Improved positioning of the tibial component in unicompartmental knee arthroplasty with patient-specific cutting blocks.

PURPOSE: Unicompartmental knee arthroplasty (UKA) has recently regained popularity for the treatment of osteoarthritis of the knee. Numerous authors have cited alignment as an important prognostic factor in the survival of UKA. Limb alignment affects not only the longevity of UKA by influencing wear of polyethylene, but also affects the unreplaced contralateral compartment. Malpositioning of the components may result in unequal wear patterns, thus further leading to early failure and additionally influencing clinical outcome as well. However, there is a lack of techniques to assure a high accuracy of the implant positioning. METHODS: In this study, we investigated tibia component alignment of 28 medial UKAs implanted with patient-specific cutting blocks. Three patients were excluded due to bad imaging. Measurements of tibial component alignment from postoperatively computed tomography (CT) scans were compared to respective CT-based preoperative plannings to assess the accuracy of implant positioning. RESULTS: Our results show excellent high accuracy of tibial implant position in tibial varus/valgus (Δ 0.3° ± 1.7°), posterior slope (Δ 1.1° ± 2.6°) and external rotation (Δ 1.5° ± 3.3°). CONCLUSION: We conclude that patient-specific cutting blocks improve the accuracy of tibia component positioning in unicompartmental knee arthroplasty. LEVEL OF EVIDENCE: Case series with no comparison group, Level IV.

[11C](R)-PK11195 positron emission tomography imaging of activated microglia in vivo in Rasmussen's encephalitis.

This study was designed to explore the feasibility of PET using [11C](R)-PK11195 as an in vivo marker of activated microglia/brain macrophages for the assessment of neuroinflammation in Rasmussen's encephalitis (RE). [11C](R)-PK11195 PET was carried out in four normal subjects, two patients with histologically confirmed RE, and three patients with clinically stable hippocampal sclerosis and low seizure frequency. Binding potential maps showing specific binding of [11C](R)-PK11195 were generated for each subject. Regional binding potential values were calculated for anatomically defined regions of interest after coregistration to and spatial transformation into the subjects' own MRI. In one patient with RE who underwent hemispherectomy, the resected, paraffin-embedded brain tissue was stained with an antibody (CR3/43) that labels activated human microglia. Whereas specific binding of [11C](R)-PK11195 in clinically stable hippocampal sclerosis was similar to that in normal brain, patients with RE showed a focal and diffuse increase in binding throughout the affected hemisphere. In RE, [11C](R)-PK11195 PET can reveal in vivo the characteristic, unilateral pattern known from postmortem neuropathologic study. PET imaging of activated microglia/brain macrophages offers a tool for investigation of a range of brain diseases where neuroinflammation is a component and in which conventional MRI does not unequivocally indicate an inflammatory tissue reaction. [11C](R)-PK11195 PET may help in the choice of appropriate biopsy sites and, further, may allow assessment of the efficacy of antiinflammatory disease-modifying treatment.

The functional anatomy of visual-tactile integration in man: a study using positron emission tomography.

The integration of neural signals from different sensory modalities is a prerequisite for many cognitive and behavioural functions. In this study, we have mapped the functional anatomy of the integration of sensory signals across the tactile and visual modalities. Using the PET radiotracer H2(15)O, regional cerebral blood flow (rCBF) changes were measured in eight normal volunteers performing crossmodal recognition of simultaneously presented visual and tactile stimuli using a modified version of the 'arc-circle test'. Whilst intramodal matching within the visual modality led to relative rCBF increases in the visual association cortex, crossmodal matching (visual-tactile), when compared to intramodal matching, was accompanied by relative rCBF increases in the anterior cingulate cortex, inferior parietal lobules, the left dorsolateral prefrontal cortex (DLPFC) and the left claustrum/insular cortex. The pattern of brain activation is congruent with areas of heteromodal and supramodal cortex and indicates that activation of multimodal areas is required to solve the crossmodal problem.

Cerebral control of unimanual and bimanual movements: an H2(15)O PET study.

We measured regional cerebral blood flow (rCBF) during unimanual and bimanual movements using H2(15)O PET. Six healthy volunteers performed unimanual, bimanual-symmetric and bimanual-asymmetric ballistic finger movements. The study was designed to minimize anticipation and preparation of movements. Data were analysed using SPM. Unpredictably paced unimanual movements resulted in significant activation of contralateral primary motor-somatosensory cortex (M1-S1) and mesial frontal cortex (p < 0.001). Performance of symmetric bimanual movements resulted in bilateral activation, but no additional activation of mesial frontal cortex was shown. Comparison of asymmetric with symmetric bimanual movements revealed additional recruitment of mesial frontal cortex (p< 0.001). We suggest that rostral mesial frontal cortex facilitates asymmetric non-mirrored bimanual finger movements.

