Accuracy of plain radiographs in diagnosing biopsy-proven malignant bone lesions.

BACKGROUND: The diagnosis of primary bone tumours is a three-fold approach based on a combination of clinical, radiological and histopathological findings. Radiographs form an integral part in the initial diagnosis, staging and treatment planning for the management of aggressive/malignant bone lesions. Few studies have been performed where the radiologist's interpretation of radiographs is compared with the histopathological diagnosis. OBJECTIVES: The study aimed to determine the frequency of bone tumours at a tertiary hospital in South Africa, and, using a systematic approach, to determine the sensitivity and specificity of radiograph interpretation in the diagnosis of aggressive bone lesions, correlating with histopathology. We also determined the inter-observer agreement in radiograph interpretation, calculated the positive and negative predictive values for aggressive/malignant bone tumours and computed the cumulative effect of multiple radiological signs to determine the yield for malignant bone tumours. METHOD: A retrospective, descriptive and correlational study was performed, reviewing the histopathological reports of all biopsies performed on suspected aggressive bone lesions during a 3-year period from 2012 to 2014. The radiographs were interpreted by three radiologists using predetermined criteria. The sensitivity and specificity of the readers' interpretation of the radiograph as 'benign/non-aggressive' or 'aggressive/malignant' were calculated against the histology, and the inter-rater agreement of the readers was computed using the Fleiss kappa values. RESULTS: Of the 88 suspected 'aggressive or malignant' bone tumours that fulfilled the inclusion criteria, 43 were infective or malignant and 45 were benign lesions at histology. Reader sensitivity in the diagnosis of malignancy/infective bone lesions ranged from 93% to 98% with a specificity of 53% - 73%. The average kappa value of 0.43 showed moderate agreement between radiological interpretation and final histology results. The four radiological signs with the highest positive predictive values were an ill-defined border, wide zone of transition, cortical destruction and malignant periosteal reaction. The presence of all four signs on radiography had a 100% yield for a malignant bone tumour or infective lesion. CONCLUSION: The use of a systemic approach in the interpretation of bone lesions on radiographs yields high sensitivity but low specificity for malignancy and infection. The presence of benign bone lesions with an aggressive radiographic appearance necessitates continuation of the triple approach for the diagnosis of primary bone tumours.

Hybrid imaging using low-dose, localizing computed tomography enhances lesion localization in renal hyperparathyroidism.

BACKGROUND: Preoperative localization of parathyroid lesions is potentially beneficial in renal patients with hyperparathyroidism. The aim of this study was to determine the localizing value of hybrid single-photon emission computed tomography combined with low-dose x-ray computed tomography (SPECT/LDCT) compared with SPECT alone and whether the LDCT improved reader confidence. PATIENTS AND METHODS: A retrospective study examined parathyroid scintigraphy results of patients previously referred with a diagnosis of renal hyperparathyroidism. All patients underwent planar scintigraphy using technetium-99m (Tc)-pertechnetate, which was immediately followed with Tc-sestamibi and SPECT/LDCT ∼60 min after sestamibi injection and a delayed static image to assess differential washout. Planar subtraction images were generated. Two nuclear physicians, assisted by a radiologist, reported on planar+SPECT images followed by planar+SPECT/LDCT images. RESULTS: Thirty-seven patients (males: 21; females: 16) were included (mean age 39 years, range: 23.9-55.5). Mean creatinine level was 878 µmol/l (109-1839), mean corrected calcium level was 2.42 mmol/l (1.77-3.64), and median parathyroid hormone level was 156.2 pmol/l (2.4 to >201). Twenty-three patients had positive planar and SPECT results (46 lesions), six had positive planar results only, and eight had negative scintigraphy results. In the patients with positive planar and SPECT results, 35 lesions were classified as eutopic and 11 as ectopic. After the addition of LDCT, localization of five eutopic lesions (on SPECT) was amended to ectopic locations (on SPECT/LDCT), principally by identifying posteriorly situated glands. The addition of LDCT led to increased confidence in localization in all cases. CONCLUSION: Compared with SPECT alone, SPECT/LDCT is beneficial in preoperative localization of lesions in renal hyperparathyroidism.