Impact of the COVID-19 pandemic on emergency healthcare utilization: a cohort study

Background

Emergency department (ED) crowding is a burden on public health, so understanding the characteristics of frequent ED users is a key concern of the healthcare system and policy makers. This study aims to examine the characteristics and healthcare-seeking behaviors in frequent ED users before and during the COVID-19 pandemic.

Methods

A retrospective observational study was conducted on ED users aged 18 years and over admitted to Taipei City Hospital in February 2019-January2020 (before pandemic) and February 2020-January2021 (during pandemic) (N = 120,011). Frequent and ED users were defined as patients with four or more ED visits in a year. Multivariate logistic regression was used to identify the predictors of frequent ED use before and during the COVID-19 pandemic.

Results

Monthly emergency department visits were significantly lower during the pandemic (by 10.1-26.8%). Frequent ED patients had shorter lengths of stay in the ED during the pandemic (212.5 vs.233.9 minutes; P < 0.0001). The proportion of ED patients receiving chest CT examination during the pandemic has increased by 0.5-0.6%. After adjusting for sociodemographic factors, triage status, mode of arrival, and copayment exemption, patients with a triage status of level 4-5 (AOR=1.60, 95% CI: 1.13-2.28), diagnosis of pneumonia (AOR=1.85, 95% CI: 1.07-3.17), giddiness (AOR=2.85, 95% CI: 1.82-4.45), dyspnea (AOR=1.85, 95% CI: 1.00-3.39), or chronic kidney disease (AOR=5.05, 95% CI: 2.66-9.59) were more likely to be frequent ED visitors during the pandemic.

Conclusions

Since SAR-CoV-2 is highly contagious, it is imperative to educate non-emergent patients to utilize outpatient medical services rather than emergency medical services to reduce the risk of COVID-19 outbreaks at the ED.

Key messages

This study found that the utilization of emergent medical services during the COVID-19 pandemic significantly decreased by 10.1%–26.8% compared to before the COVID-19 pandemic. The lengths of stay in frequent ED users during the COVID-19 pandemic were significantly shorter than that in frequent ED users before the COVID-19 pandemic.

Mask reuse during the COVID-19 pandemic: a national survey in Taiwan

Background

The use of masks is an effective measure to prevent severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) infection; however, mask reuse is not recommended. Studies examining the factors associated with mask reuse during the coronavirus disease (COVID-19) pandemic are limited. This nationwide survey aimed to determine the prevalence and factors associated with mask reuse among Taiwanese citizens during the pandemic.

Methods

From May 18 through May 31, 2020, a computer-assisted telephone interview system was used to randomly select Taiwanese citizens who were interviewed for COVID-19 preventive behaviors and knowledge on the usage of masks. Multivariate logistic regression was used to identify factors associated with mask reuse during the COVID-19 pandemic. Moreover, generalized estimating equations (GEE) were used to analyze the rate of mask reuse among participants before and during the pandemic.

Results

For a total of 1,075 participants, the overall mean age was 57.4 years, and 82.2% of participants reported mask reuse during the COVID-19 pandemic. After controlling for other covariates, participants who had a greater knowledge on mask usage or had a high supply of masks were less likely to reuse masks during the pandemic. GEE analysis showed that compared with the participants' mask wearing behaviors before the COVID-19 pandemic, they were more likely to reuse masks during the pandemic.

Conclusions

The rate of mask reuse among the general population during the pandemic was significantly higher than that before the pandemic. Individuals were less likely to reuse masks if they had adequate knowledge on mask usage or had a high supply of masks. Since mask reuse is associated with a higher risk of COVID-19 due to the possibility of wearing SAS-CoV-2-contaminated masks, it is imperative to educate people on the correct usage of masks. Further, the government should provide sufficient masks to the general population to decrease the reuse of masks.

Key messages

Mask reuse increased during the COVID-19 pandemic due to the shortage in supply. It is imperative to educate people about the correct usage of masks.

