[Show abstract][Hide abstract] ABSTRACT: The purpose of these guidelines is to assist physicians in recommending, performing, interpreting and reporting the results of FDG PET/CT for oncological imaging of adult patients. PET is a quantitative imaging technique and therefore requires a common quality control (QC)/quality assurance (QA) procedure to maintain the accuracy and precision of quantitation. Repeatability and reproducibility are two essential requirements for any quantitative measurement and/or imaging biomarker. Repeatability relates to the uncertainty in obtaining the same result in the same patient when he or she is examined more than once on the same system. However, imaging biomarkers should also have adequate reproducibility, i.e. the ability to yield the same result in the same patient when that patient would have been examined on different systems and at different imaging sites. Adequate repeatability and reproducibility are essential for the clinical management of patients and the use of FDG PET/CT within multicentre trials. A common standardized imaging procedure will help promote the appropriate use of FDG PET/CT imaging and increase the value of publications and, therefore, their contribution to evidence-based medicine. Moreover, consistency in numerical values between platforms and institutes that acquire the data will potentially enhance the role of semiquantitative and quantitative image interpretation. Precision and accuracy are additionally important as FDG PET/CT is used to evaluate tumour response as well as for diagnosis, prognosis and staging. Therefore both the previous and these new guidelines specifically aim to achieve standardized uptake value harmonization in multicentre settings
European journal of nuclear medicine and molecular imaging 12/2014; · 5.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In a previous study, we demonstrated the first evidence that the asphericity (ASP) of pretherapeutic FDG uptake in the primary tumor provides independent prognostic information in patients with head and neck cancer. The aim of this work was to confirm these results in an independent patient group examined at a different site.
FDG-PET/CT was performed in 37 patients. The primary tumor was delineated by an automatic algorithm based on adaptive thresholding. For the resulting ROIs, the metabolically active part of the tumor (MTV), SUVmax, SUVmean, total lesion glycolysis (TLG) and ASP were computed. Univariate Cox regression with respect to progression free survival (PFS) and overall survival (OS) was performed. For survival analysis, patients were divided in groups of high and low risk according to the parameter cut-offs defined in our previous work. In a second step, the cut-offs were adjusted to the present data. Univariate and multivariate Cox regression was performed for the pooled data consisting of the current and the previously described patient group (N = 68). In multivariate Cox regression, clinically relevant parameters were included.
Univariate Cox regression using the previously published cut-off values revealed TLG (hazard ratio (HR) = 3) and ASP (HR = 3) as significant predictors for PFS. For OS MTV (HR = 2.7) and ASP (HR = 5.9) were significant predictors. Using the adjusted cutoffs MTV (HR = 2.9/3.3), TLG (HR = 3.1/3.3) and ASP (HR = 3.1/5.9) were prognostic for PFS/OS. In the pooled data, multivariate Cox regression revealed a significant prognostic value with respect to PFS/OS for MTV (HR = 2.3/2.1), SUVmax (HR = 2.1/2.5), TLG (HR = 3.5/3.6), and ASP (HR = 3.4/4.4).
Our results confirm the independent prognostic value of ASP of the pretherapeutic FDG uptake in the primary tumor in patients with head and neck cancer. Moreover, these results demonstrate that ASP can be determined unambiguously across different sites.
