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 physician's access

The radiologists of Be Well Body Scan are committed to working with our colleagues in the medical community. We will make every effort to help coordinate the further evaluation of your patients if this is necessary. If you and your patient wish, we can help arrange a referral to a specialist of your patient's or your choosing.
In addition we will provide, and continually update, a review of the current literature concerning CT for total body scanning.

UPDATE ON MDCT for CARDIAC CTA

We are writing to apprise you of the advance made in Multi-Detector Cardiac Computed Tomographic Arteriography (MDCTA). This information may be helpful to you and your low to moderate risk patients who present with atypical chest pain where the cause is not obvious or may be related to non-cardiac causes. In the past two years two large multicenter studies have been performed on 523 patients, demonstrating its emergence as a powerful tool for diagnosing cardiac diseases. According to the findings of the first two prospective multicenter 64-slice scanner trials presented at the annual meeting of the Radiological Society of North America (RSNA), MDCTA is highly accurate for the detection of CAD and may be comparable to invasive angiography. Click here to read the full letter.

Coronary Artery Calcium Screening

There is a developing literature on the effectiveness of coronary artery calcium screening. One of the more comprehensive reviews can be found in the American College of Cardiology/American Heart Association Expert Consensus Document on Electron Beam Computer Tomography for the diagnosis and prognosis of Coronary Artery Disease which is summarized below. (The complete text can be found at http://circ.ahajournals.org/cgi/content/full/102/1/126 ).

Summary:
As many as half of first coronary events occur in asymptomatic people. Thus, the potential exists for many asymptomatic people to benefit from identification and risk reduction in the asymptomatic phase of coronary heart disease. The presence of extensive coronary calcium appears closely related to overall atherosclerotic coronary plaque "burden". Coronary artery calcium screening uses CT technology to calculate the amount of calcium within the coronary arteries. The results are reported as a "calcium score". A score of 0 indicates that there was no calcium detected in the coronary arteries. Extensively calcified coronary arteries can exhibit a calcium score of several hundred.

Using a calcium score of greater than or equal to 100 as defining significant coronary artery calcification, Arad, et al. found the positive predictive value for coronary calcification among men to be 18% and the negative predictive value to be 99.1%. Among women the positive predictive value of coronary calcification was 11% and the negative predictive value was 99.3%. Secci, et al. found that of 326 patients with one or more coronary risk factors who were followed for 32 months, there was a 50% prevalence of coronary calcium scores greater than 156, and that half of all hard cardiac events occur among patients with the highest quartile calcium scores.

A pooled analysis reported by the AHA Consensus Committee* shows the following positive and negative predictive values for varying levels of calcium scores:

Calcium Score15100156-160507-680
Positive Predictive Value1.5%4.8%6.4%14%
Negative Predictive Value98.5%97.9%95.9%92.2%


*Circulation 2000;102:126-140.

The AHA Writing Group Summarized Coronary Calcium Screening as follows:
  1. A negative EBCT test makes the presence of atherosclerotic plaque, including unstable plaque, very unlikely.
  2. A negative test is highly unlikely in the presence of significant luminal obstructive disease.
  3. Negative tests occur in the majority of patients who have angiographically normal coronary arteries.
  4. A negative test may be consistent with a low risk of a cardiovascular event in the next 2 to 5 years.
  5. A positive EBCT confirms the presence of a coronary atherosclerotic plaque.
  6. The greater the amount of calcium, the greater the likelihood of occlusive CAD, but there is not a 1-to-1 relationship, and findings may not be site specific.
  7. The total amount of calcium correlates best with the total amount of atherosclerotic plaque, although the true "plaque burden" is underestimated.
  8. A high calcium score may be consistent with moderate to high risk of a cardiovascular event within the next 2 to 5 years.
More information about the meaning of a calcium score can be found at: http://www.chestx-ray.com/Coronary/CorCalc.html

CT Abdomen

Performing non-enhanced CT of the abdomen in a screening population is a relatively new procedure and reflects the growth of screening for coronary artery calcification and lung cancer. While there are no comprehensive reports currently in the literature as to the sensitivity and specificity of unenhanced abdominal CT in a screening population, a fair amount of information can be gleaned from a review of the literature.

