Change detection in sparse repeat CT scans with non-rigid deformations.

BACKGROUND: Detecting and interpreting changes in the images of follow-up CT scans by the clinicians is often time-consuming and error-prone due to changes in patient position and non-rigid anatomy deformations. Thus, reconstructed repeat scan images are required, precluding reduced dose sparse-view repeat scanning. OBJECTIVE: A method to automatically detect changes in a region of interest of sparse-view repeat CT scans in the presence of non-rigid deformations of the patient's anatomy without reconstructing the original images. METHODS: The proposed method uses the sparse sinogram data of two CT scans to distinguish between genuine changes in the repeat scan and differences due to non-rigid anatomic deformations. First, size and contrast level of the changed regions are estimated from the difference between the scans' sinogram data. The estimated types of changes in the repeat scan help optimize the method's parameter values. Two scans are then aligned using Radon space non-rigid registration. Rays which crossed changes in the ROI are detected and back-projected onto image space in a two-phase procedure. These rays form a likelihood map from which the binary changed region map is computed. RESULTS: Experimental studies on four pairs of clinical lung and liver CT scans with simulated changed regions yield a mean changed region recall rate > 86%and a mean precision rate > 83%when detecting large changes with low contrast, and high contrast changes, even when small. The new method outperforms image space methods using prior image constrained compressed sensing (PICCS) reconstruction, particularly for small, low contrast changes (recall = 15.8%, precision = 94.7%). CONCLUSION: Our method for automatic change detection in sparse-view repeat CT scans with non-rigid deformations may assist radiologists by highlighting the changed regions and may obviate the need for a high-quality repeat scan image when no changes are detected.

Effect of intravenous contrast for CT abdomen and pelvis on detection of urgent and non-urgent pathology: can repeat CT within 72 hours be avoided?

PURPOSE: To determine if administering IV contrast for CT abdomen and pelvis improves detection of urgent and clinically important non-urgent pathology in patients with urgent clinical symptoms compared to patients not receiving IV contrast, and in turn to determine whether repeat CT exams on the same patient within 72 h were of low diagnostic benefit if the first CT was performed with IV contrast. METHODS: We evaluated 400 consecutive patients who had CT abdomen and pelvis (CT AP) examinations repeated within 72 h. For each patient, demographic data, reason for examination, examination time stamps, and examination technique were documented. CT AP radiology reports were reviewed and both urgent and non-urgent pathology was extracted. RESULTS: Of 400 patients, 63% had their initial CT AP without contrast. Administration of IV contrast for the first CT AP was associated with increased detection of urgent findings compared with non-contrast CT (p = 0.004) and a contrast-enhanced CT AP following an initial non-contrast CT AP examination better characterized both urgent (p = 0.002) and non-urgent findings (p < 0.001). Adherence to ACR appropriateness criteria for IV contrast administration was associated with increased detection of urgent pathology on the first CT (p = 0.02), and the second CT was more likely to be performed with IV contrast if recommended by the radiologist reading the first CT (p = 0.0006). CONCLUSION: In the absence of contraindications, encouraging urgent care physicians to preferentially order IV contrast-enhanced CT AP examinations in adherence with ACR appropriateness criteria may increase detection of urgent pathology and avoid short-term repeat CT AP.

Repeat computed tomography scans among inter-facility transferred major trauma patients in Oklahoma, 2009-2015.

PURPOSE: Computed tomography (CT) scans play a vital role in the diagnosis and evaluation of trauma patients. Repeat CT scans occurred often among transferred trauma patients. The objective was to describe CT use and identify patient- and hospital-level factors associated with repeat CT scans among inter-facility transferred major trauma patients. METHODS: A retrospective cohort study was conducted using data extracted from the Oklahoma State Trauma Registry between 2009 and 2015. Both bivariate and multivariate analyses were employed to assess the factors associated with repeat CT scans. RESULTS: During the 7-year study period, 8678 major trauma patients were transferred between acute-care hospitals in Oklahoma. Among them, 4311 patients had at least one repeat CT scan. Head CT scans were the most commonly performed as well as repeated. Bivariate analysis showed that differences in repeat CT scans were associated with age, injury type, injury severity score, head injury severity, revised trauma score, payer source, transport mode to referring facilities, and facility levels at the 5% level. Multivariate analysis showed the odds of repeat CT scans were higher for adult and geriatric patients, patients with blunt injuries, severely injured patients, patients with severe head injuries, patients with a good revised trauma score, patients discharged alive, and mode to referring facilities. CONCLUSIONS: Our study demonstrated that inter-facility transfers within an organized rural trauma system often underwent repeat CT scans. The large proportion of patients with multiple and repeated CT scans should underline the importance of trauma systems evaluating the necessity of CT scans, image-sharing capability, and obtaining appropriate scans in order to optimize use. Overall, reducing unnecessary CT scans should be an essential part of trauma care quality improvement efforts.