European journal of nuclear medicine and molecular imaging 11/2014; · 5.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: <sup>99m</sup>Tc is the standard radionuclide used for nuclear medicine imaging. In addition to gamma irradiation, <sup>99m</sup>Tc emits low-energy Auger and conversion electrons that deposit their energy within nanometers of the decay site. To study the potential for DNA damage, direct DNA binding is required. Plasmid DNA enables the investigation of the unprotected interactions between molecules and DNA that result in single-strand breaks (SSBs) or double-strand breaks (DSBs); the resulting DNA fragments can be separated by gel electrophoresis and quantified by fluorescent staining. This study aimed to compare the plasmid DNA damage potential of a <sup>99m</sup>Tc-labeled HYNIC-DAPI compound with that of <sup>99m</sup>Tc pertechnetate (<sup>99m</sup>TcO<sub>4</sub><sup>−</sup>). pUC19 plasmid DNA was irradiated for 2 or 24 hours. Direct and radical-induced DNA damage were evaluated in the presence or absence of the radical scavenger DMSO. For both compounds, an increase in applied activity enhanced plasmid DNA damage, which was evidenced by an increase in the open circular and linear DNA fractions and a reduction in the supercoiled DNA fraction. The number of SSBs elicited by <sup>99m</sup>Tc-HYNIC-DAPI (1.03) was twice that caused by <sup>99m</sup>TcO<sub>4</sub><sup>−</sup> (0.51), and the number of DSBs increased fivefold in the <sup>99m</sup>Tc-HYNIC-DAPI-treated sample compared with the <sup>99m</sup>TcO<sub>4</sub><sup>−</sup> treated sample (0.02 to 0.10). In the presence of DMSO, the numbers of SSBs and DSBs decreased to 0.03 and 0.00, respectively, in the <sup>99m</sup>TcO<sub>4</sub><sup>–</sup> treated samples, whereas the numbers of SSBs and DSBs were slightly reduced to 0.95 and 0.06, respectively, in the <sup>99m</sup>Tc-HYNIC-DAPI-treated samples. These results indicated that <sup>99m</sup>Tc-HYNIC-DAPI induced SSBs and DSBs via a direct interaction of the <sup>99m</sup>Tc-labeled compound with DNA. In contrast to these results, <sup>99m</sup>TcO<sub>4</sub><sup>−</sup> induced SSBs via radical formation, and DSBs were formed by two nearby SSBs. The biological effectiveness of <sup>99m</sup>Tc-HYNIC-DAPI increased by approximately 4-fold in terms of inducing SSBs and by approximately 10-fold in terms of inducing DSBs.
PLoS ONE 08/2014; 9(8):e104653. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose: 68Ga-labelled compounds are increasingly used for somatostatin-receptor scintigraphy because of their favourable biokinetic properties, a higher tumour-to-background contrast and higher diagnostic accuracy compared to the gamma-emitting tracer 111In-DTPA-octreotide. Recently, we have introduced the new tracer 68Ga-DOTA-3-iodo-Tyr3-Thr8-octreotide (68Ga-HA-DOTATATE). The present study demonstrates the biodistribution and radiation dosimetry ofthis tracer in humans. Patients, methods: Seven men were enrolled in this analysis. Every patient underwent a 20 min dynamic PET scan after intravenous injection of about 114 ± 9 MBq of 68Ga-HA-DOTATATE. This was followed by two whole-body scans at 30 min p. i. and 120 min p. i. Blood radioactivity concentration was determined non-invasively from a ROI drawn over the aorta. Urine was collected until the time of the last scan. Liver, spleen, kidneys and urinary bladder wall were included in the dosimetric estimation that was carried out with the software package OLINDA 1.0. Results: Physiological 68Ga-HA-DOTATATE uptake was observed in the pituitary gland, thyroid, salivary glands, liver, spleen, kidneys, urinary bladder, adrenals and intestine. Organs with the highest absorbed dose were spleen (0.26 ± 0.11 mSv/MBq), kidneys (0.14 ± 0.03 mSv/MBq) and liver (0.12 ± 0.02 mSv/MBq).The estimated effective dose was 0.024 ± 0.001 mSv/MBq. Conclusion: Our study demonstrates biokinetics and radiation exposure of the 68Ga-labelled tracer HA-DOTATATE to be comparable to other 68Ga-labelled SSR analogues in clinical use.
[Show abstract][Hide abstract] ABSTRACT: Based on the authors' previous findings concerning the radiotoxicity of(99m)Tc, the authors compared the cellular survival under the influence of this nuclide with that following exposure to the Auger electron emitter (123)I. To evaluate the relative biological effectiveness (RBE) of both radionuclides, knowledge of the absorbed dose is essential. Thus, the authors present the dose calculations and discuss the results based on different models of the radionuclide distribution. Both different target volumes and the influence of the uptake kinetics were considered.
Medical Physics 06/2014; 41(6):062503. · 3.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Diagnostic imaging with positron emission tomography (PET) is becoming increasingly more involved in oncological therapy management.
How can PET be helpful in oncological surgery?
After a short introduction into the basic principles of PET the current state of imaging as well as indications and limitations of the method are described.
