Thomas V. Lloyd

MR Imaging–guided Electrophysiological Ablation Studies in Humans with Passive Catheter Tracking: Initial Results

PURPOSE To assess if real-time magnetic resonance (MR) imaging-guided radiofrequency (RF) ablation for atrial flutter is feasible in patients. MATERIALS AND METHODS The study complied with the Declaration of Helsinki and was approved by the local ethics committee. All patients were informed about the investigational nature of the procedures and provided written informed consent. Ten patients (six men; mean age ± standard deviation, 68 years ± 10) with symptomatic atrial flutter underwent isthmus ablation. In all patients, two MR imaging conditional steerable diagnostic and ablation catheters were inserted into the coronary sinus via femoral sheaths and into the right atrium with fluoroscopic guidance. The patients were then transferred to a 1.5-T whole-body MR imager for an ablation procedure, in which the catheters were manipulated by an electrophysiologist by using a commercially available interactive real-time steady-state free precession MR imaging sequence. RESULTS All catheters were placed in standard positions successfully. Furthermore, simple programmed stimulation maneuvers were performed. In one of 10 patients, a complete conduction block was performed with MR imaging guidance. In nine of 10 patients, creating only a small number of additional touch-up lesions was necessary to complete the isthmus block with conventional fluoroscopy (median, three lesions; interquartile range, two to four lesions). CONCLUSION Real-time MR imaging-guided placement of multiple catheters is feasible in patients, with subsequent performance of stimulation maneuvers and occasional complete isthmus ablation.

Aberrant jugular bulb presenting as a middle ear mass.

Case reports of 3 patients seen with a bluish mass behind the tympanic membrane are presented. The initial diagnosis was probable glomus tumor. In 1 patient, middle ear exploration confirmed the presence of a high-lying jugular bulb. In the other 2, venography demonstrated that the jugular bulb projected superiorly into the middle ear cavity. In all 3, polytomography demonstrated a dehiscence of the bony septum which normally separates the jugular bulb from the hypotympanum. When a bony dehiscence is seen in the absence of destructive changes, a diagnosis of aberrant jugular bulb is strongly suggested.

Assessing the Electromagnetic Fields Generated By a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing Versus Accuracy

Goal: This study aims at a systematic assessment of five computational models of a birdcage coil for magnetic resonance imaging (MRI) with respect to accuracy and computational cost. Methods: The models were implemented using the same geometrical model and numerical algorithm, but different driving methods (i.e., coil “defeaturing”). The defeatured models were labeled as: specific (S2), generic (G32, G16), and hybrid (H16, H16fr-forced). The accuracy of the models was evaluated using the “symmetric mean absolute percentage error” (“SMAPE”), by comparison with measurements in terms of frequency response, as well as electric (||E⃗||) and magnetic (||B⃗||) field magnitude. Results: All the models computed the ||B⃗|| within 35% of the measurements, only the S2, G32, and H16 were able to accurately model the ||E⃗|| inside the phantom with a maximum SMAPE of 16%. Outside the phantom, only the S2 showed a SMAPE lower than 11%. Conclusions: Results showed that assessing the accuracy of ||B⃗|| based only on comparison along the central longitudinal line of the coil can be misleading. Generic or hybrid coils - when properly modeling the currents along the rings/rungs - were sufficient to accurately reproduce the fields inside a phantom while a specific model was needed to accurately model ||E⃗|| in the space between coil and phantom. Significance: Computational modeling of birdcage body coils is extensively used in the evaluation of radiofrequency-induced heating during MRI. Experimental validation of numerical models is needed to determine if a model is an accurate representation of a physical coil.

Diffuse hemangiomatosis of the colon

We report extensive colonic hemangiomatosis in two young adults. In the first, the hemangioma contiguously involved the entire colon. In the second, a large venous angioma affected the bladder, rectosigmoid, and descending colon. Venous angioma, a variant of hemangioma, is frequently confused with cavernous hemangioma because of their similar histologic appearance. The angiographic features, however, may enable a more accurate preoperative diagnosis and prevent unwarranted biopsy. We review and put into perspective pertinent previous reports of cavernous and venous angioma.

