Combined 18F-FDG and 11C-methionine PET scans in patients with newly progressive metastatic prostate cancer.

Metastatic prostate cancer may respond initially to hormone suppression, with involution of tumor sites, but ultimate tumor progression is inevitable. Our aim was to detect the proportion of bone and soft-tissue lesions that represent metabolically active tumor sites in patients with progressive metastatic prostate cancer. METHODS: In a prospective study, we compared 18F-FDG and L-methyl-11C-methionine (11C-methionine) PET with conventional imaging modalities (CIM), which included the combination of 99mTc-methylene diphosphonate scintigraphy, CT, or MRI. Twelve patients with prostate cancer, increasing levels of prostate-specific antigen (PSA), and at least 1 site (index lesion) with new or increasing disease on CIM were studied. The total numbers of soft-tissue and bone-tissue lesions, in a site-by-site comparison, were calculated for all imaging modalities. RESULTS: The sensitivities of 18F-FDG PET and 11C-methionine PET were 48% (167/348 lesions) and 72.1% (251/348 lesions), respectively, with CIM being used as the 100% reference (348/348). 11C-Methionine PET identified significantly more lesions than 18F-FDG PET (P < 0.01). All 12 patients with progressive metastatic prostate cancer had at least 1 lesion site of active metabolism for 18F-FDG or 11C-methionine, which could be used as an index lesion to monitor the metabolic response to therapy. A significant proportion of lesions (26%) had no detectable metabolism of 18F-FDG or 11C-methionine. Although technical factors cannot be totally excluded, we believe that metabolically inactive sites may be necrotic or dormant. More than 95% (251/258) of metabolically active sites (72% of the total number of lesions detected by CIM) metabolize 11C-methionine. 18F-FDG uptake is more variable, with 65% of metabolically active sites (48% of the total number of lesions detected by CIM). CONCLUSION: These findings reflect the different biologic characteristics of the lesions in a heterogeneous tumor such as prostate cancer and suggest that a time-dependent metabolic cascade may occur in advanced prostate cancer, with initial uptake of 11C-methionine in dormant sites followed by increased uptake of 18F-FDG during progression of disease.     

Radial force and wall apposition of balloon-expandable vascular stents in eccentric stenoses: an in vitro evaluation in a curved vessel model

PURPOSE: Important criteria for optimized stent implantation are high radial force and complete apposition of the stent itself. The aim of this study was to develop a simple method to assess these parameters under controlled experimental conditions and to compare vascular stents of different designs with regard to these parameters. MATERIALS AND METHODS: Five balloon-expandable stents of different designs (Jostent Flex, MAC stent, ML-Tristar, ML-Ultra, and S670) were tested. Fourteen stents of each type were implanted in a curved plastic vessel model (curve radius, 10 mm; lumen diameter, 3.5 mm) with use of a balloon inflation pressure of 12 atm. Part of the model was a nonflexible eccentric stenosis which was 2 mm or 8 mm in length. After stent implantation, a stenosis of 10%-70% was induced and radial force of the stent struts was measured at the site of the stenosis. The apposition of the stent to the vessel wall was imaged by high-resolution radiography. RESULTS: Analysis of variance showed significant differences of radial force between the tested stents (P <.001). The ML-Tristar and ML-Ultra stents had the highest radial force with maximum mean values of 687 cN and 846 cN at a stenosis of 70% in the model with the long stenosis. The radial force of the S670 stent was the lowest whereas the MAC stents showed an intermediate radial force. Radial force of the ML-Ultra stent was as much as 3.8 times higher than the force of the S670 stent (P <.001). Fifty percent of the ML-Tristar and ML-Ultra stents did not expand sufficiently to touch the vessel surface at the outer curvature. With an inflation pressure of 17 atm, complete apposition of these stents was achieved. The highest number of apposition irregularities was found in the S670 group (13 of 14 stents), whereas the MAC stents revealed the lowest number of irregular appositions (three of 14 stents). A significant correlation was found between the number of interconnecting struts and the number of irregular apposition events (P <.01). CONCLUSIONS: This model allows an accurate in vitro evaluation of different stent parameters, such as apposition to the vessel wall and radial force. None of the investigated stents showed optimal results with respect to both parameters. The apposition behavior was significantly influenced by the architecture of the stents.     

