MRI-based numerical modeling of cardiac pulsed field ablation (PFA) with sub-microsecond pulses

Background

The use of irreversible electroporation (IRE) for cardiac ablation in the management of cardiac arrhythmias, known as Pulsed Field Ablation (PFA), has gained the attention of many researchers, physicians and companies. Despite the demonstrated efficacy and safety profiles of the technique, there are still many open questions. One of them deals with the effective electric field thresholds necessary for cardiac tissue ablation.

Contrary to radiofrequency (RF) ablation, where the thermotemporal thresholds for tissue damage are well established, the electric field thresholds for effective IRE are uncertain and depend on the tissue type and the waveform characteristics of the delivered electric field.

Purpose

The use of numerical models to understand the electric field distribution and the corresponding lesion for a specific electrode geometry are widely used in IRE for cancer treatment. Models can predict ablation volumes when the field thresholds are known or can be used to estimate the field thresholds when the lesion geometry is established post-treatment. The goal of the present study was to build a subject-specific realistic 3D numerical model to assess the ability of modeling to predict PFA lesions.

Methods

PFA experiments were performed in male mongrel dogs following a protocol approved by the Mayo Clinic Institutional Animal Care and Use Committee. Briefly, animals were sedated and intubated, and two non-irrigated deflectable catheters with an 8-mm tip were positioned on both sides of the interventricular septum under fluoroscopy guidance. Submicrosecond pulses were delivered in a bipolar fashion across both catheters. Sequences of pulses of 300 ns duration (or other durations in that range) were repetitively applied with voltage levels in the kV range. 30 days after the procedure, MRI with late gadolinium enhancement (LGE) were acquired to assess the presence of ablation lesions in the treated tissue. Ventricular areas were segmented from MRI images and 3D volumes were created. The generated 3D geometries were imported into software COMSOL Multiphysics. Realistic 3D geometries of the catheters were placed in the same positions than during the experiments, fluoroscopy videos recorded during the procedures were used as a guidance.

The computed electric field intensity distributions were compared to the LGE areas to extract the range of electric field thresholds where the predicted lesion size was compatible with the real size of the LGE areas for each application site and pulsing protocol.

Results and conclusions

Our results show how the numerical model is able to reproduce the shape of the LGE fibrotic lesion areas observed 30 days after the procedure. Additionally, the model clearly confirms the dose-dependent lesion sizes observed experimentally. This study supports that numerical modeling is a valuable tool for understanding PFA treatments and that it could be used as patient-specific treatment planning tool.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie

Genome-wide methylation profiling in granulosa lutein cells of women with polycystic ovary syndrome (PCOS)

Polycystic Ovary Syndrome (PCOS) is the most common endocrine disorder amongst women of reproductive age, whose aetiology remains unclear. To improve our understanding of the molecular mechanisms underlying the disease, we conducted a genome-wide DNA methylation profiling in granulosa lutein cells collected from 16 women suffering from PCOS, in comparison to 16 healthy controls. Samples were collected by follicular aspiration during routine egg collection for IVF treatment. Study groups were matched for age and BMI, did not suffer from other disease and were not taking confounding medication. Comparing women with polycystic versus normal ovarian morphology, after correcting for multiple comparisons, we identified 106 differentially methylated CpG sites with p-values <5.8 × 10^-8 that were associated with 88 genes, several of which are known to relate either to PCOS or to ovarian function. Replication and validation of the experiment was done using pyrosequencing to analyse six of the identified differentially methylated sites. Pathway analysis indicated potential disruption in canonical pathways and gene networks that are, amongst other, associated with cancer, cardiogenesis, Hedgehog signalling and immune response. In conclusion, these novel findings indicate that women with PCOS display epigenetic changes in ovarian granulosa cells that may be associated with the heterogeneity of the disorder.