Erosion of the scapula by a benign lipoma: computed tomography diagnosis.

A lipoma eroding the scapula is diagnosed by computed tomography.

Secondary ossification center of transverse process: A bone-scan normal variant

This report describes the bone-scan appearance of significantly increased activity in a lumbar transverse process of a 15-year-old boy; we believe it represents a normal variant related to the secondary ossification center.

A numerical investigation on the effect of RF coil feed variability on global and local electromagnetic field exposure in human body models at 64 MHz

This study aims to investigate how the positions of the feeding sources of the transmit radiofrequency (RF) coil, field orientation direction with respect to the patient, and patient dimensions affect the global and local electromagnetic exposure in human body models.

Cardiovascular Magnetic Resonance-Guided Electrophysiological Interventions: Radiofrequency Ablation of Typical Atrial Flutter.

Cardiovascular magnetic resonance–guided electrophysiological ablation of typical atrial flutter was performed in 5 patients using a fully magnetic resonance-compatible mapping and ablation catheter (Vision-MR; Imricor) on a 1.5-Tesla cardiovascular magnetic resonance system (Ingenia; Philips; Figure 1). All patients were under continuous physiological monitoring (including surface vector and intracardiac electrograms, pulse oximetry, and invasive blood pressure measurements) during intravenous propofol sedation. For interventional guidance, a 3-dimensional (3D), navigator-gated whole-heart sequence (steady-state–free precession) was acquired, and a 3D surface mesh model of all cardiac cavities was reconstructed with a fully automatic segmentation algorithm (Figure 2). Active catheter tracking and real-time passive …

Metastasis to an Ectopic Kidney Presenting as a Right Lower Quadrant Mass

AbstractA case is reported of bronchogenic carcinoma metastasizing to a crossed ectopic kidney, producing a right lower quadrant abdominal mass.

MP20-10 THE ACCURACY OF MAGNETIC RESONANCE IMAGING (MPMRI) GUIDED TRANSPERINEAL FUSION PROSTATE BIOPSIES (TPFB) TO EVALUATE LESIONS ON PROSTATE MPMRI USING PROSTATECTOMY SPECIMENS AS A VALIDATION TOOL.

INTRODUCTION AND OBJECTIVES: Precise localization of tumor locus is critically important for successful focal therapy in prostate cancer. The accuracy of multiparametric MRI (mpMRI) for prostate cancer localization is still unknown. METHODS: We retrospectively analyzed 176 prostate cancer patients who underwent preoperative 3.0T multiparametric MRI (mpMRI) followed by radical prostatectomy (RP) without neoadjuvant androgen deprivation. Images of mpMRI was evaluated by a single radiologist based on PI-RADS version 2. PI-RADS score 4 or greater was considered positive. Tumor distribution was evaluated on radical prostatectomy specimen sliced at 5-mm thick and tumor volume was estimated based on planimetry. RESULTS: Of the 176 study patients, 79 (45%) had negative mpMRI. Patients with negative mpMRI had smaller index tumor compared with those with positive mpMRI with a marginal significance (1.79 0.25 vs 20.5 0.22 cc., p 1⁄4 0.05, Figure and Table). They were also more likely to have clinically insignificant cancer (Gleason score 6 and tumor volume <0.5 cc.) compared with those with positive mpMRI (Tables). However, the sensitivity and specificity for clinically significant prostate cancer was only 60% and 57%, respectively, indicating that mpMRI missed 40% of clinically significant cancer. CONCLUSIONS: Although negative mpMRI is associated with favorable pathological findings in prostate cancer patients who underwent radical prostatectomy, mpMRI could not safely exclude clinically significant index tumor. Further improvement in the accuracy for tumor localization is warranted for the possible application of mpMRI to plan focal therapy.