Multisite Concordance of DSC-MRI Analysis for Brain Tumors: Results of a National Cancer Institute Quantitative Imaging Network Collaborative Project

BACKGROUND AND PURPOSE

Standard assessment criteria for brain tumors that only include anatomic imaging continue to be insufficient. While numerous studies have demonstrated the value of DSC-MR imaging perfusion metrics for this purpose, they have not been incorporated due to a lack of confidence in the consistency of DSC-MR imaging metrics across sites and platforms. This study addresses this limitation with a comparison of multisite/multiplatform analyses of shared DSC-MR imaging datasets of patients with brain tumors.

MATERIALS AND METHODS

DSC-MR imaging data were collected after a preload and during a bolus injection of gadolinium contrast agent using a gradient recalled-echo-EPI sequence (TE/TR = 30/1200 ms; flip angle = 72°). Forty-nine low-grade (n = 13) and high-grade (n = 36) glioma datasets were uploaded to The Cancer Imaging Archive. Datasets included a predetermined arterial input function, enhancing tumor ROIs, and ROIs necessary to create normalized relative CBV and CBF maps. Seven sites computed 20 different perfusion metrics. Pair-wise agreement among sites was assessed with the Lin concordance correlation coefficient. Distinction of low- from high-grade tumors was evaluated with the Wilcoxon rank sum test followed by receiver operating characteristic analysis to identify the optimal thresholds based on sensitivity and specificity.

RESULTS

For normalized relative CBV and normalized CBF, 93% and 94% of entries showed good or excellent cross-site agreement (0.8 ≤ Lin concordance correlation coefficient ≤ 1.0). All metrics could distinguish low- from high-grade tumors. Optimum thresholds were determined for pooled data (normalized relative CBV = 1.4, sensitivity/specificity = 90%:77%; normalized CBF = 1.58, sensitivity/specificity = 86%:77%).

CONCLUSIONS

By means of DSC-MR imaging data obtained after a preload of contrast agent, substantial consistency resulted across sites for brain tumor perfusion metrics with a common threshold discoverable for distinguishing low- from high-grade tumors.

Association between obesity and risk of chronic kidney disease: A nationwide Cohort study in Taiwan

BACKGROUND AND AIMS

Increased body fat relates to enhanced inflammatory cytokine production, which, in turn, activates the renin-angiotensin-aldosterone system and increases the risk of chronic kidney disease (CKD). Herein, we aimed to examine the association between obesity and the risk of CKD in a population-representative cohort in Taiwan.

METHODS AND RESULTS

A multistage systematic sampling process was applied in the National Health Interview Survey (NHIS) 2000, 2005, and 2009. Participants were interviewed by a standardized face-to-face questionnaire to obtain information on their demographics, socioeconomic status, lifestyle factors, and body mass index (BMI). The BMI values were classified as follows: underweight (<18.5 kg/m²), normal (18.5-23.9 kg/m²), overweight (24-26.9 kg/m²), and obesity (≥27 kg/m²). The NHIS dataset was linked to National Health Insurance claims data to identify the incidence of CKD. Univariate and multivariate Cox proportional hazard models with competing risks were used to investigate the association between BMI and CKD incidence. We analyzed 45,012 subjects (mean age, 42.03 years; 50.09% males). During 374,254 person-years of follow-up, a total of 1913 new-onset CKD cases were identified. Kaplan-Meier curves comparing the four BMI groups revealed a significant difference (p < 0.01, log-rank test). After controlling for confounding factors, the relative risk of incident CKD was significantly higher in the obese group compared to the normal-weight group (adjusted hazard ratio = 1.32; 95% confidence interval: 1.17-1.49), with a significant linear trend (p < 0.01).

CONCLUSION

Obesity was suggested as an independent risk factor for CKD. Further studies focusing on the effect of losing weight on CKD prevention are warranted.