One of the better reviews of the incidents and implication of incidental findings was published in AJR in 1998. In this paper, Westbrook, et al. summarized the current literature. More recently, Hara, et al. in Radiology 2000, reported on the Incidental Extracolonic Findings at CT Colonography. This paper is important, as it may be the single paper that best simulates the screening population. In this paper, they report that 11% of patients who underwent CT colonography had highly important extracolonic findings which resulted in further examination in 7% of patients. Findings considered of high importance on CT included renal mass 3.5%, pulmonary nodule 3%, abdominal aneurysm greater than 4cm 2.6%, adrenal mass 1.9% and hepatic mass 0.75%. In addition, findings which did not result in further work up included gallstones 7.5%, renal stones 5.3%, uterine fibroids 5.3%, hepatic cyst, pulmonary granulomas, hiatal hernia and splenic granuloma each 3%.

In 1995, Smith, et al. reported on the use of un-enhanced CT scan in the evaluation of outpatients with acute flank pain. In this study, they reported that 31/210 (14.7%) of patients had findings on the CT scan unrelated to stone disease. These included an adnexal mass in 8 (3.8%) of patient's, 5 (2.4%) cases of appendicitis, 4 (1.9%) cases of diverticulitis, 1 (0.5%) liver mass (found to be a hemangioma), 1 (0.5%) leaking abdominal aortic aneurysm and 3 (1.4%) common bile duct stone.

Other work has looked at the incidence of serendipitously discovered renal cell carcinomas. Jason and Sanders reported via a chart review of 131 patients undergoing nephrectomy for renal cell carcinoma between 1989 and 1993, that 61% of patients with diagnosed renal cell carcinoma did not have any symptoms of flank pain, flank mass or hematuria - thus implying that the majority of renal cell tumors are currently found incidentally. This represents a historic increase in the incidence of incidentally detected renal cell tumors. Between 1935 and 1965 it was reported that only 7% of renal cell carcinomas were detected incidentally. Between 1961 and 1973, 13% of renal cell carcinomas were detected incidentally and between 1980 and 1984, 48% were detected incidentally. In the past, several authors have suggested that incidental renal cell carcinomas are more likely to be detected at an earlier stage of development than in patients with symptomatic tumors and that patients with incidentally detected renal cell tumors have an increased survival at 10 years compared to those in which the renal cell carcinoma was detected due to symptoms. However, in the most recent report by Jason and Sanders, there was no difference in the stage of tumor of those discovered incidentally or due to symptoms.

In a paper published in 1993, Forman, et al. evaluated the use of CT screen for co-morbid disease among patients with prostate cancer. These authors found that 66 /273 (24%) patients had findings suggestive of co-morbid disease. These included: indeterminate hepatic lesions in 25 (9%), indeterminate renal lesions in 1.4%, abdominal aneurisms less than 5cm in 11 (4%), abdominal aneurisms greater than 5cm in 0.7% and lymphoma or renal carcinoma in 1/273 (0.4%). In this specific patient population however, the high rate of co-morbid findings on CT scans did not lead to a significant change in treatment. Treatment was only changed in 4 of the 66 patients in which additional findings were discovered. These four cases included, two cases of a repair of a AAA, one case of unsuspected lymphoma and one case of a renal cell carcinoma.

Lung Cancer Screening

Recent work on the efficacy of lung cancer screening has been reported by the Early Lung Cancer Action Project (ELCAP) (Lancet, 1999). The study enrolled one thousand symptom free volunteers age 60 or older with at least 10 pack years of cigarette smoking and no previous history of cancer. Patients underwent both chest radiographs and low dose CT. Non-calcified nodules were detected in 23% of participants by low dose CT at baseline. Chest radiography detected non-calcified nodules in only 7% of participants. Malignant disease was detected in 2.7% of patients by CT and in 0.7% of participants by chest radiography. Stage one malignant disease was detected in 2.3% of participants by low dose CT and in only 0.4% of participants by chest radiography.

