Improvements in Between-Vendor MRI Harmonization of Renal T2 Mapping using Stimulated Echo Compensation.

BACKGROUND: T2 mapping is valuable to evaluate pathophysiology in kidney disease. However, variations in T2 relaxation time measurements across MR scanners and vendors may occur requiring additional correction. PURPOSE: To harmonize renal T2 measurements between MR vendor platforms, and use an extended-phase-graph-based fitting method ("StimFit") to correct stimulated echoes and reduce between-vendor variations. STUDY TYPE: Prospective. SUBJECTS: 8 healthy "travelling" volunteers (37.5% female, 32 ± 6 years) imaged on four MRI systems across three vendors at four sites, 10 healthy volunteers (50% female, 32 ± 8 years) scanned multiple times on a given MR scanner for repeatability evaluation. ISMRM/NIST system phantom scanned for evaluation of T2 accuracy. FIELD STRENGTH/SEQUENCE: 3T, multiecho spin-echo sequence. ASSESSMENT: T2 images fit using conventional monoexponential fitting and "StimFit." Mean absolute percentage error (MAPE) of phantom measurements with reference T2 values. Average cortex and medulla T2 values compared between MR vendors, with masks obtained from T2 -weighted images and T1 maps. Full-width-at-half-maximum (FWHM) T2 distributions to evaluate local homogeneity of measurements. STATISTICAL TESTS: Coefficient of variation (CV), linear mixed-effects model, analysis of variance, student's t-tests, Bland-Altman plots, P-value <0.05 considered statistically significant. RESULTS: In the ISMRM/NIST phantom, "StimFit" reduced the MAPE from 4.9%, 9.1%, 24.4%, and 18.1% for the four sites (three vendors) to 3.3%, 3.0%, 6.6%, and 4.1%, respectively. In vivo, there was a significant difference in kidney T2 measurements between vendors using a monoexponential fit, but not with "StimFit" (P = 0.86 and 0.92, cortex and medulla, respectively). The intervendor CVs of T2 measures were reduced from 8.0% to 2.6% (cortex) and 7.1% to 2.8% (medulla) with StimFit, resulting in no significant differences for the CVs of intravendor repeat acquisitions (P = 0.13 and 0.05). "StimFit" significantly reduced the FWHM of T2 distributions in the cortex and whole kidney. DATA CONCLUSION: Stimulated-echo correction reduces renal T2 variation across MR vendor platforms. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 1.

Automated renal segmentation in healthy and chronic kidney disease subjects using a convolutional neural network.

PURPOSE: Total kidney volume (TKV) is an important measure in renal disease detection and monitoring. We developed a fully automated method to segment the kidneys from T2 -weighted MRI to calculate TKV of healthy control (HC) and chronic kidney disease (CKD) patients. METHODS: This automated method uses machine learning, specifically a 2D convolutional neural network (CNN), to accurately segment the left and right kidneys from T2 -weighted MRI data. The data set consisted of 30 HC subjects and 30 CKD patients. The model was trained on 50 manually defined HC and CKD kidney segmentations. The model was subsequently evaluated on 50 test data sets, comprising data from 5 HCs and 5 CKD patients each scanned 5 times in a scan session to enable comparison of the precision of the CNN and manual segmentation of kidneys. RESULTS: The unseen test data processed by the 2D CNN had a mean Dice score of 0.93 ± 0.01. The difference between manual and automatically computed TKV was 1.2 ± 16.2 mL with a mean surface distance of 0.65 ± 0.21 mm. The variance in TKV measurements from repeat acquisitions on the same subject was significantly lower using the automated method compared to manual segmentation of the kidneys. CONCLUSION: The 2D CNN method provides fully automated segmentation of the left and right kidney and calculation of TKV in <10 s on a standard office computer, allowing high data throughput and is a freely available executable.

Laparoscopic ovariohysterectomy in goats.