Increased risk of incident osteoporosis and osteoporotic fracture in tuberculosis patients: a population-based study in a tuberculosis-endemic area

The occurrence of osteoporosis in tuberculosis, a chronic infection, has rarely been evaluated. In this study, we found significantly higher incidence rates of osteoporosis (Adjusted hazard ratio (AHR) 1.82) and osteoporotic fracture (AHR 2.33) in tuberculosis patients than matched cohorts, which suggest that osteoporosis screening should be considered in tuberculosis patients' follow-up program. The aim of this study is to determine the occurrence of incident osteoporosis in patients who completed anti-tuberculosis (TB) treatment.

INTRODUCTION

Chronic inflammatory disorders are associated with an increased risk of osteoporosis. Although TB is an infectious disease characterized by systemic inflammatory responses, the impact of active TB on incident osteoporosis is unclear. We used the Taiwan National Health Insurance Research Database to investigate the association between history of active TB and incident osteoporosis and osteoporotic fracture.

METHODS

In this nationwide retrospective cohort study, active TB patients and their age- and sex-matched controls were identified from the National Health Insurance Research Database in Taiwan during 2000-2012. The occurrence of incident osteoporosis, osteoporotic fractures, and risk factors associated with osteoporosis among TB patients and matched controls were analyzed.

RESULTS

We observed incident osteoporosis in 2.2% (n = 86) of the TB patients and in 1.1% (n = 162) of the matched controls. The incidence rate of osteoporosis was 4.31 and 1.80 per 1000 person-years, which was significantly higher in TB patients (p < 0.001). In multivariate analysis, TB was an independent risk factor for osteoporosis. The other independent factors associated with osteoporosis were older age, female sex, chronic obstructive pulmonary disease, asthma, and lower income. Moreover, we demonstrated that the occurrence of osteoporotic fracture was significantly higher in TB patients.

CONCLUSIONS

Patients with a history of active TB have a higher incidence rate of osteoporosis and osteoporotic fracture.

Obesity/overweight reduces the risk of active tuberculosis: a nationwide population-based cohort study in Taiwan

BACKGROUND

Obesity affects immune function by increasing the number of T helper lymphocytes, which may reduce the risk of tuberculosis (TB) infection. However, the effect of obesity on TB development has not been extensively studied. This nationwide population-based cohort study investigated the effect of obesity on TB development in Taiwanese adults.

METHODS

We included 46 028 adult participants (age ⩾18 years) from three rounds (2001, 2005 and 2009) of the Taiwan National Health Interview Survey. Obesity and overweight were defined as a body mass index (BMI) ⩾27 and 24-26.9 (kg/m²), respectively. Data on BMI and other covariates at baseline were collected by in-person interviews. Incident cases of active TB were identified from the National Health Insurance database. Multivariable logistic regression was used to estimate the associations of obesity and overweight with active TB, with adjustment for age, sex, smoking, alcohol consumption, socioeconomic status and other covariates.

RESULTS

In total, 241 new cases of active TB occurred during the study period. Obesity (adjusted odds ratio [AOR], 0.43; 95% confident interval [CI], 0.28-0.67) and overweight (AOR, 0.67; 95% CI, 0.49-0.91) were associated with lower risk of incident TB, after adjusting for demographic characteristics and comorbidities. There was a linear dose-response relation of BMI with active TB incidence (AOR per unit change in BMI, 0.92; 95% CI, 0.88-0.95; P <0.001).

CONCLUSION

Obesity and overweight are associated with lower risk of active TB. Future studies should investigate the underlying mechanisms and clinical and epidemiological consequences of these findings.

DOT associated with reduced all-cause mortality among tuberculosis patients in Taipei, Taiwan, 2006-2008

OBJECTIVE

To determine whether patients receiving directly observed treatment (DOT) had lower all-cause mortality than those treated with self-administered treatment (SAT) and to identify factors associated with mortality among tuberculosis (TB) patients.

DESIGN

All TB patients in Taipei, Taiwan, diagnosed between 2006 and 2008 were included in a retrospective cohort study.

RESULTS

Among 3624 TB patients, 45.5% received DOT, which was disproportionately offered to older patients and those with more underlying illness and severe TB disease. After controlling for patients' sociodemographic factors, clinical findings and underlying comorbidities, the odds of death were 40% lower (aOR 0.60, 95%CI 0.5-0.8) among patients treated with DOT than those on SAT. After adjusting for DOT, independent predictors of death included non-Taiwan birth, increasing age, male, unemployment, end-stage renal disease requiring dialysis, malignancy, acid-fast bacilli smear positivity and pleural effusion.

