ABR Nuclear Radiology common mistakes
ABR Nuclear Radiology · Understand the traps and how to avoid them.
When a phantom uniformity image appears noisy, the candidate widens the photopeak window to collect more counts, then concludes that spatial resolution has improved.
The candidate conflates sensitivity with resolution and does not account for the increased scatter fraction that a wider window accepts; this is a frequent scoring trap in gamma-camera quality-control questions.
What to do instead
State explicitly that widening the window raises count sensitivity but adds scatter, degrading contrast and the line-spread function. Assess resolution with a line source or MTF and contrast with a phantom, and report sensitivity and resolution as separate, traded-off metrics.
Calculates CT radiation dose as CTDIvol multiplied by the number of slices, or directly reports CTDIvol as the patient's effective dose.
The candidate memorizes dose metric names without their definitions and confuses a phantom-based dose index with a patient dose estimate.
What to do instead
Apply the correct chain: DLP = CTDIvol x scan length (cm); effective dose = DLP x age/region conversion coefficient. Explain that CTDIvol is a standardized 32-cm or 16-cm phantom index and does not by itself represent patient risk.
Prepares a Tc-99m dose using the generator's calibration activity without correcting for elapsed time or the ingrowth of Tc-99m after the previous elution, then administers an activity far from the prescribed dose.
The candidate follows a rote kit recipe and omits the decay equation and transient-equilibrium generator behavior under time pressure.
What to do instead
Use A = A0 exp(-0.693t/T1/2) with the correct half-life (6.0 h for Tc-99m), record the prior elution time to estimate available activity, and verify the final syringe activity in a dose calibrator before administration.
Chooses a radiopharmaceutical for a clinical question based only on half-life, such as substituting I-131 MIBG for I-123 MIBG, without checking photon energy, collimator match, or labeling chemistry.
The candidate treats half-life as the dominant selection criterion and neglects how photon energy determines collimator choice and image quality.
What to do instead
Match three variables: the tracer's photon energy to the collimator (159 keV for I-123 versus 364 keV for I-131), its half-life to the procedure duration and radiation burden, and its uptake mechanism and labeling to the clinical question.
Reports SUVmax against a fixed malignancy cutoff and compares SUV values between scans acquired on different scanners or with different reconstructions.
The candidate treats SUV as an absolute, calibrated biomarker rather than a semiquantitative index affected by vendor, reconstruction, uptake time, and body composition.
What to do instead
Use context-appropriate frameworks: Deauville criteria for lymphoma, PERCIST with SULpeak and the same scanner/reconstruction for solid-tumor response, and clinical plus morphologic correlation rather than a single SUV threshold.
Reads a fixed inferior-wall defect on a regadenoson SPECT myocardial perfusion study as infarction without reviewing attenuation correction, body habitus, or the rest images.
The candidate pattern-matches a territorial defect to coronary disease and skips the artifact checklist that explains many fixed inferior defects.
What to do instead
Compare stress and rest in both attenuation-corrected and non-corrected reconstructions, look for diaphragmatic and breast artifacts, and require reversibility or matched metabolic/viability data before calling scar.
Calls a V/Q scan high probability for pulmonary embolism on the basis of one mismatched segmental defect without a contemporaneous chest radiograph or knowledge of prior PE.
The candidate remembers that mismatched defects are abnormal but not the PIOPED thresholds and the requirement that the radiograph be clear in the corresponding region.
What to do instead
Apply explicit criteria: at least two large mismatched segmental defects (or one large plus two moderate) with a clear chest radiograph, and integrate prior PE history and clinical probability before assigning a probability category.
Attributes a solitary rib uptake on planar bone scintigraphy to metastasis in an oncology patient without SPECT/CT or trauma history.
The candidate overweights the cancer history and uses planar images alone, ignoring that solitary rib foci are usually benign fractures.
What to do instead
Obtain SPECT/CT or at least correlate with radiographs and trauma history; recognize the linear, focal rib-fracture pattern and reserve metastatic concern for multiple or characteristic axial lesions.
Uses a visually normal DaTscan to exclude Parkinson disease rather than to distinguish neurodegenerative parkinsonism from drug-induced parkinsonism or essential tremor, and misreads normal asymmetric putamen uptake as abnormal.
The candidate misunderstands the test's purpose and normal age-related, comma-shaped striatal uptake pattern.
What to do instead
State that DaTscan detects presynaptic dopaminergic loss and cannot separate Parkinson disease from atypical parkinsonian syndromes; review the normal comma shape, age-related decline, and symmetric versus asymmetric patterns before interpretation.
Prescribes a fixed I-131 activity for Graves disease or remnant ablation without documenting pregnancy or breastfeeding status, recent iodinated contrast, or the timing of antithyroid medication.
The candidate focuses on the nominal activity and omits the pre-therapy safety checklist that determines both eligibility and absorbed dose.
What to do instead
Use a structured checklist: negative beta-hCG, cessation of breastfeeding, appropriate interval after iodinated contrast, and antithyroid drug withdrawal timing; consider dosimetry when marrow or lung dose is a concern.