The PET is a functional and quantitative imaging technique, enabling detection and characterization of tumors. It is applied in pretherapeutic staging as well as in follow-up and therapy assessment. The use of PET changes the therapy management in about one third of all oncology patients. New radiopharmaceuticals and novel technologies expand the diagnostic potential.
Hybrid imaging with PET computed tomography (CT) and PET magnetic resonance imaging (MRI) further improves diagnostic imaging and increases the acceptance of PET further.
[Show abstract][Hide abstract] ABSTRACT: Standard uptake values (SUV) as well as tumor-to-blood standard uptake ratios (SUR) measured with[18F-]fluorodeoxyglucose (FDG) PET are time dependent. This poses a serious problem for reliablequantification since variability of scan start time relative to the time of injection is a persistent issue inclinical oncological Positron emission tomography (PET). In this work, we present a method for scantime correction of, both, SUR and SUV.
Assuming irreversible FDG kinetics, SUR is linearly correlated to Km (the metabolic rate of FDG),where the slope only depends on the shape of the arterial input function (AIF) and on scan time. Consideringthe approximately invariant shape of the AIF, this slope (the `Patlak time¿) is an investigationindependent function of scan time. This fact can be used to map SUR and SUV values from differentinvestigations to a common time point for quantitative comparison. Additionally, it turns out thatmodelling the invariant AIF shape by an inverse power law is possible which further simplifies thecorrection procedure. The procedure was evaluated in 15 fully dynamic investigations of liver metastasesfrom colorectal cancer and 10 dual time point (DTP) measurements. From each dynamic study,three `static scans¿ at T = 20, 35, and 55 min post injection (p.i.) were created, where the last scandefined the reference time point to which the uptake values measured in the other two were corrected.The corrected uptake values were then compared to those actually measured at the reference time.For the DTP studies, the first scan (acquired at 78.1 ± 15.9 min p.i.) served as the reference, and theuptake values from the second scan (acquired 39.2 ± 9.9 min later) were corrected accordingly andcompared to the reference.
For the dynamic data, the observed difference between uncorrected values and values at referencetime was (¿52 ± 4.5)% at T = 20 min and (¿31 ± 3.7)% at T = 35 min for SUR and (¿30 ± 6.6)%at T = 20 min and (¿16 ± 4)% at T = 35 min for SUV. After correction, the difference was reducedto (¿2.9 ± 6.6)% at T = 20 min and (¿2.7 ± 5)% at T = 35 min for SUR and (1.9% ± 6.2)% atT = 20 min and (1.7 ± 3.3)% at T = 35 min for SUV. For the DTP studies, the observed differencesof SUR and SUV between late and early scans were (48 ± 11)% and (24 ± 8.4)%, respectively. Aftercorrection, these differences were reduced to (2.6 ± 6.9)% and (¿2.4 ± 7.3)%, respectively.
If FDG kinetics is irreversible in the targeted tissue, correction of SUV and SUR for scan time variabilityis possible with good accuracy. The correction distinctly improves comparability of lesionuptake values measured at different times post injection.
[Show abstract][Hide abstract] ABSTRACT: Objective
To investigate the effect of radiation dose-escalation on local control in hypoxic versus non-hypoxic hypoxic tumours defined using [18F]fluoromisonidazole ([18F]FMISO) PET.
Materials and methods
FaDu human squamous cell carcinomas (hSCCs) growing subcutaneously in nude mice were subjected to [18F]FMISO PET before irradiation with single doses of 25 or 35 Gy under normal blood flow conditions. [18F]FMISO hypoxic volume (HV) and maximum standardised uptake value (SUVmax) were used to quantify tracer uptake. The animals were followed up for at least 120 days after irradiation. The endpoints were permanent local tumour control and time to local recurrence.
HV varied between 38 and 291 mm3 (median 105 mm3). Non-hypoxic tumours (HV below median) showed significantly better local control after single dose irradiation than hypoxic tumours (HV above median) (p = 0.046). The effect of dose was significant and not different in non-hypoxic and in hypoxic tumours (HR = 0.82 [95% CI 0.71; 0.93], p = 0.002 and HR = 0.86 [0.78; 0.95], p = 0.001, respectively). Dose escalation resulted in an incremental increase of local tumour control from low-dose hypoxic, over low-dose non-hypoxic and high-dose hypoxic to high-dose non-hypoxic tumours. SUVmax did not reveal significant association with local control at any dose level.