CONCLUSION

DOT was associated with lower all-cause mortality after controlling for confounding factors. DOT should be expanded in Taiwan to improve critical treatment outcomes among TB patients.

Realignment capability of the nCPMG sequence

The nCPMG sequence is based on a particular phase modulation of the refocusing pulse train, and was originally designed for rendering the spin echo amplitude insensitive to the initial magnetization phase. This pulse sequence has the peculiarity of being easily invertible, which enables perfect driven equilibrium experiments, in the absence of relaxation. This magnetization 'realignment' is effective for all three components. Hence the overall operation is transparent. Supporting theory is presented here, together with the first direct experimental proof of the claim. The experiment shows that, with the present stabilization sequence, perfect realignment is indeed made possible for a range of refocusing pulse nutation angles from 130° to 230°.

Cortical reorganization following anterior temporal lobectomy in patients with temporal lobe epilepsy

BACKGROUND

Functional MRI was used to study the impact of temporal lobe epilepsy (TLE) and anterior temporal lobectomy (ATL) on the cortical language network in patients with medically refractory TLE.

METHODS

Nineteen patients with medically refractory TLE and 11 healthy control subjects were enrolled in this study. Ten patients underwent left ATL (mean age 35.2 +/- 3.8 years), and 9 underwent right ATL (mean age 35.9 +/- 2.6 years). The subjects silently generated verbs in response to a series of visually presented nouns inside the scanner. Correlation analysis was performed between the subjects' performance on the clinical language tests and their neural response in the a priori cortical regions.

RESULTS

Preoperative data revealed that the patients with TLE showed increased neural activity in the right inferior frontal gyri (IFG) and middle frontal gyri (MFG). The right TLE patients demonstrated strong correlation between their language performance and the level of cortical activation within the typical language areas. However, such a correlation was absent in the left TLE patients. After the ATL surgery, the left TLE patients showed reduced activation in the left MFG and right IFG, whereas no difference was observed in the right TLE patients. In the right TLE patients, the correlation between language performance and neural response shifted from the typical language areas to the anterior cingulate cortex.

CONCLUSION

This study demonstrates that the cortical language network is affected differently by the left and right temporal lobe epilepsy and is reorganized after anterior temporal lobectomy.

Imaging considerations for in vivo 13C metabolic mapping using hyperpolarized 13C-pyruvate

One of the challenges of optimizing signal-to-noise ratio (SNR) and image quality in (13)C metabolic imaging using hyperpolarized (13)C-pyruvate is associated with the different MR signal time-courses for pyruvate and its metabolic products, lactate and alanine. The impact of the acquisition time window, variation of flip angles, and order of phase encoding on SNR and image quality were evaluated in mathematical simulations and rat experiments, based on multishot fast chemical shift imaging (CSI) and three-dimensional echo-planar spectroscopic imaging (3DEPSI) sequences. The image timing was set to coincide with the peak production of lactate. The strategy of combining variable flip angles and centric phase encoding (cPE) improved image quality while retaining good SNR. In addition, two aspects of EPSI sampling strategies were explored: waveform design (flyback vs. symmetric EPSI) and spectral bandwidth (BW = 500 Hz vs. 267 Hz). Both symmetric EPSI and reduced BW trended toward increased SNR. The imaging strategies reported here can serve as guidance to other multishot spectroscopic imaging protocols for (13)C metabolic imaging applications.