Impact of whole body positron emission tomography on initial staging and therapy in patients with squamous cell carcinoma of the oral cavity.

The aim of this study is to evaluate the additional clinical information provided by whole body positron emission tomography (PET) with fluorodeoxyglucose (FDG) for initial staging of patients with squamous cell carcinoma (SCC) of the oral cavity. PET scans from the head to the pelvic floor of 34 consecutive patients (22 male, 12 female; mean age 71 years) with histologically confirmed SCC of the oral cavity were retrospectively evaluated. Clinical information including CT of the head and neck and chest X-Ray or chest CT was compared with information on nodal involvement and distant metastases or secondary tumours obtained with PET. The primary tumour was identified with PET in 33 of 34 patients (97%). In 27 Patients (81%) the clinical N-stage was confirmed with PET. In two Patients (6%) additional pathologic loco-regional lymph nodes were found. In five patients more lymph nodes were identified with CT. Distant lesions were seen with PET imaging in bone, lung, mediastinum, liver and colon. In three patients (6%) distant metastases were correctly identified. In another four patients (12%) a secondary cancer was detected. One false positive finding was described with PET. In five of 34 patients (15%) the additional findings as revealed with PET lead to a change of treatment. Whole body PET provides relevant additional information to a standard clinical staging procedure in patients with oral cavity SCC. The detection of distant metastases and secondary primary tumours can have a great impact on patient management.

Direct comparison of F-18-FDG PET and ultrasound in the follow-up of patients with squamous cell cancer of the head and neck.

AIM: The objective of this study was to compare screening ultrasound (US) obtained in patients with squamous cell carcinoma of the head and neck with F-18-FDG PET and to evaluate if US obtained before F-18-FDG PET has the potential to enhance patient management by the detection of additional lesions. METHOD: 28 patients were prospectively included in the study (7 females and 21 males; range: 28-82 years). All had one follow-up examination after surgical treatment and/or radiotherapy using a combination of US and F-18-FDG PET on the same day (6-35 months after the end of treatment). Outcome was determined by either biopsyproven cancer recurrence or negative clinical follow-up for additional 6 months after this examination. RESULTS: Regarding only the regions of the neck evaluated with both methods, US detected 25 suspect lesions vs. 9 lesions detected by F-18-FDG PET. Descriptive statistical analysis showed better sensitivity, specificity and accuracy of F-18-FDG PET. Only in 3 patients a lesion was detected in the same anatomical region using both methods. One patient was false positive with both methods. In another patient US detected a calcified right carotid artery plaque that lead to surgical therapy. CONCLUSION: F-18-FDG PET is better for the detection of clinically relevant lesions in the follow-up of patients with squamous cell carcinoma of the head and neck. In this study, the additional value of morphological information obtained by screening US performed before the PET scan is limited. US may not be a suitable test to improve interpretation of PET examinations.

SPECT in periodic lateralized epileptiform discharges (PLEDs): a form of partial status epilepticus?

Periodic lateralized epileptiform discharges (PLEDs) are a well defined electroencephalographic entity but whether PLEDs represent an ictal condition or not remains debated. Much work has been done using electroencephalography (EEG) but new approaches using cerebral perfusion imaging may give more information about this question. We aimed to evaluate if PLEDs were associated with high regional cerebral blood flow (rCBF). We studied 18 patients with PLEDs and different pathologies, and performed brain single-photon-emission computed tomography (SPECT) during and, for three cases, after the disappearance of PLEDs. Qualitative variations and locations of rCBF were compared with PLEDs. Association with seizures and type of seizures were also assessed. SPECT showed high rCBF in 18/18 patients (100%). The location of PLEDs and high rCBF matched in 17/18 cases (94%). In the three cases where SPECT was performed after PLEDs disappeared, the high rCBF had cleared (100%). Eighteen cases (100%) presented seizures before recording of PLEDs, mainly motor (partial motor or generalized tonic-clonic). Where there was a decreased rCBF (related to a lesion) there was little relationship to PLEDs and all patients with decreased rCBF had an adjacent increased rCBF. These results confirm preliminary case reports. Hyperperfusion adds further to the argument that PLEDs may be related to a form of partial status epilepticus.