The negative effect of [18F]FMISO HV on permanent local tumour control supports the prognostic value of the pre-treatment [18F]FMISO HV. Making the assumption that variable [18F]FMISO uptake in different FaDu tumours which all have the same genetic background may serve as an experimental model of intratumoural heterogeneity, the data support the concept of dose-escalation with inhomogeneous dose distribution based on pre-treatment [18F]FMISO uptake. This result needs to be confirmed in other tumour models and using fractionated radiotherapy schedules.
Radiotherapy and Oncology 04/2014; · 4.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To assess the diagnostic value of PET/MR (positron emission tomography/magnetic resonance imaging) with FDG (18F-fluorodeoxyglucose) for lymph node staging in head and neck cancer.
This prospective study was approved by the local ethics committee; all patients signed informed consent. Thirty-eight patients with squamous cell carcinoma of the head and neck region underwent a PET scan on a conventional scanner and a subsequent PET/MR on a whole-body hybrid system after a single intravenous injection of FDG. The accuracy of PET, MR and PET/MR for lymph node metastases were compared using receiver operating characteristic (ROC) analysis. Histology served as the reference standard.
Metastatic disease was confirmed in 16 (42.1%) of 38 patients and 38 (9.7%) of 391 dissected lymph node levels. There were no significant differences between PET/MR, MR and PET and MR (p>0.05) regarding accuracy for cervical metastatic disease. Based on lymph node levels, sensitivity and specificity for metastatic involvement were 65.8% and 97.2% for MR, 86.8% and 97.0% for PET and 89.5% and 95.2% for PET/MR.
In head and neck cancer, FDG PET/MR does not significantly improve accuracy for cervical lymph node metastases in comparison to MR or PET.
European journal of radiology 04/2014; · 2.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Abstract Purpose: Epidermal growth factor receptor (EGFR) is critically involved in progression and therapy resistance of squamous cell carcinoma (SCC). Albeit EGFR targeting could improve the effect of radiotherapy on patients' outcome, the clinical results failed to meet expectations from preclinical studies. In this work, we evaluated the potential of the radionuclide Yttrium-90 ((90)Y) bound to Cetuximab ((90)Y-Cetuximab) as novel targeting approach for SCC cells in vitro. Materials and methods: FaDu and A431 cell lines were used. EGFR subcellular localization, clonogenic survival, radiation-induced γH2AX foci and EGFR signaling were examined. Cells were treated with DTPA, DTPA-Cetuximab, (90)Y and (90)Y-Cetuximab alone or in combination with external X-ray irradiation. Results: Dose- and cell line-dependently, (90)Y-Cetuximab mediated a significant reduction in clonogenicity relative to unbound (90)Y. Combined 2-Gy external radiation plus 2-Gy equivalent dose of (90)Y-Cetuximab was more effective than equivalent doses of (90)Y and X-ray radiation. Analogous effects were observed in the number of residual radiation-induced foci. Additionally, EGFR, ERK1/2 and AKT phosphorylation showed alterations upon different treatments. Conclusions: Our findings show that Cetuximab-conjugated (90)Y has a significant potential to eradicate human SCC cells. A combination of radioimmunotherapeutic compounds and external radiotherapy might be a promising treatment strategy for clinical application.
