Measuring the spatiotemporal evolution of accident hot spots.

One reality of transportation systems is that vehicular accidents can happen practically anywhere and at any time. An increasing body of research suggests though that spatial and/or temporal dependencies (i.e., clusters or hot spots) among accidents likely exist. Along with understanding where and when such spatiotemporal dependencies may occur, another important facet to consider is the geographic extent or area associated with the hot spots. For example, an accident hot spot may involve a small, isolated portion of the transportation system or a much more expansive geographic area. Better delineation and quantification of the morphological characteristics of accident hotspots can provide valuable decision support for planning for accident hot spot mitigation and prevention. As the size and shape of accident hot spots may evolve over time, the capability to track such dynamics is vital, especially with respect to the identification of processes effecting hot spot occurrence as well as assessments of the efficacy of efforts to mitigate factors underlying hot spot development. To this end, a Geographical Information Systems (GIS) based framework is outlined to facilitate the analysis of the morphological characteristics of hot spots over time. The analysis framework is applied to a case study of vehicular accidents reported over a two-year period to demonstrate its practical utility. The application results indicate that patterns of change in hot spot morphology can be effectively quantified and a variety of informative spatial and temporal patterns can be detected.

Radioembolization of hepatic tumors: flow redistribution after the occlusion of intrahepatic arteries.

PURPOSE: Radioembolization using 90yttrium is an emerging therapy option for unresectable liver malignancies. In order to reduce the number of yttrium injections, endovascular occlusion of a segmental hepatic artery has been proposed. The aim of this study was to assess whether sufficient vascular redistribution of the occluded liver segments through intrahepatic collaterals can be observed. MATERIALS AND METHODS: 27 patients with hepatocellular carcinoma (n = 16) or hepatic metastases (n = 11) were studied. Hepatic angiography was performed on average 16 days prior to radioembolization. The segment II/III artery (n = 9) or the segment IV artery (n = 18) was occluded using coils. Technectium-99m-labeled macroaggregated albumin (99mTc-MAA) was injected into the right and the remaining part of the left hepatic artery in order to identify any hepatic volume not included in the perfused area. Patients underwent a SPECT/CT on average 1 h after the 99mTc-MAA injection. Two radiologists evaluated the SPECT/CT scans regarding the presence of non-perfused hepatic segments. Furthermore, hepatic perfusion was assessed by digital subtraction angiography (DSA) on the day of radioembolization. RESULTS: In 16/27 patients (59%) a perfusion of the occluded liver segment was visible on the SPECT/CT scan. In 8/11 patients without flow redistribution at the time of the SPECT/CT, perfusion of the occluded segment through hepatic collaterals was observed during angiography prior to radioembolization. Hence, flow redistribution was eventually found in 24/27 patients (89%). CONCLUSION: Flow redistribution after the occlusion of intrahepatic arteries prior to radioembolization can be successfully induced in the majority of patients with anatomical variants of the hepatic arteries.

Diagnostic accuracy of fused positron emission tomography/magnetic resonance mammography: initial results.

OBJECTIVES: The aim of this study was to evaluate the diagnostic accuracy of fused fluoro-deoxy-D-glucose positron emission tomography/magnetic resonance mammography (FDG-PET/MRM) in breast cancer patients and to compare FDG-PET/MRM with MRM. METHODS: 27 breast cancer patients (mean age 58.9±9.9 years) underwent MRM and prone FDG-PET. Images were fused software-based to FDG-PET/MRM images. Histopathology served as the reference standard to define the following parameters for both MRM and FDG-PET/MRM: sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy for the detection of breast cancer lesions. Furthermore, the number of patients with correctly determined lesion focality was assessed. Differences between both modalities were assessed by McNemars test (p<0.05). The number of patients in whom FDG-PET/MRM would have changed the surgical approach was determined. RESULTS: 58 breast lesions were evaluated. The sensitivity, specificity, PPV, NPV and accuracy were 93%, 60%, 87%, 75% and 85% for MRM, respectively. For FDG-PET/MRM they were 88%, 73%, 90%, 69% and 92%, respectively. FDG-PET/MRM was as accurate for lesion detection (p = 1) and determination of the lesions' focality (p = 0.7722) as MRM. In only 1 patient FDG-PET/MRM would have changed the surgical treatment. CONCLUSION: FDG-PET/MRM is as accurate as MRM for the evaluation of local breast cancer. FDG-PET/MRM defines the tumours' focality as accurately as MRM and may have an impact on the surgical treatment in only a small portion of patients. Based on these results, FDG-PET/MRM cannot be recommended as an adjunct or alternative to MRM.

