Threshold-based prediction of the coagulation zone in sequential temperature mapping in MR-guided radiofrequency ablation of liver tumours

Objective

To evaluate different cut-off temperature levels for a threshold-based prediction of the coagulation zone in magnetic resonance (MR)-guided radiofrequency (RF) ablation of liver tumours.

Methods

Temperature-sensitive measurements were acquired during RF ablation of 24 patients with primary (6) and secondary liver lesions (18) using a wide-bore 1.5?T MR sytem and compared with the post-interventional coagulation zone. Temperature measurements using the proton resonance frequency shift method were performed directly subsequent to energy application. The temperature maps were registered on the contrast-enhanced follow-up MR images acquired 4?weeks after treatment. Areas with temperatures above 50°, 55° and 60°C were segmented and compared with the coagulation zones. Sensitivity and positive predictive value were calculated.

Results

No major complications occurred and all tumours were completely treated. No tumour recurrence was observed at the follow-up examination after 4?weeks. Two patients with secondary liver lesions showed local tumour recurrence after 4 and 7?months. The 60°C threshold level achieved the highest positive predictive value (87.7?±?9.9) and the best prediction of the coagulation zone.

Conclusions

For a threshold-based prediction of the coagulation zone, the 60°C cut-off level achieved the best prediction of the coagulation zone among the tested levels.

Key Points

? Temperature monitoring can be used to survey MR-guided radiofrequency ablation ? The developing ablation zone can be estimated based on post-interventional temperature measurements ? A 60°C threshold level can be used to predict the ablation zone ? The 50°C and 55°C temperature zones tend to overestimate the ablation zone     

Combined PET/MR: Where Are We Now? Summary Report of the Second International Workshop on PET/MR Imaging April 8–12, 2013, Tubingen,Germany

This workshop was held a year after the initial positron emission tomography/magnetic resonance (PET/MR) workshop in Tübingen, which was recently reported in this journal. The discussions at the 2013 workshop, however, differed substantially from those of the initial workshop, attesting to the progress of combined PET/MR as an innovative imaging modality. Discussions were focused on the search for truly novel, unique clinical and research applications as well as technical issues such as reliable and accurate approaches for attenuation and scatter correction of PET emission data. The workshop provided hands-on experience with PET and MR imaging. In addition, structured and moderated open discussion sessions, including six dialogue boards and two roundtable discussions, provided input from current and future PET/MR imaging users. This summary provides a snapshot of the current achievements and challenges for PET/MR.     

Depression and risky alcohol use: an examination of the role of difficulties regulating positive emotions in trauma-exposed individuals

Background: The co-occurrence of depression and risky alcohol use is clinically relevant given their high rates of comorbidity and reciprocal negative impact on outcomes. Emotion dysregulation is one factor that has been shown to underlie this association. However, literature in this area has been limited in its exclusive focus on emotion dysregulation stemming from negative emotions.

Objectives: The goal of the current study was to extend research by exploring the role of difficulties regulating positive emotions in depression symptom severity, risky alcohol use, and their association.

Methods: Participants were 395 trauma-exposed adults recruited from Amazon’s Mechanical Turk (MTurk) platform (56.20% female, M_age = 35.55) who completed self-report questionnaires.

Results: Zero-order correlations among depression symptom severity, the three subscales of difficulties regulating positive emotions, and risky alcohol use were positive. Two subscales of difficulties regulating positive emotions—nonacceptance of positive emotions and difficulties controlling impulsive behavior when experiencing positive emotions—accounted for the relationship between depression symptom severity and risky alcohol use.

Conclusion: Results suggest the importance of incorporating techniques focused on improving positive emotion regulation skills in interventions for risky alcohol use among individuals with depression.     

