DOI:10.2214/AJR.06.5003
AJR 2006; 186:266-267
© American Roentgen Ray Society
Value of the Single-Phase Technique in MDCT Assessment of Pancreatic Tumors
Sukru Mehmet Erturk
Brigham and Women's Hospital and Harvard Medical School Boston, MA
02120
I read with great interest the article by Imbriaco et al.
[1] in the April 2005 issue of
the AJR in which they attempted to determine the diagnostic value of
single-phase MDCT in patients with suspected pancreatic carcinoma. In that
study, the authors performed contrast-enhanced CT of the pancreas with a
scanning delay of 60 sec after the IV injection of 150 mL of nonionic contrast
material with an iodine content of 370 mg I/mL delivered at 3 mL/sec in all
patients.
Interestingly, in the discussion, the authors mention that using the
formula previously suggested by Tublin et al.
[2], the peak enhancement of
the pancreas was reached at 60 sec in their study. In my understanding, this
is a perfect case of circular reasoning, because neither in the material and
methods section nor in the results section could I find any information about
the methodology or statistical analysis the authors used to determine the
timing of peak enhancement of the pancreas. Such a purpose would have required
serial measurements of pancreatic parenchyma to obtain time-density curves
that can be used to determine the peak enhancement time. Because the authors
started the CT acquisition 60 sec after the IV injection, it should have been
impossible for them to determine the time of peak enhancement of the pancreas;
it might have occurred earlier in some patients and later in some others.
Furthermore, in their discussion, the authors also claim that, in agreement
with previous data by Kim et al.
[3], they found the contrast
material volume and injection rate to be directly related to pancreatic
parenchymal enhancement. Nevertheless, in the material and methods section,
there is no information about any effort to correlate the contrast material
volume or injection rate with pancreatic parenchymal enhancement. Nor does the
results section include any outcome related to this issue. Moreover, if the
injection rate was 3 mL/sec in all patients, as stated in the material and
methods section, by definition it was impossible to correlate the injection
rate with pancreatic parenchymal enhancement.
In conclusion, the 60-sec delay used in the study of Imbriaco et al.
[1] is an empirical choice of
the authors that is not directly related to the outcomes of the study.
Likewise, the design of the study does not allow the authors to claim that
pancreatic enhancement correlates with the injection rate of the contrast
material. These issues related to parenchymal peak enhancement still need to
be investigated.
References
- Imbriaco M, Megibow AJ, Ragozzino A, et al. Value of the
single-phase technique in MDCT assessment of pancreatic tumors.
AJR 2005; 184:1111
-1117[Abstract/Free Full Text]
- Tublin ME, Tessler FN, Cheng SL, Peters TL, McGovern PC. Effect of
injection rate of contrast medium on pancreatic and hepatic helical CT.
Radiology 1999;210
: 97-101[Abstract/Free Full Text]
- Kim T, Murakami T, Takahashi S, et al. Pancreatic CT imaging:
effects of different injection rates and doses of contrast material.
Radiology 1999;212
: 219-225[Abstract/Free Full Text]
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