Radionuclide imaging in patients with amputations of the lower leg: typical imaging patterns in five cases.

Amputation of the lower leg is not uncommon in elderly patients with chronic infections or vascular problems of the leg and foot, and most often it is performed below the knee or on the distal part of the lower leg (i.e., Syme's amputation). After operation, healing disorders with or without infection can occur, and usually structural imaging methods are performed for diagnosis. Radionuclide imaging using a combination of bone scans and infection scintigraphy can help to identify bone and soft tissue infection. Interpreting radionuclide scans is difficult, because imaging findings after amputation may depend not only on the level of resection and the disease investigated but also on the time that has elapsed since surgery. Typical imaging patterns of bone or infection scintigraphy of five patients are described

Unenhanced versus multiphase MDCT in patients with hematuria, flank pain, and a negative ultrasound.

OBJECTIVES: To compare the impact of unenhanced and contrast-enhanced multi-detector computed tomography (MDCT) for the detection of urinary stones and urinary obstruction in patients with suspected renal colic. METHODS: 95 patients with suspected renal colic underwent a three-phase MDCT for evaluation of the urinary tract. The unenhanced scan and the multiphase examination were reviewed retrospectively by two radiologists for the characterization of urinary stones and signs of obstruction. Results of unenhanced MDCT were compared with those obtained during the second review of the entire multiphase examination. RESULTS: Overall diagnosis of urinary stones revealed an accuracy of 97.0% for unenhanced, and 98.9% for multiphase MDCT with a significant difference between both protocols (mixed-effects logistic regression: odds ratio 3.3; p=0.019). With 3 versus 15 false positive ratings, multiphase MDCT was superior to unenhanced MDCT for the diagnosis of urinary stones. There was no significant difference in detecting signs of obstruction. Inter-reader agreement for overall stone detection was excellent on both unenhanced (kappa 0.84) and multiphase (kappa 0.88) MDCT. CONCLUSION: Contrast-enhanced multiphase MDCT offers distinct advantages compared to an unenhanced approach for the assessment of urinary stone disease, and therefore should be considered as a complementary examination for patients with inconclusive findings.

[Measurement of body composition in daily practice]. / Messung der Köperzusammensetzung im Praxisalltag. Genauigkeit sowie Sinn und Unsinn von Geräten zur Bestimmung der Körperzusammensetzung.

During the last few years bioimpedance analysis (BIA) devices have been heavily promoted for body composition measurements in daily medical practice. The accuracy of these devices is not exactly known. Accordingly we compared in this study 6 different BIA devices, 3 different skinfold callipers with dual energy x-ray absorptiometry (DXA) as the reference methodology. The correlation coefficient between the fat mass assessed by the BIA devices as compared to the DXA methodology varied between r = 0.880 and r = 0.947 (p for all < 0.001). The accuracy of the measurements was better in women than in men and better in individuals with a BMI > 25 kg/m2 than in individuals with a BMI < 25 kg/m2. For daily use the BIA devices are much more user-friendly than the skinfold callipers. It is obvious that the use of the BIA measurement in daily practice does not help much in the assessment of obesity but more so in the assessment (quantification) of the lean body mass (LBM).

The value of PET, CT and in-line PET/CT in patients with gastrointestinal stromal tumours: long-term outcome of treatment with imatinib mesylate.

PURPOSE: Gastrointestinal stromal tumours (GIST) are mesenchymal neoplasms of the gastrointestinal tract that are unresponsive to standard sarcoma chemotherapy. Imaging of GIST patients is done with structural and functional methods such as contrast-enhanced helical computed tomography (ceCT) and positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG). The aim of this study was to compare the prognostic power of PET and ceCT and to evaluate the clinical role of PET/CT imaging. METHODS: All patients with GIST undergoing PET or PET/CT examinations were prospectively included in this study, and the median overall survival, time to progression and treatment duration were documented. The prognostic significance of PET and ceCT criteria of treatment response was assessed and PET/CT was compared with PET and ceCT imaging. Data for 34 patients (19 male, 15 female, 21-76 years) undergoing PET or PET/CT for staging or restaging were analysed. RESULTS: In 28 patients, PET/CT and ceCT were available after introduction of treatment with the tyrosine kinase inhibitor imatinib mesylate (Gleevec; Novartis, Basel, Switzerland). Patients without FDG uptake after the start of treatment had a better prognosis than patients with residual activity. In contrast, ceCT criteria provided insufficient prognostic power. However, more lesions were found on ceCT images than on PET images, and FDG uptake was sometimes very variable. PET/CT delineated active lesions better than did the combination of PET and ceCT imaging. CONCLUSION: Both PET and PET/CT provide important prognostic information and have an impact on clinical decision-making in GIST patients. PET/CT precisely delineates lesions and thus allows for the correct planning of surgical interventions.

