Florian F. Behrendt

Image fusion in dual energy computed tomography: effect on contrast enhancement, signal-to-noise ratio and image quality in computed tomography angiography.

Objective:The aim of this study was to evaluate the influence of different weighting factors on contrast enhancement, signal-to-noise ratio (SNR), and image quality in image fusion in dual energy computed tomography (DECT) angiography. Material and Methods:Fifteen patients underwent a CT angiography of the aorta with a SOMATOM Definition Dual Source CT (DSCT; Siemens, Forchheim, Germany) in dual energy mode (DECT) (tube voltage: 80 and 140 kVp; tube current: 297 eff. mA and 70 eff. mA; collimation, 14 × 1.2 mm). Raw data were reconstructed using a soft convolution kernel (D30f). Fused images were calculated using a spectrum of weighting factors (0.0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0) generating different ratios between the 80- and 140-kVp images (eg, factor 0.5 corresponds to 50% image information from the 140- and the 80-kVp image). Both CT values and SNR were measured in the descending aorta (levels of celiac trunk, renal arteries, and aortic bifurcation), in the right and left common iliac artery and in paraaortal fat. Image quality was evaluated using a 5-point grading scale. Results were compared using paired t-tests and nonparametric paired Wilcoxon tests. Results:Statistically significant increases in mean CT values were seen in vessels when increasing weighting factors were used (all P ≤ 0.001). For example, mean CT values derived from the aorta at the level of the celiac trunk were 273.8 ± 25.8 Hounsfield units (HU), 304.0 ± 24.3 HU, 361.4 ± 22.5 HU, 418.3 ± 25.8 HU, 477.8 ± 32.2 HU, 536.2 ± 41.2 HU, 564.6 ± 45.3 HU, when the weighting factors 0.0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0 were used. The highest SNR values were found in vessels when the weighting factor 0.5 was used. The highest SNR values of the paraaortal fat were obtained for the weighting factors 0.3 and 0.5. Visual image assessment for image quality showed the highest score for the data reconstructed using the weighting factor 0.5. Conclusion:Different weighting factors used to create fused images in DECT cause statistically significant differences in CT value, SNR, and image quality. Best results were obtained using the weighting factor 0.5, which we recommend for image fusion in DECT angiography.

First evidence of PSMA expression in differentiated thyroid cancer using [68Ga]PSMA-HBED-CC PET/CT

The prostate-specific membrane antigen (PSMA) has recently emerged as a target for radionuclide imaging and therapy of prostate cancer [1, 2]. However, PSMA expression was also shown on the cell membrane of endothelial cells of tumour neovasculature in a number of other cancers such as renal cell carcinoma [3, 4], colon carcinoma, neuroendocrine tumours, melanoma or breast cancer [3]. However, to our knowledge no study has yet investigated

Jugular versus subclavian totally implantable access ports: catheter position, complications and intrainterventional pain perception.

PURPOSE To determine the safest and most tolerable method for totally implantable access ports (TIAPs) particularly in regard to patients pain perception and catheter-related complications. MATERIALS AND METHODS From January 2007 to October 2008 a subcutaneous TIAP (Bardport, Bard Access System, UT, USA) was implanted in 138 oncological patients (60 male, 78 female; 18-85 years old; mean age of 56 ± 6 years) by experienced interventional radiologists. 94 TIAP were implanted through the subclavian vein (subclavian group) and 44 TIAP were implanted through the internal jugular vein (jugular group). Intrainterventional pain perception (visual analogue scale from 1 to 10), postinterventional catheter tip migration and radiation dose were documented for each method and implantation side and differences were compared with Wilcoxon t-test. For ordinal variables, comparison of two groups was performed with the Fishers exact test. RESULTS No severe periinterventional complication occurred. Inadvertent arterial punctures without serious consequences were reported in one case for the jugular group versus four cases in the subclavian group. Significantly (p<0.05) lower pain perception, radiation dose and tip migration rate were observed in the jugular group. Catheter occlusions occurred in 4% (n=4) of the subclavian group versus 2% (n=1) of the jugular group. The corresponding values for vein thrombosis and catheter dislocation were 3% (n=3) and 1% (n=1) in the subclavian group, while none of those complications occurred in the jugular group. CONCLUSION Both techniques, the TIAP implantation via fluoroscopy-guided subclavian vein puncture and via ultrasound-guided jugular vein puncture, are feasible and safe. Regarding intrainterventional pain perception, radiation dose, postinterventional catheter tip position and port function the jugular vein puncture under ultrasound guidance seems to be advantageous.

