: The determinants of successful I-131 therapy of Graves' disease (GD) are unclear. Objective: To relate dosimetry parameters to outcome of therapy in order to identify significant determinants eu- and/or hypothyroidism after I-131 therapy, in GD patients. Design: Retrospective study. Setting: University hospital. Patients: 206 GD patients treated in our hospital between November of 1999 and January of 2011. All received I-131 therapy aiming at a total absorbed dose to the thyroid of 250 Gy based on pre-therapeutic dosimetry. Main outcome measures: Post-therapy dosimetric thyroid measurements were performed twice daily until discharge; from these measurements thyroid I-131 half-life, the total thyroid absorbed dose and the maximum dose rate after I-131 administration were calculated. Results: 48.5% of patients were hypothyroid and 28.6% of patients were euthyroid after I-131 therapy. In univariate analysis non-hyperthyroid and hyperthyroid patients only differed by gender. A lower thyroid mass, a higher activity per gram thyroid tissue, a shorter effective thyroidal I-131 half life and a higher maximum dose rate, but not the total thyroid absorbed dose, were significantly associated with hypothyroidism. In multivariate analysis, the maximum dose rate remained the only significant determinant of hypothyroidism (p<0.001). Maximum dose rates of 2.2 Gy/h and higher were associated with a 100% hypothyroidism rate. Conclusion: Not the total thyroid absorbed dose, but the maximum dose rate is a determinant of successfully achieving hypothyroidism in Graves' disease. Dosimetric concepts aiming at a specific total thyroid absorbed dose will therefore require reconsideration if our data are confirmed prospectively.
    The Journal of clinical endocrinology and metabolism. 07/2014;
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    ABSTRACT: To compare the cost-effectiveness of (99m)Tc-methoxyisobutylisonitrile (MIBI) thyroid scintigraphy and the Afirma® gene expression classifier for the assessment of cytologically indeterminate thyroid nodules. A decision tree model was used. Costs were calculated from the perspective of the German health insurance system. The robustness of the results was assessed with probabilistic sensitivity analyses using a Monte Carlo simulation. Life expectancy was 34.3 years (estimated costs per patient 1,459 - 2,224) for the MIBI scan and 34.1 years (estimated costs 3,560 - 4,071) for the molecular test. These results were confirmed by the Monte Carlo simulation. MIBI thyroid scintigraphy is more cost-effective than the gene expression classifier.
    European Journal of Nuclear Medicine 04/2014; · 4.53 Impact Factor
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    ABSTRACT: The aim of this study was to assess whether F-FDG PET combined with x-ray CT (F-FDG PET/CT) findings have a prognostic impact in patients with carcinoma of unknown primary (CUP). Seventy patients with CUP who were referred for F-FDG PET/CT were included. F-FDG PET/CT results were checked against available histologic diagnosis and follow-up data. For each patient, the SUVmax of the lesion with maximum uptake was measured. In 26% of the patients, a primary tumor was identified. The follow-up period after F-FDG PET/CT scan ranged between 3 and 45 months. Kaplan-Meier analysis revealed 1-year survival rates of 92% in the group without evidence of malignancy on F-FDG PET/CT, 78% in the group with locoregional disease, and 34% in the group with extensive disease on F-FDG PET/CT. Three-year survival rates in these groups were 73%, 71%, and 23%, respectively (P = 0.001). There was no significant survival difference between patients with regionally confined disease without identification of the primary tumor and those in whom the primary tumor was identified on F-FDG PET/CT (P = 0.25). This was also the case for patients with extensive disease (P = 0.26). The SUVmax of the lesion with maximum uptake was not significantly related to survival (P = 0.56). F-FDG PET/CT is a helpful tool for the identification of the primary tumor in patients with CUP; it is also able to provide an accurate assessment of prognosis based on the extent of the disease without the need for identification of the primary tumor.
