Enhancement of collapsed lung: a potential pitfall in CT interpretation

In the presence of a pleural effusion there may be compression of adjacent lung causing segmental atelectasis. In some effusions minor degrees of atelectasis give rise to a fine rim of enhancing lung on computerized tomographic (CT) examination which should not be misinterpreted as extravasated contrast from aortic or oesophageal lumen.     

'Shine through' on dual tracer parathyroid scintigraphy: a potential pitfall in interpretation

Dual tracer scintigraphy has become the procedure of choice for preoperative localization of parathyroid adenomas. The typical protocol used by most laboratories is to initially perform a Tc-99m sestamibi (MIBI) study with early and delayed (2-3 hours) washout phase images. This is followed by a thyroid-specific Tc-99m pertechnetate study. A potential pitfall exists if the delayed phase of the initial MIBI study shows an intense, abnormal focus of retention. This focus may interfere with interpretation of the subsequent pertechnetate study because of a "shine through" effect. To differentiate a parathyroid adenoma from a thyroid adenoma, it may be necessary to repeat the thyroid-specific pertechnetate scan on a separate day after the dual tracer study.     

Central pseudodefect of the talus: a potential ankle MR interpretation pitfall.

PURPOSE: The purpose of our study was to outline the MR features of the central pseudodefect of the talus (a normal finding that can simulate an osteochondral lesion on ankle MR studies), assess the prevalence of the central pseudodefect of the talus, and provide insight into the origin of this misleading MR appearance. METHOD: We retrospectively evaluated 31 ankle MR studies in 10 asymptomatic volunteers and 21 consecutive patients for the presence of the central pseudodefect of the talus. None of the patients had a history of trauma to the ankle. The signal, size, and shape of the pseudodefect were documented in each patient. The sagittal images were cross-referenced with the axial and coronal images in all patients in whom the central pseudodefect was identified. RESULTS: Six volunteers (60%) and 13 patients (62%) showed a curvilinear band in the middle third of the talus on far medial sagittal images, consistent with the central pseudodefect of the talus. The band measured 8-15 x 3-8 mm (mean 11 x 4 mm) and was hypointense on T1 and STIR pulse sequences. In two cases, the pseudodefect was subchondral; in the rest, it was found a few millimeters below the articular surface. On cross-referenced axial and coronal images, the band corresponded to the talar insertion site of the deep tibiotalar fibers of the deltoid ligament. CONCLUSION: The central pseudodefect of the talus is a common finding that is produced by the insertion of the tibiotalar fibers of the deltoid ligament into the talus. Familiarity with its appearance is necessary to avoid misinterpreting it as an osteochondral lesion of the talus.     

Semi-quantitative interpretation of the bone scan in metabolic bone disease

Certain easily recognisable features are commonly seen in the bone scans of patients with metabolic bone disorders. Seven such features have been numerically graded by three independent observers in the scans of 100 patients with metabolic bone disease and of 50 control subjects. The total score for each patient is defined as the metabolic index. The mean metabolic index for each group of patients with metabolic bone disease is significantly greater than that for the control group (P<0.001).     

Carpal pseudoerosions: a plain X-ray interpretation pitfall

Objective

To examine in detail images of pseudoerosion of the wrist and hand on plain radiographs.

Material and methods

The study was conducted with 28 cadaver wrists. During a single imaging session three techniques—plain radiography, tomosynthesis, and computed tomography—were used to visualize the wrist and hand specimens. For each technique, 20 radio-ulno-carpo-metacarpal sites known to present bone erosions in rheumatoid arthritis were analyzed by two radiologists using a standard system to score the cortical bone: normal, pseudoerosion, true erosion, or other pathology. Cohen’s concordance analysis was performed to determine inter-observer and intra-observer (for the senior radiologist) agreement by site and by technique. Serial sections of two cadaver specimens were examined to determine the anatomical correlation of the pseudoerosions.

Results

On the plain radiographs, the radiologists scored many images as pseudoerosion (7.3 %), particularly in the distal ulnar portion of the capitate, the distal radial portion of the hamate, the proximal ulnar portion of the base of the third metacarpal, the proximal radial portion of the base of the fourth metacarpal, the distal ulnar portion of the hamate, and the proximal portion of the base of the fifth metacarpal. The computed tomography scan revealed that none of these doubtful images corresponded to true erosions. The anatomical correlation study showed that these images could probably be attributed to ligament insertions, thinner lamina, and enhanced cortical bone transparency.