Optimization of fast spiral chemical shift imaging using least squares reconstruction: application for hyperpolarized (13)C metabolic imaging

A least-squares-based optimization and reconstruction algorithm has been developed for rapid metabolic imaging in the context of hyperpolarized (13)C. The algorithm uses a priori knowledge of resonance frequencies, J-coupling constants, and T(2)* values to enable acquisition of high-quality metabolic images with imaging times of approximately 100 ms for an 8-cm field of view (FOV) and 0.5 cm isotropic resolution. A root-mean-square error (rMSE) analysis is introduced to optimize metabolic image quality by appropriate choice of pulse sequence parameters, echo times, and signal model. By performing the reconstruction in k-space, the algorithm also allows the inclusion of the effect of chemical shift evolution during the readout period. Single-interleaf multiecho spiral chemical shift imaging (spCSI) is analyzed in detail as an illustrative example for the use of the new reconstruction and optimization algorithm. Simulation of the in vivo spectrum following the bolus injection of hyperpolarized (13)C(1) pyruvate shows that single-interleaf spiral spectroscopic imaging can achieve image quality in 100 ms, comparable to the performance of a 13-s phase-encoded chemical shift imaging (FIDCSI) experiment. Single-interleaf spCSI was also tested at a 3-T MR scanner using a phantom containing approximately 0.5-M solutions of alanine, lactate, and a pyruvate-pyruvate hydrate C(1)-C(2) ester at thermal equilibrium polarization, all enriched to 99% (13)C in the C(1) carbonyl positions. Upon reconstruction using the k-space-based least-squares technique, metabolite ratios obtained using the spCSI method were comparable to those obtained using a reference FIDCSI acquisition.

Classification of the guava wilt fungus Myxosporium psidii, the palm pathogen Gliocladium vermoesenii and the persimmon wilt fungus Acremonium diospyri in Nalanthamala

Psidium guajava wilt is known from South Africa, Malaysia and Taiwan. The fungus causing this disease, Myxosporium psidii, forms dry chains of conidia on surfaces of pseudoparenchymatous sporodochia, which develop in blisters on bark. Similar sporodochia are characteristic of Nalanthamala madreeya, the type species of Nalanthamala. Nalanthamala, therefore, is the appropriate anamorph genus for Myxosporium psidii, while Myxosporium is a nomen nudum (based on M. croceum). For M. psidii the combination Nalanthamala psidii is proposed. Nalanthamala psidii, the palm pathogen Gliocladium (Penicillium) vermoesenii, another undescribed anamorphic species from palm, two species of Rubrinectria and the persimmon pathogen Acremonium diospyri are monophyletic and belong to the Nectriaceae (Hypocreales) based on partial nuclear large subunit ribosomal DNA (LSU rDNA) analyses. Rubrinectria, therefore, is the teleomorph of Nalanthamala, in which the anamorphs are classified as N. vermoesenii, N. diospyri or Nalanthamala sp. Nalanthamala squamicola, the only other Nalanthamala species, has affinities with the Bionectriaceae and is excluded from this group. Rubrinectria/Nalanthamala species form dimorphic conidiophores and conidia in culture. Fusiform, cylindrical, or allantoid conidia arise in colorless liquid heads on acremonium-like conidiophores; ovoidal conidia with somewhat truncated ends arise in long, persistent, dry chains on penicillate conidiophores. No penicillate but irregularly branched conidiophores were observed in N. diospyri. Conidia of N. psidii that are held in chains are shorter than those of N. madreeya, of which no living material is available. Nalanthamala psidii and N. diospyri are pathogenic specifically to their hosts. They form pale yellow to pale orange or brownish orange colonies, respectively, and more or less white conidial masses. Most strains of Rubrinectria sp., Nalanthamala sp. and N. vermoesenii originate from palm hosts, form mostly greenish or olive-brown colonies and white-to-salmon conidial masses. They form a monophyletic clade to which Nalanthamala psidii and N. diospyri are related based on analyses of the internal transcribed spacer regions and 5.8S rDNA (ITS rDNA), LSU rDNA, and partial beta-tubulin gene. Few polymorphic sites in the ITS rDNA and beta-tubulin gene indicate that Nalanthamala psidii comprises two lineages, one of which has been detected only in South Africa.

