Wednesday 5th September 2007 - High kV its all new to me

Wednesday is Chest Clinic Day

Chest X rays are the firts thing any training student develops until perfection and an image which is not that difficult to achieve using CR! as I found out.

The trust employs a high kV technique on all imaging this is used as higher kV imaging proves to be less aesthetically pleasing but contains a greater diagnostic quality through providing greater penetration.

This technique provides more penetratrion (high kV) with less contrast (low mA)

To compare the exposures with a Chest X-ray;

Training Hospital

Average Male 85kV and 2.5mA
Larger Male 92kV and 3.2mA

Local Hospital employing high kV

Average Male 101kV and 0.80mA
Larger male 107kV and 1.00mA

The use of high kV is difficult to grasp at first and is reliant a little more on Radiographer knowledge of plain film and adapting the exposures rather than the computer doing some of the work for you.

With contsnt supervision exposure to a variety of pataint sizes I was becoming able to judge the pataint size and calculate whether to oncrease or decrease the kV accordingly as well as judging whether to increase the standard 0.80mA with some pataints.

As a demonstration we acquired a diagnostic image using the exposures used on placement and produced a comparable image using the high kV technique, the reasoning behind this became apparent as the image clarity is far better allowing a more diagnostic appearance of any lesions, infections.

The Chest Clinic provided an afternoons work in particular one case involving a patinet who had been suffering with shortness of breath (SOB) and a repetitive chest whheeziness.

The exam requested aroutine PA CXR which was carried out the image demonstrtated that there were abnormalities along the bi-lateral walls of the pleura, this image although diagnostic was a little over exposed and I was aked to repaet the image but decrease the kV by four.

The resulting image demonstrated that the patient had bi-lateral plaques which I was told is indicative of asbestosis a condition which develops in later life if the patient has had repeated exposure to asbestos, the radiograph displays these plaques a dark furring within the bi-pleural lining. This furring is actually a calcification.

I was told to have a look at the image and look for something else abnormal apart from the plaques, there appeared to be a thickening of the vessels at the level of the hila, not knowing what this was I was told it may be a lesion which is associated with asbestosis.

To demonstrate this further I was asked to do a Lateral Chest a new projection in my training, which i had been practicing throughout the day, this is achieved using the bucky and the iontomat.
If a mass is seen in the left lung the patinet is placed with their right side to the bucky, and right sided mass left side to the bucky, and a central chamber selected.

The lateral chest projection confirmed that the patinet had a mass lesion at the site if the hila, this I was told is the start of cancer of the pleura or mesothelima.

As the radiologist was available the films were reported on immediatley and sent to the GP, the most emotiove part of the day was watching whilst the patinet was asked if he had worked with asbestos in the past and the reaction.