Do we need a new CT scan for retreatment of intracranial SRS patients?

PURPOSE: To determine if the treatment planning computed tomography scan (CT) from an initial intracranial stereotactic radiosurgery (SRS) treatment can be used for repeat courses of SRS. METHODS AND MATERIALS: Twenty-five patients with 40 brain metastases that received multiple courses of SRS were retrospectively studied. Magnetic resonance scans from repeat SRS (rMR) courses were registered to CT scans from the initial SRS (iCT) and repeat SRS (rCT). The CT scans were then registered to find the displacement of the rMR between iCT and rCT registrations. The distance from each target to proximal skull surface was measured in 16 directions on each CT scan after registration. The mutual information (MI) coefficients from the registration process were used to evaluate image set similarity. Targets and plans from the rCTs were transferred to the iCTs, and doses were recalculated on the iCT for repeat plans. The two dose distributions were compared through 3D gamma analysis. RESULTS: The magnitude of the mean linear translations from the MR registrations was 0.6 ± 0.3 mm. The mean differences in distance from target to skull on a per target basis were 0.3 ± 0.2 mm. The MI was 0.582 ± 0.042. Registration between a comparison group of 30 CT scans that had the same data resampled and 30 scans that were intercompared with different patients gave MI = 0.721 ± 0.055 and MI = 0.359 ± 0.031, respectively. The mean gamma passing rates were 0.997 ± 0.007 for 1 mm/1% criteria. CONCLUSIONS: The rMR can be aligned to the iCT to accurately define targets. The skull shows minimal change between scans so the iCT can be used for set-up at repeat treatments. The dosimetry provided by the iCT dose calculation is adequate for repeat SRS. Treatment based on iCT is feasible.

Value of Repeat CT Brain in Mild Traumatic Brain Injury Patients with High Risk of Intracerebral Hemorrhage Progression.

Patients with mild traumatic brain injury (MTBI) with intracerebral hemorrhage (ICH), particularly those at higher risk of having ICH progression, are typically prescribed a second head Computer Tomography (CT) scan to monitor the disease development. This study aimed to evaluate the role of a repeat head CT in MTBI patients at a higher risk of ICH progression by comparing the intervention rate between patients with and without ICH progression. METHODS: 192 patients with MTBI and ICH were treated between November 2019 to December 2020 at a single level II trauma center. The Glasgow Coma Scale (GCS) was used to classify MTBI, and initial head CT was performed according to the Canadian CT head rule. Patients with a higher risk of ICH progression, including the elderly (≥65 years old), patients on antiplatelets or anticoagulants, or patients with an initial head CT that revealed EDH, contusional bleeding, or SDH > 5 mm, and multiple ICH underwent a repeat head CT within 12 to 24 h later. Data regarding types of intervention, length of stay in the hospital, and outcome were collected. The risk of further neurological deterioration and readmission rates were compared between these two groups. All patients were followed up in the clinic after one month or contacted via phone if they did not return. RESULTS: 189 patients underwent scheduled repeated head CT, 18% had radiological intracranial bleed progression, and 82% had no changes. There were no statistically significant differences in terms of intervention rate, risk of neurological deterioration in the future, or readmission between them. CONCLUSION: Repeat head CT in mild TBI patients with no neurological deterioration is not recommended, even in patients with a higher risk of ICH progression.

Clinical implementation and validation of an automated adaptive workflow for proton therapy.