Semi-automated quantification of hepatic lesions in a phantom.

Purpose:Accurate measurement is crucial for the assessment of tumor dimensions to allow accurate evaluation of tumor response. Thus, the purpose of our study was to assess the accuracy of semi-automated RECIST and volumetric measurements of liver lesions in a liver phantom with different CT acquisition parameters. Materials and Methods:A phantom of the upper abdomen with 14 hepatic lesions of different sizes (diameter: 12.0–40.0 mm), densities (45/180 HU at 120 kV), or alignment (vertical/transverse) was scanned with a 16-slice multidetector row computed tomography using varying tube currents (40/60/80/100/120/165mAseff), reconstruction kernels (Siemens B20/30/40/50/70s), or slice thicknesses (1/2/3/4/5 mm). Longest axial diameter and volume of the 14 lesions were quantified using a semi-automated software tool (SyngoOncology, Siemens Medical Solutions, Forchheim, Germany) and compared with the known real longest axial diameter and volume values of the lesions. Absolute percentage errors (APE) were calculated. Degree of agreement in longest axial diameter and volume between software and real measurements was represented graphically in Bland-Altman plots and by corresponding concordance correlation coefficient. Results:At standard soft tissue reconstruction kernel (Siemens B30s) and slice thickness (3 mm) mean absolute percentage error APE (concordance correlation coefficients) ranged between 6.93 and 14.27 (0.96 and 0.99) for longest axial diameter and between 4.98 and 10.85 (0.99 and 1.00) for volume. At varying reconstruction kernels, APE values (concordance correlation coefficients) ranged between 7.92 and 8.31 (0.98 and 0.99) for longest axial diameter and between 4.95 and 6.93 (1.00) for volume. Applying different slice sections APE values (concordance correlation coefficients) differed from 6.54 to 11.82 (0.97 and 0.99) for longest axial diameter and from 6.93 to 9.17 (1.00) for volume. Conclusions:Software quantification of longest axial diameter and volume of hepatic lesions in a phantom demonstrated a high correlation and accuracy under varying multidetector row computed tomography parameter.

Effect of different saline chaser volumes and flow rates on intravascular contrast enhancement in CT using a circulation phantom

PURPOSE To evaluate the influence of different saline chaser volumes and different saline chaser flow rates on the intravascular contrast enhancement in MDCT. MATERIALS AND METHODS In a physiological flow phantom contrast medium (120 ml, 300 mgI/ml, Ultravist 300) was administered at a flow rate of 6 ml/s followed by different saline chaser volumes (0, 30, 60 and 90 ml) at the same injection rate or followed by a 30-ml saline chaser at different injection rates (2, 4, 6 and 8 ml/s). Serial CT-scans at a level covering the pulmonary artery, the ascending and the descending aorta replica were obtained. Time-enhancement curves were computed and both pulmonary and aortic peak enhancement and peak time were determined. RESULTS Compared to contrast medium injection without a saline chaser the pushing with a saline chaser (30, 60, and 90 ml) resulted in a statistically significant increased pulmonary peak enhancement (all p=0.008) and prolonged peak time (p=0.032, p=0.024 and p=0.008, respectively). Highest aortic peak enhancement values were detected for a saline chaser volume of 30 ml. A saline chaser flow rate of 8 ml/s resulted in the highest pulmonary peak enhancement values compared to flow rates of 2, 4 and 6 ml/s (all p=0.008). Aortic peak enhancement showed the highest values for a flow rate of 6 ml/s. CONCLUSION A saline chaser volume of 30 ml and an injection rate of 6 ml/s are sufficient to best improve vascular contrast enhancement in the pulmonary artery and the aorta in MDCT.

