Whilst Computed Tomography Pulmonary Angiography (CTPA) has become popular in the last decade there is a number of contraindications for the test. certain patients just cant or are deemed inappropriate for the scan.
one of the main reasons being, a CTPA scan requires the injection of a contrast/iodine dye into the blood. about 30% of all patients have some form of iodine reaction ranging from mild to severe and life threatening....with the more severe symptoms including an anaphylactic reaction, renal failure and heart failure. This exudes, anyone with a history of contrast reactions, patients with renal issues, pregnant women. With Technegas V/Q SPECT there is no contraindications
Another argument against CTPA is the severe radiation burden compared to a V/Q SPECT scan, The radiation exposure to the breasts of women in the child-bearing age group from CT is somewhere between 65 to 250 times greater radiation dose than that from V/Q scintigraphy. Most quotes are in the 70 to 100 times range. So that is another factor that doctors have to consider, any young patients, female or pregnant patients.
From when CTPA first gained popularity over the last 10 years, nuclear medicine has come a long way with technology. 15 years ago, only planar imaging (static images looking down on the chest or from the posterior position looking at the lungs from your back). improvements to V/Q scanning are now able to produce true 3D-images (SPECT), produces clearer pictures. This has become standard practice outside the United States since nuclear medicine physicians have had access to Technegas, an agent that allows superb ventilatory (V) SPECT studies comparable in quality to the perfusion scan (Q). Now most nuclear medicine machines come with a low dose CT scan attatched that improves accuracy and image quality of the 3D images even more so = SPECT/CT
Improved so much that in a recent paper done in 2013 for the european journal of nuclear medicine and molecular imaging concluded ....
"Compared with traditional V/Q scintigraphy, both V/Q SPECT and CTPA have a higher diagnostic value and fewer inconclusive results in the diagnosis of PE. V/Q SPECT and CTPA are highly concordant and show similar diagnostic accuracy, with SPECT showing higher sensitivity and CTPA higher specificity."
(sensitivity = true positive rate = the percentage of sick people who are correctly identified as having the condition
specificity = true negative rate = the percentage of healthy people who are correctly identified as not having the condition)
"There is possibly a higher clinical value of negative SPECT studies compared to negative CTPA studies, but the clinical importance of finding a small subsegmental PE needs further elucidation. A combination of V/Q SPECT and CT may be even more accurate than V/Q SPECT or CTPA alone. More comparisons are needed, however. Each of these excellent imaging methods has the highest predictive values when there is concordance between the clinical suspicion and the test result, whereas further imaging should be performed if there is discordance."
"V/Q SPECT or V/Q SPECT/CT are available in many nuclear medicine departments, mostly during the day-time. They may provide an alternative diagnosis if PE is refuted, and are feasible in almost all patients, because there are no definitive contraindications. CTPA is usually available round-the-clock and a rapid PE or alternative diagnosis can be expected. Due to contraindications such as kidney impairment or allergy, CTPA cannot be performed in about 10 – 30 % of patients. Whereas radiation exposure was previously substantially higher for the patient with CTPA than with V/Q SPECT or V/Q SPECT/CT"
so summing up....lower dose, less risk, same accuracy....but slightly longer imaging time...with increased radiation dose rleated to increased risk of cancer....which would you chose?
CYC Price at posting:
$1.18 Sentiment: Buy Disclosure: Held
A personalised tool to help users track selected stocks. Delivering real-time notifications on price updates, announcements, and performance stats on each to help make informed investment decisions.
(20min delay)