Background and purpose: Treatment quality of proton therapy can be monitored by repeat-computed tomography scans (reCTs). However, manual re-delineation of target contours can be time-consuming. To improve the workflow, we implemented an automated reCT evaluation, and assessed if automatic target contour propagation would lead to the same clinical decision for plan adaptation as the manual workflow. Materials and methods: This study included 79 consecutive patients with a total of 250 reCTs which had been manually evaluated. To assess the feasibility of automated reCT evaluation, we propagated the clinical target volumes (CTVs) deformably from the planning-CT to the reCTs in a commercial treatment planning system. The dose-volume-histogram parameters were extracted for manually re-delineated (CTVmanual) and deformably mapped target contours (CTVauto). It was compared if CTVmanual and CTVauto both satisfied/failed the clinical constraints. Duration of the reCT workflows was also recorded. Results: In 92% (N = 229) of the reCTs correct flagging was obtained. Only 4% (N = 9) of the reCTs presented with false negatives (i.e., at least one clinical constraint failed for CTVmanual, but all constraints were satisfied for CTVauto), while 5% (N = 12) of the reCTs led to a false positive. Only for one false negative reCT a plan adaption was made in clinical practice, i.e., only one adaptation would have been missed, suggesting that automated reCT evaluation was possible. Clinical introduction hereof led to a time reduction of 49 h (from 65 to 16 h). Conclusion: Deformable target contour propagation was clinically acceptable. A script-based automatic reCT evaluation workflow has been introduced in routine clinical practice.

Value of repeat CT for nonoperative management of patients with blunt liver and spleen injury: a systematic review.

PURPOSE: To evaluate the effectiveness of routine repeat computed tomography (CT) for nonoperative management (NOM) of adults with blunt liver and/or spleen injury. METHODS: We conducted a systematic review of randomized and non-randomized controlled trials (RCTs), quasi-experimental and observational studies of repeat CT in adult patients with blunt abdominal injury. We searched Medline, Embase, Web of Science, and Cochrane Central from their inception to October 2020 using Cochrane guidelines. Primary outcomes were change in clinical management (e.g., emergency surgery, embolization, blood transfusion, clinical surveillance), mortality, and complications. Secondary outcomes were hospital readmission and length of stay. RESULTS: Search results yielded 1611 studies of which 28 studies including 2646 patients met our inclusion criteria. The majority reported on liver (n = 9) or spleen injury (n = 16) or both (n = 3). No RCTs were identified. Meta-analyses were not possible because no study performed direct comparisons of study outcomes across intervention groups. Only seven of the twenty-eight studies reported whether repeat CT was routine or prompted by clinical indication. In these 7 studies, among the 254 repeat CT performed, 188 (74%) were routine and 8 (4%) of these led to a change in clinical management. Of the 66 (26%) repeated CT prompted by clinical indication, 31 (47%) led to a change in management. We found no data allowing comparison of any other outcomes across intervention groups. CONCLUSION: Routine repeat CT without clinical indication is not useful in the management of patients with liver and/or spleen injury. However, effect estimates were imprecise and included studies were of low methodological quality. Given the risks of unnecessary radiation and costs associated with repeat CT, future research should aim to estimate the frequency of such practices and assess practice variation. LEVEL OF EVIDENCE: Systematic reviews and meta-analyses, Level II.

Benefit of adaptive CT-based treatment planning in high-dose-rate endorectal brachytherapy for rectal cancer.

PURPOSE: In this planning study, we investigated the dosimetric benefit of repeat CT-based treatment planning at each fraction vs. the use of a single CT-based treatment plan for all fractions for high-dose-rate endorectal brachytherapy (HDREBT) for rectal cancer. METHODS AND MATERIALS: We included 11 patients that received a CT scan with applicator in situ for all three fractions. The treatment plan of the first fraction was projected on the repeat CT scans to simulate the use of a single treatment plan. In addition, replanning was performed on the repeat CT scans, and these were compared to the corresponding projected treatment plans. RESULTS: Repeat CT-based treatment planning resulted on average in a 21% higher (p = 0.01) conformity index compared to single CT-based treatment planning. Projecting the initial treatment plan to the repeat CT scans of fraction two and three, 12/22 fractions reached a CTV D98 of 85% of the prescribed dose of 7 Gy, which increased to 14/22 using replanning. For the remaining fractions, median CTV D98 was 4.2 Gy, and an intervention would be necessary to correct applicator balloon setup or to remove remaining air and/or feces between the CTV and the applicator. CONCLUSIONS: Using a single CT-based treatment plan for all fractions may result in a suboptimal treatment at later fractions. Therefore, repeat CT imaging should be the minimal standard practice in HDREBT for rectal cancer to determine whether an intervention would be necessary. Replanning based on repeat CT imaging resulted in more conformal treatment plans and is therefore recommended.

Routine surveillance imaging following mild traumatic brain injury with intracranial hemorrhage may not be necessary.