Emergency thoracotomy in the pre-hospital setting: a procedure requiring clarification.

OBJECTIVE: The aim of this study is to investigate the influence of Emergency Thoracotomy (ET) on mortality in a group of patients suffering from severe thoracic trauma requiring Helicopter Emergency Medical Service (HEMS) transfer to hospital. This is not clearly defined especially when thoracotomy takes place in the pre-hospital setting. METHODS: A retrospective review of 670 consecutive patients with severe thoracic trauma, transferred to The Royal London Hospital by HEMS between November 1994 and December 2002. ET (on scene, in the Accident and Emergency (A&E) department or in the operating theatre) was performed in 53 patients (7.7%). Both univariate and multivariate analyses were performed to evaluate ET as an independent predictor of mortality. RESULTS: There were 510 males and 160 females with a mean Injury Severity Score (ISS) of 35.12+/-17.5. Univariate analysis identified ET to be a predictor of mortality (OR=0.15, 95% CI=0.07-0.30). However, with multivariate analysis, ET was not found to be an independent predictor of mortality (OR=1.93, 95% CI=0.61-6.1). The independent predictors of mortality identified were: age>60 years (OR 5.57, 95% CI 2.19-14.16), Glasgow Coma Score <8 at the scene (OR=7.4, 95% CI=3.15-17.46), ISS>25 (OR 5.3, 95% CI=1.64-17.11), need for intubation at the scene (OR=2.80, 95% CI=1.022-7.69), oxygen saturation in A&E (<89%) (OR=2.39, 95% CI=1.13-5.05), haemothorax (OR=3.30, 95% CI=1.53-7.13) and bilateral injury (OR=3.1, 95% CI=1.51-6.61). CONCLUSIONS: Our study has shown that when confounding variables are accounted for, ET is not a predictor of mortality following severe chest trauma. This implies that in a well-selected group of patients it may be a significant and life-saving procedure.     

Is three-dimensional computed tomography reconstruction justified before endovascular aortic aneurysm repair?

OBJECTIVES: The endovascular management of abdominal aortic aneurysm (AAA) relies on accurate preoperative imaging for proper patient selection and operative planning. Three-dimensional (3-D) computed tomography (CT) with reformatted images perpendicular to blood flow has gained popularity as a method of AAA assessment and image-based planning before endovascular aneurysm repair (EVAR). The current study was undertaken to determine the interobserver agreement of AAA measurements obtained with axial CT and reformatted 3-D CT and to compare the consistency of the 2 methods in selecting patients for EVAR. METHODS: Eight observers assessed the axial CT and reformatted 3-D CT scans for 5 patients with AAAs to determine whether the patients were candidates for EVAR. 3-D CT with multiplanar reformatted images was performed by Medical Media Systems (MMS). Each observer measured the length and diameter of the proximal neck, maximal AAA, aortic bifurcation, common iliac diameter, and aortic angulation. The proximal neck and common iliac arteries were also assessed for thrombus, calcification, and tortuosity. Agreement of the measurements on axial CT scans was compared with those on MMS CT scans by calculating the kappa statistic. Complete agreement was defined as kappa = 1.0. The limits of agreement between observers were also calculated. RESULTS: The cumulative interobserver agreement of MMS CT scans (kappa =.81) was greater than for axial CT scans (kappa =.59). The kappa value for each of the diameter measurements was greater with the MMS CT scans. In 79% of cases the observers' measurements were less than 2 mm from the mean with MMS CT, compared with 59% for axial CT. The kappa value for deciding whether a patient was an endograft candidate on the basis of aortic neck was greater with the MMS CT (0.92 vs 0.63). The limits of agreement between observers were also better with the MMS CT. CONCLUSIONS: The interobserver agreement in planning EVAR is significantly better with MMS CT compared with traditional axial CT. The routine use of MMS CT appears justified before EVAR to improve the accuracy and consistency of patient selection.     