    Clinical nuclear medicine 12/2013; · 3.92 Impact Factor
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    ABSTRACT: The aim of the present study was to investigate the diagnostic and prognostic value of combined (18)F-2-fluorodeoxyglucose positron emission tomography and contrast enhanced X-ray computed tomography (FDG-PET/CT) in women with a suspicion of recurrent ovarian cancer. We retrospectively reviewed 48 patients with a suspicion of recurrent ovarian cancer who were referred to our department for combined FDG-PET/CT. Median follow-up was 25 months. 38/48 (79%) patients showed pathological findings on PET/CT. 17/48 (35%) of patients died of ovarian cancer. One FDG-PET/CT was false positive and one was false negative, leading to a sensitivity and positive predictive value of 97% and a specificity and negative predictive value of 90%. 33/48 (69%) underwent a change in therapy following FDG-PET/CT. There was a significantly better survival in FDG-PET/CT negative than in positive patients (p=0.04). In the FDG-PET/CT negative group no patients had died of ovarian cancer during follow-up. Remarkably, there was no difference in survival between patients who only had peritoneal metastases on FDG-PET/CT and those who also had extraperitoneal metastases (p=0.71). A negative FDG-PET/CT has a high negative predictive value for the presence of disease and, more importantly, is associated with a very good disease-specific survival rate.
    European journal of radiology 12/2013; · 2.65 Impact Factor
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    ABSTRACT: In patients with differentiated thyroid carcinoma (DTC), metastases can either show iodine-131 (I) uptake on whole-body scintigraphy or F-2-fluoro-2-deoxy-D-glucose (F-FDG) uptake on combined PET and X-ray computed tomography (PET/CT), or a mix of both. The present study investigates the relationship between uptake patterns and prognosis in DTC patients, using thyroglobulin doubling time (TgDT) as a surrogate marker of prognosis. We retrospectively examined F-FDG PET/CT and I WBS in 65 DTC patients who were referred to our department of nuclear medicine for F-FDG PET/CT between May 2007 and June 2011. Eight patients were excluded from analysis because of other diseases that caused intense F-FDG uptake or because of failure to show I WBS uptake. F-FDG uptake was seen in 30 out of 57 (53%) patients, of whom 14 showed some degree of I uptake. In these 30 positive scans, we identified a total of 181 F-FDG-positive lesions. Of these, 60 lesions (33%) showed concurrent I uptake on whole-body scintigraphy. Of the nine patients with a positive TgDT in the patient group eight had F-FDG-positive, I-negative lesions, indicating poorer prognosis for this group. In this initial exploratory retrospective study there appears to be an association between a positive TgDT and F-FDG-positive, I-negative metastases, which should encourage further studies in order to establish whether F-FDG PET-CT is the preferred primary imaging modality in patients with a positive TgDT. Roughly two-thirds of patients with a negative TgDT will show at least some degree of I positivity, potentially enabling further I therapy.
    Nuclear Medicine Communications 11/2013; · 1.38 Impact Factor
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    European Journal of Nuclear Medicine 10/2013; · 4.53 Impact Factor
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    ABSTRACT: Molecular imaging of apoptosis is frequently discussed for monitoring cancer therapies. Here, we compare the low molecular weight phosphatidylserine-targeting ligand zinc(2+)-dipicolylamine (Zn(2+)-DPA) with the established but reasonably larger protein annexin V. Molecular apoptosis imaging with the fluorescently labelled probes annexin V (750 nm, 36 kDa) and Zn(2+)-DPA (794 nm, 1.84 kDa) was performed in tumour-bearing mice (A431). Three animal groups were investigated: untreated controls and treated tumours after 1 or 4 days of anti-angiogenic therapy (SU11248). Additionally, μPET with (18) F-FDG was performed. Imaging data were displayed as tumour-to-muscle ratio (TMR) and validated by quantitative immunohistochemistry. Compared with untreated control tumours, TUNEL staining indicated significant apoptosis after 1 day (P < 0.05) and 4 days (P < 0.01) of treatment. Concordantly, Zn(2+)-DPA uptake increased significantly after 1 day (P < 0.05) and 4 days (P < 0.01). Surprisingly, annexin V failed to detect significant differences between control and treated animals. Contrary to the increasing uptake of Zn(2+)-DPA, (18) F-FDG tumour uptake decreased significantly at days 1 (P < 0.05) and 4 (P < 0.01). Increase in apoptosis during anti-angiogenic therapy was detected significantly better with the low molecular weight probe Zn(2+)-DPA than with the annexin V-based probe. Additionally, significant treatment effects were detectable as early using Zn(2+)-DPA as with measurements of the glucose metabolism using (18) F-FDG. • The detection of apoptosis by non-invasive imaging is important in oncology. • A new low molecular weight probe Zn (2+)-DPA shows promise in depicting anti-angiogenic effects. • The small Zn (2+)-DPA ligand appears well suited for monitoring therapy. • Treatment effects are detectable just as early with Zn (2+)-DPA as with (18) F-FDG.