Conclusion

Knowledge of the anatomical carpal localizations where pseudoerosions commonly occur is a necessary prerequisite for analysis of plain radiographs performed to diagnose or monitor rheumatoid arthritis.     

CT结肠成像中病人变换体位时升结肠的转动——影像诊断中一个潜在的缺陷

目的研究CT结肠成像(CTC)中,病人从仰卧转为俯卧时升结肠转动的程度与方式。方法数据库内37例(43个适于研究的病变)经过CTC与结肠镜检查的病人被纳     

Ascending colon rotation following patient positional change during CT colonography: a potential pitfall in interpretation

Objective  

To investigate the degree and pattern of ascending colonic rotation as patients moved from supine to prone positions during CTC.     

The uterine blush. A potential false-positive in Meckel's scan interpretation

To determine the presence, prevalence, and clinical importance of Tc-99 pertechnetate uterine uptake, this retrospective analysis of 71 Meckel's scans was undertaken. Specifically, each study was evaluated for the presence of a focal accumulation of radiotracer cephalad to the bladder. Patients received an intravenous dose of 150 microCi/kg of Tc-99 pertechnetate. Each study consisted of 15 one minute anterior serial gamma camera images, and a 15, 30, and 60 minute anterior, right lateral and posterior scintiscan. Menstrual histories were obtained from all patients except two. No males (33/33), nor premenstrual (13/13), menopausal (4/4) or posthysterectomy (2/2) patients revealed a uterine blush. Eleven of 15 patients (73%) with regular menses demonstrated a uterine blush. They were in the menstrual or secretory phases of their cycle. Four demonstrated no uterine uptake, had regular periods, but were in the proliferative phase of their cycle. Two with irregular periods, and one with no recorded menstrual history, manifested the blush. Radiotracer should be expected in the uterus during the menstrual and secretory phases of the menstrual cycle. It is a manifestation of a normal physiologic phenomenon, and must be recognized to prevent false-positive Meckel's scan interpretations.     

Ovarian conservation at hysterectomy: a potential diagnostic pitfall

Three patients who were evaluated by computed tomography (CT) for possible recurrent tumour of the cervix are described. Two had proven carcinoma and the third had non-Hodgkin's lymphoma of the cervix. In each, soft tissue masses in the iliac fossa, close to the iliopsoas muscles, were demonstrated. The position, shape, symmetry and, in one patient, the presence of surgical clips led to the correct diagnosis that these soft tissue masses were normal ovaries which had been moved out of the true pelvis at the time of hysterectomy. Such ovarian conservation creates a potential cause of error as the ovaries can then simulate enlarged nodal masses.     

Iatrogenic FDG foci in the lungs: a pitfall of PET image interpretation

Ohne Zusammenfassung     

Cecal mobility: a potential pitfall of CT colonography

OBJECTIVE: On CT colonography, feces is differentiated from a polyp primarily by texture and mobility. When feces is soft-tissue in density and polypoid in shape, only its mobility is the clue to the correct diagnosis. There are reports of false-negative examinations caused by the mobility of bowel mimicking lesion movement. We studied the mobility of the cecum as seen on CT colonography to determine how often this potential pitfall exists. CONCLUSION: Rotation of the cecum is geometrically complex and occurs in several planes. It explains previous anecdotal reports of false-negative diagnoses. When solid feces is suspected in the cecum based on mobility, the reviewer should take the time to carefully analyze mobility of the cecum using multiplanar images.     

Meckel's scan: pitfall in patients with active small bowel bleeding

Potential for a false-positive Meckel's scan is highlighted in this patient with intermittent, low-volume small bowel bleeding. Meckel's scan showed late appearance of focal activity mimicking a positive diverticulum finding. This was secondary to extravasated tracer during a coincidental bleeding as shown by a Tc-99m tagged red blood cell scan obtained 2 days earlier. Inaccurate diagnosis of Meckel diverticulum was avoided by: 1) noticing the late appearance in relationship to the gastric uptake, and 2) showing motility of the focus on delayed dynamic imaging that confirmed transit of extravasated tracer along the small bowel with peristalsis. Subsequent capsule endoscopy showed a bleeding ulcer in the ileum.     

