Besides the well-known DNA double-helix, non-canonical nucleic acid structures regulate crucial biological activities. Among these oddities, guanine-rich DNA sequences can form unusual four-stranded secondary structures called G-quadruplexes (G4s). G4-prone sequences have been found in the genomes of most species, and G4s play important roles in essential processes such as transcription, replication, genome integrity and epigenetic regulation. Here, we present a short overview of G-quadruplexes followed by a detailed description of the biophysical and biochemical methods used to characterize G4s in vitro. The principles, experimental details and possible shortcomings of each method are discussed to provide a comprehensive view of the techniques used to study these structures. We aim to provide a set of guidelines for standardizing research on G-quadruplexes; these guidelines are not meant to be a dogmatic set of rules, but should rather provide useful information on the methods currently used to study these fascinating motifs.

METHODS: These recommendations apply to adults with glioblastoma who have been previously treated with first-line radiation or chemoradiotherapy and who are suspected of experiencing tumor progression.
OBJECTIVE: In patients with previously treated glioblastoma, is standard contrast-enhanced magnetic resonance imaging including diffusion weighted imaging useful for diagnosing tumor progression and differentiating progression from treatment-related changes?
METHODS: Magnetic resonance imaging with and without gadolinium enhancement including diffusion weighted imaging is recommended as the imaging surveillance method to detect the progression of previously diagnosed glioblastoma.
OBJECTIVE: In patients with previously treated glioblastoma, does magnetic resonance spectroscopy add useful information for diagnosing tumor progression and differentiating progression from treatment-related changes beyond that derived from standard magnetic resonance imaging with and without gadolinium enhancement?
METHODS: Magnetic resonance spectroscopy is recommended as a diagnostic method to differentiate true tumor progression from treatment-related imaging changes or pseudo-progression in patients with suspected progressive glioblastoma.
OBJECTIVE: In patients with previously treated glioblastoma, does magnetic resonance perfusion add useful information for diagnosing tumor progression and differentiating progression from treatment-related changes beyond that derived from standard magnetic resonance imaging with and without gadolinium enhancement?
METHODS: Magnetic resonance perfusion is suggested as a diagnostic method to differentiate true tumor progression from treatment-related imaging changes or pseudo-progression in patients with suspected progressive glioblastoma.
OBJECTIVE: In patients with previously treated glioblastoma, does the addition of single-photon emission computed tomography (SPECT) provide additional useful information for diagnosing tumor progression and differentiating progression from treatment-related changes beyond that derived from standard magnetic resonance imaging with and without gadolinium enhancement?
METHODS: Single-photon emission computed tomography imaging is suggested as a diagnostic method to differentiate true tumor progression from treatment-related imaging changes or pseudo-progression in patients with suspected progressive glioblastoma.
OBJECTIVE: In patients with previously treated glioblastoma, does 18F-fluorodeoxyglucose positron emission tomography add useful information for diagnosing tumor progression and differentiating progression from treatment-related changes beyond that derived from standard magnetic resonance imaging with and without gadolinium enhancement?
METHODS: The routine use of 18F-fluorodeoxyglucose positron emission tomography to identify progression of glioblastoma is not recommended.
OBJECTIVE: In patients with previously treated glioblastoma, does positron emission tomography with amino acid agents add useful information for diagnosing tumor progression and differentiating progression from treatment-related changes beyond that derived from standard magnetic resonance imaging with and without gadolinium enhancement?
METHODS: It is suggested that amino acid positron emission tomography be considered to assist in the differentiation of progressive glioblastoma from treatment related changes.

OBJECTIVE: Erythema is the most common presenting sign in patients with skin diseases, and various methods to treat erythema symptoms have become common. To evaluate changes in erythema, a reliable device that can support objective diagnosis is required. We developed a novel photography-based system for erythema diagnosis that provides a high-resolution three-view photograph taken in a consistent photography environment with a curved surface light source and can be integrated with optimized image processing algorithms.
METHODS: A new diagnostic algorithm was applied to photographs from 32 patients to determine areas of erythema automatically. To assess the performance in comparison to dermatologists\' evaluations, five dermatologists independently evaluate the areas of erythema, and we defined an area called the clinical consensus area of erythema (CCAE), which is based on the majority opinion of dermatologists during evaluation. The CCAE values obtained were compared with the erythema areas determined by the system\'s diagnostic algorithm.
RESULTS: Forty-one photographs with areas of erythema were evaluated by the proposed system and by dermatologists. The results obtained with the proposed system had a mean accuracy of 93.18% with a standard deviation of 3.52% when compared with the CCAE results. The results also showed that the proposed system could detect erythema areas without any pigmentation. In contrast to assessments by individual dermatologists, use of the CCAE reduced the amount of error that occurred owing to bias or subjectivity.
CONCLUSIONS: A new erythema evaluation system was developed and validated through CCAE, suggesting that the system can support dermatologists\' objective diagnoses of erythema.