The authors conclude that low dose CT can greatly improve the likelihood of detection of small non-calcified nodules and diagnose lung cancer at an early and potentially more curable stage. An excellent review of the benefits and drawbacks of screening for lung cancer can be found in the New England Journal of Medicine (2000; 343:1627-1633). This article reviews some fundamental concepts about screening; including the concept of lead time bias, length time bias and over diagnosis bias. This article points out that several trials have confirmed that CT is more sensitive than conventional chest radiography for the detection of lung nodules and that some of these nodules prove to be lung cancer. CT was also able to detect more cases of lung cancer than chest radiographs and more patients screened by CT had resectable early stage disease than patients screened by chest radiographs. However, the true clinical significance of small tumors found by screening CT is unknown and the effect of screening on mortality is under future investigation. Given the design of the currently reported non randomized trial, only inferences regarding the effect that screening CT may have on lung cancer mortality are possible.

Recommendation for follow-up of pulmonary nodules detected at low dose CT:
The ELCAP Protocol recommends the following guidelines for diagnostic investigation of non-calcified nodules detected on low dose CT.
  1. Diagnostic CT scan of the chest with high resolution imaging of the nodule or nodules. If high resolution CT shows benign calcifications not identified on the low dose CT and the nodule demonstrated smooth edges and size less than 20mm, the nodule is classified as benign. If these criteria were not met by all non-calcified nodules, further investigation was recommended depending on the size (average length and width) of the non-calcified nodule.
  2. Non-calcified nodules 5mm or less in size: Follow-up by high resolution CT in 3 months. If there has been growth, repeat high resolution CT at 6, 12 and 24 months. If no growth is noted over 2 years, the nodule is classified as benign.
  3. Non-calcified nodules 6-10mm in size: Assessment recommended on an individual basis for the possibility of undertaking a biopsy. If no biopsy would be possible, follow-up as described above is recommended.
  4. Non-calcified nodules 11mm or greater in size: The protocol recommends biopsy according to current standards of care by fine needle aspiration, video assisted thoracoscopy, bronchoscopy, or a combination of these methods.
Selected Bibliography for Physician Access Section:
  1. Westbrook JI, Braithwaite J, McIntosh JH. The Outcomes for Patients with Incidental Lesions: serendipitous or iatrogenic? AJR 1998; 171(5):1193-1196.
  2. Hara AK, Johnson CD, MacCarty RL, et al. Incidental Extracolonic Findings at CT Colonography. Radiology 2000; 215(2):353-357.
  3. Smith RC, Verga M, McCarthy S, et al. Diagnosis of Acute Flank Pain: Value of Unenhanced Helical CT. AJR 1996; 166:97-101.
  4. Jayson M, Sanders H. Increased Incidence of Serendipitously Discovered Renal Cell Carcinoma. Urology 1998; 51:203-205.
  5. Forman HP, Heiken JP, Brink JA, et al. CT Screening for Comorbid Disease in Patients with Prostatic Carcinoma: Is It Cost-Effective? AJR 1994; 162(5):1125-1128.
  6. Arad Y, Spadaro M, Goodman KG, et al. Prediction of coronary events with electron beam computed tomography: 19-month follow-up of 1173 asymptomatic subjects. Circulation 1996; 93:1951-1953.
  7. Secci A, Wong N, Tang W, et al. Electron beam computed tomographic coronary calcium as a predictor of coronary events: comparison of two protocols. Circulation 1997; 96:1122-1129.
  8. American College of Cardiology/American Heart Association Expert Consensus Document on Electron-Beam Computed Tomography for the Diagnosis and Prognosis of Coronary Artery Disease. Circulation 2000; 102:126-140.
  9. Henschke C, McCauley DI, Yankelevitz DF, et al. Early Lung Cancer Action Project: overall design and findings from baseline screening. Lancet 1999; 357:99-105.
  10. Patz EF, Goodman PC, Bepler G. Screening for Lung Cancer. New England Journal of Medicine 2000; 343:1627-1633.
  11. Kubik AK, Parkin DM, Zatloukal P. Czech Study on Lung Cancer Screening. Cancer 2000; 89:2363-2368.
  12. Parkin DM, Moss SM. Lung Cancer Screening. Cancer 2000; 89:2369-2376.
  13. Kaneko M, Eguchi K, Ohmatsu H, et al. Peripheral Lung Cancer: Screening and Detection with Low-Dose Spiral CT versus Radiography. Radiology 1996; 201:798-802.
  14. ACRIN Lung Cancer Screening Study Protocol: http://www.acrin.org/current_protocols.html
  15. National Cancer Institute (NCI): Lung Screening Study: http://www3.cancer.gov/prevention/lss/moop1.html
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