Osteonecrosis of the Upper Extremity: MRI-Based Zonal Patterns and Differential Diagnosis

Regarding the upper extremity, osteonecrosis can relate to the humeral head and to any carpal bone, most commonly the lunate (Kienböck's disease), scaphoid (Preiser's disease and nonunion), and capitate bone (osteonecrosis of the capitate head). In children and adolescents, osteochondrosis is an important differential diagnosis at the epiphyses. Appropriate imaging of osteonecrosis depends on knowledge about blood supply, biomechanical load, and bone repair mechanisms. Contrast-enhanced MRI (ceMRI) enables the differentiation of up to three mostly band-shaped zones: necrotic tissue (proximal), hypervascular repair tissue (intermediate), and viable bone (distal). To distinguish between necrotic and repair zones, intravenous gadolinium is recommended in MRI. Osteosclerosis and insufficiency fractures in early and intermediate stages as well as osteoarthritis in advanced stages are best depicted using high-resolution CT (HRCT). The combination of HRCT and ceMRI allows for exact classification of osteonecrosis regarding morphology and viability.

Expression of genes controlling steroid metabolism and action in granulosa-lutein cells of women with polycystic ovaries

INTRODUCTION

Aberrant function of granulosa cells has been implicated in the pathophysiology of PCOS.

MATERIALS & METHODS

Granulosa lutein (GL) cells were collected during oocyte retrieval for IVF/ICSI. RT-qPCR was used to compare gene expression between 12 control women, 12 with ovulatory PCO and 12 with anovulatory PCOS. To examine which genes are directly regulated by androgens, GL cells from an additional 12 control women were treated in-vitro with 10 nM dihydrotestosterone (DHT).

RESULTS

GL cells from women with PCOS showed reduced expression of CYP11A1 3-fold (p = 0.005), HSD17B1 1.8-fold (p = 0.02) and increased expression of SULT1E1 7-fold (p = 0.0003). Similar results were seen in ovulatory women with PCO. GL cells treated with 10 nM DHT showed a 4-fold (p = 0.03) increase in expression of SULT1E1 and a 5-fold reduction in SRD5A1 (p = 0.03).

CONCLUSIONS

These findings support the notion that aberrant regulation of steroid metabolism or action play a part in ovarian dysfunction in PCOS.

The direct and indirect effects of kisspeptin-54 on granulosa lutein cell function

STUDY QUESTION

What are the in vivo and in vitro actions of kisspeptin-54 on the expression of genes involved in ovarian reproductive function, steroidogenesis and ovarian hyperstimulation syndrome (OHSS) in granulosa lutein (GL) cells when compared with traditional triggers of oocyte maturation?

SUMMARY ANSWER

The use of kisspeptin-54 as an oocyte maturation trigger augmented expression of genes involved in ovarian steroidogenesis in human GL cells including, FSH receptor (FSHR), LH/hCG receptor (LHCGR), steroid acute regulatory protein (STAR), aromatase, estrogen receptors alpha and beta (ESR1, ESR2), 3-beta-hydroxysteroid dehydrogenase type 2 (3BHSD2) and inhibin A (INHBA), when compared to traditional maturation triggers, but did not alter markers of OHSS.

WHAT IS KNOWN ALREADY

hCG is the most widely used trigger of oocyte maturation, but is associated with an increased risk of OHSS. The use of GnRH agonists to trigger oocyte maturation is a safer alternative to hCG. More recently, kisspeptin-54 has emerged as a novel therapeutic option that safely triggers oocyte maturation even in women at high risk of OHSS. Kisspeptin indirectly stimulates gonadotropin secretion by acting on hypothalamic GnRH neurons. Kisspeptin and its receptor are also expressed in the human ovary, but there is limited data on the direct action of kisspeptin on the ovary.

STUDY DESIGN SIZE, DURATION

Forty-eight women undergoing IVF treatment for infertility consented to kisspeptin-54 triggering and/or granulosa cell collection and were included in the study. Twelve women received hCG, 12 received GnRH agonist and 24 received kisspeptin-54 to trigger oocyte maturation. In the kisspeptin-54 group, 12 received one injection of kisseptin-54 (9.6 nmol/kg) and 12 received two injections of kisspeptin-54 at a 10 h interval (9.6 nmol/kg × 2).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Follicular fluid was aspirated and pooled from follicles during the retrieval of oocytes for IVF/ICSI. GL cells were isolated and either RNA extracted immediately or cultured in vitro ± kisspeptin or hCG.

