Optimized 3D brachial plexus MR neurography using deep learning reconstruction

OBJECTIVE

To evaluate whether 'fast,' unilateral, brachial plexus, 3D magnetic resonance neurography (MRN) acquisitions with deep learning reconstruction (DLR) provide similar image quality to longer, 'standard' scans without DLR.

MATERIALS AND METHODS

An IRB-approved prospective cohort of 30 subjects (13F; mean age = 50.3 ± 17.8y) underwent clinical brachial plexus 3.0 T MRN with 3D oblique-coronal STIR-T2-weighted-FSE. 'Standard' and 'fast' scans (time reduction = 23-48%, mean = 33%) were reconstructed without and with DLR. Evaluation of signal-to-noise ratio (SNR) and edge sharpness was performed for 4 image stacks: 'standard non-DLR,' 'standard DLR,' 'fast non-DLR,' and 'fast DLR.' Three raters qualitatively evaluated 'standard non-DLR' and 'fast DLR' for i) bulk motion (4-point scale), ii) nerve conspicuity of proximal and distal suprascapular and axillary nerves (5-point scale), and iii) nerve signal intensity, size, architecture, and presence of a mass (binary). ANOVA or Wilcoxon signed rank test compared differences. Gwet's agreement coefficient (AC2) assessed inter-rater agreement.

RESULTS

Quantitative SNR and edge sharpness were superior for DLR versus non-DLR (SNR by + 4.57 to + 6.56 [p < 0.001] for 'standard' and + 4.26 to + 4.37 [p < 0.001] for 'fast;' sharpness by + 0.23 to + 0.52/pixel for 'standard' [p < 0.018] and + 0.21 to + 0.25/pixel for 'fast' [p < 0.003]) and similar between 'standard non-DLR' and 'fast DLR' (SNR: p = 0.436-1, sharpness: p = 0.067-1). Qualitatively, 'standard non-DLR' and 'fast DLR' had similar motion artifact, as well as nerve conspicuity, signal intensity, size and morphology, with high inter-rater agreement (AC2: 'standard' = 0.70-0.98, 'fast DLR' = 0.69-0.97).

CONCLUSION

DLR applied to faster, 3D MRN acquisitions provides similar image quality to standard scans. A faster, DL-enabled protocol may replace currently optimized non-DL protocols.

Postoperative Lumbar Fusion Bone Morphogenic Protein-Related Epidural Cyst Formation

Bone morphogenetic protein is broadly used in spinal surgery to enhance fusion rates. Several complications have been associated with the use of bone morphogenetic protein, including postoperative radiculitis and pronounced bone resorption/osteolysis. Bone morphogenetic protein-related epidural cyst formation may represent another complication that has not been described aside from limited case reports. In this case series, we retrospectively reviewed imaging and clinical findings of 16 patients with epidural cysts on postoperative MR imaging following lumbar fusion. In 8 patients, mass effect on the thecal sac or lumbar nerve roots was noted. Of these, 6 patients developed new postoperative lumbosacral radiculopathy. During the study period, most patients were managed conservatively, and 1 patient required revision surgery with cyst resection. Concurrent imaging findings included reactive endplate edema and vertebral bone resorption/osteolysis. Epidural cysts had characteristic findings on MR imaging in this case series and may represent an important postoperative complication in patients following bone morphogenetic protein-augmented lumbar fusion.

Evaluation of hypoparathyroidism following laryngectomy

BACKGROUND

Hypoparathyroidism is a recognised complication following laryngectomy; it is associated with significant short-and long-term morbidity. This study aimed to further characterise this condition, identify risk factors and describe preventative and management strategies in a large cohort.

MATERIALS AND METHODS

This was a retrospective study at a tertiary referral centre for head and neck cancers. All consecutive patients who had total laryngectomy over an eight-year period were included.