International Journal of Radiation Biology 03/2014; · 1.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The treatment of loosened total hip replacement (THR) acetabular components may require the management of severe bone defects. Although being applied for decades, there is only limited scientific data about the osteointegration of cancellous bone allografts (CBA) and other void fillers. Monitoring of periprosthetic bone regeneration could possibly help to optimize this process thereby reducing late failure rates. The aim of this study was to show osteometabolic changes in periprosthetic CBA after THR revision with the use of sodium-[18F]-fluoride (NaF) and positron emission tomography (PET). Patients, methods: Twelve patients undergoing THR revision with the use of CBA were prospectively enrolled in the study. Nine patients completed all necessary examinations and were included in the evaluation. The temporal pattern of osteointegration was assessed via NaF-PET at one (PET1) and six weeks (PET2) after surgery. CBA, tantalum implants, supraacetabular regions ipsilateral and contralateral, and parasymphyseal pubic bones were delineated as volumes of interest (VOI) in postop CT scans, which were then merged with the PET data. Results: In comparison to the contralateral supraacetabular reference bone, a significant 1.5-fold increase of osteometabolic activity from PET1 to PET2 was seen in the CBA region. Also, the ipsilateral supraacetabular host bone showed a higher NaF-influx in week 6, compared to the first postoperative week. The supraacetabular site exhibited a significantly 1.8- to 2-fold higher influx and uptake than bone regions in non-operated sites. Tantalum implants had a low NaF influx at both time points investigated. Conclusion: Using NaF-PET osteometabolic changes of CBA and implant-bone-interfaces can be monitored. Applying this method we demonstrated early periprosthetic temporal bone regeneration patterns in THR cup revision patients.
[Show abstract][Hide abstract] ABSTRACT: Quantitative positron emission tomography (PET) requires accurate scanner calibration, which is commonly performed using phantoms. It is not clear to what extent this procedure ensures quantitatively correct results in vivo, since certain conditions differ between phantom and patient scans. Aim: We, therefore, have evaluated the actual quantification accuracy in vivo of PET under clinical routine conditions. Patients, methods:We determined the activity concentration in the bladder in patients undergoing routine [18F]FDG whole body investigations with three different PET scanners (Siemens ECAT EXACT HR+ PET: n = 21; Siemens Biograph 16 PET/CT: n = 16; Philips Gemini-TF PET/CT: n = 19). Urine samples were collected immediately after scan. Activity concentration in the samples was determined in well counters cross-calibrated against the respective scanner. The PET (bladder) to well counter (urine sample) activity concentration ratio was determined. Results: Activity concentration in the bladder (PET) was systematically lower than in the urine samples (well counter). The patient-averaged PET to well counter ratios for the investigated scanners are (mean ± SEM): 0.881 ± 0.015 (ECAT HR+), 0.898 ± 0.024 (Biograph 16), 0.932 ± 0.024 (Gemini-TF). These values correspond to underestimates by PET of 11.9%, 10.2%, and 6.8%, respectively. Conclusions: The investigated PET systems consistently underestimate activity concentration in the bladder. The comparison of urine samples with PET scans of the bladder is a straightforward means for in vivo evaluation of the expectable quantification accuracy. The method might be interesting for multi-center trials, for additional quality assurance in PET and for investigation of PET/MR systems for which clear proof of sufficient quantitative accuracy in vivo is still missing.
[Show abstract][Hide abstract] ABSTRACT: Over recent decades interest in diagnosis and treatment of neuroendocrine tumours (NET) has steadily grown. The basis for diagnosis and therapy of NET with radiolabelled somatostatin (hsst) analogues is the variable overexpression of hsst receptors (hsst1-5 receptors). We hypothesized that radiometal derivatives of DOTA-iodo-Tyr(3)-octreotide analogues might be excellent candidates for somatostatin receptor imaging. We therefore explored the diagnostic potential of (68)Ga-DOTA-iodo-Tyr(3)-octreotate [(68)Ga-DOTA,3-iodo-Tyr(3),Thr(8)]octreotide ((68)Ga-HA-DOTATATE; HA, high-affinity) compared to the established (68)Ga-DOTA-Tyr(3)-octreotate ((68)Ga-DOTATATE) in vivo.
The study included 23 patients with known somatostatin receptor-positive metastases from NETs, thyroid cancer or glomus tumours who were investigated with both (68)Ga-HA-DOTATATE and (68)Ga-DOTATATE. A patient-based and a lesion-based comparative analysis was carried out of normal tissue distribution and lesion detectability in a qualitative and a semiquantitative manner.