MAIN RESULTS AND THE ROLE OF CHANCE

GL cells from women who had received kisspeptin-54 had a 14-fold and 8-fold higher gene expression of FSHR and a 2-fold (ns) and 2.5-fold (P < 0.05) higher expression of LHCGR than GL cells from women who had received hCG or GnRH agonist, respectively. CYP19A1 expression was 3.6-fold (P < 0.05) and 4.5-fold (P < 0.05) higher, STAR expression was 3.4-fold (P < 0.01) and 1.8-fold (P < 0.05) higher, HSD3B2 expression was 7.5- (P < 0.01) and 2.5-fold higher (P < 0.05), INHBA was 2.5-fold (P < 0.01) and 2.5-fold (P < 0.01) higher in GL cells from women who had received kisspeptin-54 than hCG or GnRHa, respectively. ESR1 (P < 0.05) and ESR2 (P < 0.05) both showed 3-fold higher expression in cells from kisspeptin treated than GnRHa treated women. Markers of vascular permeability and oocyte growth factors were unchanged (VEGFA, SERPINF1, CDH5, amphiregulin, epiregulin). Gene expression of kisspeptin receptor was unchanged. Whereas treating GL cells in vitro with hCG induced steroidogenic gene expression, kisspeptin-54 had no significant direct effects on either OHSS genes or steroidogenic genes.

LIMITATIONS REASONS FOR CAUTION

Most women in the study had PCOS, which may limit applicability to other patient groups. For the analysis of the in vitro effects of kisspeptin-54, it is important to note that GL cells had already been exposed in vivo to an alternate maturation trigger.

WIDER IMPLICATIONS OF THE FINDINGS

The profile of serum gonadotropins seen with kisspeptin administration compared to other triggers more closely resemble that of the natural cycle as compared with hCG. Thus, kisspeptin could potentially permit an ovarian environment augmented for steroidogenesis, in particular progesterone synthesis, which is required for embryo implantation.

STUDY FUNDING/COMPETING INTEREST(S)

Dr Owens is supported by an Imperial College London PhD Scholarship. Dr Abbara is supported by an National Institute of Health Research Academic Clinical Lectureship. The authors do not have any conflict of interest to declare.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT01667406.

Multiple endocrine neoplasia 2 in Cyprus: evidence for a founder effect

PURPOSE

Multiple endocrine neoplasia type 2 (MEN2) affects patients with RET proto-oncogene mutations. This cohort study refers to patients who were diagnosed with familial medullary thyroid carcinoma (MTC) and underwent RET genetic testing in Cyprus between years 2002 and 2017.

METHODS AND PATIENTS

Forty patients underwent RET testing by Sanger sequencing of exons 10-11 and 13-16. Genotyping with STR genetic markers flanking the RET gene along with Y-chromosome genotyping and haplogroup assignment was also performed.

RESULTS

RET mutations were identified in 40 patients from 11 apparently unrelated Cypriot families and two non-familial sporadic cases. Nine probands (69.2%) were heterozygous for p.Cys618Arg, one (7.7%) for p.Cys634Phe, one (7.7%) for the somatic delE632-L633 and two (15.4%) for p.Met918Thr mutations. The mean age at MTC diagnosis of patients carrying p.Cys618Arg was 36.8 ± 14.2 years. The age of pheo diagnosis ranged from 26 to 43 years and appeared simultaneously with MTC in 5/36 (13.9%) cases. The high frequency of the p.Cys618Arg mutation suggested a possible ancestral mutational event. Haplotype analysis was performed in families with and without p.Cys618Arg. Six microsatellite markers covering the RET gene and neighboring regions identified one core haplotype associated with all patients carrying p.Cys618Arg mutation.

CONCLUSIONS

The mutation p.Cys618Arg is by far the most prevalent mutation in Cyprus followed by other reported mutations of variable clinical significance. The provided molecular evidence speculates p.Cys618Arg mutation as an ancestral mutation that has spread in Cyprus due to a possible founder effect.