[Selective internal radiotherapy (SIRT) for hepatocellular carcinoma]. / Selektive interne Radiotherapie (SIRT) beim hepatozellulären Karzinom.

Microsphere-based radioembolization represents a new generation of therapeutics in interventional oncology. The intrahepatic application of radioactive microspheres via the hepatic artery allows locoregional therapy of diffuse or multifocal liver tumors, for which to date systemic therapy was the only remaining option. The current standard for this selective internal radiotherapy or radioembolization is yttrium-90 glass or resin microspheres. This review discusses the indications, the technique, and the therapeutic results of microsphere-based radioembolization.

Angiography-based C-arm CT for the assessment of extrahepatic shunting before radioembolization.

PURPOSE: To retrospectively assess the accuracy of angiography-based C-arm CT for the detection of extrahepatic shunting before SIRT. MATERIALS AND METHODS: 30 patients (mean age: 64+/-12 years) with hypervascularized hepatic tumors underwent hepatic angiography, coil embolization of gastrointestinal collaterals and 99mTc-macroaggregated albumin (MAA) SPECT/CT before SIRT. Before MAA injection via a microcatheter from the intended treatment position, an angiography and angiography-based C-arm CT (XperCT, Philips Healthcare) were acquired. Angiographies and XperCT were performed from 48 microcatheter positions followed by MAA injections and MAA-SPECT/CT. MAA-SPECT/CT served as the reference standard for determining the accuracy of hepatic arteriography and C-arm CT for the detection of extrahepatic shunting. RESULTS: MAA-SPECT/CT revealed extrahepatic shunting in 5 patients (17%). Hepatic arteriography yielded a true negative in 22 (73%), a false negative in 5 (17%), and an unclear result in 3 patients (10%). C-arm CT yielded a true positive in 3 (10%), true negative in 24 (80%), false positive in 1 (3%), and false negative in 2 patients (7%). The specificity and the NPV of hepatic arteriography for the detection of extrahepatic shunting were 88% and 81%, respectively. For C-arm CT the sensitivity, specificity, PPV, NPV, and accuracy for the detection of extrahepatic shunting were 60%, 96%, 75%, 92%, and 90%, respectively. CONCLUSION: C-arm CT offers additional information to angiography when assessing SIRT patients for extrahepatic shunting. More accurate detection of extrahepatic shunting may optimize the workflow in SIRT preparations by avoiding unnecessary repeat angiographies.

Computer-aided detection (CAD) and assessment of malignant lesions in the liver and lung using a novel PET/CT software tool: initial results.

PURPOSE: To determine the feasibility of a PET/CT software tool (PET computer-aided detection: PET-CAD) for automated detection and assessment of pulmonary and hepatic lesions. MATERIALS AND METHODS: 20 consecutive patients with colorectal liver metastases and 20 consecutive patients suffering from non-small cell lung cancer (NSCLC) were examined with FDG-PET/CT. In a first step the maximum standardized uptake values (SUV (max)) of non-tumorous liver and lung tissues were determined manually. This value was used as a threshold value for software-based lesion detection. The number of lesions detected, their SUV (max), and their sizes in the x, y, and z-planes, as automatically provided by PET-CAD, were compared to visual lesion detection and manual measurements on CT. RESULTS: The sensitivity for automated detection was 96 % (86 - 99 %) for colorectal liver metastases and 90 % (70 - 99 %) for lung lesions. The positive predictive value was 80 % for liver and 68 % for lung lesions. The mean SUV (max) of all lung lesions was 9.3 and 8.8 for the liver lesions. When assessed by PET-CAD, the mean lesion sizes for liver lesions in the x, y, and z-planes were 4.3 cm, 4.6 cm, and 4.2 cm compared to 3.5 cm, 3.8 cm, and 3.6 cm for manual measurements. The mean lesion sizes of lung lesions were 7.4 cm, 7.7 cm, and 8.4 cm in the x, y, and z-planes when assessed by PET-CAD compared to 5.8 cm, 6.1 cm, and 7.1 cm when measured manually. Using manual assessment, the lesion sizes were significantly smaller in all planes (p < 0.005). CONCLUSION: Software tools for automated lesion detection and assessment are expected to improve the clinical PET/CT workflow. Before implementation in the clinical routine, further improvements to the measurement accuracy are required.