    European Radiology 10/2013; · 4.34 Impact Factor
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    ABSTRACT: To investigate the quantitative and qualitative differences between combined positron emission tomography and computed X-ray tomography (PET/CT) enhanced with contrast medium with either an iodine concentration 300mg/ml or 370mg/ml. 120 consecutive patients scheduled for F-18-Fluorodeoxyglucose (FDG) PET/CT were included. The first (second) 60 patients received contrast medium with 300 (370) mg iodine/ml. Intravenous injection protocols were adapted for an identical iodine delivery rate (1.3mg/s) and body surface area (BSA) adapted iodine dose (22.26gI/m(2)). Maximum and mean standardized uptake values (SUVmax; SUVmean) and contrast enhancement (HU) were determined in the ascending aorta, the abdominal aorta, the inferior vena cava, the portal vein, the liver and the right kidney in the venous contrast medium phase. PET data were evaluated visually for the presence of malignancy and image quality. Both media caused significantly higher values for HU, SUVmean and SUVmax for the enhanced PET/CT than the non-enhanced one (all p<0.01). There were no significant differences in the degree of increase of HU, SUVmean and SUVmax between the two contrast media at any anatomic site (all p>0.05). Visual evaluation of lesions showed no differences between contrast and non-contrast PET/CT or between the two different contrast media (p=0.77). When using a constant iodine delivery rate and total iodine dose in a BSA adapted injection protocol, there are no quantitative or qualitative differences in either CT or PET between contrast media with an iodine concentration of 300mg/ml and 370mg/ml, respectively.
    European journal of radiology 09/2013; · 2.65 Impact Factor
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    ABSTRACT: To compare the effects of two different contrast medium concentrations for use in computed X-ray tomography (CT) employing two different injection protocols on positron emission tomography (PET) reconstruction in combined 2-(18)F-desoxyglucose (FDG) PET/CT in patients with a suspicion of lung cancer. 120 patients with a suspicion of lung cancer were enrolled prospectively. PET images were reconstructed with the non-enhanced and venous phase contrast CT obtained after injection of iopromide 300mg/ml or 370mg/ml using either a fixed-dose or a body surface area adapted injection protocol. Maximum and mean standardized uptake values (SUVmax and SUVmean) and contrast enhancement (HU) were determined in the subclavian vein, ascending aorta, abdominal aorta, inferior vena cava, portal vein, liver and kidney and in the suspicious lung lesion. PET data were evaluated visually for the presence of malignancy and image quality. At none of the sites a significant difference in the extent of the contrast enhancement between the four different protocols was found. However, the variability of the contrast enhancement at several anatomical sites was significantly greater in the fixed dose groups than in the BSA groups for both contrast medium concentrations. At none of the sites a significant difference was found in the extent of the SUVmax and SUVmean increase as a result of the use of the venous phase contrast enhanced CT for attenuation. Visual clinical evaluation of lesions showed no differences between contrast and non-contrast PET/CT (P=0.32). Contrast enhanced CT for attenuation correction in combined PET/CT in lung cancer affects neither the clinical assessment nor image quality of the PET-images. A body surface adapted contrast medium protocol reduces the interpatient variability in contrast enhancement.