Clinical parameters of ovarian hyperstimulation syndrome following different hormonal triggers of oocyte maturation in IVF treatment

OBJECTIVE

Ovarian hyperstimulation syndrome (OHSS) is a serious iatrogenic condition, predominantly related to the hormone used to induce oocyte maturation during IVF treatment. Kisspeptin is a hypothalamic neuropeptide that has recently been demonstrated to safely trigger final oocyte maturation during IVF treatment even in women at high risk of OHSS. However, to date, the safety of kisspeptin has not been compared to current hormonal triggers of oocyte maturation.

DESIGN

We conducted a retrospective single-centre cohort study investigating symptoms and clinical parameters of early OHSS in women at high risk of OHSS (antral follicle count or total number of follicles on day of trigger ≥23) triggered with human chorionic gonadotrophin (hCG) (n = 40), GnRH agonist (GnRHa; n = 99) or kisspeptin (n = 122) at Hammersmith Hospital IVF unit, London, UK (2013-2016).

RESULTS

Clinical Parameters of OHSS: Median ovarian volume was larger following hCG (138 ml) than GnRHa (73 ml; P < .0001), and in turn kisspeptin (44 ml; P < .0001). Median ovarian volume remained enlarged 20-fold following hCG, 8-fold following GnRHa and 5-fold following kisspeptin compared to prestimulation ovarian volumes. Mean (±SD) ascitic volumes were lesser following GnRHa (9 ± 44 ml) and kisspeptin (5 ± 8 ml) than hCG (62 ± 84 ml; P < .0001). Symptoms of OHSS were most frequent following hCG and least frequent following kisspeptin. Diagnosis of OHSS: The odds ratio for OHSS diagnosis was 33.6 (CI 12.6-89.5) following hCG and 3.6 (CI 1.8-7.1) following GnRHa, when compared to kisspeptin.

CONCLUSION

Triggering oocyte maturation by inducing endogenous gonadotrophin release is preferable to the use of exogenous hCG in women at high risk of OHSS.

Fibroids that do not distort the uterine cavity and IVF success rates: an observational study using extensive matching criteria

OBJECTIVE

To assess the impact of non-cavity-distorting fibroids on in vitro fertilisation (IVF) pregnancy outcomes.

DESIGN

A retrospective, matched, single-centre, cohort study was performed.

SETTING

The IVF unit of a tertiary, university hospital.

POPULATION

We analysed all women with non-cavity-distorting uterine fibroids undergoing IVF/intracytoplasmic sperm injection (ICSI) cycles from 1 January 2011 to 1 May 2015.

METHODS

Each woman was matched with two separate controls of the same age (±6 months), stimulation protocol (gonadotropin-releasing hormone agonist or antagonist), starting dose of follicle-stimulating hormone (FSH), number of embryos transferred (one or two), day of transfer (day 3 or day 5), and no uterine fibroids identified by transvaginal ultrasound.

MAIN OUTCOME MEASURES

Clinical pregnancy and live birth rates.

RESULTS

Our study demonstrates that the presence of non-cavity-distorting fibroids appears to negatively affect clinical pregnancy (odds ratio, OR 0.62; 95% confidence interval, 95% CI 0.41-0.94) and live birth rates (OR 0.58; 95% CI 0.48-0.78) in patients undergoing their first IVF/ICSI cycle, when matched with controls of the same age, starting dose of FSH, stimulation protocol, number of embryos, and day of embryo transfer. The deleterious effect of fibroids on live birth rates was significant in women with two or more fibroids (OR 0.47; 95% CI 0.26-0.83) and in women with fibroids of ≥30 mm in diameter (OR 0.41; 95% CI 0.19-0.89). The negative impact of non-cavity-distorting fibroids was also present in women with an embryo transfer on day 5 (OR 0.58; 95% CI 0.35-0.94). Conversely, in women with single fibroids of <30 mm in diameter, no difference in pregnancy outcomes was identified.

CONCLUSIONS

A well-designed, adequately powered, randomised controlled trial is required to address the role of medical or surgical interventions in patients with intramural and subserosal fibroids before undergoing fertility treatment.

TWEETABLE ABSTRACT

Non-cavity-distorting fibroids negatively affect pregnancy rates after IVF.