Semi-quantitative interpretation of the bone scan in metabolic bone disease: definition and validation of the metabolic index.

Certain easily recognisable features are commonly seen in the bone scans of patients with metabolic bone disorders. Seven such features have been numerically graded by three independent observers in the scans of 100 patients with metabolic bone disease and of 50 control subjects. The total score for each patient is defined as the metabolic index. The mean metabolic index for each group of patients with metabolic bone disease is significantly greater than that for the control group (P less than 0.001).     

Fat necrosis of breast: a potential pitfall in breast MRI

Fat necrosis is a benign nonsuppurative inflammatory process of adipose tissue. Occasionally fat necrosis may mimic a breast cancer clinically, mammographically, and sonographically. There have been some previous reports on the MR imaging of the fat necrosis. In some MR findings of fat necrosis, it was difficult to distinguish it from malignant lesions. We report a case of fat necrosis presenting the irregular enhancement with the non-enhancing area of central areas on MRI.     

Abscesses with enteric communication: a potential pitfall in computed tomography

We retrospectively reviewed the clinical and radiologic records of 17 patients with proven abdominal abscesses with enteric communication. Computed tomography was able to correctly diagnose an abdominal abscess in only 11 of these 17 patients. The six patients whose abscesses were missed with CT fell into three categories. Two patients had near water density fluid collections mistaken for fluid-filled loops of bowel. Two patients had large gas and fluid-filled collections mistaken for bowel, and two patients had collections containing a large amount of orally administered contrast material that were mistaken for contrast-filled loops of bowel. Retrospective examination of plain abdominal and/or digital scout radiography revealed findings suggestive of an abscess in 48% of the 17 patients, including two of the six CT false-negatives.     

Solitary hot spots in the ribs on bone scan: value of thin-section reformatted computed tomography to exclude radiography-negative fractures

PURPOSE: The purpose of this study was to classify solitary, scintigraphy-positive and radiography-negative rib lesions and to clarify the features of rib fractures by using thin-section reformatted helical computed tomography (CT). METHODS: Forty-seven patients whose whole-body bone scans showed a solitary hot spot in a rib as their first abnormal scintigraphic finding and whose plain radiograph showed negative or indeterminate results were examined by thin-section reformatted CT. Final diagnosis was based on follow-up over a 20-month period. RESULTS: The final diagnosis included 17 cases of fractures where CT findings were fracture line, focal sclerosis, and callus formation. Fourteen ribs demonstrated intramedullary, focal osteosclerosis, and 8 ribs did not demonstrate any abnormalities. Four metastatic lesions appeared as intramedullary mixture of osteolysis and osteosclerosis, or bone destruction. Four intramedullary lesions with cystic appearance remained unchanged. CONCLUSIONS: Thin-section reformatted helical CT delineated minute, radiographically occult fractures of the rib. Excluding fractures, helical CT can avoid further unnecessary examinations.     

Lung scan interpretation: a physiologic, user-friendly approach.

A physiologically-oriented, user-friendly algorithm for interpretation of ventilation-perfusion (V/P) lung scans was compared to the widely used Biello criteria. The physiologic algorithm relies primarily on the observer's degree of certainty that a V/P mismatch is present rather than on the size (relative to a whole segment) and number of V/P mismatches. One hundred five patients who had undergone a ventilation study with 133Xe gas, a perfusion study with 99mTc-MAA and pulmonary angiography were reviewed. Each V/P lung scan was interpreted once with the physiologic algorithm and once with the Biello criteria by two observers. Fifty-nine percent of the 105 studies were classified as indeterminate with the physiologic algorithm versus 62% with the Biello criteria. The prevalence of pulmonary embolism in the high probability, indeterminate, low probability and normal categories for the physiologic algorithm were 60%, 26%, 7% and 0%, respectively; and for the Biello criteria were 50%, 31%, 11% and 0%, respectively. Analysis of the data with receiver-operating-characteristic curves indicated that the physiologic algorithm performed better than the Biello criteria (p less than 0.05). In addition, the physiologic algorithm has the advantages of being more intuitive and easier to remember. We conclude that further evaluation of the physiologic approach for the interpretation of V/P lung scans is warranted.