RESULTS

A total of 140 patients were included. Rates of transient and long-term hypoparathyroidism were 14.3% and 10.1%, respectively. The following factors were significantly associated with transient post-surgical hypocalcaemia or hypoparathyroidism: total thyroidectomy (relative risk, RR, 4.33; 95% confidence interval, CI, 1.86-10.10), oesophagectomy (RR 6.05; 95% CI 2.92-12.53) and female sex (RR 3.23; 95% CI 1.45-7.19). In addition, total thyroidectomy (RR 5.89; 95% CI 1.94-17.86), central neck dissection (RR 3.97; 95% CI 1.42-11.10), oesophagectomy (RR 9.38; 95% CI 4.13-21.3), pharyngectomy (RR 7.14; 95% CI 2.08-24.39) and female sex (RR 5.52; 95% CI 1.95-15.63) were risk factors for long-term hypoparathyroidism. There was variability in the use of preventative measures, monitoring and management of hypocalcaemia and hypoparathyroidism following total laryngectomy.

CONCLUSIONS

Transient hypocalcaemia and long-term hypoparathyroidism occur in a significant proportion of patients after laryngectomy. A standard protocol is required to improve care.

The association between lumbar paraspinal muscle functional cross-sectional area on MRI and regional volumetric bone mineral density measured by quantitative computed tomography

Osteosarcopenia is a common condition among elderly and postmenopausal female patients. Site-specific bone mineral density is more predictive of bone-related complications. Few studies have investigated muscle-bone associations. Our results demonstrated that in women, significant positive associations between paraspinal muscles FCSA and vBMD exist at different lumbosacral levels. These regional differences should be considered when interpreting bone-muscle associations in the lumbar spine.

INTRODUCTION

There is increasing evidence between bone and muscle volume associations. Previous studies have demonstrated comorbidity between osteoporosis and sarcopenia. Recent studies showed that sarcopenic subjects had a fourfold higher risk of concomitant osteoporosis compared to non-sarcopenic individuals. Although site-specific bone mineral density (BMD) assessments were reported to be more predictive of bone-related complications after spinal fusions than BMD assessments in general, there are few studies that have investigated level-specific bone-muscle interactions. The aim of this study is to investigate the associations between muscle functional cross-sectional area (FCSA) on magnetic resonance imaging (MRI) and site-specific quantitative computed tomography (QCT) volumetric bone mineral density (vBMD) in the lumbosacral region among spine surgery patients.

METHODS

We retrospectively reviewed a prospective institutional database of posterior lumbar fusion patients. Patients with available MRI undergoing posterior lumbar fusion were included. Muscle measurements and FCSA were conducted and calculated utilizing a manual segmentation and custom-written program at the superior endplate of the L3-L5 vertebrae level. vBMD measurements were performed and calculated utilizing a QCT pro software at L1-L2 levels and bilateral sacral ala. We stratified by sex for all analyses.

RESULTS

A total of 105 patients (mean age 61.5 years and 52.4% females) were included. We found that female patients had statistically significant lower muscle FCSA than male patients. After adjusting for age and body mass index (BMI), there were statistically significant positive associations between L1-L2 and S1 vBMD with L3 psoas FCSA as well as sacral ala vBMD with L3 posterior paraspinal and L5 psoas FCSA. These associations were not found in males.

CONCLUSIONS

Our results demonstrated that in women, significant positive associations between the psoas and posterior paraspinal muscle FCSA and vBMD exist in different lumbosacral levels, which are independent of age and BMI. These regional differences should be considered when interpreting bone and muscle associations in the lumbar spine.

Gradient nonlinearity calibration and correction for a compact, asymmetric magnetic resonance imaging gradient system

Due to engineering limitations, the spatial encoding gradient fields in conventional magnetic resonance imaging cannot be perfectly linear and always contain higher-order, nonlinear components. If ignored during image reconstruction, gradient nonlinearity (GNL) manifests as image geometric distortion. Given an estimate of the GNL field, this distortion can be corrected to a degree proportional to the accuracy of the field estimate. The GNL of a gradient system is typically characterized using a spherical harmonic polynomial model with model coefficients obtained from electromagnetic simulation. Conventional whole-body gradient systems are symmetric in design; typically, only odd-order terms up to the 5th-order are required for GNL modeling. Recently, a high-performance, asymmetric gradient system was developed, which exhibits more complex GNL that requires higher-order terms including both odd- and even-orders for accurate modeling. This work characterizes the GNL of this system using an iterative calibration method and a fiducial phantom used in ADNI (Alzheimer's Disease Neuroimaging Initiative). The phantom was scanned at different locations inside the 26 cm diameter-spherical-volume of this gradient, and the positions of fiducials in the phantom were estimated. An iterative calibration procedure was utilized to identify the model coefficients that minimize the mean-squared-error between the true fiducial positions and the positions estimated from images corrected using these coefficients. To examine the effect of higher-order and even-order terms, this calibration was performed using spherical harmonic polynomial of different orders up to the 10th-order including even- and odd-order terms, or odd-order only. The results showed that the model coefficients of this gradient can be successfully estimated. The residual root-mean-squared-error after correction using up to the 10th-order coefficients was reduced to 0.36 mm, yielding spatial accuracy comparable to conventional whole-body gradients. The even-order terms were necessary for accurate GNL modeling. In addition, the calibrated coefficients improved image geometric accuracy compared with the simulation-based coefficients.