The Influence of Vibration on Muscle Activation and Rate of Force Development during Maximal Isometric Contractions

At present there appears to be a need for research conducted on the effects of vibration on the contractile ability of skeletal muscle tissue. The aim of this study was to address this issue by examining the effects of a superimposed muscle/tendon vibration at 50.42±1.16 Hz (acceleration 13.24 ± 0.18ms^-2: displacement ≈5mm) on muscular activation and maximal isometric contraction. Sixteen participants with a mean age, body mass, and height of 22 ± 4.4 years, 73.2 ± 11.7 kg and 173.1 ± 9.7 cms, respectively, were recruited for this study. Electromyography and accelerometry from the rectus femoris, and maximal isometric force data characteristics were collected from the dominant limb under conditions of vibration, and no-vibration. A superimposed 50 Hz vibration was used during the contraction phase for the maximal isometric leg extension for the condition of vibration. A one-way ANOVA revealed no significant (p > 0.05) differences between the vibration and no-vibration conditions for peak normalized EMG_RMS (84.74% Vs 88.1%) values. An ANOVA revealed significant (p > 0.05) differences between the peak fundamental frequencies of the FFT between the conditions vibration (27.1 ± 12.2 Hz) and no-vibration (9.8 ± 3.5 Hz). Peak isometric force, peak rate of force development, rate of force development at times 0.05, 0.01, 0.1, 0.5 seconds, and rate of force development at 50, 75, and 90% of peak force were not significantly different. The results of this study suggest that the application of vibration stimulation at 50 Hz during the contraction does not contribute to muscle activation, or enhance force production for maximal isometric contractions.

Key Points

• The application of a vibratory stimulation to the human body increases the normal acceleration resulting in an increase in force and a change in performance
• This study was to address this issue by examining the effects of a direct superimposed muscle/tendon vibration at 50 Hz on isometric strength characteristics
• No improvement or change in isometric force or rate of force development
• No changes to peak normalized EMG_RMS values

Key words: Strength, oscillations, isometric, peak, muscle activation     

Medial portal technique for single-bundle anatomical Anterior Cruciate Ligament (ACL) reconstruction

The aim of the paper is to describe the medial portal technique for anatomical single-bundle anterior cruciate ligament (ACL) reconstruction. Placement of an ACL graft within the anatomical femoral and tibial attachment sites is critical to the success and clinical outcome of ACL reconstruction. Non-anatomical ACL graft placement is the most common technical error leading to recurrent instability following ACL reconstruction. ACL reconstruction has commonly been performed using a transtibial tunnel technique in which the ACL femoral tunnel is drilled through a tibial tunnel positioned in the posterior half of the native ACL tibial attachment site. ACL reconstruction performed using a transtibial tunnel technique often results in a vertical ACL graft, which may fail to control the combined motions of anterior tibial translation and internal tibial rotation which occur during the pivot-shift phenomenon. The inability of a vertically oriented ACL graft to control these combined motions may result in the patient experiencing continued symptoms of instability due to the pivot-shift phenomenon. The medial portal technique in which the ACL femoral tunnel is drilled through an anteromedial or accessory anteromedial portal allows consistent anatomical ACL tunnel placement. This paper describes the advantages of the medial portal technique, indications for the technique, patient positioning, proper portal placement, anatomical femoral and tibial tunnel placement, graft tensioning and fixation.     

Intraprostatic testosterone and dihydrotestosterone. Part I: concentrations and methods of determination in men with benign prostatic hyperplasia and prostate cancer

Owing to inconsistencies and methodological differences, the present peer-reviewed literature lacks conclusive data on the intraprostatic levels of androgens, in particular dihydrotestosterone (DHT), in untreated benign prostatic hyperplasia (BPH) and prostate cancer. To date, no difference has been shown between DHT concentrations in normal prostatic tissue and BPH, and nor has a difference been shown in DHT concentrations between the histologically distinct regions of the prostate. Recent literature has also failed to show a consistent difference in androgen level between BPH and prostate cancer. The role of intraprostatic DHT in the pathogenesis of BPH and in the initiation and progression of prostate cancer thus remains to be established. Increased knowledge of the mechanisms of the androgenic steroid pathways in prostatic diseases, with a special focus on intraprostatic androgen levels may lead to more optimized and more personalized forms of treatment, and probably new therapeutic targets as well.     

