Revisiting detection of in-transit metastases in melanoma patients using digital 18F-FDG PET/CT with small-voxel reconstruction

AIM

To evaluate the use of digital ¹⁸F-FDG PET/CT with small-voxels reconstruction for detecting in-transit metastases in melanoma patients with primary lesion located on the upper or lower limbs, in comparison with standard reconstruction and European Association of Nuclear Medicine Research limited (EARL)-compliant reconstruction mimicking former generation PET systems.

METHODS

Forty-six PET examinations acquired in list mode on a Vereos digital PET/CT system were reconstructed with (1) the standard reconstruction [2 iterations, 10 subsets (2i10s), point-spread function (PSF) modelling and time-of-flight enabled, no post-filtering and voxel size of 2 mm], (2) a small-voxel reconstruction using 1 mm voxels otherwise using the same parameters, (3) an EARL-compliant reconstruction mimicking a former generation system. Comparison of results across these reconstructions was made for a blind randomized review using a 3-point scale for the presence of in-transit metastases and image quality as well as for tumour-to-background (T/B) ratios and noise level in reference organs.

RESULTS

Seven of the thirty-two EARL-compliant images classified as negative moved to positive on 1mm_PSF images, and 5 of the 6 EARL-compliant images classified as indeterminate moved to positive on 1mm_PSF images (P = 0.01). Amongst a total of 20 PET examinations classified as positive using the 1mm_PSF reconstruction, fifteen were considered true positive, five false positive results occurred. Twenty-four patients with 1 mm PSF images were classified as negative, none of those under active surveillance experienced in-transit metastases during the 17 months following their PET examination. The positive likelihood ratio for the 1 mm reconstruction was much higher than that observed for EARL-compliant images (14.7 vs 7.82). Importantly, negative likelihood ratios for the 1 mm and 1mm_PSF reconstruction were almost perfect. Compared to EARL-compliant data, T/B ratios extracted from the 1mm_PSF showed a 2.84-fold increase (P < 0.001). A similar pattern of statistically significant increase was observed for noise level in organs of reference. Image quality for the torso was found to be significantly lower for 1mm_PSF reconstruction (P = 0.03). Image quality for the limbs was found to be better for 1mm_PSF (P < 0.001).

CONCLUSION

Digital PET with small-voxel reconstruction brings an additional value for the detection of in-transit metastases by reducing the number of indeterminate findings and making up for falsely negative scans using former generation PET systems. An acquisition encompassing lower or upper limbs as appropriate should be performed.

Dermoscopic Features of Toenail Onychomycosis

BACKGROUND

Onychomycosis is the most common infectious nail disorder. Direct mycologic examination is still the cornerstone of diagnosis; however, it may take several weeks to obtain a result. Recently some dermoscopic patterns that can be useful in the diagnosis of onychomycosis were described. However, published data on dermoscopic features of onychomycosis are still limited.

METHODS

We performed a prospective dermoscopic study of patients with positive fungal culture between April and December 2016. Patients with a final diagnosis of psoriasis or lichen planus were excluded from the study. Dermoscopy (polarized and nonpolarized) was performed.

RESULTS

Thirty-seven patients were enrolled, 24 women and 13 men (median ± SD age, 48.6 ± 16.1 years). Nail samples were culture positive for Trichophyton rubrum (89.2%), Trichophyton interdigitale (8.1%), and Candida albicans (2.7%). Distal and lateral subungual onychomycosis was the most frequent clinical subtype (59.5%). The most frequent dermoscopic features were subungual keratosis (73.0%), distal subungual longitudinal striae (70.3%), spikes of the proximal margin of an onycholytic area (59.5%), transverse superficial leukonychia (29.7%), and linear hemorrhage (13.5%). Brown chromonychia was most frequently seen with nonpolarized dermoscopy (66.6% versus 24%; P = .027).

CONCLUSIONS

Specific dermoscopic signs of onychomycosis are mostly related to the proximal invasion of the nail plate. Detection of these signs is simple and can, in some cases, help avoid mycologic testing.

Retronychia Clinical Features and Surgical Treatment

Retronychia is a newly described condition characterized by the embedding of the nail plate into the proximal nail fold. It mainly affects the great toe unilaterally as a result of mechanical factors. It is rarely reported, and its pathogenesis is not fully understood. Nail plate avulsion represents both a diagnostic and a therapeutic approach. We describe a 34-year-old woman with a medical history of congenital malalignment of the toenails, diagnosed as having retronychia, and emphasize the disease pathogenesis and surgical procedure.