(68)Ga-HA-DOTATATE and (68)Ga-DOTATATE showed comparable uptake in the liver (SUVmean 8.9 ± 2.2 vs. 9.3 ± 2.5, n.s.), renal cortex (SUVmean 13.3 ± 3.9 vs. 14.5 ± 3.7, n.s.) and spleen (SUVmean 24.0 ± 6.7 vs. 22.9 ± 7.3, n.s.). A somewhat higher pituitary uptake was found with (68)Ga-HA-DOTATATE (SUVmean 6.3 ± 1.8 vs. 5.4 ± 2.1, p < 0.05). On a lesion-by-lesion basis a total of 344 lesions were detected. (68)Ga-HA-DOTATATE demonstrated 328 lesions (95.3 % of total lesions seen), and (68)Ga-DOTATATE demonstrated 332 lesions (96.4 %). The mean SUVmax of all lesions was not significantly different between (68)Ga-HA-DOTATATE and (68)Ga-DOTATATE (17.8 ± 11.4 vs. 16.7 ± 10.7, n.s.).
Our analysis demonstrated very good concordance between (68)Ga-HA-DOTATATE and (68)Ga-DOTATATE PET data. As the availability and use of (68)Ga-HA-DOTATATE is not governed by patent restrictions it may be an attractive alternative to other (68)Ga-labelled hsst analogues.
European Journal of Nuclear Medicine 02/2014; · 4.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aims of this study were to determine the quantitative parameters of ventilation (V) and perfusion (Q) PET scans assessing V/Q quotients in patients with various lung pathologies, as well as the influence of patient position on regional perfusion patterns.
Fifty-three patients (24 male and 29 female) underwent lung scintigraphy with Ga-labelled radiopharmaceuticals. Ga Galligas and B20 microspheres used for V and Q imaging were produced in-house. Images were acquired under a standard setup with two emission scans of the whole lung in the supine (S) position (acquisition time 3 min/bed position) on a PET/CT scanner combined with low-dose computed tomography (CT) for attenuation correction. In 27 patients the Q scan was repeated in the prone (P) position. Parametric images were calculated (V/Q, P/S when applicable) for each patient. Patients were grouped according to diagnostic findings, and V/Q ratio distributions were further analysed. Gradients of the regional blood flow in both the supine and prone position were calculated.
The results from visual interpretation could be confirmed with parametric images. Voxel-wise V/Q analysis revealed significant differences in descriptive parameters such as median, mean and SD between normal patients and patients with acute and previous pulmonary embolism. Skewness and kurtosis were not significantly different. The effect of gravitation could be demonstrated by significant position-dependent changes of the gradients in the ventral-dorsal and apical-basal directions.
PET/CT using Ga-labelled tracers allows the application of quantitative procedures to improve functional pulmonary imaging in clinical diagnosis and research.
Nuclear Medicine Communications 02/2014; · 1.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Spontaneous breathing (SB) in the early phase of the acute respiratory distress syndrome is controversial. Biphasic positive airway pressure/airway pressure release ventilation (BIPAP/APRV) is commonly used, but the level of SB necessary to maximize potential beneficial effects is unknown.
Experimental acute respiratory distress syndrome was induced by saline lung lavage in anesthetized and mechanically ventilated pigs (n = 12). By using a Latin square and crossover design, animals were ventilated with BIPAP/APRV at four different levels of SB in total minute ventilation (60 min each): (1) 0% (BIPAP/APRV0%); (2) greater than 0 to 30% (BIPAP/APRV>0-30%); (3) greater than 30 to 60% (BIPAP/APRV>30-60%); and (4) greater than 60% (BIPAP/APRV>60%). Gas exchange, hemodynamics, and respiratory variables were measured. Lung aeration was assessed by high-resolution computed tomography. The distribution of perfusion was marked with Ga-labeled microspheres and evaluated by positron emission tomography.
The authors found that higher levels of SB during BIPAP/APRV (1) improved oxygenation; (2) decreased mean transpulmonary pressure (stress) despite increased inspiratory effort; (3) reduced nonaerated lung tissue, with minimal changes in the distribution of perfusion, resulting in decreased low aeration/perfusion zones; and (4) decreased global strain (mean ± SD) (BIPAP/APRV0%: 1.39 ± 0.08; BIPAP/APRV0-30%: 1.33 ± 0.03; BIPAP/APRV30-60%: 1.27 ± 0.06; BIPAP/APRV>60%: 1.25 ± 0.04, P < 0.05 all vs. BIPAP/APRV0%, and BIPAP/APRV>60% vs. BIPAP/APRV0-30%).
