Early assessment of brain maturation by MR imaging segmentation in neonates and premature infants

PURPOSE: We evaluated the impact of premature extrauterine life on brain maturation. PATIENTS AND METHODS: Twelve neonates underwent MR imaging at 40 (39.64 +/- 0.98) weeks (full term). Fifteen premature infants underwent 2 MR imaging examinations, after birth (preterm at birth) and at 40 weeks (41.03 +/- 1.33) (preterm at term). A 3D MR imaging technique was used to measure brain volumes compared with intracranial volume: total brain volume, cortical gray matter, myelinated white matter, unmyelinated white matter, basal ganglia (BG), and CSF. RESULTS: The average absolute volume of intracranial volume (269.8 mL +/- 36.5), total brain volume (246.5 +/- 32.3), cortical gray matter (85.53 mL +/- 22.23), unmyelinated white matter (142.4 mL +/-14.98), and myelinated white matter (6.099 mL +/-1.82) for preterm at birth was significantly lower compared with that for the preterm at term: the average global volume of intracranial volume (431.7 +/- 69.98), total brain volume (391 +/- 66,1), cortical gray matter (179 mL +/- 41.54), unmyelinated white matter (185.3 mL +/- 30.8), and myelinated white matter (10.66 mL +/- 3.05). It was also lower compared with that of full-term infants: intracranial volume (427.4 mL +/- 53.84), total brain volume (394 +/- 49.22), cortical gray matter (181.4 +/- 29.27), unmyelinated white matter (183.4 +/- 27.37), and myelinated white matter (10.72 +/- 4.63). The relative volume of cortical gray matter (30.62 +/- 5.13) and of unmyelinated white matter (53.15 +/- 4.8) for preterm at birth was significantly different compared with the relative volume of cortical gray matter (41.05 +/- 5.44) and of unmyelinated white matter (43.22 +/- 5.11) for the preterm at term. Premature infants had similar brain tissue volumes at 40 weeks to full-term infants. CONCLUSION: MR segmentation techniques demonstrate that cortical neonatal maturation in moderately premature infants at term and term-born infants was similar.     

Diagnostic imaging of calculi in the upper urinary tract--sonography vs. computerized tomography

The choice of the most suitable technique for radiologic evaluation of upper urinary tract stones depends on the precise clinical questions that have to be answered. Many of these questions can still be answered by plain films of the abdomen and excretory urography. This review addresses the value of ultrasonography and computed tomography (CT) with respect to the two most important clinical questions, i.e. 1) presence/extent of obstruction/hydronephrosis and perinephric abscess in patients with acute flank pain; and 2) precise location, number and size of calculi. Because its sensitivity is comparable with CT and it is widely available, ultrasonography in the hands of experienced clinicians/radiologists may be preferred for evaluation of patients with acute flank pain. However, it must be emphasized that ultrasonography may totally miss acute ureteral obstruction/hydronephrosis within the first 12-24 hours. In children as well as in pregnant women, ultrasonography is still the technique of choice, but it may be replaced by magnetic resonance urography in the future. For precise stone location or detection of calcifications, however, the speed, safety and accuracy of unenhanced helical CT make this the most sensitive method and therefore the technique of choice. It also detects urinary calculi more accurately and exposes patients to less radiation than the traditional combined plain abdominal film/intravenous urography. Furthermore, CT can most readily reveal alternative diagnoses in patients with acute flank pain and other intraabdominal pathologies than stones.     

Diffusion‐weighted imaging outside the brain: Consensus statement from an ISMRM‐sponsored workshop

The significant advances in magnetic resonance imaging (MRI) hardware and software, sequence design, and postprocessing methods have made diffusion‐weighted imaging (DWI) an important part of body MRI protocols and have fueled extensive research on quantitative diffusion outside the brain, particularly in the oncologic setting. In this review, we summarize the most up‐to‐date information on DWI acquisition and clinical applications outside the brain, as discussed in an ISMRM‐sponsored symposium held in April 2015. We first introduce recent advances in acquisition, processing, and quality control; then review scientific evidence in major organ systems; and finally describe future directions. J. Magn. Reson. Imaging 2016;44:521–540.     