Sonographic diagnosis of a neonatal gastric perforation presenting with scrotal swelling

Neonatal gastric perforation is a rare, serious and frequently fatal condition of unclear etiology. The most common clinical presentation include tachypnea, respiratory distress, abdominal distension and cyanosis. We report an unusual case of neonatal gastric perforation presenting as erythematous scrotal swelling mimicking testicular torsion. This clinical presentation is unusual and early diagnosis and treatment is essential in order to prevent significant mortality and morbidity.

Gadolinium-enhanced preoperative MRI scans as a prognostic parameter in scaphoid nonunion

The purpose of this prospective study was to correlate preoperative gadolinium-enhanced MRI scans with intraoperative bleeding of the proximal fragment and postoperative union in a series of consecutive patients with established scaphoid nonunions. In 60 patients (6 females, 54 males) with a mean age of 29 years, scaphoid perfusion was judged preoperatively as normal, impaired or absent using a gadolinium-enhanced MRI scan. Scaphoid reconstruction was performed using a nonvascularized bone graft and screw fixation. Perfusion of the proximal fragment was assessed intraoperatively in 49 of 60 patients; compromised or absent vascularity was predicted with a specificity of 90% by contrast-enhanced MRI. However, there was no significant correlation between preoperative MRI assessment of vascularity and subsequent union of the scaphoid.

Avascular necrosis (AVN) of the proximal fragment in scaphoid nonunion: is intravenous contrast agent necessary in MRI?

PURPOSE

The purpose of this prospective study is to assess the diagnostic value of intravenously applied contrast agent for diagnosing osteonecrosis of the proximal fragment in scaphoid nonunion, and to compare the imaging results with intraoperative findings.

MATERIALS AND METHODS

In 88 patients (7 women, 81 men) suffering from symptomatic scaphoid nonunion, preoperative MRI was performed (coronal PD-w FSE fs, sagittal-oblique T1-w SE nonenhanced and T1-w SE fs contrast-enhanced, sagittal T2*-w GRE). MRI interpretation was based on the intensity of contrast enhancement: 0 = none, 1 = focal, 2 = diffuse. Intraoperatively, the osseous viability was scored by means of bleeding points on the osteotomy site of the proximal scaphoid fragment: 0=absent, 1 = moderate, 2 = good.

RESULTS

Intraoperatively, 17 necrotic, 29 compromised, and 42 normal proximal fragments were found. In nonenhanced MRI, bone viability was judged necrotic in 1 patient, compromised in 20 patients, and unaffected in 67 patients. Contrast-enhanced MRI revealed 14 necrotic, 21 compromised, and 53 normal proximal fragments. Judging surgical findings as the standard of reference, statistical analysis for nonenhanced MRI was: sensitivity 6.3%, specificity 100%, positive PV 100%, negative PV 82.6%, and accuracy 82.9%; statistics for contrast-enhanced MRI was: sensitivity 76.5%, specificity 98.6%, positive PV 92.9%, negative PV 94.6%, and accuracy 94.3%. Sensitivity for detecting avascular proximal fragments was significantly better (p<0.001) in contrast-enhanced MRI in comparison to nonenhanced MRI.

CONCLUSION

Viability of the proximal fragment in scaphoid nonunion can be significantly better assessed with the use of contrast-enhanced MRI as compared to nonenhanced MRI. Bone marrow edema is an inferior indicator of osteonecrosis. Application of intravenous gadolinium is recommended for imaging scaphoid nonunion.

[Early radiological diagnostics for scapholunate dissociation (SLD)]

The partial tear of the scapholunate ligament (pre-dynamic stage of SLD) as well as the complete tear (dynamic stage) does not lead to carpal malalignment. However, if the completely ruptured ligament is accompanied by lesions of the extrinsic ligaments, both the scaphoid and the lunate are malaligned already at rest (static stage of SLD). Later, osteoarthritis will develop, beginning in the radioscaphoid compartment, progressing to the midcarpal joint, and ending in a carpal collapse (osteoarthrotic stage of SLD). Dynamic SLD is detectable only in stress views and in cinematography. The high utility of MRI for directly visualizing the injured ligament is emphasized: reparation tissue is focally enhanced at the rupture site by intravenously applied contrast agent; the individual segments of the scapholunate ligament can be visualized in direct MR arthrography, therefore allowing differentiation of partial and complete ligamentous tears.