    European journal of radiology 07/2013; · 2.65 Impact Factor
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    ABSTRACT: Both iodine delivery rate (IDR) and iodine concentration are decisive factors for vascular enhancement in computed tomographic angiography. It is unclear, however, whether the use of high-iodine concentration contrast media is beneficial to lower iodine concentrations when IDR is kept identical. This study evaluates the effect of using different iodine concentrations on intravascular attenuation in a circulation phantom while maintaining a constant IDR. A circulation phantom with a low-pressure venous compartment and a high-pressure arterial compartment simulating physiological circulation parameters was used (heart rate, 60 beats per minute; stroke volume, 60 mL; blood pressure, 120/80 mm Hg). Maintaining a constant IDR (2.0 g/s) and a constant total iodine load (20 g), prewarmed (37°C) contrast media with differing iodine concentrations (240-400 mg/mL) were injected into the phantom using a double-headed power injector. Serial computed tomographic scans at the level of the ascending aorta (AA), the descending aorta (DA), and the left main coronary artery (LM) were obtained. Total amount of contrast volume (milliliters), iodine delivery (grams of iodine), peak flow rate (milliliter per second), and intravascular pressure (pounds per square inch) were monitored using a dedicated data acquisition program. Attenuation values in the AA, the DA, and the LM were constantly measured (Hounsfield unit [HU]). In addition, time-enhancement curves, aortic peak enhancement, and time to peak were determined. All contrast injection protocols resulted in similar attenuation values: the AA (516 [11] to 531 [37] HU), the DA (514 [17] to 531 [32] HU), and the LM (490 [10] to 507 [17] HU). No significant differences were found between the AA, the DA, and the LM for either peak enhancement (all P > 0.05) or mean time to peak (AA, 19.4 [0.58] to 20.1 [1.05] seconds; DA, 21.1 [1.0] to 21.4 [1.15] seconds; LM, 19.8 [0.58] to 20.1 [1.05] seconds). This phantom study demonstrates that constant injection parameters (IDR, overall iodine load) lead to robust enhancement patterns, regardless of the contrast material used. Higher iodine concentration itself does not lead to higher attenuation levels. These results may stimulate a shift in paradigm toward clinical usage of contrast media with lower iodine concentrations (eg, 240 mg iodine/mL) in individual tailored contrast protocols. The use of low-iodine concentration contrast media is desirable because of the lower viscosity and the resulting lower injection pressure.
    Investigative radiology 07/2013; · 4.85 Impact Factor
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    ABSTRACT: Objectives To investigate simultaneous dual-isotope SPECT/CT with two differently radioisotope-labelled albumin-microsphere fractions for treatment planning of hepatic radioembolisation. Methods In addition to 99mTechnetium-labelled albumin microspheres (commercially available), we performed labelling with 111Indium. Binding stability of 111Indium-labelled microspheres was tested in vitro and in vivo in mice. Simultaneous dual-isotope SPECT/CT imaging was validated in an anthropomorphic torso phantom; subsequently, dual-isotope SPECT/CT was performed under in-vivo conditions in pigs (n = 3) that underwent transarterial injection of 99mTechnetium- and 111Indium-labelled microspheres in the liver (right and left hepatic artery, respectively), in both kidneys and in the gluteal musculature. In total, n = 18 transarterial injections were performed. Results In-vitro testing and in-vivo studies in mice documented high binding stability for both 99mTechnetium-labelled and 111Indium-labelled microsphere fractions. In phantom studies, simultaneous dual-isotope SPECT/CT enabled reliable separation of both isotopes. In pigs, the identified deposition of both isotopes could be accurately matched with intended injection targets (100 %, 18/18 intended injection sites). Furthermore, an incidental deposition of 99mTechnetium-labelled microspheres in the stomach could be correlated to the test injection into a right hepatic artery. Conclusion Simultaneous dual-isotope SPECT/CT after transarterial injection with 99mTechnetium- and 111Indium-labelled microspheres is feasible. Thus, it may offer additional, valuable information compared to single 99mTechnetium-labelled albumin examinations. Key Points • Simultaneous dual-isotope SPECT/CT with 111 In- and 99m Tc-labelled albumin microspheres is feasible. • Differentiation of two microsphere fractions after transarterial injection is possible. • The origin of an extra-hepatic microsphere deposition can be correlated to the corresponding artery. • This technique could reduce the setup time for selective internal radiation treatment.
    European Radiology 06/2013; · 4.34 Impact Factor
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    ABSTRACT: OBJECTIVE. The objective of our study was to identify the iodine concentration that yields the highest intravascular contrast enhancement in MDCT angiography by intraindividual comparison in an animal model. MATERIALS AND METHODS. Six pigs underwent repeated chest MDCT examinations under standardized conditions using the same contrast medium (iopromide) with different iodine concentrations (150, 240, 300, and 370 mg I/mL). The contrast injection protocol was adapted to ensure an identical iodine delivery rate of 1.5 g I/s and the same total iodine dose of 300 mg/kg of body weight for all studies. Dynamic CT scans were acquired at the levels of the pulmonary artery and the ascending and descending aorta. Pulmonary and aortic peak enhancement values as well as time to peak (TTP) were calculated from time-enhancement curves. RESULTS. Pulmonary and aortic peak contrast enhancement values were significantly higher with the 240 and 300 mg I/mL contrast media than the 150 and 370 mg I/mL contrast media (e.g., ascending aorta: 240 vs 150, p = 0.0070; 300 vs 150, p = 0.0096; 240 vs 370, p = 0.0262; 300 vs 370, p = 0.0079). TTP values tended to be lower for the 150 mg I/mL contrast medium than for the contrast media with higher iodine concentrations. CONCLUSION. Comparison of contrast media with iodine concentrations ranging from 150 to 370 mg I/mL showed that contrast enhancement was significantly improved with the use of 240 and 300 mg I/mL contrast media given a fixed identical iodine delivery and normalized total iodine load in a porcine model. Contrast media with a moderate iodine concentration are most suitable for obtaining the highest intravascular contrast enhancement in CT angiography.