[Selective internal radiotherapy (radioembolization) and radiation therapy for HCC--current status and perspectives]. / Selektive interne Radiotherapie (Radioembolisation) und Strahlentherapie beim HCC--Stand und Perspektiven.

Microsphere and particle technologies for the selective transport of tumoricidal agents or radiation represent a new generation of therapeutics in interventional oncology. The intrahepatic application of radioactive microspheres via the hepatic artery, for instance, allows locoregional therapy of diffuse or multifocal liver tumours, for which to date systemic therapy was the only remaining option. Current standards for this selective internal radiotherapy or radioembolisation are 90-yttrium glass or resin microspheres. Indication, technique, and the current results are extensively discussed. In addition to 90-yttrium microspheres, other radiopharmaceuticals, such as 131-iodine or 188-rhenium lipiodol, have been successful used for SIRT. As a result of new, more selective radiation techniques, internal radiotherapy for the locoregional treatment of HCC has been recently complemented by an increasing use of percutaneous radiotherapy.

Efficacy of azimilide and dofetilide in the dog right atrial enlargement model of atrial flutter.

INTRODUCTION: Azimilide dihydrochloride blocks both the rapid (I(Kr)) and slow (I(Ks)) components of the delayed rectified K+ current; dofetilide blocks only I(Kr). Their efficacies were assessed on atrial flutter reentrant circuits in dogs with surgically induced right atrial enlargement. METHODS AND RESULTS: Multiple biopsies of the tricuspid valve and banding of the pulmonary artery in male mongrel dogs made them susceptible, about 3 weeks postoperatively, to stimulation-induced sustained (5 min or longer) atrial flutter. Azimilide 3 mg/kg administered intravenously (i.v.) terminated flutter in 8 of 8 dogs, but a slower, nonsustained arrhythmia could be reinduced in 5. In these 5 dogs, azimilide 10 mg/kg terminated flutter and prevented reinduction. This dose increased effective refractory period significantly more in the slow conduction zone (25%) than in the normal zone (17%) and increased flutter cycle length (37%). Termination followed progressive conduction delay in the slow zone of the reentrant circuit. Dofetilide 1 microg/kg i.v. terminated flutter in 6 of 6 dogs, but the arrhythmia could be reinduced. At 3 microg/kg, flutter terminated in all dogs and could not be reinduced. Dofetilide also increased the effective refractory period significantly more in the slow zone (17%) than in the normal zone (12%) and increased cycle length (33%), leading to interruption of the arrhythmia circuit. CONCLUSION: In the canine right atrial enlargement model of circus movement atrial flutter, both azimilide 10 mg/kg i.v. and dofetilide 3 microg/kg i.v. were 100% effective in terminating flutter and preventing reinduction. Efficacy relied on a similar mechanism of differentially prolonged refractoriness in the slow conduction component of the reentrant circuit where drug-induced termination occurred.

Effects of azimilide dihydrochloride on circus movement atrial flutter in the canine sterile pericarditis model.