Risk to breeding success of Ardeids by contaminants in Hong Kong: evidence from trace metals in feathers

The feathers of two Ardeid species, the Little Egret (Egretta garzetta) and the Black-crowned Night Heron (Nycticorax nycticorax) were collected from six egretries and two egretries respectively, located in different areas in the New Territories of Hong Kong, including the Mai Po Marshes (within a Ramsar site). These feathers were digested and concentrations (microg/g dry weight) of copper (4.6-19.4), iron (8.1-641.3), manganese (0.4-19.4), zinc (51.3-183.5), lead (0.1-5.1), cadmium (0.01-0.15), chromium (0.06-1.7) and mercury (0.0-7.1) were determined by ICP-AES, ICP-MS and CVAAS. The levels of manganese, mercury and lead found were equal to or less than the concentrations found in previous investigations, reflecting a slight downward trend most apparent with lead. As a general rule, the levels of lead and mercury were higher in the egretries close to the polluted Deep Bay. A probabilistic risk assessment of the possible adverse effects on the breeding success of the Little Egret was carried out with respect to mercury, lead and cadmium. It was concluded that mercury (0.5-7.1 microg/g dry weight feathers) probably has had adverse effects at the Au Tau egretry of the Little Egrets, but there was no evidence of adverse effects at other egretries. The probabilistic analysis also indicated a low likelihood of adverse effects of mercury on the breeding of the Black-crowned Night Herons at A Chau (0.3-1.2 microg/g) and Mai Po Village (0.0-1.4 microg/g). The evidence for the effects of lead and cadmium was limited but suggested there may possibly be adverse effects with lead but not cadmium.

High b-value diffusion-weighted MRI of normal brain

PURPOSE

As MR scanner hardware has improved, allowing for increased gradient strengths, we are able to generate higher b values for diffusion-weighted (DW) imaging. Our purpose was to evaluate the appearance of the normal brain on DW MR images as the diffusion gradient strength ("b value") is increased from 1,000 to 3,000 s/mm2.

METHOD

Three sets of echo planar images were acquired at 1.5 T in 25 normal subjects (mean age 61 years) using progressively increasing strengths of a diffusion-sensitizing gradient (corresponding to b values of 0, 1,000, and 3,000 s/mm2). All other imaging parameters remained constant. Qualitative assessments of trace images were performed by two neuroradiologists, supplemented by quantitative measures of MR signal and noise in eight different anatomic regions.

RESULTS

As gradient strength increased from b = 1,000 to 3,000, both gray and white matter structures diminished in signal as expected based on their relative diffusion coefficients [calculated average apparent diffusion coefficient (ADC) values: gray matter = 8.5 x 10(-4) mm2/s, white matter = 7.5 x 10(-4) mm2/s]. The signal-to-noise ratios for the b = 1,000 images were approximately 2.2 times higher than for the b = 3,000 images (p < 0.0001). As the strength of the diffusion-sensitizing gradient increased, white matter became progressively hyperintense to gray matter. Relative to the thalamus, for example, the average MR signal intensity of white matter structures increased by an average of 27.5%, with the densely packed white matter tracts (e.g., middle cerebellar peduncle, tegmentum, and internal capsule) increasing the most.

CONCLUSION

Brain DW images obtained at b = 3,000 appear significantly different from those obtained at b = 1,000, reflecting expected loss of signal from all areas of brain in proportion to their ADC values. Consequently, when all other imaging parameters are held constant, b = 3,000 DW images appear significantly noisier than b = 1,000 images, and white matter tracts are significantly more hyperintense than gray matter structures.

False cerebral activation on BOLD functional MR images: study of low-amplitude motion weakly correlated to stimulus

BACKGROUND AND PURPOSE

Movements of the participant during blood oxygen level-dependent (BOLD) functional MR imaging cerebral activation studies are known to produce occasionally regions of false activation, especially when these movements are relatively large (>3 mm) and highly correlated with the stimulus. We investigated whether minimal (<1 mm), weakly correlated movements in a controlled functional MR imaging model could produce false activation artifacts that could potentially mimic regions of true activation in size, location, and statistical significance.