Skaphoidfraktur und -pseudarthrose

Scaphoid fractures, which involve approximately two-thirds of all wrist injuries, are often not detected during initial radiographic examination. By using high-resolution CT and dedicated MRI, it is possible to recognize scaphoid fractures soon at the first diagnostic approach and to assess fragment stability. CT imaging provides all the relevant information of the fracture extent and of the fracture healing in the follow-up. MRI is most sensitive in the detection of scaphoid fractures; however, fracture signs must be differentiated from those of a bone bruise. Both the initially overseen scaphoid fracture and the unsuccessful healing can lead to the natural history of scaphoid nonunion. In the injured scaphoid, CT imaging is essential for depicting the osseous morphology, whereas contrast-enhanced MRI is crucial for assessing the viability of the proximal fragment.

Carpal instability

This review addresses the pathoanatomical basics as well as the clinical and radiological presentation of instability patterns of the wrist. Carpal instability mostly follows an injury; however, other diseases, like CPPD arthropathy, can be associated. Instability occurs either if the carpus is unable to sustain physiologic loads ("dyskinetics") or suffers from abnormal motion of its bones during movement ("dyskinematics"). In the classification of carpal instability, dissociative subcategories (located within proximal carpal row) are differentiated from non-dissociative subcategories (present between the carpal rows) and combined patterns. It is essential to note that the unstable wrist initially does not cause relevant signs in standard radiograms, therefore being "occult" for the radiologic assessment. This paper emphasizes the high utility of kinematographic studies, contrast-enhanced magnetic resonance imaging (MRI) and MR arthrography for detecting these predynamic and dynamic instability stages. Later in the natural history of carpal instability, static malalignment of the wrist and osteoarthritis will develop, both being associated with significant morbidity and disability. To prevent individual and socio-economic implications, the hand surgeon or orthopedist, as well as the radiologist, is challenged for early and precise diagnosis.

Comprehensive MR angiography of the lower limbs: a hybrid dual-bolus approach including the pedal arteries

The purpose of this study was to include the pedal vasculature into the coverage of peripheral multistation magnetic resonance angiography (3DceMRA). A total of 216 patients suffering from peripheral vascular disease were examined with a modified hybrid dual-bolus technique. The cruropedal arteries were acquired first with two sagittal slabs and time-resolved 3D sequences. Then the aortofemoral vessels were visualized using the bolus-chase technique and a second contrast injection. Interventional procedures were performed in 104 patients, and in 69 of those, the cruropedal vessels were also examined with digital subtraction angiography (iaDSA). Using 3DceMRA, the cruropedal arteries were displayed with both excellent and good quality in 95% (205/216 cases), and without any venous overlay in 94% (203/216 cases). The aortofemoral vessels were not jeopardized by the first contrast injection. With iaDSA as the standard of reference, observed sensitivity of 3DceMRA was found in ranges from 80% (29%, 99%) to 100% (86%, 100%) for assessing significant stenoses, and observed specificity ranged between 93% [80%, 98%] and 100% (82%, 100%). In conclusion, hybrid dual-bolus 3DceMRA significantly reduces the limitations of standard single-bolus 3DceMRA in anatomic coverage and temporal resolution of the cruropedal arteries, thus providing high-quality images of the entire peripheral vasculature.

Zur Differenzialdiagnostik des „signalkompromittierten” Os lunatum in der MR-Tomographie

PURPOSE

To define both the underlying pathology and diagnostic criteria in lunates presenting with conspicuous signal pattern in MRI.

MATERIALS AND METHODS

The retrospective evaluation of 2940 MRI examinations revealed 203 patients with signal alterations of the lunate. All MRI examinations were performed on 1.5-Tesla platforms using dedicated surface coils and an intravenous contrast agent. To establish a definitive diagnosis, a total of 252 MRI examinations (49 follow-ups), 22 CT examinations and 4 arthroscopic studies were obtained in addition to the obligatory conventional radiographs.

