Feasibility of high-dose dobutamine stress SSFP Cine MRI at 3 Tesla with patient adaptive local RF Shimming using dual-source RF transmission: initial results.

PURPOSE: To investigate the feasibility of high-dose dobutamine stress (HDDS) imaging using SSFP sequences at 3 T employing patient-adaptive local RF-shimming using a dual-source RF transmission system. MATERIALS AND METHODS: 13 Patients underwent a HDDS protocol on a 3 T MRI scanner (Achieva 3.0T-TX, Philips Healthcare), equipped with a dual-source RF transmission system. SSFP cine sequences using patient-adaptive local RF-shimming (RF-S) were compared to cine images acquired without additional shimming. Image quality was evaluated on a 4-point grading scale and number of non-diagnostic segments assessed. Contrast (CN) between myocardium (SIM) and blood pool (SIB) was calculated [(SIB-SIM)/(SIB+SIM)]. RESULTS: Image quality both at rest and maximum stress was significantly improved with RF-S (ED:3.56±0.5 vs. 3.23±0.63; ES:3.4±0.5 vs. 3.1±0.7) compared to no RF-S (ED:2.9±0.72 vs. 2.15±0.78; ES:2.64±0.74 vs. 1.95±0.76; p<0.01). The amount of non-diagnostic segments was significantly reduced when using RF-S at rest and stress (3 vs. 39; 19 vs. 78, p<0.05). All HDDS studies were diagnostic if performed with RF-S (n=13/13) in comparison to conventional shimming (n=5/13). Image contrast was improved for SSFP sequences with RF-S (0.53±0.08) compared to conventional images (0.46±0.09, p=0.06). CONCLUSION: Patient-adaptive local RF-shimming using a dual-source RF transmission system allows for reliable SSFP imaging in a clinical high-dose dobutamine stress protocol at 3 T. RF-S significantly improves image quality and reduces the number of non-diagnostic myocardial segments.

[Irreversible electroporation - a new kid on the block?]. / Irreversible Elektroporation - "a new kid on the block?".

CLINICAL/METHODICAL ISSUE: Minimally invasive tumor therapies are well established options in multi-modal oncological therapy regimes. So far the methods applied have been of a thermal nature and thus there are inherent limitations, most of all the so-called heat-sink effect. STANDARD RADIOLOGICAL METHODS: Radiofrequency ablation (RFA) and laser-induced thermotherapy (LITT) are well-established techniques. METHODICAL INNOVATIONS: Irreversible electroporation (IRE) could potentially become a novel therapy option with an enlarged spectrum of treatable lesions, i.e. close to blood vessels and potentially a lower rate of complications. PERFORMANCE: The IRE technique is currently the subject of early prospective trials and clinical studies have not yet shown any serious side effects. However, complete tumor ablation was not achieved in all cases (46 out of 69). ACHIEVEMENTS: Preclinical as well as clinical studies seem to show a promising efficiency in tumor ablation as well as a favorable complication profile especially with tumors in thermally critical locations. PRACTICAL RECOMMENDATIONS: Clinical long-term studies are currently under way assessing safety as well as efficiency. The data published so far look promising and considerably enlarge the spectrum of ablation techniques.

Dobutamine stress tagging and gradient-echo imaging for detection of coronary heart disease at 3 T.

OBJECTIVE: The purpose of this study was to evaluate the feasibility and diagnostic accuracy of a combined spoiled gradient-echo (sGRE) and tagged gradient-echo (SPAMM-GRE) protocol for detection of coronary artery disease (CAD) during high-dose dobutamine stress at 3 T. METHOD: The study protocol was approved by the local ethics committee. For stress testing, a standard high-dose dobutamine protocol was employed. Image quality at the highest stress level and diagnostic accuracy of the sGRE and SPAMM-GRE sequences were compared. The final study population consisted of 37 patients. RESULTS: The mean image quality score was 2.6±0.6 for the sGRE sequence and 2.4±0.6 for the SPAMM-GRE sequence (p>0.05). Sensitivity, specificity and diagnostic accuracy were 0.81, 0.86, 0.84 and 0.88, 0.86, 0.86 for the sGRE and SPAMM-GRE, respectively. In three cases with new wall motion abnormalities (WMAs), detected by sGRE and SPAMM-GRE, WMAs were detected at a lower stress level by tagging. CONCLUSION: The combined sGRE and SPAMM-GRE high-dose dobutamine protocol at 3 T is feasible and delivers good diagnostic accuracy. Tagging increases the sensitivity of high-dose dobutamine stress testing for detection of CAD and may allow for detection of new WMAs at lower stress levels compared with sGRE alone.