OBJECTIVE To describe a minimally invasive 3-portal laparoscopic approach for elective ovariohysterectomy and the outcome of that procedure in a population of goats. DESIGN Descriptive clinical study. ANIMALS 16 healthy client-owned goats. PROCEDURES Food but not water was withheld from all goats for 24 hours before the procedure. Goats were anesthetized and positioned in dorsal recumbency. Three laparoscopic portals were created in the caudoventral portion of the abdomen, and the abdomen was insufflated to a maximum pressure of 10 mm Hg. A blunt-tip vessel sealer and divider device was used to transect the left and right mesovarium and mesometrium and uterus, and the resected tissue was removed from the abdomen. After hemostasis was verified, the portals were closed in a routine manner and anesthesia was discontinued. Goats were discharged from the hospital 24 hours after the procedure, and owners were contacted by telephone or email to obtain short- and long-term follow-up information by use of standardized questions. RESULTS All procedures were performed by a surgeon and assistant surgeon. The procedure was not complex and was easily learned. No intraoperative complications were reported, and only 1 goat required rescue analgesia post-operatively. No other postoperative complications were recorded. Median surgery time was 43 minutes (range, 20 to 65 minutes). All owners were satisfied with the outcome of the procedure, and several perceived that the procedure improved goat behavior. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that laparoscopic ovariohysterectomy was a viable alternative for elective sterilization of female goats.

Exploring the relative efficacy of motion artefact correction techniques for EEG data acquired during simultaneous fMRI.

Simultaneous EEG-fMRI allows multiparametric characterisation of brain function, in principle enabling a more complete understanding of brain responses; unfortunately the hostile MRI environment severely reduces EEG data quality. Simply eliminating data segments containing gross motion artefacts [MAs] (generated by movement of the EEG system and head in the MRI scanner's static magnetic field) was previously believed sufficient. However recently the importance of removal of all MAs has been highlighted and new methods developed. A systematic comparison of the ability to remove MAs and retain underlying neuronal activity using different methods of MA detection and post-processing algorithms is needed to guide the neuroscience community. Using a head phantom, we recorded MAs while simultaneously monitoring the motion using three different approaches: Reference Layer Artefact Subtraction (RLAS), Moiré Phase Tracker (MPT) markers and Wire Loop Motion Sensors (WLMS). These EEG recordings were combined with EEG responses to simple visual tasks acquired on a subject outside the MRI environment. MAs were then corrected using the motion information collected with each of the methods combined with different analysis pipelines. All tested methods retained the neuronal signal. However, often the MA was not removed sufficiently to allow accurate detection of the underlying neuronal signal. We show that the MA is best corrected using the RLAS combined with post-processing using a multichannel, recursive least squares (M-RLS) algorithm. This method needs to be developed further to enable practical utility; thus, WLMS combined with M-RLS currently provides the best compromise between EEG data quality and practicalities of motion detection.

Concentrations of serum amyloid A and plasma fibrinogen in horses undergoing emergency abdominal surgery.

OBJECTIVE: To compare the perioperative response of serum amyloid A (SAA) to fibrinogen in horses requiring exploratory celiotomy for colic and to determine if SAA could be used to predict complications and outcome. DESIGN: Prospective observational clinical study. SETTING: University teaching hospital. ANIMALS: Eighteen horses undergoing exploratory celiotomy for colic. Inclusion criteria for the study included survival and anesthetic recovery from exploratory celiotomy, no history of surgery within the past year. INTERVENTIONS: Blood was obtained via jugular venipuncture before surgery (time 0) and at 24, 48, 72, and 96 hours after recovery from anesthesia. MEASUREMENTS AND MAIN RESULTS: Quantitative and semiquantitative fibrinogen, SAA, total nucleated cell counts, and total protein were evaluated at each time point. Multivariable linear regression was used to assess differences at each time point and after grouping horses according to duration of colic prior to surgery, strangulating surgical lesion or not, presence of systemic inflammatory response syndrome (SIRS) on admission, and postsurgical complications. Significant (P < 0.05) increases in SAA concentrations occurred in all cases after surgery compared to fibrinogen concentration, which only demonstrated a mild, clinically insignificant increase postsurgery. SAA concentrations were also significantly increased (P < 0.05) in cases identified with SIRS prior to surgery and postoperatively at 48 (P = 0.05) and 72 hours (P = 0.02) in horses that developed complications. CONCLUSIONS: Measurement of SAA is a more sensitive indicator of inflammation than fibrinogen in the perioperative period of horses requiring exploratory celiotomy for colic. Serial measurement of SAA at 48, 72, and 96 hours after surgery may be helpful to determine risk of complications and guide postoperative management. Measurement of SAA on admission also allows for quantification of SIRS when it is detected clinically.