RESULTS

Incorporating all clinical data, radiographs and MRI examinations succeeded in assigning a diagnosis in 136 signal-compromised lunates (67.0 %), whereas additional diagnostic procedures or follow-up examinations were required for the definitive diagnosis in 57 cases (33.0 %). The most frequent entities were 51 cases of Kienbock's disease (25.1 %), 47 cases of ulnolunate-(triquetral) impaction syndromes (23.2 %) and 44 cases of intra-osseous ganglion cysts (21.7 %). Other pathologies included 23 degenerative, 19 traumatic and 10 inflammatory changes as well as 9 congenital conditions. For MRI assessment of the altered lunate, the most important parameters were location and morphology as well as involvement of the articular and osseous structures of the carpus.

CONCLUSION

The lunate may be affected by different pathological states of the wrist. In total, only one quarter of the signal-compromised lunate represented Kienboeck's disease.

Amylin receptors: molecular composition and pharmacology

Several receptors which bind the hormone AMY (amylin) with high affinity have now been identified. The minimum binding unit is composed of the CT (calcitonin) receptor at its core, plus a RAMP (receptor activity modifying protein). The receptors have been named AMY1(a), AMY2(a) and AMY3(a) in accordance with the association of the CT receptor (CT(a)) with RAMP1, RAMP2 and RAMP3 respectively. The challenge is now to determine the localization and pharmacological nature of each of these receptors. Recent attempts to achieve these aims will be briefly discussed.

In vitro autoradiographic localization of calcitonin and amylin binding sites in monkey brain

Calcitonin (CT) and amylin are related peptides with potent central actions, including suppression of appetite and gastric acid secretion. Little is known about the distribution and binding characteristics of amylin receptors in species other than rat; therefore, in this study, by using in vitro autoradiography, we have mapped the distribution of 125I-rat amylin binding sites in the monkey brain and compared this distribution to that of binding sites for 125I-salmon CT (125I-sCT). Highest densities of 125I-amylin binding were in the hypothalamus, including the arcuate nucleus and parts of the ventromedial hypothalamic nuclei, and the solitary nucleus. Rostrally, moderate to high density binding was present in parts of the preoptic area, bed nucleus of the stria terminalis, amygdala and accumbens nucleus (Acb). Caudally, binding of amylin was more restricted, with moderate to high density binding present only in dorsal raphe, and area postrema. The primary visual cortex displayed strong and periodic CT binding in layer 4. The subcortical pattern of distribution of amylin and CT receptors in the monkey was similar to that seen previously in the rat, although the relative densities of binding to different brain structures were not always conserved. As with rat, monkey amylin receptors were a subset of the sites labeled with 125I-sCT. Analysis of receptor specificity indicated a greater relative potency of CT peptides in competing for 125I-amylin binding in monkey, when compared to rat, while, there was a decrease in the relative potency of CT gene-related peptides, potentially due to differences the level of receptor activity modifying proteins (RAMPs) in monkey versus rat brain. Amylin receptors in primates are likely to perform a similar role to those in rats; however, the interaction of the receptors with related peptides may differ.

[Diagnostic angiography using multi-slice spiral CT in acute obstruction of the basilar artery]

OBJECTIVE

To evaluate the diagnostic efficiency of CT angiography in case of clinical signs of acute brainstem infarction for the therapeutic management of catheter-based local thrombolysis.

MATERIAL AND METHODS

3 patients (2 males, 1 female) suffering from an acute onset of brainstem symptoms and being suspicious of an occluded basilar artery were included into this report. 1 patient underwent selective vertebral arteriography. 2 patients were initially examined with CT angiography using a 4-row scanner and 100 ml intravenous contrast agent.

RESULTS

In one patient, an occlusion of the basilar artery was excluded with catheter-based angiography. Subsequently, the patient was treated with systemic thrombolysis using r-tPA because of a thalamus infarction seen in MRI. 2 patients who have been initially examined with CT angiography presented with complete occlusions of the basilar arteries. These patients underwent r-tPA thrombolysis by means of superselective micro-catheter approaches of the vertebrobasilar vessels. CT angiography was very useful for determinating the occlusion length of the basilar artery pre-therapeutically, and in 1 case for ruling out an occluded vertrebral artery for catheterization. All patients recovered well under thrombolytic therapy applied systemically or selectively.

