most spns are benign. summarizing 5 massive series of resected
spns seen on chest radiographs, 22–26 siegelman et al. twenty seven noted
that 53. 9% were granulomas, twenty eight. 3% were bronchogenic carcinomas
or different primary malignancies, vi. 6% were hamartomas,
and three. 5% were metastases. an excellent higher proportion of all radiographically
detected spns are presumably benign, as a result of nodules
that seem calcified on chest radiographs are rarely resected.
the challenge in evaluating spns is to avoid invasive procedures
in patients who have benign nodules while not allowing
potentially curable bronchogenic carcinomas the time to progress
to additional advanced or maybe unresectable disease. this may be an
space of active, ongoing analysis ; though, the several approaches
that are tried attest to the dearth of complete success for
most modalities to date. a proper spn analysis acknowledges
the following key points :
one. imaging at one purpose in time relies heavily on morphologic
characteristics in distinguishing benign from malignant
spns.
two. calcification is that the single best morphologic indicator of
benignancy.
three. behavior ( i. e., lack of growth ) is so much higher than any morphologic
criterion at predicting benignancy.
four. any predictor of benignancy should err on the facet of
intervention—it is higher to resect a benign spn unnecessarily
than erroneously to decision a malignant spn benign.
with these key points in mind and realizing the significant
expense ( and that in a few cases radiation dose ) of radiologic tests,
it's perpetually best to start out the analysis of the spn by seeking
recent radiographs for comparison. this saves cash, radiation,
and infrequently time, and supplys the possibility for proving that a
lesion is benign, notwithstanding what its morphology is. a lesion
that's stable for two years or additional is thought-about to be benign,
though the exception occurs for ground glass nodules at ct,
that could represent terribly indolent adenocarcinomas. the flip
facet is that virtually notwithstanding what the morphology is, a growing
lesion has declared itself to be one that ought to be resected.
the dearth of vigor with that recent films are pursued is generally
disappointing ; if the patient were an in depth relative, we'd all
strive plenty tougher to spare him or her unnecessary tests that involve
( potentially fatal ) injection of intravenous contrast. and
consider this—how several adults forty years of age or older have
never had a prior chest radiograph ? within the u. s., the
variety should be vanishingly little.
whereas the concept of stability seems, on the surface,
to be fairly straightforward, in apply it is quite difficult
to
work out if a nodule has grown, notably if it's small
( e. g., but one cm in diameter ). this can be true for each conventional
radiography and for ct. for example, a nodule that
has increased from ten to 11 mm in diameter could show no
apparent, significant modification in size at radiography or on axial
ct scans ; though, this represents a volume increase of 33%.
to maximize the ability to detect such changes in size, it's
necessary to optimize each ct imaging parameters, furthermore as
postprocessing techniques. notably for little nodules, the
best results could be obtained using skinny section ( one to two. five mm ),
overlapping ct sections with 3d volumetric reconstructions
( fig. twenty six. seven ). twenty eight, 29 during addition, all follow-up scans ought to be performed
using a similar techniques. volumetric measurements
could be affected by several factors, together with section thickness
and spacing, x-ray dose, motion artifact, respiratory or cardiac
phase, nodule location, and that intraobserver/extraobserver variability ;
thus, in general, volume differences but about
25% ought to be regarded with skepticism. twenty eight, 30–36
typically, the clinical call is created to prospectively
follow an spn with imaging, to demonstrate stability ; this
raises queries a fewppropriate scanning intervals. one
study based mostly on phantom exams and that in vivo nodules, using
automatic segmentation for lesion boundary definition, found
that ct follow-up at thirty days might detect interval growth for
all malignant lesions larger than one cm, and for lesions as small
as five mm with a doubling time faster than 150 days. thirty seven even for
5-mm lesions with slower doubling times, a second follow-up
ct thirty days later rendered growth detectable during all cases. in
a subsequent study of thirteen patients, all 5 malignant nodules
had doubling times but 177 days, and all eight benign
nodules had doubling times larger than 395 days. 38 though,
different authors have found that a big proportion of
malignant tumors have a lot of longer doubling times ( 465
days ), and also therefore short-term follow-up could not be helpful
in several patients
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