Mimicking of cerebral autoregulation by flow-dependent cerebrovascular resistance: a feasibility study

Understanding circulatory autoregulation is essential for improving physiological control of rotary blood pumps and support conditions during cardiopulmonary bypass (CPB). Cerebral autoregulation (CAR), arguably the most critical, is the body's intrinsic ability to maintain sufficient cerebral blood flow (CBF) despite changes in aortic perfusion pressure. It is therefore imperative to include this mechanism into computational fluid dynamics (CFD), particle image velocimetry (PIV), or mock circulation loop (MCL) studies. Without such inclusions, potential losses of CBF are overestimated. In this study, a mathematical model to mimic CAR is implemented in a MCL‐ and PIV‐validated CFD model. A three‐dimensional model of the human vascular system was created from magnetic resonance imaging records. Numerical flow simulations were performed for physiological conditions and CPB. The inlet flow was varied between 4.5 and 6 L/min. Arterial outlets were modeled using vessel‐specific, flow‐dependent cerebrovascular resistances (CVRs), resulting in a variation of the pressure drop between 0 and 80 mm Hg. CBF is highly dependent on the level of CAR during CPB. By varying the CVR parameters up to the beginning of plateau phase, it can be regulated between 0 and 80% of physiological CBF. So while implementing autoregulation, CBF remains unchanged during a simulated native cardiac output of 5 L/min or CPB support of 6 L/min. Neglecting CAR, constant backflow from the brain occurs for some cannula positions. Using flow‐dependent CVR, CBF returns to its baseline at a rate of recovery of 0.25 s. Results demonstrate that modeling of CAR by flow‐dependent CVR delivers feasible results. The presented method can be used to optimize physiological control of assist devices dependent upon different levels of CAR representing different patients.     

Implementation of cerebral autoregulation into computational fluid dynamics studies of cardiopulmonary bypass

Peri‐ or postoperative neurological complications are among the main risks for patients undergoing extracorporeal circulatory support (ECC). Two of the main reasons are an increased risk for strokes and altered flow conditions leading to cerebral hypoperfusion. This is strongly affected by cerebral autoregulation, which is the body's intrinsic ability to provide sufficient cerebral blood flow (CBF) despite changes in cerebral perfusion pressure (CPP). This complex mechanism has been mainly neglected in numerical studies, which have often been applied for analysis of ECC. In this study, a mathematical model is presented to implement cerebral autoregulation into computational fluid dynamics (CFD) studies. CFD simulations of cardiopulmonary bypass (CPB) were performed in a 3D model of the cardiovascular system, with flow variations between 4.5–6 L/min. Cerebral outlets were modeled using an equation to calculate CBF based on CPP. Assuming full regulation, CBF was kept constant for CPP between 80 and 120 mm Hg. A deviation in CBF of 20% occurred for CPP between 55–80 mm Hg and 120–145 mm Hg, respectively. The level of regulation was varied to take possible impairment of cerebral autoregulation into account. Furthermore, chronic hypertension was modeled by increasing the baseline CPP. Results indicate that even for full autoregulation, CBF is decreased during CPB. It is even lower for impaired autoregulation and hypertensive patients, demonstrating the strong impact of autoregulation on CBF. It is therefore imperative to include this mechanism into CFD studies. The presented model can help to improve CPB support conditions based on patient‐specific autoregulation parameters.     

Cavitation bubble cluster activity in the breakage of kidney stones by lithotripter shockwaves

BACKGROUND AND PURPOSE: There is strong evidence that cavitation bubble activity contributes to stone breakage and that shockwave-bubble interactions are involved in the tissue trauma associated with shockwave lithotripsy. Cavitation control may thus be a way to improve lithotripsy. MATERIALS AND METHODS: High-speed photography was used to analyze cavitation bubble activity at the surface of artificial and natural kidney stones during exposure to lithotripter shockwaves in vitro. RESULTS: Numerous individual bubbles formed on the surfaces of stones, but these bubbles did not remain independent but rather combined to form clusters. Bubble clusters formed at the proximal and distal ends and at the sides of stones. Each cluster collapsed to a narrow point of impact. Collapse of the proximal cluster eroded the leading face of the stone, and the collapse of clusters at the sides of stones appeared to contribute to the growth of cracks. Collapse of the distal cluster caused minimal damage. CONCLUSION: Cavitation-mediated damage to stones is attributable, not to the action of solitary bubbles, but to the growth and collapse of bubble clusters.