Effects of ibopamine on renal haemodynamics in patients with severe congestive heart failure

The effects of a single dose of ibopamine on renal haemodynamics, sodium excretion, blood pressure (BP) and heart rate (HR) were investigated in 10 patients (aged 52-82 years) with severe congestive heart failure (CHF) who were in NYHA class IV. All patients used ACE inhibitors, digoxin and diuretics. After determining baseline values, ibopamine 100 mg was administered. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured simultaneously using radio pharmaceuticals. An increase in GFR and ERPF was observed during 3 and 2 h, with a maximum of 15 and 11%, respectively. The ratio GFR/ERPF representing the filtration fraction (FF) was markedly elevated at baseline, 34%, and remained unchanged. No clinically significant increase of sodium excretion was found. No changes in blood pressure, heart rate, plasma renin activity (PRA) and aldosterone or norepinephrine were observed. We conclude that ibopamine increases both ERPF and GFR in patients with severe CHF, possibly as a consequence of both inotropic cardiac and specific renal effects with equal preglomerular and postglomerular vasodilation. The lack of the presumed fall in FF may be the consequence of the expected DA1-induced renal vasodilation, partially reversed by the alpha adrenergic properties of ibopamine for this dose. Ibopamine caused no clinically significant natriuresis in these salt-depleted patients. No changes in PRA, aldosterone and catecholamines were found.

Long-term efficacy, curative potential, and carcinogenicity of topical mechlorethamine chemotherapy in cutaneous T cell lymphoma

Complete responses lasting from 4 to 14 years were documented in 65 of 331 (20%) patients with cutaneous T cell lymphoma treated with topical mechlorethamine (HN2) between 1968 and 1982. Such long-lasting remissions occurred most often, but not invariably, in patients with patch or plaque phase mycosis fungoides without palpable lymphadenopathy (stage Ia or Ib). The likelihood of a continuous remission was enhanced by initiation of treatment before an unequivocal pathologic diagnosis. Despite the long-lasting responses in these patients, however, relapses have been documented in 11 (17%) of these patients, and all relapses occurred within 8 years of discontinuing maintenance topical chemotherapy. Thus, in our experience, a continuous remission lasting 8 or more years provides evidence that cutaneous T cell lymphoma can be eradicated by aggressive topical chemotherapy. This circumstance was observed in 35 patients, representing a cure rate of at least 11% overall. In addition, when compared with the general population of the United States, patients who received topical HN2 were at an 8.6-fold and a 1.8-fold increased risk for the development of squamous cell carcinoma and enhanced for Hodgkin's disease and colon cancer but not for systemic cancers known to be induced by systemic administration of alkylating drugs. These results compare favorably with experiences with topical HN2 chemotherapy at other centers but raise questions about the risks associated with long-term administration for maintenance of remissions.

Respiratory responsiveness in male alcoholics after withdrawal

Peripheral and central chemosensitivity were assessed in eight abstinent male alcoholic patients and in seven healthy normal male subjects. Hypoxic rebreathing (15% O2, 7% CO2) was used to stimulate the peripheral and central chemoreceptors together. Hyperoxic rebreathing (93% O2, 7% CO2) was used to examine the central chemoreceptor response independently of the peripheral chemoreceptors. Minute ventilation was examined in relation to end-tidal PACO2 under the two conditions. Neither peripheral nor central chemoreceptor responses were significantly altered in the alcoholic as compared to the control subjects. Abnormal chemoreceptor function is therefore unlikely to be an important factor in the development of abnormal respiratory events during sleep in abstinent alcoholic subjects.