Do hardware artefacts influence the performance of head and neck PET scans in patients with oral cavity squamous cell cancer?

OBJECTIVE: The purpose of this study was to evaluate the influence of (68)Ge-based and CT-based attenuation correction as well as two standard image reconstruction algorithms on the appearance of artefacts due to dental hardware. Additionally, the intensity of such artefacts was compared with (18)F-fluorodeoxyglucose (FDG) uptake in patients with known oral cavity squamous cell cancer. METHODS: Thirty-two metallic and non-metallic objects used for dentistry/dental surgery were scanned in a water-bath filled with FDG on a combined PET/CT scanner. Images were reconstructed with either CT-based or (68)Ge-based transmission data and by using iterative reconstruction or filtered backprojection. The intensity of artefacts was assessed visually using a subjective scale from 0 (no artefact visible) to 4 (very strong artefact), and by quantitative measurements. In a second study, images of 30 patients with known squamous cell cancer and dental hardware were retrospectively analysed by two observers, again using a visual assessment grading system. Wilcoxon signed rank test was used for statistical comparisons. RESULTS: Eighteen of 32 objects caused artefacts, which were visible with both attenuation correction methods. CT-based attenuation correction was visually more intense than (68)Ge-based attenuation correction (P<0.0001), and the measured (18)F concentration was also higher (P=0.0002). No difference was found between the reconstruction algorithms. In 28 of 30 patients the primary tumour was visible. FDG uptake in the primary tumour was significantly higher than measured (18)F concentration in artefacts (P<0.0001). CONCLUSION: Attenuation correction of PET images generates artefacts adjacent to dental hardware that mimic FDG uptake. In this series, the primary lesion was discriminated from artefacts.

Interfemur variation of bone mineral density in patients receiving high-dose thyroxin therapy.

In order to evaluate the interfemoral variability of bone mineral density (BMD) in patients receiving thyroxin (T4) replacement therapy, dual-energy X-ray absorptiometry (DXA) was performed on both hips and the lumbar spine of 114 individuals. BMD was measured in 47 patients under T4 therapy in suppressive doses because of histologically proven thyroid cancer and 67 age-matched controls free of any known local or generalized disorder that would affect the bones and joints. Variation in BMD between both hips was determined for four different regions of interest, i.e., Ward's triangle, intertrochanteric region, trochanter, and femoral neck. No significant difference in hip BMD was found between patients and controls. Even though some individuals had large interfemoral BMD variation, no significant difference in hip BMD variability between the groups was observed. In patients under suppressive T4 replacement therapy, BMD measurement in one hip is suitable to predict BMD of the other hip and therefore unilateral hip measurement may be adequate.

[Therapy of osteoporosis: bisphosphonates, SERM's, teriparatide and strontium]. / Osteoporosebehandlung: Bisphosphonate, SERM's, Teriparatide und Strontium.

The therapy of osteoporosis is mostly based upon the use of drugs which inhibit bone resorption. Among these, the bisphosphonate family is the best known and mostly used by clinicians. Both second and third generation bisphosphonates, like alendronate and risedronate, are now available as weekly tablets which have facilitated the patient compliance to treatment together with a decreased occurrence of gastrointestinal side effects. These compounds are used efficiently to treat postmenopausal osteoporosis and osteoporosis of men as well. Their use did provide good evidence of increased bone mineral density (BMD) and a reduction in fracture rates. The use of intravenous bisphosphonates such as Zoledronate, Ibandronate and Pamidronate remains in most of the cases limited to special indications such as intolerance to the oral formulations and treatment of patients with bone metastases. The selective estrogen modulators (SERM's) family is limited to a single product on the market as of now, Raloxifene, which does inhibit bone resorption and is well documented by postmenopausal women to increase BMD and reduce vertebral fractures. In addition, a large range of positive nonosseous effects have been documented such as the reduction of the incidence of breast cancer. Other substances do have a strong anabolic effect such as Teriparatide, a recombinant human formulation of PTH 1-34. This compound has demonstrated good efficacy in postmenopausal women, increasing vertebral and hip BMD and reducing the incidence of fractures at both sites. The exact role of Teriparatide in the clinical setting is still open but its overall impact in the therapy of osteoporosis could be major due to its major efficiency over shorter periods of time. Strontium ranelate, a new divalent Strontium salt taken orally, acts both as an anti-catabolic and anabolic agent. The first results provided with strontium ranelate are very promising due to its major effect on the increase in BMD both at the vertebral and hip sites and its ability to reduce the incidence of fractures at both locations. Additional data are awaited to confirm these initial positive results.