[Unclear acute respiratory failure in a 64-year-old woman after coronary intervention]. / Unklare akute respiratorische Insuffizienz bei einer 64-jährigen Patientin nach Koronarintervention.

HISTORY AND ADMISSION FINDINGS: Due to a retroperitoneal hematoma after cardiac catheterization a 64 year-old woman received two concentrates of red blood cells. Within two hours after transfusion the patient developed acute dyspnoea, anxiety and shivering. INVESTIGATIONS: Computertomography (CT) of the chest revealed a new bilateral, basally accented pulmonary edema. Pulmonary embolism was ruled out. A cardiac cause in terms of cardiogenic shock had been excluded by echocardiography and other non-invasive measurements. Moreover, no circulatory overload (transfusion-associated circulatory overload [TACO]) after transfusion was presented and the stable size of the retroperitoneal hematoma excluded haemorrhagic shock. Hence, the clinical pattern pointed towards a transfusion-related acute lung injury (TRALI). TREATMENT AND COURSE: The patient was intubated and a catecholamine medication was initiated. The weaning process proceeded without complications and the patient was extubated after several days. In the following chest x-ray no pulmonary residuals were left. After two weeks the patient was transferred to a rehabilitation unit. CONCLUSION: TRALI is a life-threatening and an often unconsidered complication after transfusion of plasma containing blood products. According to the criteria of the european haemovigilance networks (EHN-criteria), TRALI is diagnosed by clinical and radiological parameters. In case of suspicious TRALI the involved transfusion center has to be informed. By a crossmatch between donor plasma and recipient granulocytes the causal antibodies are detected in most cases. In 17% of cases no antibodies are detected.

[Avascular necrosis of the bone after organ transplantation]. / Avaskuläre Knochennekrose nach Organtransplantation.

Avascular bone necrosis under immunosuppressive therapy is a well known sequel following solid organ transplantation. Most cases affect hip, knees or shoulders in more than one location and occur in connection with the use of high-dose steroids. In this 50 year old female immunosuppressive therapy consisted of sirolimus and mycophenolate mofetil after a renal transplantation 2 years ago. Steroids had been completely withdrawn after avascular necrosis of the femoral head. Physical examination revealed a reddened and painful left ankle. C-reactive protein was elevated while autoimmune antibodies, rheumatoid factor and screening for reactive arthritis remained negative. Joint fluid examination ruled out infection or gout. Plain radiographs were normal. Under the presumptive diagnosis of erysipelas antibiotic therapy was started, however, without success. Magnetic resonance imaging finally revealed bilateral tibial and tarsal bone necrosis as the underlying cause. In conclusion, avascular bone necrosis should remain an important differential diagnosis in patients with bone or joint pain and a history of organ transplantation, regardless of the present use of steroid therapy.

Distinct muscle imaging patterns in myofibrillar myopathies.