CONCLUSION

Cerebral multi-slice CT angiography is a fast and save technique for detecting or ruling out an acute basilar artery occlusion. Thus, in cases of equivocal clinical signs CT angiography is recommended before the decision of thrombolytic therapy is made.

[Direct MR arthrography of the wrist in comparison with arthroscopy: a prospective study on 125 patients]

OBJECTIVE

In literature the diagnostic value of MRI for detecting lesions of the carpal ligaments and the TFCC is judged controversially. The aim of the following study is to determine the diagnostic accuracy of direct MR arthrography for depicting and staging of intraarticular lesions of the wrist.

MATERIAL AND METHODS

One day before undergoing arthroscopy, 125 patients suffering from wrist pain were examined with direct MR arthrography in a prospective and blinded study. A mixture of contrast medium (iodine-containing contrast medium and gadopentetate in relation 200 : 1) was injected into both radiocarpal and midcarpal joints. The following sequences were acquired on a 1.5T scanner: coronal T1-weighted SE, coronal fat-saturated T1-weighted SE, coronal T1-/T2*-DESS-3D, and sagittal T2*-weighted MEDIC. MRI results were compared with arthroscopic findings using statistical analysis (SEN = sensitivity, SPE = specificity, PPV = positive predictive value, NPV = negative predictive value, ACC = accuracy).

RESULTS

In comparison to arthroscopy as the accepted diagnostic gold standard, the following results were found for MR arthrography. Detection of TFCC lesions: SEN 97.1 %, SPE 96.4 %, PPV 97.1 %, NPV 96.4 %, ACC 96.8 %. Detection of complete tears of the scapholunate ligament: SEN 91.7 %, SPE 100 %, PPV 100 %, NPV 99.1%, ACC 99.2%. Detection of partial tears: SEN 62.5 %, SPE 100 %, PPV 100 %, NPV 94.8 %, ACC 95.2 %. Detection of cartilage defects: SEN 84.2 %, SPE 96.2 %, PPV 80 %, NPV 97.1 %, ACC 94.4 %. In total, only three lesions of the lunotriquetral ligament were present.

CONCLUSION

Direct MR arthrographic imaging is well suited for detecting intraarticular lesions of the wrist. The presented diagnostic results of MR arthrography are superior to the results of unenhanced MRI reported in the literature. Direct MR arthrography as a reliable diagnostic tool is strongly recommended if lesions of the scapholunate ligament and the triangular fibrocartilage complex are suspected. In contrast, an attitude of caution must be adopted in diagnosing lesions of the articular cartilage of the wrist.

[TFCC-lesion. MR arthrography vs. arthroscopy of the wrist]

In a blinded study from January to July 2000, 125 patients suffering from specific complaints of the wrist were examined with direct MR arthrography prospectively. Within 24 hours an arthroscopy of the wrist was performed. With the MR arthrography in 70 patients or 56% of all patients injury of the TFCC was diagnosed. In 65 patients this could be verified arthroscopically. In the remaining 55 patients no TFCC lesion was diagnosed with the MR arthrography. However lesions were found via arthroscopy in three cases,were MRI findings expected an intact TFCC. In the remaining 52 cases the MRT could exclude a lesion of the TFCC correctly. An agreement of the MRT and arthroscopic results could be determined in 93.6% of the cases (correlation). The diagnosis of a TFCC lesion by means of MRI was correct in 94% of the cases (sensitivity), the exclusion of such lesion in 89% (specificity). Positive or negative predictive values of 91% or 93% were achieved. Since neither a specificity nor a sensitivity of 100% can be reached at the moment, the MR arthrography cannot replace the arthroscopy. However it could be a potent additional tool for wrist diagnosis if intraarticular contrast is used. It can facilitate the diagnostics and the indication for surgery at the ulnocarpal wrist and help to reduce arthroscopic interventions that are only for diagnostic purposes and without any therapeutic consequences. With improvement of the technique of magnet resonance tomography we can expect further increase of accuracy and the clinical use of the MR arthrography in the diagnostic workup at the ulnocarpal wrist.