INTRODUCTION: The effects of a Class III agent, azimilide dihydrochloride, on atrial flutter circuits were studies in a functional model of single loop reentrant atrial flutter using dogs, 3 to 5 days after production of sterile pericarditis. METHODS AND RESULTS: A computerized mapping system was used to construct activation maps from 138 to 222 epicardial sites in the right atrium. Doses of 3, 10, and 30 mg/kg i.v. azimilide dihydrochloride were analyzed in 8 dogs in which sustained atrial flutter lasting more than 30 minutes was induced by burst pacing. Atrial flutter was always due to single loop circus movement reentry in the lower right atrium. At 3 mg/kg, azimilide dihydrochloride terminated atrial flutter in 2 dogs; however, atrial flutter was reinduced. At 10 mg/kg, atrial flutter was terminated in all 8 dogs but was reinduced in 4 dogs with slower rate. At 30 mg/kg, atrial flutter was terminated in the remaining 4 dogs and could not be reinduced. Atrial flutter cycle length always increased prior to termination. Isochronal activation maps showed that the increase in cycle length was due to additional conduction delays in the slow zone of the reentrant circuit. The site of termination was always located within the slow conduction zone situated in the lower right atrium between the line of functional conduction block and the AV ring. Effective refractory periods (ERPs) were measured at selected sites in the slow zone and normal zone at twice diastolic threshold for the 10 mg/kg dose. Azimilide preferentially prolonged ERP in the slow zone (42.4 +/- 20.1 msec, mean +/- SD) compared with the normal zone (23.3 +/- 15.4 msec, P < 0.0001). The increase in cycle length corresponded with the increase in ERP in the slow zone. CONCLUSIONS: In a functional model of circus movement atrial flutter, azimilide dihydrochloride terminates and prevents reinduction of atrial flutter by a preferential increase in refractoriness leading to further conduction delay and conduction block in the slow zone of the functional reentrant circuit.

[Preliminary study on the variability of the fetal cerebral velocimetry in various vessels of the Circle of Willis]. / Etude préliminaire de la variabilité de la vélocimétrie cérébrale foetale au niveau des différents vaisseaux du polygone de Willis.

The authors have tried to analyse in a small series, the possibility as well as the variability of blood flow velocity waveforms in the different vessels of the circle of willis using colour Doppler. Fourteen patients were assessed. The 14 fetuses were of normal growth and/or had normal umbilical arterial blood flow velocity waveforms as well as normal uterine blood flow. The mean term at the time of examination was 23.8 +/- 2.9 standard deviation with the extremes going from 28.5 standard deviation to 40.5. The examinations were carried out using colour Doppler (Acuson) machine by the abdominal route with a 3.5-5 MHz bi-frequency sound. The vessels that were explored were the middle cerebral artery (CM), posterior cerebral artery (CP), the internal carotid artery (CI), the anterior cerebral artery (CA) in the region of the circle of Willis. CM and CA were able to be recorded in 100% of the cases, CP and CI in 93% of cases (13 out of 14 cases). The difference between he mean index (D/S, D = residual velocity in the diastole, S = maximum velocity in the systole) in each of these vessels was not statistically significant. In 3 out of 16 measurements (19%) the CP index was considered to be pathological while the index in the other vessels was normal, or when a different form of measurement was carried out in the region of CP, it was normal. This was also the case once for CA, but never for CM or CI.(ABSTRACT TRUNCATED AT 250 WORDS)

[Clinical study of preoperative radiotherapy of bladder cancer].

From May 1982 to Nov. 1987, 33 patients with bladder carcinoma were treated with preoperative radiotherapy (20 Gy/5fr) and total cystectomy. The over all 3-year survival rate was 70%. For T1 and T2, 3-year survival rate was 100%, but only 55% and 0% for T3 and T4 respectively. In 23 out of 33 patients, preoperative T-stage was confirmed by TUR-BT. Down-Staging was recognized in 7 out of 23 patients (30%). They were 0 out of 1 patients for Tcis (0%), 2 of 3 for T1 (67%), 3 of 6 for T2 (50%), 2 of 11 for T3 (18%) and 0 of 2 for T4 (0%). This protocol of preoperative radiotherapy is thought to be favorable for T1 and T2 bladder carcinoma, but inadequate for T3 and T4 tumors. Consequently, it is considered that higher dose radiotherapy and postoperative chemotherapy are necessary for T3 and T4 bladder carcinoma.

Küntscher nailing of femoral fractures associated with Austin Moore's prosthesis.

The management of fractures occurring below the tip of an Austin Moore prosthesis varies greatly. Four cases are presented which provides difficulties have been overcome. The new method involves the insertion of a Küntscher nail posterior of the stem of the prosthesis.