OBJECTIVE: To compare muscle imaging findings in different subtypes of myofibrillar myopathies (MFM) in order to identify characteristic patterns of muscle alterations that may be helpful to separate these genetic heterogeneous muscular disorders. METHODS: Muscle imaging and clinical findings of 46 patients with MFM were evaluated (19 desminopathy, 12 myotilinopathy, 11 filaminopathy, 1 alphaB-crystallinopathy, and 3 ZASPopathy). The data were collected retrospectively in 43 patients and prospectively in 3 patients. RESULTS: In patients with desminopathy, the semitendinosus was at least equally affected as the biceps femoris, and the peroneal muscles were never less involved than the tibialis anterior (sensitivity of these imaging criteria to detect desminopathy in our cohort 100%, specificity 95%). In most of the patients with myotilinopathy, the adductor magnus showed more alterations than the gracilis muscle, and the sartorius was at least equally affected as the semitendinosus (sensitivity 90%, specificity 93%). In filaminopathy, the biceps femoris and semitendinosus were at least equally affected as the sartorius muscle, and the medial gastrocnemius was more affected than the lateral gastrocnemius. The semimembranosus mostly showed more alterations than the adductor magnus (sensitivity 88%, specificity 96%). Early adult onset and cardiac involvement was most often associated with desminopathy. In patients with filaminopathy, muscle weakness typically beginning in the 5th decade of life was mostly pronounced proximally, while late adult onset (>50 years) with distal weakness was more often present in myotilinopathy. CONCLUSIONS: Muscle imaging in combination with clinical data may be helpful for separation of distinct myofibrillar myopathy subtypes and in scheduling of genetic analysis.

Dynamin 2-related centronuclear myopathy: clinical, histological and genetic aspects of further patients and review of the literature.

Centronuclear myopathy (CNM) is a slowly progressive congenital myopathy with characteristic histopathological findings of chains of centrally located myonuclei in a large number of muscle fibers. Recently, different missense mutations in the dynamin 2 gene (DNM2, 19p13.2) have been shown to cause autosomal dominant CNM. We re-evaluated patients with a histopathological diagnosis of CNM and report on the clinical phenotype, the biopsy findings and the genetic results of these patients and review the current literature. Two of the three patients showed an unusually late disease onset (> 40 years). Interestingly, intramuscular nerve fascicles found in the muscle biopsy of a patient harboring the E368K DNM2 mutation contained nerve fibers with disproportionately thin myelin sheaths. Schwann cells of unmyelinated nerve fibers showed abnormal plasma membrane and basal lamina protrusions, indicating peripheral nerve involvement.

High-resolution myocardial perfusion imaging at 3 T: comparison to 1.5 T in healthy volunteers.

The purpose of this study was to evaluate high-resolution (HR) myocardial first-pass perfusion in healthy volunteers at 3 T compared to a typical clinical imaging protocol at 1.5 T, with respect to overall image quality and the presence of subendocardial dark rim artifacts. Myocardial first-pass rest perfusion studies were performed at both field strengths using a T1-weighted saturation-recovery segmented k-space gradient-echo sequence combined with parallel imaging (Gd-DTPA 0.05 mmol/kg). Twenty-six healthy volunteers underwent (1) a HR perfusion scan at 3 T(pixel size 3.78 mm(2)) and (2) a standard perfusion approach at 1.5 T(pixel size 9.86 mm(2)). The contrast enhancement ratio (CER) and overall image quality (4-point grading scale: 4: excellent; 1: non-diagnostic) were assessed, and a semiquantitative analysis of dark rim artifacts was performed for all studies. CER was slightly higher (1.31 +/- 0.32 vs. 1.14 +/- 0.34; p<0.01), overall image quality was significantly improved (3.03 +/- 0.43 vs. 2.37 +/- 0.39; p<0.01), and the number of dark rim artifacts (139 +/- 2.09 vs. 243 +/- 2.33; p<0.01) was significantly reduced for HR perfusion imaging at 3 T compared to the standard approach at 1.5 T. HR myocardial rest perfusion at 3 T is superior to the typical clinical perfusion protocol performed at 1.5 T with respect to the overall image quality and presence of subendocardial dark rim artifacts.

Cardiac stress MR imaging with dobutamine.