Kinetics of lymphocytes in Hodgkin's disease

Summary Lymphocyte kinetics was studied in 4 patients withHodgkin's disease (Stage III A and IV B) by means of a single i. v. injection of³H-thymidine (0.15 Ci/g body weight) and autoradiographic analysis of the labelling pattern of blood and tissue lymphocytes over a period of 7–25 days.The cause of the blood lymphocytopenia in the three lymphopenic patients was the accelerated turnover of the majority of the blood lymphocytes. The average turn-over time of the blood lymphocytes in these patients was about 5 days as compared to 27 days in aHodgkin patient without lymphopenia and to 50 days in non-lymphopenic tumour patients. The turnover times of the small blood lymphocytes were about 14 days in the lymphopenic Hodgkin patients and 70–115 days in hematologically normal patients. Lymphocytopoiesis seemed to be increased in the lymph nodes and in the blood inHodgkin's disease. The blood lymphocyte production index was was 61–259 lymphocytes/mm³/day as compared to 40–50 lymphocytes/mm³/day in hematologically normal patients. The generation time of the lymphopoietic cells was estimated to be approximately 24 hours.Our data suggest that the activity of the disease was correlated with accelerated turnover of lymphocytes and increased lymphocytopoiesis.

---

Zusammenfassung Bei 4 Patienten mit Lymphogranulomatose (Stadium III A und IV B) wurde die Kinetik von Blut- und Gewebslymphozyten nach einer Einzelinjektion von³H-Thymidin autoradiographisch untersucht.Bei den 3 lymphopenischen Patienten war die Lymphopenie des Blutes durch einen gesteigerten Umsatz der Blutlymphozyten bedingt. Die mittlere Umsatzzeit der Blutlymphozyten betrug bei diesen Patienten 5 Tage, verglichen mit einer mittleren Umsatzzeit von 27 Tagen bei einem Lymphogranulom-Patienten ohne Lymphopenie und von etwa 50 Tagen bei nicht-lymphopenischen Tumorpatienten. Die mittlere Umsatzzeit der kleinen Blutlymphozyten wurde bei den lymphopenischen Lymphogranulomatose-Patienten mit 14 Tagen und bei nicht-lymphopenischen Tumorpatienten mit 70–115 Tagen berechnet. Die Lymphozytopoese bei den Lymphogranulomatose-Patienten war erhöht. Das galt gleichermaßen für die vergrößerten Lymphknoten und das Blut. Der Blutlymphozyten-Produktionsindex betrug 61-259 Lymphozyten/mm³/Tag im Vergleich zu 40–50 Lymphozyten/mm³/Tag bei hämatologisch normalen Patienten. Die Generationszeit der lymphopoetischen Zellen ließ sich auf 24 Stunden schätzen.Die Befunde weisen darauf hin, daß bei der Lymphogranulomatose die Aktivität des Krankheitsprozesses mit gesteigertem Lymphozytenumsatz und stimulierter Lymphozytopoese korreliert ist.

---

---

Research carried out in the Forschergruppe für Experimentelle und Klinische Leukämieforschung, supported by the Deutsche Forschungsgemeinschaft.     

Effect of surfaces on fluid-phase prekallikrein activation

The activation of prekallikrein by factor XII fragments (XIIf), during incubation in plastic tubes was previously noted to be increased by high molecular weight (HMW) kininogen as well as other plasma proteins. In this report, we investigated the mechanism responsible for this increase. Although we confirmed that HMW kininogen, bovine serum albumin, fibrinogen, cold insoluble globulin, and mixed phospholipids apparently increased prekallikrein activation, we found that the product of prekallikrein activation (kallikrein) lost substantial activity in less than 0.5 min after exposure to a variety of fresh surfaces. This loss was partially prevented by the presence of various proteins and phospholipids. Similar protection against inactivation of XIIf, the enzyme in this reaction, was also found. In contrast, no loss of the substrate, prekallikrein, was observed during incubation. The loss of kallikrein activity was found to be proportional to the surface area of the incubation vessel as well as the concentration of kallikrein. Further loss of kallikrein activity could also be prevented by pretreating the vessel with kallikrein. We therefore conclude that various substances apparently affect prekallikrein activation in a purified system by preventing the enzyme and product in the reaction mixture from losing activity due to adsorption to a surface.     

