Skin ultrasonography and magnetic resonance; new clinical applications and instrumentation

Abstract Background Technological advances in skin ultrasonography and magnetic resonance are discussed. Methods Literature review. Results 40 publications cited. Conclusion This article illustrates crucial contributions made by the Editors, the Editorial Board and this Journal to these fields.


Ultrasound instrumentation
For many decades two relatively small companies Cortex (DermaScan unit, Denmark) and Taberna Pro Medicum (DUB unit, Germany) had dominated the field of HFUS.DermaScan and DUB machines provide HFUS of 20 MHz and higher (up to 100 MHz).New machines in addition to HFUS also have Doppler mode for blood vessel visualization and mapping, advanced specialty software, iCloud storage, telemedicine and Ios & Android capability, and a high-definition imaging at a fraction of the cost.Zemtsov, being a board-certified Mohs surgeon with extensive expertise in Superficial Radiation Therapy (SRT) uses in his practice Clarius L20 HD 3 Ultra-High Frequency Linear Scanner.This machine has automatic depth adjustable frequency between 8 and 20 MHz and a maximum penetration/visualization depth of 4 cm.

New diagnostic ultrasound application
Yu and coworkers reported that HFUS image guided SRT (IG-SRT) is superior to non-image guided SRT. of cutaneous squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) utilizing IG-SRT in a study of 2917 patients. 5,6Furthermore, Zemtsov while proposing Appropriate Use Criteria (AUC) for SRT emphasized in his recommendations the importance of utilization of HFUS while performing SRT. 799.3%IG-SRT cure rate for BCC and SCC is at least as high as can be achieved with the treatment of these cancers with Mohs surgery. 5,6Zemtsov has been treating with IG-SRT and SRT at least a thousand patients at University Dermatology Center (UDC) offices.IG-SRT allows at initial consultation correctly to determine tumor depth and thus to determine an appropriate D 50 for a correct level of treatment energy and for a correct placement of radiation fields.During IG-SRT therapy again HFUS allows for SRT tumor response monitoring and to maintain an appropriate placement of radiation fields.Finally, after proposed SRT AUC were published 7 Zemtsov and the coauthor Cognetta, who is also an Associate Editor of this Journal and the SRT expert, were contacted by individuals who had a concern with our recommendation that SRT should be only administered by board certified Mohs surgeons and radiation oncologists.In all fairness Zemtsov was taught SRT by late professor Neldner who was a medical dermatologist (before Zemtsov started teaching SRT to dermatology residents).Therefore, the time will determine appropriate qualifications for SRT and IG-SRT administration; at UDC Mohs surgeons, radiation oncologists and radiation therapists work as a collaborative team in administering IG-SRT.
The Doppler feature in HFUS to visualize blood vessels opened numerous new possibilities and clinical applications for dermatologists, plastic, cosmetic, and ENT surgeons.HFUS is now used as an imaging guide to visualize supratrochlear and supraorbital arteries during filler injections in a glabellar area and thus prevent inadvertent administration of the filler material into these vessels that can lead to potentially catastrophic results such as a blindness. 8HFUS is now used both to make sure that paramedian forehead interpolation flap contains a supratrochlear artery and there is an adequate blood flow in this flap prior to the pedicle division. 9Skin ultrasonography is also utilized for an exact administration of hyaluronidase to remove an excessive and/or inappropriately placed hyaluronic acid cosmetic filler; HFUS also prevents inadvertent arterial hyaluronidase injection during this procedure. 10Furthermore, HFUS is used to detect hyaluronic acid granulomas. 11Finally, HFUS is useful to guide to prevent parotid gland damage during cosmetic thread facial lifting and to diagnose a damage to either a Stensen's duct or a parotid gland that occurs during these procedures. 12

Therapeutic ultrasonography
Newly developed high frequency and high-intensity focused ultrasound (HIFU) showed efficacy in tattoo removal; both as an adjuvant therapy to laser surgery and as a primary treatment modality for this indication. 13HIFU also appears to have potential as a therapeutic modality in removal of warts 14 and as a skin rejuvenation treatment. 15

