Radiology Comes Through for Sexual Imaging

There's a lot we don't know about the human body.

How can this be, after radiologists and other physicians have spent the past 113 years scanning every known body part?

Simple answer -- most medical imaging is done on sick people. In general, this is not a bad idea, since imaging procedures can occasionally have significant side effects.

Unfortunately, this also means that a lot of normal body functions remain under- or even un-imaged. This includes images of what actually goes on during sexual intercourse.

A lot of the ins and outs of the old in-and-out have been elucidated by researchers such as Alfred Kinsey, William Masters, Virginia Johnson, and Shere Hite. However, we still have a lot to learn.

Enter the field of sexual imaging -- a field that seems to be pursued avidly by scientists and laypersons alike. In the past decade, ultrasound, magnetic resonance imaging (MRI) and even X-rays have been used to go where no eyeball has gone before.

Sexual imaging has some obvious difficulties. For starters, both researchers and their subjects have to overcome some of the personal and societal baggage that is still associated with sex. As one researcher put it:

It took years, a lobby, undesired publicity, and a godsend (two tablets of sildenafil (aka Viagra) 25 mg) to obtain our images.

Even when you've got someone willing to do it in front of an audience and someone else willing to watch, access to the really interesting details remains challenging. Despite all manner of cunning lenses, mirrors and probes, many of the places where genitalia meet other genitalia (and other orifices) have, until recently, remained dark, private and inaccessible.

X-rays

In what one might truly consider "lay" research, Belgian artist Wim Delvoye asked several friends to paint parts of their bodies with barium, and then X-rayed them having sex in a medical clinic, presumably after hours. Delvoye has turned several of these images into stained-glass windows.

Some of the these radiographs can be startlingly graphic, but shed a bit of light on some of the messy details of what actually happens during sex. The downside of this adventure is the ionizing radiation exposure to each of the gonads, thyroid glands and eyeballs in these images. Eek.

Ultrasound

In 2006, Deng et al published Real-time three-dimensional ultrasound visualization of erection and artificial coitus. No ionizing radiation to worry about here. However, the authors state:

For the first volunteer scanned with the water bath alone, the penis failed to erect within 30 min.

Imagine that -- someone couldn't get it up while surrounded by a group of researchers holding ultrasonic probes. To me, this sounds a lot like an alien abduction scene -- except without the aliens and without the abduction.

The other four volunteers in this study were given an artificial vagina made of gel, which apparently

...successfully initiated and maintained the erection and allowed artificial intercourse.

From what I can tell, this particular artificial unit is still Not Found in Stores.

MRI

Like ultrasound, MRI does not use ionizing radiation. Unlike ultrasound, MRI allows one to avoid the whole surrounded-by-probes-and-eyeballs scene, and sexual acts can be imaged in the relative privacy of the MRI scanner.

MRI has been used to study blood flow and size of female genital and pelvic organs during sexual arousal. Not surprisingly, blood flow increases in the labia minora, clitoris and in the vagina.

MRI has also been used by Pretorius et al

... to non-invasively monitor the intravaginal distribution of an applied intravaginal gel, we performed high-resolution magnetic resonance imaging (MRI) of the female pelvis before, during and after both real and simulated sexual intercourse.

The good news: intercourse did a really great job of spreading the gel. The bad news (for men, at least): a plastic phallus worked just as well as a real one.

When reading through these research papers, it is quickly apparent that some of these studies were a whole lot more fun than others.

My favorite is the pioneering work by Schultz et al, published in 1999. To my knowledge, this is the first reported use of MRI to image actual coitus while it was in progress. Their subjects performed missionary work that even an atheist could support.

This study sounds like a lot of fun, but was probably more grueling than one might think. First, many patients find the bore of an MR scanner to be close quarters to the point of claustrophobia -- even without sharing the space with a naked partner. My hat is off to anyone who can crawl into an already-occupied MR scanner, much less successfully "dock" with their partner. Second, only one couple was able to successfully perform coitus without the use of Viagra. The authors suggest that the success of this non-Viagra couple may be because

...as amateur street acrobats they are trained and used to performing under stress.

Unlike the men, all of the women had a complete sexual response. However, any anxiety the men in the study felt due to their need for Viagra may have been somewhat mitigated by the study's finding that

Scanning of the position of the human genitals during coitus gives a convincing impression of the enormous size of the average penis in erection.

Balm indeed for a troubled male ego.


One surprising discovery was the shape the penis assumes during coitus. Even Leonardo da Vinci got this wrong. He, along with everyone else, assumed that a phallus in flagrante delicto is pretty much the same shape as one that is just plain old flagrante out in the open. In fact, a penis bends into the shape of a boomerang during penetration.

Another surprise -- in contrast to the bimanual estimates of uterine size made over 30 years before by Masters and Johnson, this study did not show any increase in size of the uterus during sexual arousal.

Replication of results is the very heart of the scientific method. This is doubly true when one is screwing for science. You will therefore be happy to know that this valuable work has been carefully extended by Faix et al to other pages of the Kama Sutra. They carefully imaged couples not only in missionary position, but also in reversed missionary position and rear entry position. Their findings may be troubling to some men -- despite some persistent fantasies, the penis does not actually extend any further cephalad than the north end of the vagina.

Note: Despite the date of this post, the papers quoted here are all actual research papers from the actual medical literature.