Fibrinogen biosynthesis in isolated guinea pig megakaryocytes

Fibrinogen synthesis was investigated in guinea pig megakaryocytes. Purified megakaryocytes were incubated with 35S-methionine in methionine-free incubation medium for 18 hours. Newly synthesized fibrinogen in megakaryocyte lysates enriched with purified carrier guinea pig fibrinogen was immunoprecipitated with a specific anti- guinea pig fibrinogen antiserum produced in rabbits. Proteins in the immunoprecipitates were analyzed with a 3.5% to 10.0% gradient polyacrylamide slab gel electrophoresis and auto-radiography. Radioactivity was detected in a protein band of 340,000 daltons. In order to verify fibrinogen synthesis, immunoprecipitate was analyzed by two-dimensional slab gel electrophoresis: (1) the first dimension separated unreduced fibrinogen using a 3.5% to 10.0% gradient gel; (2) following reduction by 2-beta-mercaptoethanol, fibrinogen chains were separated in the second dimension using a 10% gel. Alpha, beta, and gamma fibrinogen chains, which represented carrier guinea pig plasma fibrinogen, were visualized by Coomassie brilliant blue. Autoradiography identified the incorporation of radioactivity into the three fibrinogen chains. In control experiments, immunoprecipitates, produced by exposing megakaryocyte lysates to preimmune rabbit serum and goat anti-rabbit IgG, were also analyzed by the two-dimensional gel system. Radioactivity was not detected in sites corresponding to the migration of fibrinogen subunits. The study demonstrates that isolated guinea pig megakaryocytes can synthesize fibrinogen. The electrophoretic mobility of newly synthesized fibrinogen and subunits is similar to that of guinea pig plasma fibrinogen.     

Pulmonary vascular effects of hydralazine in a canine preparation of pulmonary thromboembolism

Pulmonary arterial pressure (PAP)-flow coordinates were obtained in 14 anesthetized dogs before and after pulmonary hypertension was induced with autologous blood clots. Cardiac output (CO) was altered by systemic arteriovenous fistulas. The PAP-CO coordinates were always rectilinear. Before emboli, the mean vascular closing or outflow pressure (the pressure intercept of the PAP-CO line) was 8.8 +/- 2.1 (SD) mm Hg. Emboli increased PAP (15.1 +/- 1.6 to 36.5 +/- 3.5 mm Hg; p less than .001) and decreased CO (3.8 +/- 0.6 to 2.4 +/- 0.8 liters X min-1; p less than .001). Incremental resistance (the slope of the PAP-CO line) only increased slightly. On the other hand, the marked increase in PAP was predominantly due to an increase in effective outflow pressure (from 8.8 +/- 2.1 to 28.6 +/- 3.6; p less than .001). Hydralazine was administered in a dose sufficient to double CO. This did not affect PAP and caused an inconsistent and small decrease in incremental resistance. However, a consistently significant decrease in effective outflow pressure, averaging 23%, was observed. In this canine preparation of pulmonary hypertension the predominant effect of hydralazine appears to be a decrease in the mean vascular closing or outflow pressure.     

The effects of colloid solutions on renal proximal tubular cells in vitro

Renal failure is a common complication of critically ill patients. Colloids such as hydroxyethyl starch (HES), gelatin, or albumin are regularly used for intravascular volume resuscitation, but there are increasing reports about the nephrotoxic side effects of synthetic colloids in septic patients. Therefore, we investigated the influence of colloids (HES130/0.4 (Voluven?), gelatin (Gelafundin?), human albumin, and the crystalloid Sterofundin? ISO on cell viability of human proximal tubular (HK-2) cells. HK-2 cells were incubated with colloids (0.1%-4%) and with equivalent volumes of the crystalloid solution Sterofundin ISO. After 21 hours, cell viability of HK-2 cells was measured by EZ4U assay (dye XTT). Application of HES130/0.4 decreased cell viability significantly in a concentration-dependent manner (86.80% ± 10.79% by 0.5% HES down to 24.02% ± 4.27% by 4% HES). Human albumin (>1.25%) as well as gelatin (>1%) also showed deleterious effects on HK-2 cells. Interestingly, in lower concentrations, human albumin and the crystalloid solution Sterofundin ISO were cytoprotective in comparison with the NaCl control. In conclusion, synthetic and natural colloids showed a harmful impact on HK-2 cells in higher concentrations without any prior proinflammatory stimulus. HES130/0.4 exhibited the most distinctive harmful impact, whereas the application of crystalloid Sterofundin ISO revealed cytoprotective effects.     

Triple arthrodesis

A triple arthrodesis is a fusion of the talocalcaneal, calcaneal cuboid, and talonavicular joints. The purpose is to create a well-aligned, plantigrade, and stable foot for patients with deformity or progressive neurologic and arthritic conditions. This article is a comprehensive overview of the procedure. However effective, triple arthrodesis is a challenging procedure for even the most skilled surgeon.