    American Journal of Roentgenology 05/2013; 200(5):1151-6. · 2.90 Impact Factor
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    ABSTRACT: PURPOSE: Small animal imaging is of growing importance for preclinical research and drug development. Tumour xenografts implanted in mice can be visualized with a clinical PET/CT (cPET); however, it is unclear whether early treatment effects can be monitored. Thus, we investigated the accuracy of a cPET versus a preclinical μPET using 18F-FDG for assessing early treatment effects. MATERIALS AND METHODS: The spatial resolution and the quantitative accuracy of a clinical and preclinical PET were evaluated in phantom experiments. To investigate the sensitivity for assessing treatment response, A431 tumour xenografts were implanted in nude mice. Glucose metabolism was measured in untreated controls and in two therapy groups (either one or four days of antiangiogenic treatment). Data was validated by γ-counting of explanted tissues. RESULTS: In phantom experiments, cPET enabled reliable separation of boreholes≥5mm whereas μPET visualized boreholes≥2mm. In animal studies, μPET provided significantly higher tumour-to-muscle ratios for untreated control tumours than cPET (3.41±0.87 vs. 1.60±.0.28, respectively; p<0.01). During treatment, cPET detected significant therapy effects at day 4 (p<0.05) whereas μPET revealed highly significant therapy effects even at day one (p<0.01). Correspondingly, γ-counting of explanted tumours indicated significant therapy effects at day one and highly significant treatment response at day 4. Correlation with γ-counting was good for cPET (r=0.74; p<0.01) and excellent for μPET (r=0.85; p<0.01). CONCLUSION: Clinical PET is suited to investigate tumour xenografts≥5mm at an advanced time-point of treatment. For imaging smaller tumours or for the sensitive assessment of very early therapy effects, μPET should be preferred.
    European journal of radiology 02/2013; · 2.65 Impact Factor
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    ABSTRACT: OBJECTIVES: To evaluate the effect of contrast medium dose adjustment for body surface area (BSA) compared with a fixed-dose protocol in combined positron emission tomography (PET) and computed tomography (CT) (PET/CT). METHODS: One hundred and twenty patients were prospectively included for (18)F-2-deoxy-fluor-glucose ((18)F-FDG)-PET/CT consisting of a non-enhanced and a venous contrast-enhanced CT, both used for PET attenuation correction. The first 60 consecutive patients received a fixed 148-ml contrast medium dose. The second 60 patients received a dose that was based on their calculated BSA. Mean and maximum standardised FDG uptake (SUVmean and SUVmax) and contrast enhancement (HU) were measured at multiple anatomical sites and PET reconstructions were evaluated visually for image quality. RESULTS: A decrease in the variance of contrast enhancement in the BSA group compared with the fixed-dose group was seen at all anatomical sites. Comparison of tracer uptake SUVmean and SUVmax between the fixed and the BSA group revealed no significant differences at all anatomical sites (all P > 0.05). Comparison of the overall image quality scores between the fixed and the BSA group showed no significant difference (P = 0.753). CONCLUSIONS: BSA adjustment results in increased interpatient homogeneity of contrast enhancement without affecting PET values. In combined PET/CT, a BSA adjusted contrast medium protocol should be used preferably. KEY POINTS : • Intravenous contrast medium is essential for many applications of PET/CT • Body surface area adjustment of contrast medium helps standardise contrast enhancement • Underdosing or overdosing of contrast medium will be reduced • PET image quality is not influenced • BSA adjusted contrast medium protocol should be used preferably in combined PET/CT.