Sleep apnoea in alcoholic patients after withdrawal

Respiration during sleep was studied in 16 withdrawn alcoholic patients and in 12 control subjects. The alcoholic patients had increased numbers of central (P less than 0.01) and of obstructive (P less than 0.05) apnoea and of hypopnoea episodes (P less than 0.01) as compared with controls. Significant positive associations were found between the frequencies of central apnoea (P less than 0.05) or hypopnoea (P less than 0.01) and clinical evidence of central nervous system damage in the alcoholic patients. Hypopnoea also showed a significant association with vagal neuropathy (P less than 0.05), assessed by tests of cardioreflexes. We conclude that abnormal respiratory events are common in abstinent alcoholic patients and that they are likely to be at least partly related to nervous damage.

Alcoholic vagal neuropathy: recovery following prolonged abstinence

Cardiac vagal reflexes were studied in 11 alcoholic subjects, 1 to 6 weeks after withdrawal and again after up to 27 months of continued abstinence. On initial investigation six subjects had vagal neuropathy. On the second occasion only two subjects had vagal neuropathy and significant improvement was seen in the total patient group with regard to heart rate responses to standing, Valsalva's manoeuvre and atropine infusion. Vagal neuropathy in alcoholics may be reversible with abstinence and/or improved nutrition.

Erectile impotence in chronic alcoholics

Erectile impotence is a common complaint in alcoholics, but its mechanism is unknown. We have studied nocturnal penile erection in 13 alcoholics who complained of impotence. Seven had normal erections and their impotence was therefore psychogenic. Six were found to have diminished or absent nocturnal erections. Plasma concentrations of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were elevated in this latter group, with the exception of one patient who had only raised FSH. They also had more evidence of neurological damage than the other seven alcoholics, and two had evidence of damage to the parasympathetic nervous system. Investigation of erection during sleep in alcoholic patients with impotence may be useful in differentiating clinically between patients with psychogenic causes and patients with organic causes of impotence.

Parasympathetic denervation of the iris in alcoholics with vagal neuropathy

Parasympathetic innervation of the pupil was studied in 30 alcoholics. Twelve alcoholics had cardiac vagal neuropathy. The resting pupillary diameters in this group were larger, and pupil responses to methacholine were greater, than in control subjects or alcoholics without vagal neuropathy. These observations imply that lesions in the parasympathetic supply to the pupil may occur in alcoholics with other evidence of autonomic neuropathy involving the parasympathetic system.

Release of glucagon in male alcoholics with vagal neuropathy

There is evidence supporting involvement of the parasympathetic nervous system in the control of glucagon secretion. We have investigated the possible role of vagal neuropathy in alcoholics as a cause of alcoholic hypoglycemia. Slow infusions of insulin (2.4 U/hr) were carried out in ten male alcoholics, four with and six without evidence of vagal neuropathy, and in six male controls. The fall in blood glucose levels and the rise in serum glucagon levels in the alcoholics with or without vagal neuropathy were not significantly different from controls. We conclude that vagal neuropathy in alcoholics has no effect on the glucagon response to hypoglycemia.

Modified lipoprotein lipase activities, rates of lipogenesis, and lipolysis as factors leading to lipid depletion in C57BL mice bearing the preputial gland tumor, ESR-586

The biochemical basis for the observed depletion of adipose tissue in C57BL mice bearing a transplantable nonmetastasizing preputial gland tumor, ESR-586, has been investigated. The results have shown that there are a number of significant changes in both deposition and mobilization of lipid as the tumor grows. The first change, before the tumor reached 2 g, was a decline in the activity of adipose tissue lipoprotein lipase to levels normally found in starved animals. This was accompanied by a slight increase in lipoprotein lipase activity in heart and appearance of substantial activity in large tumors. Together, these would result in impaired uptake of exogenous fatty acids by adipose tissue, and dietary lipid would be directed away from storage. This was followed by a marked decline in endogenous lipid synthesis in adipose tissue which commenced when the tumor weighed between 2 and 3 g, as measured in vivo by the incorporation of radioactivity into lipid from tritiated water. The basal rate of lipolysis was enhanced 2-fold in epididymal fat pads from mice bearing tumors that weighed between 2 and 4 g, although there was no difference in the epinephrine-stimulated activity.