METHODS

A life-size brain phantom was constructed by embedding vials of a dilute carboxylic acid solution within a gadolinium-doped gelatin mold. Imaging was performed at 1.5 T using a 2D spiral sequence (3,000/5 [TR/TE]; flip angle, 88 degrees; matrix, 64 x 64; field of view, 24 cm; section thickness, 5 mm). Controlled, in-plane, submillimeter movements of the phantom were generated using a pneumatic system and were made to correlate with a hypothetical "boxcar" stimulus over the range 0.31 < r < 0.96. Regions of false activation were sought using standard statistical methods (SPM96) that excluded phantom edges and accounted for spatial extent (regions tested at P < .05, corrected for multiple comparisons). A similar experiment was performed on a resting volunteer.

RESULTS

The pneumatic system provided motion control with average in-plane displacements and rotations of 0.74 mm and 0.47 degrees, respectively, in the 18 data sets analyzed. No areas of false activation in the phantom were identified for poorly correlated motions (r < 0.52). Above this level, false activations occurred with increasing frequency, scaling in size and number with the degree of motion correlation. For motions with r > 0.67, areas of false activation were seen in every experiment. For a statistical threshold of P = .001, the median number of falsely activated regions was 3.5, with a mean size of 71.7 voxels (approximately 5 cc). Areas of possibly false activation of average size 72.5 voxels resulting from passive motion of the resting human participant were observed in two of four experiments.

CONCLUSION

Participant movements of 1 mm or less that are only modestly correlated with a blocked stimulus paradigm can produce appreciable false activation artifacts on BOLD functional MR imaging studies, even when strict image realignment methods are used to prevent them.

Dynamic breast MRI with spiral trajectories: 3D versus 2D

A three-dimensional (3)D spiral sequence was developed for dynamic breast magnetic resonance (MR) imaging with much improved image quality. Partial Z phase encoding was applied to obtain thinner slices for a coverage of the whole breast. Comparison between the 3D and a previously developed multi-slice 2D spiral sequences was performed on ten healthy volunteers without contrast and five breast patients with gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA). The 3D spiral images had significantly less off-resonance blurring and spiral artifacts. With a small compromise on temporal resolution (7.7 seconds in 2D and 10.6 seconds in 3D), we obtained 32 interpolated 3-5 mm slices (with 20 Z phase encodes) for a full coverage of 10-16 cm breast with the same 1 x 1 mm2 in-plane resolution as the 2D sequence, which had 12 8-13 mm slices. Contrast between glandular and soft tissue in normal breasts was increased by about 25%. The reduced repetition time in the 3D spiral acquisition led to an increased Gd-enhanced signal. The difference between the enhancement of malignant and benign lesions increased by sevenfold. We expect that this new development could lead to improved specificity in characterizing breast lesions using MR imaging.

Breast disease: dynamic spiral MR imaging

PURPOSE

To compare various subjective, empiric, and pharmacokinetic methods for interpreting findings at dynamic magnetic resonance (MR) imaging of the breast.

MATERIALS AND METHODS

Dynamic spiral breast MR imaging was performed in 52 women suspected of having or with known breast disease. Gadolinium-enhanced images were obtained at 12 locations through the whole breast every 7.8 seconds for 8.5 minutes after bolus injection of contrast material. Time-signal intensity curves from regions of interest corresponding to 57 pathologically proved lesions were analyzed by means of a two-compartment pharmacokinetic model, and the diagnostic performance of various parameters was analyzed.

RESULTS

Findings included invasive carcinoma in 17 patients, isolated ductal carcinoma in situ (DCIS) in six, and benign lesions in 34. Although some overlap between carcinomas and benign diagnoses was noted for all parameters, receiver operating characteristic analysis indicated that the exchange rate constant had the greatest overall ability to discriminate benign and malignant disease. The elimination rate constant and washout were the most specific parameters. The exchange rate constant, wash-in, and extrapolation point were the most sensitive parameters. DCIS was not consistently distinguished from benign disease with any method.

CONCLUSION

Dynamic spiral breast MR imaging proved an excellent method with which to collect contrast enhancement data rapidly enough that accurate comparisons can be made between many analytic methods.