Cutaneous magnetic resonance historical note
Zemtsov, who has a graduate degree in Magnetic Resonance is credited in obtaining first skin MRI images of skin lesions; both melanocytic 16 and non-melanocytic ones. 17The MRI images showed excellent correlation with histological findings, such as lesions depth. 17Furthermore, Zemtsov obtained first in vivo Magnetic Resonance spectra (MRS). 18,19sed on these findings he was asked and published on this topic an Editorial in Archives of Dermatology 20 {now JAMA Dermatology).
These results and subsequent publications by other physicians resulted in all medical insurances in the US to cover MRI scans of skin malignant tumors.Finally, while performing MRS studies Zemtsov discovered phosphocreatine in a cutaneous tissue; a molecule that plays a crucial role in skin bioenergetic pathways. 18,19Bernard Querleux, PhD, who is an Associate Editor of this Journal, was also a pioneer in skin MRI, MRS, and ultrasonography fields. 21,22

MRI and MRS instrumentation
To obtain both human in vivo MR images or MR spectra the same scanners containing superconducting magnets are used (the MRS requires a purchase of a separate software and it's primarily available only at academic institutions}.Initial MR scanners had magnetic field strength of 1.5 T (tesla)-newer machines have a strength of 3T. In

New MRI/MRS applications
The purpose of skin MRI (like general radiology applications) is to measure preoperatively tumor depth, to assess an extent of underlying tissue involvement (such as orbit involvement etc.), and to evaluate tumor recurrence under skin flaps or grafts. 16,17,20,23MRI can be also used to monitor tumor response to therapy and to determine the type of malignancy present. 20Nowadays it became apparent that skin MRI is a technique of choice to discover the presence of a perineural involvement in high-risk cutaneous squamous cell carcinomas 24 (especially when a patient exhibit symptoms suggestive of cranial nerve involvement). 24waguchi and coworkers recently confirmed Zemtsov findings 16 that skin melanoma produce hyperintensive T1 images 25 (due to paramagnetic properties of melanin that acts as MRI contrast material).
The same research group confirmed another Zemtsov suggestion 17,20 that certain radiological criteria are more characteristic in MRI images of basal cell versus squamous cell carcinomas 26 (ulceration and protrusion into the fat in SCC and hyperintense T2 images in BCC).
Furthermore, recent reports demonstrated the utility of MRI in evaluating dermatofibrosarcoma tumors 27 as with tumors mentioned above in this paragraph MRI was useful in designing a surgical excision and in differentiating between this tumor and other lesions. 27w skin/skin related MRI diagnostic applications include MRI evaluation of scalp alopecia 28,29 (primary use is to evaluate effectiveness of new therapies-see MRS discussion below), abnormal brain MRI findings in patients with atopic deramtitis 30 and use of brain functional MRI to evaluate changes induced by skin pricking/itch/pain sensation. 31,32 the field of skin MRS no new studies appeared recently.

Therapeutic magnetic fields and thermal MRI
Spinning oscillating magnetic fields induce within malignant cells oxygen radical molecules causing cellular apoptosis. 38This is a mechanism of a new investigational device called "oncomagnetic helmet" for treatment glioblastoma brain tumors 39 (technically this clearly is not a magnetic resonance phenomenon since no Larmour frequency is applied to generate quantum states).Both in the US and Europe there are efforts to develop a Thermal MRI machine that in addition to diagnostic information will also generate radiofrequency induced tumor ablating heat in MRI guided area 40 (for example it may allow neuroradiologists, utilizing Thermal MRI, instead of neurosurgeons to treat glioblastomas).

CONCLUSION
This review summarizes the advances in Skin Ultrasonography and Magnetic Resonance.Furthermore, this article illustrates crucial contributions made by the Editors, the Editorial Board and this Journal to these fields.
1997 Zemtsov at a joint ISSI/ISDIS Congress in Vienna Austria suggested a development of a portable MRI machine utilizing permanent (instead of superconducting} magnets.25 years later portable MRI is both a reality and is approved for clinical use-Swoop Portable MRI (produced by Hyperfine, Inc).