[Bone ultrasound and diagnosis of osteoporosis: correlation of 2 quantitative ultrasound methods with bone density]. / Skelettaler Ultraschall und Osteoporose-Diagnostik: Korrelation von zwei quantitativen Ultraschallverfahren mit der Knochendichte.

In this study, 96 women (mean +/- SD, 65.3 +/- 13.2 years) were investigated by bone mineral densitometry (DXA, Hologic QDR 2000) and quantitative ultrasound (QUS) of the tibia (n = 96; Sound-Scan2000, Myriad) and phalanges (n = 84: DBM Sonic 1200, IGEA). We observed a good correlation of QUS measurement with bone mineral content (BMD) on lumbar spine and both hips (Ward and Neck). Correlation of the two QUS-techniques measuring at different skeletal sites within the same patient was good. QUS instruments measuring at the various skeletal sites and their suitability for screening patients at risk of osteoporosis are discussed. The usefulness of the different QUS methods and the best measuring site for the assessment of fracture risk in osteoporotic patients still have to be established.

PET attenuation coefficients from CT images: experimental evaluation of the transformation of CT into PET 511-keV attenuation coefficients.

The CT data acquired in combined PET/CT studies provide a fast and essentially noiseless source for the correction of photon attenuation in PET emission data. To this end, the CT values relating to attenuation of photons in the range of 40-140 keV must be transformed into linear attenuation coefficients at the PET energy of 511 keV. As attenuation depends on photon energy and the absorbing material, an accurate theoretical relation cannot be devised. The transformation implemented in the Discovery LS PET/CT scanner (GE Medical Systems, Milwaukee, Wis.) uses a bilinear function based on the attenuation of water and cortical bone at the CT and PET energies. The purpose of this study was to compare this transformation with experimental CT values and corresponding PET attenuation coefficients. In 14 patients, quantitative PET attenuation maps were calculated from germanium-68 transmission scans, and resolution-matched CT images were generated. A total of 114 volumes of interest were defined and the average PET attenuation coefficients and CT values measured. From the CT values the predicted PET attenuation coefficients were calculated using the bilinear transformation. When the transformation was based on the narrow-beam attenuation coefficient of water at 511 keV (0.096 cm(-1)), the predicted attenuation coefficients were higher in soft tissue than the measured values. This bias was reduced by replacing 0.096 cm(-1) in the transformation by the linear attenuation coefficient of 0.093 cm(-1) obtained from germanium-68 transmission scans. An analysis of the corrected emission activities shows that the resulting transformation is essentially equivalent to the transmission-based attenuation correction for human tissue. For non-human material, however, it may assign inaccurate attenuation coefficients which will also affect the correction in neighbouring tissue.

PET-CT-guided percutaneous puncture of an infected cyst in autosomal dominant polycystic kidney disease: case report.

An infected cyst in autosomal dominant polycystic kidney disease was identified with a combined positron emission tomographic (PET) and computed tomographic (CT) system, an experimental setup mimicking an integrated CT-PET scanner. Image fusion of fluorine 18 fluorodeoxyglucose PET and CT images allowed exact localization of the infected cyst among many cysts identified on previous CT and magnetic resonance images. Confirmation was obtained instantly, followed by CT-guided percutaneous puncture. Integrated imaging systems hold promise for direct PET-guided puncture of areas of increased fluorodeoxyglucose uptake by using the anatomic accuracy of CT.

[11C](R)-PK11195 PET imaging of microglial activation in multiple system atrophy.

Microglia, the brain's intrinsic macrophages, bind (R)-PK11195 when activated by neuronal injury. The authors used [11C](R)-PK11195 PET to localize in vivo microglial activation in patients with multiple system atrophy (MSA). Increased [11C](R)-PK11195 binding was primarily found in the dorsolateral prefrontal cortex, putamen, pallidum, pons, and substantia nigra, reflecting the known distribution of neuropathologic changes in MSA. Providing an indicator of disease activity, [11C](R)-PK11195 PET can thus be used to characterize the in vivo neuropathology of MSA.