Stress testing for detection of ischemia-induced wall-motion abnormalities has become a mainstay for noninvasive diagnosis and risk stratification of patients with suspected coronary artery disease (CAD). Recent technical developments in magnetic resonance imaging (MRI), including the adoption of balanced steady-state free precession (b-SSFP) sequences-preferentially in combination with parallel imaging techniques-have led to a significant reduction of imaging time and improved patient safety. The stress protocol includes application of high-dose dobutamine (up to 40 microg/kg/min) combined with fractionated atropine (up to a maximal dose of 1.0 mg). High-dose dobutamine stress MRI revealed good sensitivity (83-96%) and specificity (80-100%) for detection of significant CAD. Myocardial tagging methods have been shown to further increase sensitivity for CAD detection. Severe complications (sustained tachycardia, ventricular fibrillation, myocardial infarction, cardiogenic shock) are rare but may be expected in 0.1-0.3% of patients. Dobutamine stress MRI has emerged as a reliable and safe clinical alternative for noninvasive assessment of CAD. New pulse sequences, such as real-time imaging, might obviate the need for breath holding and electrocardiogram (ECG) triggering in patients with severe dyspnoea and cardiac arrhythmias, which may further improve the clinical impact and acceptance of stress MRI in the future.

[Long-term fate of left atrial thrombi and incidence of cerebral embolism under continuous anticoagulation therapy]. / MR-tomographische Evaluation der Inzidenz zerebraler Embolien bei Patienten mit Vorhofflimmern und linksatrialen Thromben.

PURPOSE: Patients (pts.) with atrial fibrillation (AF) and atrial thrombi are known to have an increased risk for cerebral embolism. However, little is known about the clinical course of atrial thrombi and the incidence of cerebral embolism in those patients during anticoagulation therapy. The high sensitivity of MR imaging (MRI) including diffusion-weighted imaging (DWI) suggests that this technique could provide an improved estimate of cerebral embolism associated with the presence of left atrial thrombi. The aims of this prospective study were to evaluate 1) the prevalence of clinically silent and apparent cerebral embolism in pts. with newly diagnosed AF and atrial thrombi using MRI/DWI, 2) the long-term fate of atrial thrombi under continues anticoagulation therapy and 3) the incidence of cerebral embolism during a follow-up period of 12 months with continuous anticoagulation therapy. MATERIALS AND METHODS: The study group consisted of 32 pts. with 1) newly diagnosed AF and evidence of left atrial (LA) thrombi detected by TEE and 2) a new start of anticoagulation therapy [International Normalized Ratio (INR) 2.0 - 3.0]. 19 pts. with 1) newly diagnosed AF and no evidence of atrial thrombi and 2) an equivalent anticoagulation regimen served as the control group. In both groups a) MRI/DWI studies of the brain (weeks 0, 4, 8, 12, 20, 28, 36, 44, and 52), b) transesophageal echocardiographic studies (TEE) for assessment of LA-Thrombi (weeks 0 and 52) and c) clinical neurological assessments (weeks 0, 20 and 52) were performed. RESULTS: In the study group (AF and LA-Thrombi) 11 out of 32 pts. (34 %) displayed signs of acute (n = 8) or chronic (n = 3) cerebral embolism in the initial MRI studies. In 4 out of 32 pts. (13 %), MRI/DWI depicted new or additional cerebral emboli (n = 12) during the follow-up period despite continuous anticoagulation therapy. 2 (n = 2/4; 50 %) of these patients had clinically apparent neurological deficits. In the control group 1 out of 19 pts. (5 %) showed evidence of chronic cerebral embolism as assessed by MRI/DWI at the beginning of the study (week 0). No embolic cerebral lesions were detected during the 12-month follow-up. Within 12 months only 63 % (n = 20/32) of LA thrombi in the study group resolved completely under anticoagulation. CONCLUSION: 1. The incidence of clinically inapparent cerebral emboli in pts. with newly diagnosed AF and atrial thrombi is much higher than the incidence of clinically apparent emboli and has been underestimated in the past. 2. New cerebral embolism may occur even with continued effective anticoagulation therapy in 13 % of pts. 3. Only 63 % of atrial thrombi resolve completely within 12 months under anticoagulation therapy.