Laparoscopic inguinal hernioplasty in a ram.

CASE DESCRIPTION: A 4-month-old Hampshire ram underwent open right inguinal herniorrhaphy and unilateral castration following herniation that developed after a kick injury. Seven months later, the ram was reevaluated because of scrotal swelling of 1 month's duration as well as suspected left inguinal hernia. CLINICAL FINDINGS: The ram had marked scrotal swelling. Palpation of the left testicle revealed no abnormalities. Ultrasonographic examination revealed heterogenous tissue within the cranial and medial portions of the scrotum with pronounced accumulation of hypoechoic fluid at the scrotal apex. Examination findings indicated left-sided indirect inguinal herniation of omentum. TREATMENT AND OUTCOME: To preserve fertility, left inguinal hernioplasty without castration was performed. The ram was anesthetized and placed in dorsal recumbency, and laparoscopic abdominal evaluation revealed omental entrapment within the left inguinal ring. The omentum was removed, and a polypropylene mesh was secured over the internal inguinal ring with an articulating hernia stapler. Following mesh placement, a dorsally based peritoneal flap was elevated and secured over the mesh repair. The ram recovered well from surgery; there was no repeated herniation following the surgical correction, and the ram was able to breed successfully without complication. CLINICAL RELEVANCE: Laparoscopic mesh hernioplasty can be successful in rams with inguinal hernias when preservation of fertility is preferred.

Comparison of radiography, nuclear scintigraphy, and magnetic resonance imaging for detection of specific conditions of the distal tarsal bones of horses: 20 cases (2006-2010).

OBJECTIVE: To describe pathological findings identified with MRI in the distal tarsal bones of horses with unilateral hind limb lameness attributable to tarsal pain and to compare the usefulness of MRI with that of radiography and nuclear scintigraphy in evaluation of this region. DESIGN: Retrospective case series. ANIMALS: 20 lame horses. PROCEDURES: In all horses, MRI, radiography (4 standard projections), and nuclear scintigraphy of the tarsus had been performed. Horses were excluded if the results of all 3 imaging modalities were not available or if lameness was detected in more than 1 limb. Pathological changes identified with MRI were cross-referenced with the findings determined with other imaging modalities. RESULTS: Compared with MRI findings, the following lesions were identified with radiography: medullary and subchondral bone sclerosis in 9 of 16 horses, pathological changes related to osseous hyperintensity in 0 of 10 horses, and osteoarthritis in 5 of 8 horses. Standard radiographic projections did not aid in the identification of fracture of the distal tarsal bones (3 horses). Location of increased radiopharmaceutical uptake with nuclear scintigraphy corresponded with the location of pathological changes detected with MRI in all horses. The intensity of the radiopharmaceutical uptake on nuclear scintigraphic images did not correspond with the severity of the pathological changes identified with MRI. CONCLUSIONS AND CLINICAL RELEVANCE: Radiography was unreliable for the detection of pathological changes related to osseous hyperintensity identified with MRI, fracture, and subchondral bone sclerosis in the equine tarsus. Nuclear scintigraphy was effective in localizing pathological changes, but MRI provided superior anatomic detail.