Intraindividual Comparison of Contrast Media Concentrations for Combined Abdominal and Thoracic MDCT

OBJECTIVE The purpose of this study was an intraindividual comparison of the degrees of MDCT contrast enhancement achieved with agents containing 300 and 370 mg I/mL. SUBJECTS AND METHODS Seventy-five patients underwent baseline and follow-up MDCT of the chest and abdomen with contrast media containing a high concentration of iodine (iopromide 370 mg I/mL) and standard iodine concentration (iopromide 300 mg I/mL). The total iodine load (37 g) and the iodine delivery rate (1.29 g/s) were identical for the two protocols. Contrast enhancement in the chest (right and left ventricles, pulmonary trunk, descending aorta) and the abdomen (aorta, inferior vena cava, portal vein, and liver) was determined. Results were compared by use of paired Students t tests, and p was adjusted with Bonferroni correction for multiple comparisons (p <or= 0.0056). RESULTS Contrast enhancement was significantly higher for the 300 mg I/mL protocol than for the 370 mg I/mL protocol at all anatomic sites in the chest except the left ventricle (right ventricle, 359 +/- 100 H vs 320 +/- 102 H, p = 0.003; pulmonary trunk, 334 +/- 96 H vs 303 +/- 89 H, p = 0.003; left ventricle, 310 +/- 54 H vs 300 +/- 51 H, p = 0.036; descending aorta, 300 +/- 63 H vs 277 +/- 57 H, p = 0.0002). No statistically significant differences were found in the abdomen (all p > 0.0056). CONCLUSION Given equivalent iodine load and delivery rate, the use of 300 mg I/mL contrast medium results in better contrast enhancement than use of 370 mg I/mL contrast medium in CT of the chest. For the portal venous phase of CT of the abdomen, there was no significant difference in contrast enhancement for the two concentrations of iodine.

18 F-NaF PET/CT: EANM procedure guidelines for bone imaging

The aim of this guideline is to provide minimum standards for the performance and interpretation of 18F-NaF PET/CT scans. Standard acquisition and interpretation of nuclear imaging modalities will help to provide consistent data acquisition and numeric values between different platforms and institutes and to promote the use of PET/CT modality as an established diagnostic modality in routine clinical practice. This will also improve the value of scientific work and its contribution to evidence-based medicine.

Contrast enhancement in chest multidetector computed tomography: intraindividual comparison of 300 mg/ml versus 400 mg/ml iodinated contrast medium.

RATIONALE AND OBJECTIVES We sought to intraindividually compare intravascular contrast enhancement in multidector computed tomography (MDCT) of the chest using contrast media (CM) containing 300 and 400 mg iodine/ml. MATERIALS AND METHODS Seventy-one patients underwent repeated MDCT scanning of the chest at baseline and follow-up. CM with standard iodine (protocol A: 300 mg iodine/ml; Iopromide 300) and high iodine concentration (protocol B: 400 mg iodine/ml; Iomeprol 400) were used. The iodine delivery rate (1.29 g iodine/s) and total iodine load (37 g iodine) were identical for the two protocols. Contrast enhancement was measured in the right and left ventricles, pulmonary trunk, right and left pulmonary arteries, and ascending and descending aortas. Results were compared using paired t-tests; P values were adjusted using Bonferroni correction (P <or= .005). RESULTS Contrast enhancement values showed no statistically significant differences between the two protocols at all anatomic sites (all P > .005). In the right ventricle, pulmonary trunk, and right and left pulmonary arteries, higher attenuation values for protocol A were detected compared to protocol B (379.0 +/- 110.5 vs. 349.8 +/- 117.6, 354.5 +/- 112.2 vs 330.9 +/- 118.3, 348.6 +/- 106.0 vs. 321.8 +/- 109.9, and 347.9 +/- 102.4 vs. 321.0 +/- 104.9 HU, respectively). After the lung circulation (left ventricle, ascending aorta, and descending aorta), attenuation values were marginally higher for protocol B. Using both protocols resulted in suitable contrast enhancement with a mean pulmonary attenuation higher than 300 HU. CONCLUSIONS Using an adapted injection protocol, the administration of 300 and 400 mg iodine CM resulted in a suitable intravascular contrast enhancement in the chest. The use of 400 mg iodine CM does not lead to a statistically significant improvement in contrast enhancement compared to the 300 mg iodine CM.

Intravascular enhancement with identical iodine delivery rate using different iodine contrast media in a circulation phantom.

PurposeBoth 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. Materials and MethodsA 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. ResultsAll 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). ConclusionsThis 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.

Differences in predicted and actually absorbed doses in peptide receptor radionuclide therapy

PURPOSE 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. METHODS Physiologically based pharmacokinetic models were developed. Gamma camera and serum measurements of ten patients with metastasizing neuroendocrine tumors were conducted using111 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. RESULTS 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. CONCLUSIONS 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.