BACKGROUND: Mild traumatic brain injury (mTBI) comprises the majority of pediatric traumatic brain injury. Children with mTBI even with traumatic intracranial hemorrhage (tICH) rarely experience a clinically significant neurologic decline (CSND). The utility of routine surveillance imaging in the pediatric population also remains controversial, especially owing to concerns about the risks of radiation exposure at a young age. This study aims to identify demographic or injury-related characteristics that may facilitate recognition of children at risk of progression with mTBI. METHODS: We performed a retrospective review of patients <16 years old with mTBI (GCS 13-15) and tICH admitted to a Level I pediatric trauma center between 2009 and 2014. Management of these patients was directed by the Cincinnati Children's Hospital Medical Center Minor Head Injury Algorithm. We reviewed each chart with emphasis on patient demographics, injury specific data, and radiographic or clinical progression. RESULTS: 154 patients met inclusion criteria with mean age of 4 [0-16]; 116 sustained an tICH and 38 patients had isolated skull fractures. Repeat neuroimaging was obtained in 68 patients (59%). Only 9 patients (13%) with tICH had radiographic progression, none of which resulted in CSND. In addition, 9 patients experienced CSND, leading to neurosurgical intervention in 6 patients. Notably, none of these patients had repeat imaging prior to their neurologic changes. Both CSND and need for intervention were significantly higher in patients with epidural hematomas than other types of tICH (19.2% vs. 1.1%, p = 0.002). Of 154 patients, 19 did not have documented follow-up, 135 were seen as outpatients and 65 (48%) had follow up neuroimaging. All patients who had surveillance imaging in the outpatient setting had stable or resolved tICH. CONCLUSION: Few children with mTBI and tICH experience clinical decline. Importantly, all patients that required neurosurgical intervention were identified by clinical changes rather than via repeat imaging. Our study suggests that in the vast majority of cases, clinical monitoring alone is safe and sufficient in patients in order to avoid exposure to repeat radiographic imaging. LEVEL OF EVIDENCE: Level III, prognostic and epidemiological.

The Clinical Impact of a Web-Based Image Repository on Radiation Exposure in Injured Children.

PURPOSE: The long-term cancer risks for children exposed to radiologic images can be two to three times higher than for adults because children are more sensitive to radiation and have a longer lifetime in which to accumulate exposure from CT scans. Injured children often undergo repeat CT imaging if they are transferred from non-pediatric hospitals to a Level I pediatric trauma center (PTC). This study determined the impact of a statewide web-based image repository (WBIR) on repeat imaging among transferred injured children. METHODS: All injured children who underwent CT imaging and were transferred to the PTC in 2010 (pre-WBIR) and 2013 (post-WBIR) were included. Patient-level factors studied included demographics, body region of scan, Injury Severity Score, and Emergency Department (ED) disposition. Change from pre to post on rate of repeat imaging was assessed. RESULTS: Two hundred fifty-four and 233 children, with a median age of 7.3 years, were transferred to the Children's Hospital in 2010 and 2013, respectively. Repeat imaging levels at the PTC were lower post-WBIR than pre-WBIR (20% versus 33%, odds ratio [OR] 0.54, P = .005). Images of the head decreased most significantly (60% versus 33%, OR 0.33). Images performed at Level II and III trauma centers were repeated less often after WBIR. CONCLUSIONS: The WBIR significantly reduced repeat imaging among injured children transferred to a PTC, especially children transferred from Level II and Level III trauma centers, children with lower-acuity injuries, and children with initial scans of the head. Radiation savings are expected to be beneficial to children.

The Value of Early Diagnosis in the Management and the Prognosis of Delayed Traumatic Intracerebral Hematoma

Ten cases of delayed traumatic intracerebral hematomas(DTICH) were found retrospectively among 129 patients with traumatic intracranial hematoma in about 3-year period. The interval from cranial injury to diagnosis of DTICH varied from 1 day to 13 day. The diagnosis was made on repeat computerized tomographic(CT) scans, obtained following neurological deterioration, lack of improvement and/or increase of intracranial pressure(ICP). For early diagnosis of DTICH, continuous ICP monitoring was more effective than routinely repeating CT scan and neurological observation. To analyse the factors influencing the prognosis, we divided DTICH into four groups by initial CT findings:Group I, one case, had negative CT scan on admission. In group II, two cases, an area of parenchymal contusion was noted on the initial CT scan with DTICH subsequently developing in the contused region. In group III, six cases, the initial CT scan showed intracranial hematoma and prior surgical management was done on admission. Group IV, one case, showed generalized brain edema. The prognoses of group III and IV were poorer than those of group I and II. The overall mortality was about 20%. We also discussed the pathogenesis and prognostic factors of DTICH in light of pertinent literatures.