Type:
Educational Exhibit
Keywords:
Neoplasia, Tissue characterisation, Computer Applications-Detection, diagnosis, CT, Retroperitoneum, Kidney, Abdomen
Authors:
C. B. McConville, D. M. Neeson, P. Blair; Belfast/UK
DOI:
10.26044/ecr2019/C-2950
Background
Spectral CT scanning has the ability to improve the radiologist's performance beyond that of conventional CT. Conventional CT can present us with lots of unanswerable questions when incidental renal and adrenal nodules are identified. Many of these require supplementary imaging for definitive characterisation.
On review of such further imaging,
we feel,
with the benefit of hindsight,
that many of these studies could have been avoided with appropriate use of the spectral application during the initial CT study.
A key finding for renal lesion characterisation in the differentiation of benign or malignant pathology is the absence or presence of enhancement. On standard contrast enhanced CT studies,
enhancement is often implied based on lesion density measured in Hounsfield units (HU),
however a possible pitfall is when dealing with a hyperdense renal cyst. Virtual non-contrast (VNC) images can alleviate this problem by demonstrating through deduction whether the density is secondary to contrast enhancement or due to the intrinsic nature of the lesion.2 Iodine density (ID) maps further add confidence by reliably demonstrating absence of iodine uptake and hence lack of enhancement within these hyperdense benign renal lesions.3
When dealing with incidental adrenal lesions on cross sectional imaging a key feature is to establish whether or not the lesion is likely to be a benign adenoma. On conventional CT the most useful finding is the unenhanced HU measurement. Patients commonly present for contrast CT without a protocolled unenhanced phase which otherwise would permit the recording of this important parameter in these common incidental findings. This problem can be overcome through use of VNC which permits the measurement of the lesion's unenhanced density therefore confidentially permitting a benign diagnosis in the case of a lipid rich adenoma4,
5 and with confirmation of absent enhancement in haemorrhagic hyperdense cysts.2