    European Radiology 02/2013; · 4.34 Impact Factor
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    ABSTRACT: A small positron-generating branch in 90-Yttrium (90Y) decay enables post-therapy dose assessment in liver cancer radioembolization treatment. The aim of this study was to validate clinical 90Y PET quantification, focusing on scanner linearity as well as acquisition and reconstruction parameter impact on scanner calibration. Data from three dedicated phantom studies (activity range: 55.2 MBq ¡V 2.1 GBq) carried out on a Philips Gemini TF 16 PET/CT scanner were analyzed after reconstruction with up to 361 parameter configurations. For activities above 200 MBq, scanner linearity could be confirmed with relative error margins < 4%. An acquisitiontime- normalized calibration factor of 1.04 MBqª s / CNTS was determined for the employed scanner. Stable activity convergence was found in hot phantom regions with relative differences in summed image intensities between .3.6% and +2.4%. Absolute differences in background noise artifacts between .79.9% and +350% were observed. Quantitative accuracy was dominated by subset size selection in the reconstruction. Using adequate segmentation and optimized acquisition parameters, the average activity recovery error induced by the axial scanner sensitivity profile was reduced to +2.4% ¡Ó 3.4% (mean ¡Ó standard deviation). We conclude that post-therapy dose assessment in 90Y PET can be improved using adapted parameter setups.
    IEEE transactions on medical imaging. 10/2012;
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    ABSTRACT: Completely implantable access ports for high pressure contrast media injection have been in use in clinical routine for a relatively short time. The purpose of our study was to compare a high pressure port system with a standard port system with regard to implantation and complications. In 94 oncological patients a completely implantable access port was implanted. Patients (n = 49) planned for oncological follow-up computed tomography (CT) received a high pressure port system. Other patients (n = 45) received a standard port system. Intrainterventional pain perception, postinterventional catheter tip migration and complications were analyzed. No major periinterventional complications occurred. Intrainterventional pain perception was not significantly different between the two groups. A significantly lower rate of tip migration was observed in the high pressure port group (P = 0.03) and when the port system was implanted on the right side (P = 0.03). In the standard port group catheter occlusion occurred in three patients (7%) and a catheter loop in one patient (2%) whereas no such complications occurred within the high pressure port group. Venous thrombosis was detected in one patient (2%) with a high pressure port; this did not occur in the standard port group. Implantation and use of a high pressure port device is safe and reliable: the complications are comparable to those of a standard port device. High pressure port systems should be considered for implantation, especially in patients who will require frequent CTs.
    Journal of Medical Imaging and Radiation Oncology 10/2012; 56(5):532-7. · 0.98 Impact Factor
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    ABSTRACT: An important assumption in dosimetry prior to radionuclide therapy is the equivalence of pretherapeutic and therapeutic biodistribution. In this study the authors investigate if this assumption is justified in sst2-receptor targeting peptide therapy, as unequal amounts of peptide and different peptides for pretherapeutic measurements and therapy are commonly used. Physiologically based pharmacokinetic models were developed. Gamma camera and serum measurements of ten patients with metastasizing neuroendocrine tumors were conducted using (111)In-DTPAOC. The most suitable model was selected using the corrected Akaike information criterion. Based on that model and the estimated individual parameters, predicted and measured (90)Y-DOTATATE excretions during therapy were compared. The residence times for the pretherapeutic (measured) and therapeutic scenarios (simulated) were calculated. Predicted and measured therapeutic excretion differed in three patients by 10%, 31%, and 7%. The measured pretherapeutic and therapeutic excretion differed by 53%, 56%, and 52%. The simulated therapeutic residence times of kidney and tumor were 3.1 ± 0.6 and 2.5 ± 1.2 fold higher than the measured pretherapeutic ones. To avoid the introduction of unnecessary inaccuracy in dosimetry, using the same substance along with the same amount for pretherapeutic measurements and therapy is recommended.
    Medical Physics 09/2012; 39(9):5708-17. · 2.91 Impact Factor

Publication Stats

309 Citations
179.73 Total Impact Points

Institutions

  • 2008–2014
    • University Hospital RWTH Aachen
      • Department of Neurology
      Aachen, North Rhine-Westphalia, Germany
  • 2006–2013
    • RWTH Aachen University
      • • Department of Nuclear Medicine
      • • Department of Diagnostic and Interventional Radiology
      Aachen, North Rhine-Westphalia, Germany