Artefacts in spiral-CT images and their relation to pitch and subject morphology

Wilting, J. E.; Timmer, Jan

doi:10.1007/s003300050673

Cited by 35 publications

(21 citation statements)

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“…These artifacts induced by the vertebrae, the ribs and the air in the stomach may also account for the lower detection rate of small metastases. Artefacts associated with spiral CT are reported in the literature, and Witling and Timmer demonstrated on cadaver studies that the artefacts increased with increased table speed and that they were less severe when the pitch is reduced [28,29]. Comparing protocols 2 and 3 did not reveal a significant difference in the detection of small hepatic lesions.…”

Section: Discussionmentioning

confidence: 98%

Detection of liver metastases under 2 cm: comparison of different acquisition protocols in four row multidetector-CT (MDCT)

et al. 2005

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This study compared different acquisition protocols performance to detect small liver metastases (<2 cm). Thirty consecutive patients with histologically proven hepatic metastases were explored by MDCT at the liver equilibrium phase by four successive acquisitions. We compared the following protocols (1-4): 5/30/1.5 (section thickness/table speed/pitch); 5/15/0.75; 5/11.25/0.75; and 2.5/15/1.5 with the same X-ray dose. The gold standard was based on patient radiological follow-up. Evolutive lesions were considered as true positive (TP). The described lesions, not found on the follow-up exams despite tumoral progression, were considered as false positive (FP). Stable lesions could not be considered as metastasis and were eliminated. One hundred and seventy-six lesions were detected: 61 TP and 91 FP. Twenty-four lesions were eliminated.The mean kappa values for protocols 1, 2, 3 and 4 were, respectively, 0.43, 0.68, 0.73 and 0.51 (0.61-0.80: substantial agreement) and the mean areas under the ROC curve were, respectively, 0.76, 0.87, 0.86 and 0.80. The results of protocols 2 and 3 were significantly superior to those of protocols 1 and 4. MDCT protocols using thin sections or an increased table speed are less efficient in detecting small metastases.

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Section: Discussionmentioning

confidence: 98%

Detection of liver metastases under 2 cm: comparison of different acquisition protocols in four row multidetector-CT (MDCT)

et al. 2005

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“…Increasing tube current improves the signal-to-noise ratio. Decreasing pitch and slice thickness have a similar effect by increasing effective mAs [13,16]. Increased slice thickness of reformatted images, smooth reconstruction filters, and increased window width improve image quality [13].…”

Section: Computed Tomographymentioning

confidence: 89%

Shoulder arthroplasty

2008

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Shoulder prostheses are now commonly used. Clinical results and patient satisfaction are usually good. The most commonly used types are humeral hemiarthroplasty, unconstrained total shoulder arthroplasty, and semiconstrained inversed shoulder prosthesis. Complications of shoulder arthroplasty depend on the prosthesis type used. The most common complications are prosthetic loosening, glenohumeral instability, periprosthetic fracture, rotator cuff tears, nerve injury, infection, and deltoid muscle dysfunction. Standard radiographs are the basis of both pre- and postoperative imaging. Skeletal scintigraphy has a rather limited role because there is overlap between postoperative changes which may persist for up to 1 year and early loosening and infection. Sonography is most commonly used postoperatively in order to demonstrate complications (hematoma and abscess formation) but may also be useful for the demonstration of rotator cuff tears occurring during follow-up. CT is useful for the demonstration of bone details both pre- and postoperatively. MR imaging is mainly used preoperatively, for instance for demonstration of rotator cuff tears.

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“…Scanner calibration and periodic maintenance by performing a series of quality control tests can help minimize scannerbased artifacts. The ring artifact-the most common scannerbased artifact-can be seen on transaxial CT images for various reasons, such as improper CT number calibration, the presence of any object during air calibration, defective detector elements, or a defective detector module (2,3). Sometimes the ring artifact can appear for accidental reasons such as a contrast drop on the detector or CT tube (4).…”

Section: Discussionmentioning

confidence: 99%

“…Hence, quality control testing of PET/CT equipment, both at acceptance and periodically, is mandatory to achieve the best results (1). Artifacts on CT images, though independent of PET image acquisition, can still degrade the quality of PET images during processing and interpretation (2). Non-scanner-based CT artifacts are caused mainly by improper selection of acquisition parameters and by metallic implants, patient motion, and improper patient preparation (2,3).…”

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confidence: 99%

An Unusual Cause of the Ring Artifact on Transaxial CT Images

Jha

Purandare

Rangarajan

2015

J. Nucl. Med. Technol.

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Artifacts and image quality are two sides of the same coin. The ring artifact is scanner-based and caused mainly by either a miscalibrated element or a defective element of a detector row. We describe a rare cause of the ring artifact that appeared on a transaxial CT image because of a loose electronic contact. To our knowledge, this particular cause of the ring artifact has not been described in literature. Adi agnostic outcome from PET/CT imaging is the product of images that combine quality, reliability, and reproducibility. Hence, quality control testing of PET/CT equipment, both at acceptance and periodically, is mandatory to achieve the best results (1). Artifacts on CT images, though independent of PET image acquisition, can still degrade the quality of PET images during processing and interpretation (2). Non-scanner-based CT artifacts are caused mainly by improper selection of acquisition parameters and by metallic implants, patient motion, and improper patient preparation (2,3). Scanner-based artifacts may appear because of a sudden breakdown of the system. CASE REPORTWe encountered the ring artifact on a transaxial CT image while performing routine PET/CT on a 64-slice timeof-flight Gemini TF 64 scanner (Philips) (Fig. 1A, arrows). The artifact persisted on the CT scan of the uniformity phantom (Fig. 1B, arrows) and remained even after cleaning of the Mylar (DuPont Teijin Films) window with warm water. The service engineer performed the bad-detector test to rule out the possibility that the artifact was caused by defective detector modules. Modules 21 and 26 did not pass the test. Two possibilities for the defect were suspected, either an electronic issue within the detector module or a loose connection between the module and the motherboard. Because the first cause would have required replacing the detector module, we tried to rule out the second cause-a loose connection. Both modules were reset in the motherboard, and the bad-detector test was repeated. This time the test did not reveal a problem with any of the modules, including 21 and 26. We then performed CT scanning of the uniformity phantom and found that the ring artifact had disappeared (Fig. 1D). We repeated the scan to confirm disappearance of the artifact. Before starting clinical imaging, we performed an air calibration test. We resumed clinical imaging after obtaining a satisfactory result from this test, and the ring artifact was not present on the clinical images (Fig. 1C). DISCUSSIONThe CT artifacts described in literature are categorized as physics-based, patient-based, or scanner-based (3). Scanner

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Artefacts in spiral-CT images and their relation to pitch and subject morphology

Cited by 35 publications

References 0 publications

Detection of liver metastases under 2 cm: comparison of different acquisition protocols in four row multidetector-CT (MDCT)

Detection of liver metastases under 2 cm: comparison of different acquisition protocols in four row multidetector-CT (MDCT)

Shoulder arthroplasty

An Unusual Cause of the Ring Artifact on Transaxial CT Images

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