In a saline lung lavage model of experimental acute respiratory distress syndrome in pigs, levels of SB during BIPAP/APRV higher than currently recommended for clinical practice, that is, 10 to 30%, improve oxygenation by increasing aeration in dependent lung zones without relevant redistribution of perfusion. In presence of lung recruitment, higher levels of SB reduce global stress and strain despite an increase in inspiratory effort.
[Show abstract][Hide abstract] ABSTRACT: Rationale and Objectives
The purpose of this study was to evaluate the sensitivity and specificity of positron emission tomography/magnetic resonance imaging (PET/MR) with 18F-fluorodeoxyglucose (FDG) for nodal involvement in malignant lymphoma.
Materials and Methods
Twenty-seven patients with malignant lymphoma (16 men and 11 women; mean age, 45 years) were included in this retrospective study. The patients underwent FDG PET/MR after intravenous injection of FDG (176–357 MBq FDG, 282 MBq on average). Follow-up imaging and histology served as the standard of reference.
One-hundred and twenty-seven (18.1%) of 702 lymph node stations were rated as having lymphoma involvement based on the standard of reference. One-hundred and twenty-four (17.7%) of 702 lymph node stations were rated as positive by FDG PET/MR. The sensitivity and specificity of FDG PET/MR for lymph node station involvement were 93.8% and 99.4%.
FDG PET/MR is feasible for lymphoma staging and has a high sensitivity and specificity for nodal involvement in lymphoma. Comparison with PET/CT is necessary to determine whether FDG PET/MR can replace PET/CT for lymphoma staging.
[Show abstract][Hide abstract] ABSTRACT: Somatostatin receptor scintigraphy is an established modality for imaging well-differentiated neuroendocrine tumors. It is known that inflammatory diseases (eg, tuberculosis) may also accumulate somatostatin receptor analogs. Here, we present the case of a 69-year-old patient with a neuroendocrine tumor of the rectum showing uptake of Ga DOTATATE in 2 vertebrae that was caused by vertebral hemangiomas. This could be clearly demonstrated on the CT scan. Although studies outlining the normal distribution of Ga DOTATATE exist, uptake in vertebral hemangiomas has not been described yet. As the case shows, vertebral hemangiomas should be kept in mind as a benign differential diagnosis.
Clinical nuclear medicine 10/2013; · 3.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose: Accurate volumetric tumor delineation is of increasing importance in radiation treatment planning. Many tumors exhibit only moderate tracer uptake heterogeneity and delineation methods using an adaptive threshold lead to robust results. These methods use a tumor reference value R (e.g., ROI maximum) and the tumor background Bg to compute the volume reproducing threshold. This threshold corresponds to an isocontour which defines the tumor boundary. However, the boundaries of strongly heterogeneous tumors can not be described by an isocontour anymore and therefore conventional threshold methods are not suitable for accurate delineation. The aim of this work is the development and validation of a delineation method for heterogeneous tumors.Methods: The new method (voxel-specific threshold method, VTM) can be considered as an extension of an adaptive threshold method (lesion-specific threshold method, LTM), where instead of a lesion-specific threshold for the whole ROI, a voxel-specific threshold is computed by determining for each voxel Bg and R in the close vicinity of the voxel. The absolute threshold for the considered voxel is then given by Tabs = T × (R - Bg) + Bg, where T = 0.39 was determined with phantom measurements. Validation: 30 clinical datasets from patients with non-small-cell lung cancer were used to generate 30 realistic anthropomorphic software phantoms of tumors with different heterogeneities and well-known volumes and boundaries. Volume delineation was performed with VTM and LTM and compared with the known lesion volumes and boundaries.Results: In contrast to LTM, VTM was able to reproduce the true tumor boundaries accurately, independent of the heterogeneity. The deviation of the determined volume from the true volume was (0.8 ± 4.2)% for VTM and (11.0 ± 16.4)% for LTM.Conclusions: In anthropomorphic software phantoms, the new method leads to promising results and to a clear improvement of volume delineation in comparison to conventional background-corrected thresholding. In the next step, the suitability for clinical routine will be further investigated.
Medical Physics 08/2013; 40(8):082503. · 3.01 Impact Factor