High signal intensity in dentate nucleus and globus pallidus on unenhanced T1‐weighted MR images in three patients with impaired renal function and vascular calcification

Gadolinium‐based contrast agents (primarily those with linear chelates) are associated with a dose‐dependent signal hyperintensity in the dentate nucleus and the globus pallidus on unenhanced T1‐weighted MRI following administration to selected patients with normal renal function. The accumulation of gadolinium has also been reported in the skin, heart, liver, lung, and kidney of patients with impaired renal function suffering from nephrogenic systemic fibrosis (NSF). Here we report on three patients with impaired renal function and vascular calcification (two with confirmed NSF) whose unenhanced T1‐weighted MRIs showed conspicuous high signal intensity in the dentate nucleus and the globus pallidus after they had been exposed to relatively low doses of linear gadolinium‐based contrast agents (0.27, 0.45, and 0.68 mmol/kg). Signal ratios between dentate nucleus and pons and between globus pallidus and thalamus were comparable with previously reported measurements in subjects without renal impairment. Of note, all three analysed patients suffered from transient signs of neurological disorders of undetermined cause. In conclusion, the exposure to 0.27‐0.68 mmol/kg of linear gadolinium‐based contrast agent was associated with probable gadolinium accumulation in the brain of three patients suffering from impaired renal function and vascular calcification. © 2016 The Authors. Contrast Media & Molecular Imaging published by John Wiley & Sons Ltd.     

Predicting and monitoring cancer treatment response with diffusion‐weighted MRI

An imaging biomarker that would provide for an early quantitative metric of clinical treatment response in cancer patients would provide for a paradigm shift in cancer care. Currently, nonimage based clinical outcome metrics include morphology, clinical, and laboratory parameters, however, these are obtained relatively late following treatment. Diffusion‐weighted MRI (DW‐MRI) holds promise for use as a cancer treatment response biomarker as it is sensitive to macromolecular and microstructural changes which can occur at the cellular level earlier than anatomical changes during therapy. Studies have shown that successful treatment of many tumor types can be detected using DW‐MRI as an early increase in the apparent diffusion coefficient (ADC) values. Additionally, low pretreatment ADC values of various tumors are often predictive of better outcome. These capabilities, once validated, could provide for an important opportunity to individualize therapy thereby minimizing unnecessary systemic toxicity associated with ineffective therapies with the additional advantage of improving overall patient health care and associated costs. In this report, we provide a brief technical overview of DW‐MRI acquisition protocols, quantitative image analysis approaches and review studies which have implemented DW‐MRI for the purpose of early prediction of cancer treatment response. J. Magn. Reson. Imaging 2010. © 2010 Wiley‐Liss, Inc.     

Pretherapeutic staging of recurrent laryngeal carcinoma: clinical findings and imaging studies compared with histopathology.

OBJECTIVE: To assess the accuracy of preoperative imaging studies and clinical and endoscopic examinations for recurrent laryngeal carcinoma evaluation. STUDY DESIGN AND SETTING: A retrospective comparative study was performed at a university department on 42 recurrent laryngeal carcinomas. Surgical specimens were cut into whole-organ slices. Histologic findings were compared with the findings of the different preoperative diagnostic modalities. RESULTS: The craniocaudal tumor spread was correctly evaluated by endoscopy and imaging studies in 52% and 24%, respectively, and the contralateral tumor spread in 50% and 52%, respectively. The sensitivity, specificity, and accuracy for detection of tumor infiltration of the thyroid was 48%, 88%, and 64% and of the cricoid 47%, 80%, and 67%. The accuracy of recurrent tumor classification (crT) was 50%; most tumors were underclassified. CONCLUSION: The inadequately evaluated tumor spread and the inadequately classified recurrent tumors were underestimated and underclassified in most cases, respectively.     

Functional imaging of the parotid glands using blood oxygenation level dependent (BOLD)-MRI at 1.5T and 3T

PURPOSE: To evaluate the function of the parotid glands before and during gustatory stimulation, using an intrinsic susceptibility-weighted MRI method (blood oxygenation level dependent, BOLD-MRI) at 1.5T and 3T. MATERIALS AND METHODS: A total of 10 and 13 volunteers were investigated at 1.5T and 3T, respectively. Measurements were performed before and during gustatory stimulation using ascorbate. Circular regions of interest (ROIs) were delineated in the left and right parotid glands, and in the masseter muscle for comparison. The effects of stimulation were evaluated by calculating the difference between the relaxation rates, DeltaR(2)*. Baseline and stimulation were statistically compared (Student's t-tests), merging both parotid glands. RESULTS: The averaged DeltaR(2)* values prestimulation obtained in all parotid glands were stable (-0.61 to 0.38 x 10(-3) seconds(-1)). At 3T, these values were characterized by an initial drop (to -2.7 x 10(-3) seconds(-1)) followed by a progressive increase toward the baseline. No significant difference was observed between baseline and parotid gland stimulation at 1.5T, neither for the masseter muscle at both field strengths. A considerable interindividual variability (over 76%) was noticed at both magnetic fields. CONCLUSION: BOLD-MRI at 3T was able to detect DeltaR(2)* changes in the parotid glands during gustatory stimulation, consistent with an increase in oxygen consumption during saliva production.     

Laryngeal involvement by differentiated thyroid carcinoma

BACKGROUND: Invasion of the larynx by differentiated thyroid gland carcinoma is uncommon but causes serious morbidity and mortality when present. METHODS: The clinicopathologic characteristics of 5 patients in which a total laryngectomy had to be performed for differentiated thyroid carcinoma are analyzed. Special reference is paid to the histologic intralaryngeal tumor spread, which is evaluated on whole-organ section. RESULTS: All patients presented with hoarseness and/or dyspnea. Two patients are alive at 44 and 115 months. One patient died of intercurrent disease 2 months and 2 patients with disease 6 and 14 months after surgery. In all cases, intralaryngeal tumor spread was observed. Invasion of the larynx occurs by direct extension or by posterior tumor growth around the edge of the thyroid cartilage. CONCLUSION: In rare cases, differentiated thyroid carcinoma can widely infiltrate the larynx, making total laryngectomy unavoidable. The diagnosis of intralaryngeal tumor spread is done by imaging and endoscopy.     

Diffusion-weighted imaging of the parotid gland: Influence of the choice of b-values on the apparent diffusion coefficient value

PURPOSE: To determine how the ADC value of parotid glands is influenced by the choice of b-values. MATERIALS AND METHODS: In eight healthy volunteers, diffusion-weighted echo-planar imaging (DW-EPI) was performed on a 1.5 T system, with b-values (in seconds/mm2) of 0, 50, 100, 150, 200, 250, 300, 500, 750, and 1000. ADC values were calculated by two alternative methods (exponential vs. logarithmic fit) from five different sets of b-values: (A) all b-values; (B) b=0, 50, and 100; (C) b=0 and 750; (D) b=0, 500, and 1000; and (E) b=500, 750, and 1000. RESULTS: The mean ADC values for the different settings were (in 10(-3) mm2/second, exponential fit): (A) 0.732+/-0.019, (B) 2.074+/-0.084, (C) 0.947+/-0.020, (D) 0.890+/-0.023, and (E) 0.581+/-0.021. ADC values were significantly (P <0.001) different for all pairwise comparisons of settings (A-E) of b-values, except for A vs. D (P=0.172) and C vs. D (P=0.380). The ADC(B) was significantly higher than ADC(C) or ADC(D), which was significantly higher than ADC(E). ADC values from exponential vs. logarithmic fit (P=0.542), as well as left vs. right parotid gland (P=0.962), were indistinguishable. CONCLUSION: The ADC values calculated from low b-value settings were significantly higher than those calculated from high b-value settings. These results suggest that not only true diffusion but also perfusion and saliva flow may contribute to the ADC.     

Diffusion-weighted MR imaging including bi-exponential fitting for the detection of recurrent or residual tumour after (chemo)radiotherapy for laryngeal and hypopharyngeal cancers

Objectives

To assess whether diffusion-weighted magnetic resonance imaging (DW-MRI) including bi-exponential fitting helps to detect residual/recurrent tumours after (chemo)radiotherapy of laryngeal and hypopharyngeal carcinoma.

Methods

Forty-six patients with newly-developed/worsening symptoms after (chemo)radiotherapy for laryngeal/hypopharyngeal cancers were prospectively imaged using conventional MRI and axial DW-MRI. Qualitative (visual assessment) and quantitative analysis (mono-exponentially: total apparent diffusion coefficient [ADC_T], and bi-exponentially: perfusion fraction [F_P] and true diffusion coefficient [ADC_D]) were performed. Diffusion parameters of tumour versus post-therapeutic changes were compared, with final diagnosis based on histopathology and follow-up. Mann-Whitney U test was used for statistical analysis.

Results

Qualitative DW-MRI combined with morphological images allowed the detection of tumour with a sensitivity of 94% and specificity 100%. ADC_T and ADC_D values were lower in tumour with values 120 ± 49 × 10⁻⁵ mm²/s and 113 ± 50 × 10⁻⁵ mm²/s, respectively, compared with post-therapeutic changes with values 182 ± 41 × 10⁻⁵ mm²/s (P < 0.0002) and 160 ± 47 × 10⁻⁵ mm²/s (P < 0.003), respectively. F_P values were significantly lower in tumours than in non-tumours (13 ± 9% versus 31 ± 16%, P < 0.0002), with F_P being the best quantitative parameter for differentiation between post-therapeutic changes and recurrence.

Conclusions

DW-MRI in combination with conventional MRI substantially improves detection and exclusion of tumour in patients with laryngeal and hypopharyngeal cancers after treatment with (chemo)radiotherapy on both qualitative and quantitative analysis, with F_P being the best quantitative parameter in this context.

Key Points

• DW-MRI is increasingly used to detect tumour recurrence.

• DW-MRI allows accurate post-treatment recurrence detection in laryngeal or hypopharyngeal cancer

• ADC values in recurrent tumour are lower than in benign tissue alterations

• Both qualitative and quantitative DW-MRI approaches allow detection of recurrence

• DW-MRI can easily be added to daily clinical routine imaging